Add protobuf 2.2.0a sources

This is the contents of protobuf-2.2.0a.tar.bz2 from
http://code.google.com/p/protobuf/downloads/list and
is the base code for the javamicro code generator.

Change-Id: Ie9a0440a824d615086445b6636944484b3155afa

36 files changed, 12092 insertions, 0 deletions

diff --git a/python/README.txt b/python/README.txt
new file mode 100644
index 0000000..96f1a73
--- /dev/null
+++ b/python/README.txt
@@ -0,0 +1,73 @@
+Protocol Buffers - Google's data interchange format
+Copyright 2008 Google Inc.
+
+This directory contains the Python Protocol Buffers runtime library.
+
+Normally, this directory comes as part of the protobuf package, available
+from:
+
+  http://code.google.com/p/protobuf
+
+The complete package includes the C++ source code, which includes the
+Protocol Compiler (protoc).  If you downloaded this package from PyPI
+or some other Python-specific source, you may have received only the
+Python part of the code.  In this case, you will need to obtain the
+Protocol Compiler from some other source before you can use this
+package.
+
+Development Warning
+===================
+
+The Python implementation of Protocol Buffers is not as mature as the C++
+and Java implementations.  It may be more buggy, and it is known to be
+pretty slow at this time.  If you would like to help fix these issues,
+join the Protocol Buffers discussion list and let us know!
+
+Installation
+============
+
+1) Make sure you have Python 2.4 or newer.  If in doubt, run:
+
+     $ python -V
+
+2) If you do not have setuptools installed, note that it will be
+   downloaded and installed automatically as soon as you run setup.py.
+   If you would rather install it manually, you may do so by following
+   the instructions on this page:
+
+     http://peak.telecommunity.com/DevCenter/EasyInstall#installation-instructions
+
+3) Build the C++ code, or install a binary distribution of protoc.  If
+   you install a binary distribution, make sure that it is the same
+   version as this package.  If in doubt, run:
+
+     $ protoc --version
+
+4) Run the tests:
+
+     $ python setup.py test
+
+   If some tests fail, this library may not work correctly on your
+   system.  Continue at your own risk.
+
+   Please note that there is a known problem with some versions of
+   Python on Cygwin which causes the tests to fail after printing the
+   error:  "sem_init: Resource temporarily unavailable".  This appears
+   to be a bug either in Cygwin or in Python:
+     http://www.cygwin.com/ml/cygwin/2005-07/msg01378.html
+   We do not know if or when it might me fixed.  We also do not know
+   how likely it is that this bug will affect users in practice.
+
+5) Install:
+
+     $ python setup.py install
+
+   This step may require superuser privileges.
+
+Usage
+=====
+
+The complete documentation for Protocol Buffers is available via the
+web at:
+
+  http://code.google.com/apis/protocolbuffers/
diff --git a/python/ez_setup.py b/python/ez_setup.py
new file mode 100755
index 0000000..b7a9849
--- /dev/null
+++ b/python/ez_setup.py
@@ -0,0 +1,281 @@
+#!python
+
+# This file was obtained from:
+#   http://peak.telecommunity.com/dist/ez_setup.py
+# on 2009/4/17.
+
+"""Bootstrap setuptools installation
+
+If you want to use setuptools in your package's setup.py, just include this
+file in the same directory with it, and add this to the top of your setup.py::
+
+    from ez_setup import use_setuptools
+    use_setuptools()
+
+If you want to require a specific version of setuptools, set a download
+mirror, or use an alternate download directory, you can do so by supplying
+the appropriate options to ``use_setuptools()``.
+
+This file can also be run as a script to install or upgrade setuptools.
+"""
+import sys
+DEFAULT_VERSION = "0.6c9"
+DEFAULT_URL     = "http://pypi.python.org/packages/%s/s/setuptools/" % sys.version[:3]
+
+md5_data = {
+    'setuptools-0.6b1-py2.3.egg': '8822caf901250d848b996b7f25c6e6ca',
+    'setuptools-0.6b1-py2.4.egg': 'b79a8a403e4502fbb85ee3f1941735cb',
+    'setuptools-0.6b2-py2.3.egg': '5657759d8a6d8fc44070a9d07272d99b',
+    'setuptools-0.6b2-py2.4.egg': '4996a8d169d2be661fa32a6e52e4f82a',
+    'setuptools-0.6b3-py2.3.egg': 'bb31c0fc7399a63579975cad9f5a0618',
+    'setuptools-0.6b3-py2.4.egg': '38a8c6b3d6ecd22247f179f7da669fac',
+    'setuptools-0.6b4-py2.3.egg': '62045a24ed4e1ebc77fe039aa4e6f7e5',
+    'setuptools-0.6b4-py2.4.egg': '4cb2a185d228dacffb2d17f103b3b1c4',
+    'setuptools-0.6c1-py2.3.egg': 'b3f2b5539d65cb7f74ad79127f1a908c',
+    'setuptools-0.6c1-py2.4.egg': 'b45adeda0667d2d2ffe14009364f2a4b',
+    'setuptools-0.6c2-py2.3.egg': 'f0064bf6aa2b7d0f3ba0b43f20817c27',
+    'setuptools-0.6c2-py2.4.egg': '616192eec35f47e8ea16cd6a122b7277',
+    'setuptools-0.6c3-py2.3.egg': 'f181fa125dfe85a259c9cd6f1d7b78fa',
+    'setuptools-0.6c3-py2.4.egg': 'e0ed74682c998bfb73bf803a50e7b71e',
+    'setuptools-0.6c3-py2.5.egg': 'abef16fdd61955514841c7c6bd98965e',
+    'setuptools-0.6c4-py2.3.egg': 'b0b9131acab32022bfac7f44c5d7971f',
+    'setuptools-0.6c4-py2.4.egg': '2a1f9656d4fbf3c97bf946c0a124e6e2',
+    'setuptools-0.6c4-py2.5.egg': '8f5a052e32cdb9c72bcf4b5526f28afc',
+    'setuptools-0.6c5-py2.3.egg': 'ee9fd80965da04f2f3e6b3576e9d8167',
+    'setuptools-0.6c5-py2.4.egg': 'afe2adf1c01701ee841761f5bcd8aa64',
+    'setuptools-0.6c5-py2.5.egg': 'a8d3f61494ccaa8714dfed37bccd3d5d',
+    'setuptools-0.6c6-py2.3.egg': '35686b78116a668847237b69d549ec20',
+    'setuptools-0.6c6-py2.4.egg': '3c56af57be3225019260a644430065ab',
+    'setuptools-0.6c6-py2.5.egg': 'b2f8a7520709a5b34f80946de5f02f53',
+    'setuptools-0.6c7-py2.3.egg': '209fdf9adc3a615e5115b725658e13e2',
+    'setuptools-0.6c7-py2.4.egg': '5a8f954807d46a0fb67cf1f26c55a82e',
+    'setuptools-0.6c7-py2.5.egg': '45d2ad28f9750e7434111fde831e8372',
+    'setuptools-0.6c8-py2.3.egg': '50759d29b349db8cfd807ba8303f1902',
+    'setuptools-0.6c8-py2.4.egg': 'cba38d74f7d483c06e9daa6070cce6de',
+    'setuptools-0.6c8-py2.5.egg': '1721747ee329dc150590a58b3e1ac95b',
+    'setuptools-0.6c9-py2.3.egg': 'a83c4020414807b496e4cfbe08507c03',
+    'setuptools-0.6c9-py2.4.egg': '260a2be2e5388d66bdaee06abec6342a',
+    'setuptools-0.6c9-py2.5.egg': 'fe67c3e5a17b12c0e7c541b7ea43a8e6',
+    'setuptools-0.6c9-py2.6.egg': 'ca37b1ff16fa2ede6e19383e7b59245a',
+}
+
+import sys, os
+try: from hashlib import md5
+except ImportError: from md5 import md5
+
+def _validate_md5(egg_name, data):
+    if egg_name in md5_data:
+        digest = md5(data).hexdigest()
+        if digest != md5_data[egg_name]:
+            print >>sys.stderr, (
+                "md5 validation of %s failed!  (Possible download problem?)"
+                % egg_name
+            )
+            sys.exit(2)
+    return data
+
+def use_setuptools(
+    version=DEFAULT_VERSION, download_base=DEFAULT_URL, to_dir=os.curdir,
+    download_delay=15
+):
+    """Automatically find/download setuptools and make it available on sys.path
+
+    `version` should be a valid setuptools version number that is available
+    as an egg for download under the `download_base` URL (which should end with
+    a '/').  `to_dir` is the directory where setuptools will be downloaded, if
+    it is not already available.  If `download_delay` is specified, it should
+    be the number of seconds that will be paused before initiating a download,
+    should one be required.  If an older version of setuptools is installed,
+    this routine will print a message to ``sys.stderr`` and raise SystemExit in
+    an attempt to abort the calling script.
+    """
+    was_imported = 'pkg_resources' in sys.modules or 'setuptools' in sys.modules
+    def do_download():
+        egg = download_setuptools(version, download_base, to_dir, download_delay)
+        sys.path.insert(0, egg)
+        import setuptools; setuptools.bootstrap_install_from = egg
+    try:
+        import pkg_resources
+    except ImportError:
+        return do_download()       
+    try:
+        pkg_resources.require("setuptools>="+version); return
+    except pkg_resources.VersionConflict, e:
+        if was_imported:
+            print >>sys.stderr, (
+            "The required version of setuptools (>=%s) is not available, and\n"
+            "can't be installed while this script is running. Please install\n"
+            " a more recent version first, using 'easy_install -U setuptools'."
+            "\n\n(Currently using %r)"
+            ) % (version, e.args[0])
+            sys.exit(2)
+        else:
+            del pkg_resources, sys.modules['pkg_resources']    # reload ok
+            return do_download()
+    except pkg_resources.DistributionNotFound:
+        return do_download()
+
+def download_setuptools(
+    version=DEFAULT_VERSION, download_base=DEFAULT_URL, to_dir=os.curdir,
+    delay = 15
+):
+    """Download setuptools from a specified location and return its filename
+
+    `version` should be a valid setuptools version number that is available
+    as an egg for download under the `download_base` URL (which should end
+    with a '/'). `to_dir` is the directory where the egg will be downloaded.
+    `delay` is the number of seconds to pause before an actual download attempt.
+    """
+    import urllib2, shutil
+    egg_name = "setuptools-%s-py%s.egg" % (version,sys.version[:3])
+    url = download_base + egg_name
+    saveto = os.path.join(to_dir, egg_name)
+    src = dst = None
+    if not os.path.exists(saveto):  # Avoid repeated downloads
+        try:
+            from distutils import log
+            if delay:
+                log.warn("""
+---------------------------------------------------------------------------
+This script requires setuptools version %s to run (even to display
+help).  I will attempt to download it for you (from
+%s), but
+you may need to enable firewall access for this script first.
+I will start the download in %d seconds.
+
+(Note: if this machine does not have network access, please obtain the file
+
+   %s
+
+and place it in this directory before rerunning this script.)
+---------------------------------------------------------------------------""",
+                    version, download_base, delay, url
+                ); from time import sleep; sleep(delay)
+            log.warn("Downloading %s", url)
+            src = urllib2.urlopen(url)
+            # Read/write all in one block, so we don't create a corrupt file
+            # if the download is interrupted.
+            data = _validate_md5(egg_name, src.read())
+            dst = open(saveto,"wb"); dst.write(data)
+        finally:
+            if src: src.close()
+            if dst: dst.close()
+    return os.path.realpath(saveto)
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+def main(argv, version=DEFAULT_VERSION):
+    """Install or upgrade setuptools and EasyInstall"""
+    try:
+        import setuptools
+    except ImportError:
+        egg = None
+        try:
+            egg = download_setuptools(version, delay=0)
+            sys.path.insert(0,egg)
+            from setuptools.command.easy_install import main
+            return main(list(argv)+[egg])   # we're done here
+        finally:
+            if egg and os.path.exists(egg):
+                os.unlink(egg)
+    else:
+        if setuptools.__version__ == '0.0.1':
+            print >>sys.stderr, (
+            "You have an obsolete version of setuptools installed.  Please\n"
+            "remove it from your system entirely before rerunning this script."
+            )
+            sys.exit(2)
+
+    req = "setuptools>="+version
+    import pkg_resources
+    try:
+        pkg_resources.require(req)
+    except pkg_resources.VersionConflict:
+        try:
+            from setuptools.command.easy_install import main
+        except ImportError:
+            from easy_install import main
+        main(list(argv)+[download_setuptools(delay=0)])
+        sys.exit(0) # try to force an exit
+    else:
+        if argv:
+            from setuptools.command.easy_install import main
+            main(argv)
+        else:
+            print "Setuptools version",version,"or greater has been installed."
+            print '(Run "ez_setup.py -U setuptools" to reinstall or upgrade.)'
+
+def update_md5(filenames):
+    """Update our built-in md5 registry"""
+
+    import re
+
+    for name in filenames:
+        base = os.path.basename(name)
+        f = open(name,'rb')
+        md5_data[base] = md5(f.read()).hexdigest()
+        f.close()
+
+    data = ["    %r: %r,\n" % it for it in md5_data.items()]
+    data.sort()
+    repl = "".join(data)
+
+    import inspect
+    srcfile = inspect.getsourcefile(sys.modules[__name__])
+    f = open(srcfile, 'rb'); src = f.read(); f.close()
+
+    match = re.search("\nmd5_data = {\n([^}]+)}", src)
+    if not match:
+        print >>sys.stderr, "Internal error!"
+        sys.exit(2)
+
+    src = src[:match.start(1)] + repl + src[match.end(1):]
+    f = open(srcfile,'w')
+    f.write(src)
+    f.close()
+
+
+if __name__=='__main__':
+    if len(sys.argv)>2 and sys.argv[1]=='--md5update':
+        update_md5(sys.argv[2:])
+    else:
+        main(sys.argv[1:])
+
+
+
+
+
+
diff --git a/python/google/__init__.py b/python/google/__init__.py
new file mode 100755
index 0000000..de40ea7
--- /dev/null
+++ b/python/google/__init__.py
@@ -0,0 +1 @@
+__import__('pkg_resources').declare_namespace(__name__)
diff --git a/python/google/protobuf/__init__.py b/python/google/protobuf/__init__.py
new file mode 100755
index 0000000..e69de29
--- /dev/null
+++ b/python/google/protobuf/__init__.py
diff --git a/python/google/protobuf/descriptor.py b/python/google/protobuf/descriptor.py
new file mode 100755
index 0000000..8e3fc2e
--- /dev/null
+++ b/python/google/protobuf/descriptor.py
@@ -0,0 +1,433 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+# TODO(robinson): We probably need to provide deep-copy methods for
+# descriptor types.  When a FieldDescriptor is passed into
+# Descriptor.__init__(), we should make a deep copy and then set
+# containing_type on it.  Alternatively, we could just get
+# rid of containing_type (iit's not needed for reflection.py, at least).
+#
+# TODO(robinson): Print method?
+#
+# TODO(robinson): Useful __repr__?
+
+"""Descriptors essentially contain exactly the information found in a .proto
+file, in types that make this information accessible in Python.
+"""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+class DescriptorBase(object):
+
+  """Descriptors base class.
+
+  This class is the base of all descriptor classes. It provides common options
+  related functionaility.
+  """
+
+  def __init__(self, options, options_class_name):
+    """Initialize the descriptor given its options message and the name of the
+    class of the options message. The name of the class is required in case
+    the options message is None and has to be created.
+    """
+    self._options = options
+    self._options_class_name = options_class_name
+
+  def GetOptions(self):
+    """Retrieves descriptor options.
+
+    This method returns the options set or creates the default options for the
+    descriptor.
+    """
+    if self._options:
+      return self._options
+    from google.protobuf import descriptor_pb2
+    try:
+      options_class = getattr(descriptor_pb2, self._options_class_name)
+    except AttributeError:
+      raise RuntimeError('Unknown options class name %s!' %
+                         (self._options_class_name))
+    self._options = options_class()
+    return self._options
+
+
+class Descriptor(DescriptorBase):
+
+  """Descriptor for a protocol message type.
+
+  A Descriptor instance has the following attributes:
+
+    name: (str) Name of this protocol message type.
+    full_name: (str) Fully-qualified name of this protocol message type,
+      which will include protocol "package" name and the name of any
+      enclosing types.
+
+    filename: (str) Name of the .proto file containing this message.
+
+    containing_type: (Descriptor) Reference to the descriptor of the
+      type containing us, or None if we have no containing type.
+
+    fields: (list of FieldDescriptors) Field descriptors for all
+      fields in this type.
+    fields_by_number: (dict int -> FieldDescriptor) Same FieldDescriptor
+      objects as in |fields|, but indexed by "number" attribute in each
+      FieldDescriptor.
+    fields_by_name: (dict str -> FieldDescriptor) Same FieldDescriptor
+      objects as in |fields|, but indexed by "name" attribute in each
+      FieldDescriptor.
+
+    nested_types: (list of Descriptors) Descriptor references
+      for all protocol message types nested within this one.
+    nested_types_by_name: (dict str -> Descriptor) Same Descriptor
+      objects as in |nested_types|, but indexed by "name" attribute
+      in each Descriptor.
+
+    enum_types: (list of EnumDescriptors) EnumDescriptor references
+      for all enums contained within this type.
+    enum_types_by_name: (dict str ->EnumDescriptor) Same EnumDescriptor
+      objects as in |enum_types|, but indexed by "name" attribute
+      in each EnumDescriptor.
+    enum_values_by_name: (dict str -> EnumValueDescriptor) Dict mapping
+      from enum value name to EnumValueDescriptor for that value.
+
+    extensions: (list of FieldDescriptor) All extensions defined directly
+      within this message type (NOT within a nested type).
+    extensions_by_name: (dict, string -> FieldDescriptor) Same FieldDescriptor
+      objects as |extensions|, but indexed by "name" attribute of each
+      FieldDescriptor.
+
+    options: (descriptor_pb2.MessageOptions) Protocol message options or None
+      to use default message options.
+  """
+
+  def __init__(self, name, full_name, filename, containing_type,
+               fields, nested_types, enum_types, extensions, options=None):
+    """Arguments to __init__() are as described in the description
+    of Descriptor fields above.
+    """
+    super(Descriptor, self).__init__(options, 'MessageOptions')
+    self.name = name
+    self.full_name = full_name
+    self.filename = filename
+    self.containing_type = containing_type
+
+    # We have fields in addition to fields_by_name and fields_by_number,
+    # so that:
+    #   1. Clients can index fields by "order in which they're listed."
+    #   2. Clients can easily iterate over all fields with the terse
+    #      syntax: for f in descriptor.fields: ...
+    self.fields = fields
+    for field in self.fields:
+      field.containing_type = self
+    self.fields_by_number = dict((f.number, f) for f in fields)
+    self.fields_by_name = dict((f.name, f) for f in fields)
+
+    self.nested_types = nested_types
+    self.nested_types_by_name = dict((t.name, t) for t in nested_types)
+
+    self.enum_types = enum_types
+    for enum_type in self.enum_types:
+      enum_type.containing_type = self
+    self.enum_types_by_name = dict((t.name, t) for t in enum_types)
+    self.enum_values_by_name = dict(
+        (v.name, v) for t in enum_types for v in t.values)
+
+    self.extensions = extensions
+    for extension in self.extensions:
+      extension.extension_scope = self
+    self.extensions_by_name = dict((f.name, f) for f in extensions)
+
+
+# TODO(robinson): We should have aggressive checking here,
+# for example:
+#   * If you specify a repeated field, you should not be allowed
+#     to specify a default value.
+#   * [Other examples here as needed].
+#
+# TODO(robinson): for this and other *Descriptor classes, we
+# might also want to lock things down aggressively (e.g.,
+# prevent clients from setting the attributes).  Having
+# stronger invariants here in general will reduce the number
+# of runtime checks we must do in reflection.py...
+class FieldDescriptor(DescriptorBase):
+
+  """Descriptor for a single field in a .proto file.
+
+  A FieldDescriptor instance has the following attriubtes:
+
+    name: (str) Name of this field, exactly as it appears in .proto.
+    full_name: (str) Name of this field, including containing scope.  This is
+      particularly relevant for extensions.
+    index: (int) Dense, 0-indexed index giving the order that this
+      field textually appears within its message in the .proto file.
+    number: (int) Tag number declared for this field in the .proto file.
+
+    type: (One of the TYPE_* constants below) Declared type.
+    cpp_type: (One of the CPPTYPE_* constants below) C++ type used to
+      represent this field.
+
+    label: (One of the LABEL_* constants below) Tells whether this
+      field is optional, required, or repeated.
+    default_value: (Varies) Default value of this field.  Only
+      meaningful for non-repeated scalar fields.  Repeated fields
+      should always set this to [], and non-repeated composite
+      fields should always set this to None.
+
+    containing_type: (Descriptor) Descriptor of the protocol message
+      type that contains this field.  Set by the Descriptor constructor
+      if we're passed into one.
+      Somewhat confusingly, for extension fields, this is the
+      descriptor of the EXTENDED message, not the descriptor
+      of the message containing this field.  (See is_extension and
+      extension_scope below).
+    message_type: (Descriptor) If a composite field, a descriptor
+      of the message type contained in this field.  Otherwise, this is None.
+    enum_type: (EnumDescriptor) If this field contains an enum, a
+      descriptor of that enum.  Otherwise, this is None.
+
+    is_extension: True iff this describes an extension field.
+    extension_scope: (Descriptor) Only meaningful if is_extension is True.
+      Gives the message that immediately contains this extension field.
+      Will be None iff we're a top-level (file-level) extension field.
+
+    options: (descriptor_pb2.FieldOptions) Protocol message field options or
+      None to use default field options.
+  """
+
+  # Must be consistent with C++ FieldDescriptor::Type enum in
+  # descriptor.h.
+  #
+  # TODO(robinson): Find a way to eliminate this repetition.
+  TYPE_DOUBLE         = 1
+  TYPE_FLOAT          = 2
+  TYPE_INT64          = 3
+  TYPE_UINT64         = 4
+  TYPE_INT32          = 5
+  TYPE_FIXED64        = 6
+  TYPE_FIXED32        = 7
+  TYPE_BOOL           = 8
+  TYPE_STRING         = 9
+  TYPE_GROUP          = 10
+  TYPE_MESSAGE        = 11
+  TYPE_BYTES          = 12
+  TYPE_UINT32         = 13
+  TYPE_ENUM           = 14
+  TYPE_SFIXED32       = 15
+  TYPE_SFIXED64       = 16
+  TYPE_SINT32         = 17
+  TYPE_SINT64         = 18
+  MAX_TYPE            = 18
+
+  # Must be consistent with C++ FieldDescriptor::CppType enum in
+  # descriptor.h.
+  #
+  # TODO(robinson): Find a way to eliminate this repetition.
+  CPPTYPE_INT32       = 1
+  CPPTYPE_INT64       = 2
+  CPPTYPE_UINT32      = 3
+  CPPTYPE_UINT64      = 4
+  CPPTYPE_DOUBLE      = 5
+  CPPTYPE_FLOAT       = 6
+  CPPTYPE_BOOL        = 7
+  CPPTYPE_ENUM        = 8
+  CPPTYPE_STRING      = 9
+  CPPTYPE_MESSAGE     = 10
+  MAX_CPPTYPE         = 10
+
+  # Must be consistent with C++ FieldDescriptor::Label enum in
+  # descriptor.h.
+  #
+  # TODO(robinson): Find a way to eliminate this repetition.
+  LABEL_OPTIONAL      = 1
+  LABEL_REQUIRED      = 2
+  LABEL_REPEATED      = 3
+  MAX_LABEL           = 3
+
+  def __init__(self, name, full_name, index, number, type, cpp_type, label,
+               default_value, message_type, enum_type, containing_type,
+               is_extension, extension_scope, options=None):
+    """The arguments are as described in the description of FieldDescriptor
+    attributes above.
+
+    Note that containing_type may be None, and may be set later if necessary
+    (to deal with circular references between message types, for example).
+    Likewise for extension_scope.
+    """
+    super(FieldDescriptor, self).__init__(options, 'FieldOptions')
+    self.name = name
+    self.full_name = full_name
+    self.index = index
+    self.number = number
+    self.type = type
+    self.cpp_type = cpp_type
+    self.label = label
+    self.default_value = default_value
+    self.containing_type = containing_type
+    self.message_type = message_type
+    self.enum_type = enum_type
+    self.is_extension = is_extension
+    self.extension_scope = extension_scope
+
+
+class EnumDescriptor(DescriptorBase):
+
+  """Descriptor for an enum defined in a .proto file.
+
+  An EnumDescriptor instance has the following attributes:
+
+    name: (str) Name of the enum type.
+    full_name: (str) Full name of the type, including package name
+      and any enclosing type(s).
+    filename: (str) Name of the .proto file in which this appears.
+
+    values: (list of EnumValueDescriptors) List of the values
+      in this enum.
+    values_by_name: (dict str -> EnumValueDescriptor) Same as |values|,
+      but indexed by the "name" field of each EnumValueDescriptor.
+    values_by_number: (dict int -> EnumValueDescriptor) Same as |values|,
+      but indexed by the "number" field of each EnumValueDescriptor.
+    containing_type: (Descriptor) Descriptor of the immediate containing
+      type of this enum, or None if this is an enum defined at the
+      top level in a .proto file.  Set by Descriptor's constructor
+      if we're passed into one.
+    options: (descriptor_pb2.EnumOptions) Enum options message or
+      None to use default enum options.
+  """
+
+  def __init__(self, name, full_name, filename, values,
+               containing_type=None, options=None):
+    """Arguments are as described in the attribute description above."""
+    super(EnumDescriptor, self).__init__(options, 'EnumOptions')
+    self.name = name
+    self.full_name = full_name
+    self.filename = filename
+    self.values = values
+    for value in self.values:
+      value.type = self
+    self.values_by_name = dict((v.name, v) for v in values)
+    self.values_by_number = dict((v.number, v) for v in values)
+    self.containing_type = containing_type
+
+
+class EnumValueDescriptor(DescriptorBase):
+
+  """Descriptor for a single value within an enum.
+
+    name: (str) Name of this value.
+    index: (int) Dense, 0-indexed index giving the order that this
+      value appears textually within its enum in the .proto file.
+    number: (int) Actual number assigned to this enum value.
+    type: (EnumDescriptor) EnumDescriptor to which this value
+      belongs.  Set by EnumDescriptor's constructor if we're
+      passed into one.
+    options: (descriptor_pb2.EnumValueOptions) Enum value options message or
+      None to use default enum value options options.
+  """
+
+  def __init__(self, name, index, number, type=None, options=None):
+    """Arguments are as described in the attribute description above."""
+    super(EnumValueDescriptor, self).__init__(options, 'EnumValueOptions')
+    self.name = name
+    self.index = index
+    self.number = number
+    self.type = type
+
+
+class ServiceDescriptor(DescriptorBase):
+
+  """Descriptor for a service.
+
+    name: (str) Name of the service.
+    full_name: (str) Full name of the service, including package name.
+    index: (int) 0-indexed index giving the order that this services
+      definition appears withing the .proto file.
+    methods: (list of MethodDescriptor) List of methods provided by this
+      service.
+    options: (descriptor_pb2.ServiceOptions) Service options message or
+      None to use default service options.
+  """
+
+  def __init__(self, name, full_name, index, methods, options=None):
+    super(ServiceDescriptor, self).__init__(options, 'ServiceOptions')
+    self.name = name
+    self.full_name = full_name
+    self.index = index
+    self.methods = methods
+    # Set the containing service for each method in this service.
+    for method in self.methods:
+      method.containing_service = self
+
+  def FindMethodByName(self, name):
+    """Searches for the specified method, and returns its descriptor."""
+    for method in self.methods:
+      if name == method.name:
+        return method
+    return None
+
+
+class MethodDescriptor(DescriptorBase):
+
+  """Descriptor for a method in a service.
+
+  name: (str) Name of the method within the service.
+  full_name: (str) Full name of method.
+  index: (int) 0-indexed index of the method inside the service.
+  containing_service: (ServiceDescriptor) The service that contains this
+    method.
+  input_type: The descriptor of the message that this method accepts.
+  output_type: The descriptor of the message that this method returns.
+  options: (descriptor_pb2.MethodOptions) Method options message or
+    None to use default method options.
+  """
+
+  def __init__(self, name, full_name, index, containing_service,
+               input_type, output_type, options=None):
+    """The arguments are as described in the description of MethodDescriptor
+    attributes above.
+
+    Note that containing_service may be None, and may be set later if necessary.
+    """
+    super(MethodDescriptor, self).__init__(options, 'MethodOptions')
+    self.name = name
+    self.full_name = full_name
+    self.index = index
+    self.containing_service = containing_service
+    self.input_type = input_type
+    self.output_type = output_type
+
+
+def _ParseOptions(message, string):
+  """Parses serialized options.
+
+  This helper function is used to parse serialized options in generated
+  proto2 files. It must not be used outside proto2.
+  """
+  message.ParseFromString(string)
+  return message;
diff --git a/python/google/protobuf/internal/__init__.py b/python/google/protobuf/internal/__init__.py
new file mode 100755
index 0000000..e69de29
--- /dev/null
+++ b/python/google/protobuf/internal/__init__.py
diff --git a/python/google/protobuf/internal/containers.py b/python/google/protobuf/internal/containers.py
new file mode 100755
index 0000000..d8a825d
--- /dev/null
+++ b/python/google/protobuf/internal/containers.py
@@ -0,0 +1,227 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Contains container classes to represent different protocol buffer types.
+
+This file defines container classes which represent categories of protocol
+buffer field types which need extra maintenance. Currently these categories
+are:
+  - Repeated scalar fields - These are all repeated fields which aren't
+    composite (e.g. they are of simple types like int32, string, etc).
+  - Repeated composite fields - Repeated fields which are composite. This
+    includes groups and nested messages.
+"""
+
+__author__ = 'petar@google.com (Petar Petrov)'
+
+
+class BaseContainer(object):
+
+  """Base container class."""
+
+  # Minimizes memory usage and disallows assignment to other attributes.
+  __slots__ = ['_message_listener', '_values']
+
+  def __init__(self, message_listener):
+    """
+    Args:
+      message_listener: A MessageListener implementation.
+        The RepeatedScalarFieldContainer will call this object's
+        TransitionToNonempty() method when it transitions from being empty to
+        being nonempty.
+    """
+    self._message_listener = message_listener
+    self._values = []
+
+  def __getitem__(self, key):
+    """Retrieves item by the specified key."""
+    return self._values[key]
+
+  def __len__(self):
+    """Returns the number of elements in the container."""
+    return len(self._values)
+
+  def __ne__(self, other):
+    """Checks if another instance isn't equal to this one."""
+    # The concrete classes should define __eq__.
+    return not self == other
+
+
+class RepeatedScalarFieldContainer(BaseContainer):
+
+  """Simple, type-checked, list-like container for holding repeated scalars."""
+
+  # Disallows assignment to other attributes.
+  __slots__ = ['_type_checker']
+
+  def __init__(self, message_listener, type_checker):
+    """
+    Args:
+      message_listener: A MessageListener implementation.
+        The RepeatedScalarFieldContainer will call this object's
+        TransitionToNonempty() method when it transitions from being empty to
+        being nonempty.
+      type_checker: A type_checkers.ValueChecker instance to run on elements
+        inserted into this container.
+    """
+    super(RepeatedScalarFieldContainer, self).__init__(message_listener)
+    self._type_checker = type_checker
+
+  def append(self, value):
+    """Appends an item to the list. Similar to list.append()."""
+    self.insert(len(self._values), value)
+
+  def insert(self, key, value):
+    """Inserts the item at the specified position. Similar to list.insert()."""
+    self._type_checker.CheckValue(value)
+    self._values.insert(key, value)
+    self._message_listener.ByteSizeDirty()
+    if len(self._values) == 1:
+      self._message_listener.TransitionToNonempty()
+
+  def extend(self, elem_seq):
+    """Extends by appending the given sequence. Similar to list.extend()."""
+    if not elem_seq:
+      return
+
+    orig_empty = len(self._values) == 0
+    new_values = []
+    for elem in elem_seq:
+      self._type_checker.CheckValue(elem)
+      new_values.append(elem)
+    self._values.extend(new_values)
+    self._message_listener.ByteSizeDirty()
+    if orig_empty:
+      self._message_listener.TransitionToNonempty()
+
+  def remove(self, elem):
+    """Removes an item from the list. Similar to list.remove()."""
+    self._values.remove(elem)
+    self._message_listener.ByteSizeDirty()
+
+  def __setitem__(self, key, value):
+    """Sets the item on the specified position."""
+    # No need to call TransitionToNonempty(), since if we're able to
+    # set the element at this index, we were already nonempty before
+    # this method was called.
+    self._message_listener.ByteSizeDirty()
+    self._type_checker.CheckValue(value)
+    self._values[key] = value
+
+  def __getslice__(self, start, stop):
+    """Retrieves the subset of items from between the specified indices."""
+    return self._values[start:stop]
+
+  def __setslice__(self, start, stop, values):
+    """Sets the subset of items from between the specified indices."""
+    new_values = []
+    for value in values:
+      self._type_checker.CheckValue(value)
+      new_values.append(value)
+    self._values[start:stop] = new_values
+    self._message_listener.ByteSizeDirty()
+
+  def __delitem__(self, key):
+    """Deletes the item at the specified position."""
+    del self._values[key]
+    self._message_listener.ByteSizeDirty()
+
+  def __delslice__(self, start, stop):
+    """Deletes the subset of items from between the specified indices."""
+    del self._values[start:stop]
+    self._message_listener.ByteSizeDirty()
+
+  def __eq__(self, other):
+    """Compares the current instance with another one."""
+    if self is other:
+      return True
+    # Special case for the same type which should be common and fast.
+    if isinstance(other, self.__class__):
+      return other._values == self._values
+    # We are presumably comparing against some other sequence type.
+    return other == self._values
+
+
+class RepeatedCompositeFieldContainer(BaseContainer):
+
+  """Simple, list-like container for holding repeated composite fields."""
+
+  # Disallows assignment to other attributes.
+  __slots__ = ['_message_descriptor']
+
+  def __init__(self, message_listener, message_descriptor):
+    """
+    Note that we pass in a descriptor instead of the generated directly,
+    since at the time we construct a _RepeatedCompositeFieldContainer we
+    haven't yet necessarily initialized the type that will be contained in the
+    container.
+
+    Args:
+      message_listener: A MessageListener implementation.
+        The RepeatedCompositeFieldContainer will call this object's
+        TransitionToNonempty() method when it transitions from being empty to
+        being nonempty.
+      message_descriptor: A Descriptor instance describing the protocol type
+        that should be present in this container.  We'll use the
+        _concrete_class field of this descriptor when the client calls add().
+    """
+    super(RepeatedCompositeFieldContainer, self).__init__(message_listener)
+    self._message_descriptor = message_descriptor
+
+  def add(self):
+    new_element = self._message_descriptor._concrete_class()
+    new_element._SetListener(self._message_listener)
+    self._values.append(new_element)
+    self._message_listener.ByteSizeDirty()
+    self._message_listener.TransitionToNonempty()
+    return new_element
+
+  def __getslice__(self, start, stop):
+    """Retrieves the subset of items from between the specified indices."""
+    return self._values[start:stop]
+
+  def __delitem__(self, key):
+    """Deletes the item at the specified position."""
+    del self._values[key]
+    self._message_listener.ByteSizeDirty()
+
+  def __delslice__(self, start, stop):
+    """Deletes the subset of items from between the specified indices."""
+    del self._values[start:stop]
+    self._message_listener.ByteSizeDirty()
+
+  def __eq__(self, other):
+    """Compares the current instance with another one."""
+    if self is other:
+      return True
+    if not isinstance(other, self.__class__):
+      raise TypeError('Can only compare repeated composite fields against '
+                      'other repeated composite fields.')
+    return self._values == other._values
diff --git a/python/google/protobuf/internal/decoder.py b/python/google/protobuf/internal/decoder.py
new file mode 100755
index 0000000..83d6fe0
--- /dev/null
+++ b/python/google/protobuf/internal/decoder.py
@@ -0,0 +1,209 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Class for decoding protocol buffer primitives.
+
+Contains the logic for decoding every logical protocol field type
+from one of the 5 physical wire types.
+"""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+import struct
+from google.protobuf import message
+from google.protobuf.internal import input_stream
+from google.protobuf.internal import wire_format
+
+
+
+# Note that much of this code is ported from //net/proto/ProtocolBuffer, and
+# that the interface is strongly inspired by WireFormat from the C++ proto2
+# implementation.
+
+
+class Decoder(object):
+
+  """Decodes logical protocol buffer fields from the wire."""
+
+  def __init__(self, s):
+    """Initializes the decoder to read from s.
+
+    Args:
+      s: An immutable sequence of bytes, which must be accessible
+        via the Python buffer() primitive (i.e., buffer(s)).
+    """
+    self._stream = input_stream.InputStream(s)
+
+  def EndOfStream(self):
+    """Returns true iff we've reached the end of the bytes we're reading."""
+    return self._stream.EndOfStream()
+
+  def Position(self):
+    """Returns the 0-indexed position in |s|."""
+    return self._stream.Position()
+
+  def ReadFieldNumberAndWireType(self):
+    """Reads a tag from the wire. Returns a (field_number, wire_type) pair."""
+    tag_and_type = self.ReadUInt32()
+    return wire_format.UnpackTag(tag_and_type)
+
+  def SkipBytes(self, bytes):
+    """Skips the specified number of bytes on the wire."""
+    self._stream.SkipBytes(bytes)
+
+  # Note that the Read*() methods below are not exactly symmetrical with the
+  # corresponding Encoder.Append*() methods.  Those Encoder methods first
+  # encode a tag, but the Read*() methods below assume that the tag has already
+  # been read, and that the client wishes to read a field of the specified type
+  # starting at the current position.
+
+  def ReadInt32(self):
+    """Reads and returns a signed, varint-encoded, 32-bit integer."""
+    return self._stream.ReadVarint32()
+
+  def ReadInt64(self):
+    """Reads and returns a signed, varint-encoded, 64-bit integer."""
+    return self._stream.ReadVarint64()
+
+  def ReadUInt32(self):
+    """Reads and returns an signed, varint-encoded, 32-bit integer."""
+    return self._stream.ReadVarUInt32()
+
+  def ReadUInt64(self):
+    """Reads and returns an signed, varint-encoded,64-bit integer."""
+    return self._stream.ReadVarUInt64()
+
+  def ReadSInt32(self):
+    """Reads and returns a signed, zigzag-encoded, varint-encoded,
+    32-bit integer."""
+    return wire_format.ZigZagDecode(self._stream.ReadVarUInt32())
+
+  def ReadSInt64(self):
+    """Reads and returns a signed, zigzag-encoded, varint-encoded,
+    64-bit integer."""
+    return wire_format.ZigZagDecode(self._stream.ReadVarUInt64())
+
+  def ReadFixed32(self):
+    """Reads and returns an unsigned, fixed-width, 32-bit integer."""
+    return self._stream.ReadLittleEndian32()
+
+  def ReadFixed64(self):
+    """Reads and returns an unsigned, fixed-width, 64-bit integer."""
+    return self._stream.ReadLittleEndian64()
+
+  def ReadSFixed32(self):
+    """Reads and returns a signed, fixed-width, 32-bit integer."""
+    value = self._stream.ReadLittleEndian32()
+    if value >= (1 << 31):
+      value -= (1 << 32)
+    return value
+
+  def ReadSFixed64(self):
+    """Reads and returns a signed, fixed-width, 64-bit integer."""
+    value = self._stream.ReadLittleEndian64()
+    if value >= (1 << 63):
+      value -= (1 << 64)
+    return value
+
+  def ReadFloat(self):
+    """Reads and returns a 4-byte floating-point number."""
+    serialized = self._stream.ReadBytes(4)
+    return struct.unpack(wire_format.FORMAT_FLOAT_LITTLE_ENDIAN, serialized)[0]
+
+  def ReadDouble(self):
+    """Reads and returns an 8-byte floating-point number."""
+    serialized = self._stream.ReadBytes(8)
+    return struct.unpack(wire_format.FORMAT_DOUBLE_LITTLE_ENDIAN, serialized)[0]
+
+  def ReadBool(self):
+    """Reads and returns a bool."""
+    i = self._stream.ReadVarUInt32()
+    return bool(i)
+
+  def ReadEnum(self):
+    """Reads and returns an enum value."""
+    return self._stream.ReadVarUInt32()
+
+  def ReadString(self):
+    """Reads and returns a length-delimited string."""
+    bytes = self.ReadBytes()
+    return unicode(bytes, 'utf-8')
+
+  def ReadBytes(self):
+    """Reads and returns a length-delimited byte sequence."""
+    length = self._stream.ReadVarUInt32()
+    return self._stream.ReadBytes(length)
+
+  def ReadMessageInto(self, msg):
+    """Calls msg.MergeFromString() to merge
+    length-delimited serialized message data into |msg|.
+
+    REQUIRES: The decoder must be positioned at the serialized "length"
+      prefix to a length-delmiited serialized message.
+
+    POSTCONDITION: The decoder is positioned just after the
+      serialized message, and we have merged those serialized
+      contents into |msg|.
+    """
+    length = self._stream.ReadVarUInt32()
+    sub_buffer = self._stream.GetSubBuffer(length)
+    num_bytes_used = msg.MergeFromString(sub_buffer)
+    if num_bytes_used != length:
+      raise message.DecodeError(
+          'Submessage told to deserialize from %d-byte encoding, '
+          'but used only %d bytes' % (length, num_bytes_used))
+    self._stream.SkipBytes(num_bytes_used)
+
+  def ReadGroupInto(self, expected_field_number, group):
+    """Calls group.MergeFromString() to merge
+    END_GROUP-delimited serialized message data into |group|.
+    We'll raise an exception if we don't find an END_GROUP
+    tag immediately after the serialized message contents.
+
+    REQUIRES: The decoder is positioned just after the START_GROUP
+      tag for this group.
+
+    POSTCONDITION: The decoder is positioned just after the
+      END_GROUP tag for this group, and we have merged
+      the contents of the group into |group|.
+    """
+    sub_buffer = self._stream.GetSubBuffer()  # No a priori length limit.
+    num_bytes_used = group.MergeFromString(sub_buffer)
+    if num_bytes_used < 0:
+      raise message.DecodeError('Group message reported negative bytes read.')
+    self._stream.SkipBytes(num_bytes_used)
+    field_number, field_type = self.ReadFieldNumberAndWireType()
+    if field_type != wire_format.WIRETYPE_END_GROUP:
+      raise message.DecodeError('Group message did not end with an END_GROUP.')
+    if field_number != expected_field_number:
+      raise message.DecodeError('END_GROUP tag had field '
+                                'number %d, was expecting field number %d' % (
+          field_number, expected_field_number))
+    # We're now positioned just after the END_GROUP tag.  Perfect.
diff --git a/python/google/protobuf/internal/decoder_test.py b/python/google/protobuf/internal/decoder_test.py
new file mode 100755
index 0000000..98e4647
--- /dev/null
+++ b/python/google/protobuf/internal/decoder_test.py
@@ -0,0 +1,256 @@
+#! /usr/bin/python
+#
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Test for google.protobuf.internal.decoder."""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+import struct
+import unittest
+from google.protobuf.internal import decoder
+from google.protobuf.internal import encoder
+from google.protobuf.internal import input_stream
+from google.protobuf.internal import wire_format
+from google.protobuf import message
+import logging
+import mox
+
+
+class DecoderTest(unittest.TestCase):
+
+  def setUp(self):
+    self.mox = mox.Mox()
+    self.mock_stream = self.mox.CreateMock(input_stream.InputStream)
+    self.mock_message = self.mox.CreateMock(message.Message)
+
+  def testReadFieldNumberAndWireType(self):
+    # Test field numbers that will require various varint sizes.
+    for expected_field_number in (1, 15, 16, 2047, 2048):
+      for expected_wire_type in range(6):  # Highest-numbered wiretype is 5.
+        e = encoder.Encoder()
+        e.AppendTag(expected_field_number, expected_wire_type)
+        s = e.ToString()
+        d = decoder.Decoder(s)
+        field_number, wire_type = d.ReadFieldNumberAndWireType()
+        self.assertEqual(expected_field_number, field_number)
+        self.assertEqual(expected_wire_type, wire_type)
+
+  def ReadScalarTestHelper(self, test_name, decoder_method, expected_result,
+                           expected_stream_method_name,
+                           stream_method_return, *args):
+    """Helper for testReadScalars below.
+
+    Calls one of the Decoder.Read*() methods and ensures that the results are
+    as expected.
+
+    Args:
+      test_name: Name of this test, used for logging only.
+      decoder_method: Unbound decoder.Decoder method to call.
+      expected_result: Value we expect returned from decoder_method().
+      expected_stream_method_name: (string) Name of the InputStream
+        method we expect Decoder to call to actually read the value
+        on the wire.
+      stream_method_return: Value our mocked-out stream method should
+        return to the decoder.
+      args: Additional arguments that we expect to be passed to the
+        stream method.
+    """
+    logging.info('Testing %s scalar input.\n'
+                 'Calling %r(), and expecting that to call the '
+                 'stream method %s(%r), which will return %r.  Finally, '
+                 'expecting the Decoder method to return %r'% (
+        test_name, decoder_method,
+        expected_stream_method_name, args, stream_method_return,
+        expected_result))
+
+    d = decoder.Decoder('')
+    d._stream = self.mock_stream
+    if decoder_method in (decoder.Decoder.ReadString,
+                          decoder.Decoder.ReadBytes):
+      self.mock_stream.ReadVarUInt32().AndReturn(len(stream_method_return))
+    # We have to use names instead of methods to work around some
+    # mox weirdness.  (ResetAll() is overzealous).
+    expected_stream_method = getattr(self.mock_stream,
+                                     expected_stream_method_name)
+    expected_stream_method(*args).AndReturn(stream_method_return)
+
+    self.mox.ReplayAll()
+    result = decoder_method(d)
+    self.assertEqual(expected_result, result)
+    self.assert_(isinstance(result, type(expected_result)))
+    self.mox.VerifyAll()
+    self.mox.ResetAll()
+
+  VAL = 1.125  # Perfectly representable as a float (no rounding error).
+  LITTLE_FLOAT_VAL = '\x00\x00\x90?'
+  LITTLE_DOUBLE_VAL = '\x00\x00\x00\x00\x00\x00\xf2?'
+
+  def testReadScalars(self):
+    test_string = 'I can feel myself getting sutpider.'
+    scalar_tests = [
+        ['int32', decoder.Decoder.ReadInt32, 0, 'ReadVarint32', 0],
+        ['int64', decoder.Decoder.ReadInt64, 0, 'ReadVarint64', 0],
+        ['uint32', decoder.Decoder.ReadUInt32, 0, 'ReadVarUInt32', 0],
+        ['uint64', decoder.Decoder.ReadUInt64, 0, 'ReadVarUInt64', 0],
+        ['fixed32', decoder.Decoder.ReadFixed32, 0xffffffff,
+         'ReadLittleEndian32', 0xffffffff],
+        ['fixed64', decoder.Decoder.ReadFixed64, 0xffffffffffffffff,
+        'ReadLittleEndian64', 0xffffffffffffffff],
+        ['sfixed32', decoder.Decoder.ReadSFixed32, long(-1),
+         'ReadLittleEndian32', long(0xffffffff)],
+        ['sfixed64', decoder.Decoder.ReadSFixed64, long(-1),
+         'ReadLittleEndian64', 0xffffffffffffffff],
+        ['float', decoder.Decoder.ReadFloat, self.VAL,
+         'ReadBytes', self.LITTLE_FLOAT_VAL, 4],
+        ['double', decoder.Decoder.ReadDouble, self.VAL,
+         'ReadBytes', self.LITTLE_DOUBLE_VAL, 8],
+        ['bool', decoder.Decoder.ReadBool, True, 'ReadVarUInt32', 1],
+        ['enum', decoder.Decoder.ReadEnum, 23, 'ReadVarUInt32', 23],
+        ['string', decoder.Decoder.ReadString,
+         unicode(test_string, 'utf-8'), 'ReadBytes', test_string,
+         len(test_string)],
+        ['utf8-string', decoder.Decoder.ReadString,
+         unicode(test_string, 'utf-8'), 'ReadBytes', test_string,
+         len(test_string)],
+        ['bytes', decoder.Decoder.ReadBytes,
+         test_string, 'ReadBytes', test_string, len(test_string)],
+        # We test zigzag decoding routines more extensively below.
+        ['sint32', decoder.Decoder.ReadSInt32, -1, 'ReadVarUInt32', 1],
+        ['sint64', decoder.Decoder.ReadSInt64, -1, 'ReadVarUInt64', 1],
+        ]
+    # Ensure that we're testing different Decoder methods and using
+    # different test names in all test cases above.
+    self.assertEqual(len(scalar_tests), len(set(t[0] for t in scalar_tests)))
+    self.assert_(len(scalar_tests) >= len(set(t[1] for t in scalar_tests)))
+    for args in scalar_tests:
+      self.ReadScalarTestHelper(*args)
+
+  def testReadMessageInto(self):
+    length = 23
+    def Test(simulate_error):
+      d = decoder.Decoder('')
+      d._stream = self.mock_stream
+      self.mock_stream.ReadVarUInt32().AndReturn(length)
+      sub_buffer = object()
+      self.mock_stream.GetSubBuffer(length).AndReturn(sub_buffer)
+
+      if simulate_error:
+        self.mock_message.MergeFromString(sub_buffer).AndReturn(length - 1)
+        self.mox.ReplayAll()
+        self.assertRaises(
+            message.DecodeError, d.ReadMessageInto, self.mock_message)
+      else:
+        self.mock_message.MergeFromString(sub_buffer).AndReturn(length)
+        self.mock_stream.SkipBytes(length)
+        self.mox.ReplayAll()
+        d.ReadMessageInto(self.mock_message)
+
+      self.mox.VerifyAll()
+      self.mox.ResetAll()
+
+    Test(simulate_error=False)
+    Test(simulate_error=True)
+
+  def testReadGroupInto_Success(self):
+    # Test both the empty and nonempty cases.
+    for num_bytes in (5, 0):
+      field_number = expected_field_number = 10
+      d = decoder.Decoder('')
+      d._stream = self.mock_stream
+      sub_buffer = object()
+      self.mock_stream.GetSubBuffer().AndReturn(sub_buffer)
+      self.mock_message.MergeFromString(sub_buffer).AndReturn(num_bytes)
+      self.mock_stream.SkipBytes(num_bytes)
+      self.mock_stream.ReadVarUInt32().AndReturn(wire_format.PackTag(
+          field_number, wire_format.WIRETYPE_END_GROUP))
+      self.mox.ReplayAll()
+      d.ReadGroupInto(expected_field_number, self.mock_message)
+      self.mox.VerifyAll()
+      self.mox.ResetAll()
+
+  def ReadGroupInto_FailureTestHelper(self, bytes_read):
+    d = decoder.Decoder('')
+    d._stream = self.mock_stream
+    sub_buffer = object()
+    self.mock_stream.GetSubBuffer().AndReturn(sub_buffer)
+    self.mock_message.MergeFromString(sub_buffer).AndReturn(bytes_read)
+    return d
+
+  def testReadGroupInto_NegativeBytesReported(self):
+    expected_field_number = 10
+    d = self.ReadGroupInto_FailureTestHelper(bytes_read=-1)
+    self.mox.ReplayAll()
+    self.assertRaises(message.DecodeError,
+                      d.ReadGroupInto, expected_field_number,
+                      self.mock_message)
+    self.mox.VerifyAll()
+
+  def testReadGroupInto_NoEndGroupTag(self):
+    field_number = expected_field_number = 10
+    num_bytes = 5
+    d = self.ReadGroupInto_FailureTestHelper(bytes_read=num_bytes)
+    self.mock_stream.SkipBytes(num_bytes)
+    # Right field number, wrong wire type.
+    self.mock_stream.ReadVarUInt32().AndReturn(wire_format.PackTag(
+        field_number, wire_format.WIRETYPE_LENGTH_DELIMITED))
+    self.mox.ReplayAll()
+    self.assertRaises(message.DecodeError,
+                      d.ReadGroupInto, expected_field_number,
+                      self.mock_message)
+    self.mox.VerifyAll()
+
+  def testReadGroupInto_WrongFieldNumberInEndGroupTag(self):
+    expected_field_number = 10
+    field_number = expected_field_number + 1
+    num_bytes = 5
+    d = self.ReadGroupInto_FailureTestHelper(bytes_read=num_bytes)
+    self.mock_stream.SkipBytes(num_bytes)
+    # Wrong field number, right wire type.
+    self.mock_stream.ReadVarUInt32().AndReturn(wire_format.PackTag(
+        field_number, wire_format.WIRETYPE_END_GROUP))
+    self.mox.ReplayAll()
+    self.assertRaises(message.DecodeError,
+                      d.ReadGroupInto, expected_field_number,
+                      self.mock_message)
+    self.mox.VerifyAll()
+
+  def testSkipBytes(self):
+    d = decoder.Decoder('')
+    num_bytes = 1024
+    self.mock_stream.SkipBytes(num_bytes)
+    d._stream = self.mock_stream
+    self.mox.ReplayAll()
+    d.SkipBytes(num_bytes)
+    self.mox.VerifyAll()
+
+if __name__ == '__main__':
+  unittest.main()
diff --git a/python/google/protobuf/internal/descriptor_test.py b/python/google/protobuf/internal/descriptor_test.py
new file mode 100755
index 0000000..eb9f2be
--- /dev/null
+++ b/python/google/protobuf/internal/descriptor_test.py
@@ -0,0 +1,113 @@
+#! /usr/bin/python
+#
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Unittest for google.protobuf.internal.descriptor."""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+import unittest
+from google.protobuf import descriptor_pb2
+from google.protobuf import descriptor
+
+class DescriptorTest(unittest.TestCase):
+
+  def setUp(self):
+    self.my_enum = descriptor.EnumDescriptor(
+        name='ForeignEnum',
+        full_name='protobuf_unittest.ForeignEnum',
+        filename='ForeignEnum',
+        values=[
+          descriptor.EnumValueDescriptor(name='FOREIGN_FOO', index=0, number=4),
+          descriptor.EnumValueDescriptor(name='FOREIGN_BAR', index=1, number=5),
+          descriptor.EnumValueDescriptor(name='FOREIGN_BAZ', index=2, number=6),
+        ])
+    self.my_message = descriptor.Descriptor(
+        name='NestedMessage',
+        full_name='protobuf_unittest.TestAllTypes.NestedMessage',
+        filename='some/filename/some.proto',
+        containing_type=None,
+        fields=[
+          descriptor.FieldDescriptor(
+            name='bb',
+            full_name='protobuf_unittest.TestAllTypes.NestedMessage.bb',
+            index=0, number=1,
+            type=5, cpp_type=1, label=1,
+            default_value=0,
+            message_type=None, enum_type=None, containing_type=None,
+            is_extension=False, extension_scope=None),
+        ],
+        nested_types=[],
+        enum_types=[
+          self.my_enum,
+        ],
+        extensions=[])
+    self.my_method = descriptor.MethodDescriptor(
+        name='Bar',
+        full_name='protobuf_unittest.TestService.Bar',
+        index=0,
+        containing_service=None,
+        input_type=None,
+        output_type=None)
+    self.my_service = descriptor.ServiceDescriptor(
+        name='TestServiceWithOptions',
+        full_name='protobuf_unittest.TestServiceWithOptions',
+        index=0,
+        methods=[
+            self.my_method
+        ])
+
+  def testEnumFixups(self):
+    self.assertEqual(self.my_enum, self.my_enum.values[0].type)
+
+  def testContainingTypeFixups(self):
+    self.assertEqual(self.my_message, self.my_message.fields[0].containing_type)
+    self.assertEqual(self.my_message, self.my_enum.containing_type)
+
+  def testContainingServiceFixups(self):
+    self.assertEqual(self.my_service, self.my_method.containing_service)
+
+  def testGetOptions(self):
+    self.assertEqual(self.my_enum.GetOptions(),
+                     descriptor_pb2.EnumOptions())
+    self.assertEqual(self.my_enum.values[0].GetOptions(),
+                     descriptor_pb2.EnumValueOptions())
+    self.assertEqual(self.my_message.GetOptions(),
+                     descriptor_pb2.MessageOptions())
+    self.assertEqual(self.my_message.fields[0].GetOptions(),
+                     descriptor_pb2.FieldOptions())
+    self.assertEqual(self.my_method.GetOptions(),
+                     descriptor_pb2.MethodOptions())
+    self.assertEqual(self.my_service.GetOptions(),
+                     descriptor_pb2.ServiceOptions())
+
+if __name__ == '__main__':
+  unittest.main()
diff --git a/python/google/protobuf/internal/encoder.py b/python/google/protobuf/internal/encoder.py
new file mode 100755
index 0000000..3ec3b2b
--- /dev/null
+++ b/python/google/protobuf/internal/encoder.py
@@ -0,0 +1,280 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Class for encoding protocol message primitives.
+
+Contains the logic for encoding every logical protocol field type
+into one of the 5 physical wire types.
+"""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+import struct
+from google.protobuf import message
+from google.protobuf.internal import wire_format
+from google.protobuf.internal import output_stream
+
+
+# Note that much of this code is ported from //net/proto/ProtocolBuffer, and
+# that the interface is strongly inspired by WireFormat from the C++ proto2
+# implementation.
+
+
+class Encoder(object):
+
+  """Encodes logical protocol buffer fields to the wire format."""
+
+  def __init__(self):
+    self._stream = output_stream.OutputStream()
+
+  def ToString(self):
+    """Returns all values encoded in this object as a string."""
+    return self._stream.ToString()
+
+  # Append*NoTag methods.  These are necessary for serializing packed
+  # repeated fields.  The Append*() methods call these methods to do
+  # the actual serialization.
+  def AppendInt32NoTag(self, value):
+    """Appends a 32-bit integer to our buffer, varint-encoded."""
+    self._stream.AppendVarint32(value)
+
+  def AppendInt64NoTag(self, value):
+    """Appends a 64-bit integer to our buffer, varint-encoded."""
+    self._stream.AppendVarint64(value)
+
+  def AppendUInt32NoTag(self, unsigned_value):
+    """Appends an unsigned 32-bit integer to our buffer, varint-encoded."""
+    self._stream.AppendVarUInt32(unsigned_value)
+
+  def AppendUInt64NoTag(self, unsigned_value):
+    """Appends an unsigned 64-bit integer to our buffer, varint-encoded."""
+    self._stream.AppendVarUInt64(unsigned_value)
+
+  def AppendSInt32NoTag(self, value):
+    """Appends a 32-bit integer to our buffer, zigzag-encoded and then
+    varint-encoded.
+    """
+    zigzag_value = wire_format.ZigZagEncode(value)
+    self._stream.AppendVarUInt32(zigzag_value)
+
+  def AppendSInt64NoTag(self, value):
+    """Appends a 64-bit integer to our buffer, zigzag-encoded and then
+    varint-encoded.
+    """
+    zigzag_value = wire_format.ZigZagEncode(value)
+    self._stream.AppendVarUInt64(zigzag_value)
+
+  def AppendFixed32NoTag(self, unsigned_value):
+    """Appends an unsigned 32-bit integer to our buffer, in little-endian
+    byte-order.
+    """
+    self._stream.AppendLittleEndian32(unsigned_value)
+
+  def AppendFixed64NoTag(self, unsigned_value):
+    """Appends an unsigned 64-bit integer to our buffer, in little-endian
+    byte-order.
+    """
+    self._stream.AppendLittleEndian64(unsigned_value)
+
+  def AppendSFixed32NoTag(self, value):
+    """Appends a signed 32-bit integer to our buffer, in little-endian
+    byte-order.
+    """
+    sign = (value & 0x80000000) and -1 or 0
+    if value >> 32 != sign:
+      raise message.EncodeError('SFixed32 out of range: %d' % value)
+    self._stream.AppendLittleEndian32(value & 0xffffffff)
+
+  def AppendSFixed64NoTag(self, value):
+    """Appends a signed 64-bit integer to our buffer, in little-endian
+    byte-order.
+    """
+    sign = (value & 0x8000000000000000) and -1 or 0
+    if value >> 64 != sign:
+      raise message.EncodeError('SFixed64 out of range: %d' % value)
+    self._stream.AppendLittleEndian64(value & 0xffffffffffffffff)
+
+  def AppendFloatNoTag(self, value):
+    """Appends a floating-point number to our buffer."""
+    self._stream.AppendRawBytes(
+        struct.pack(wire_format.FORMAT_FLOAT_LITTLE_ENDIAN, value))
+
+  def AppendDoubleNoTag(self, value):
+    """Appends a double-precision floating-point number to our buffer."""
+    self._stream.AppendRawBytes(
+        struct.pack(wire_format.FORMAT_DOUBLE_LITTLE_ENDIAN, value))
+
+  def AppendBoolNoTag(self, value):
+    """Appends a boolean to our buffer."""
+    self.AppendInt32NoTag(value)
+
+  def AppendEnumNoTag(self, value):
+    """Appends an enum value to our buffer."""
+    self.AppendInt32NoTag(value)
+
+
+  # All the Append*() methods below first append a tag+type pair to the buffer
+  # before appending the specified value.
+
+  def AppendInt32(self, field_number, value):
+    """Appends a 32-bit integer to our buffer, varint-encoded."""
+    self.AppendTag(field_number, wire_format.WIRETYPE_VARINT)
+    self.AppendInt32NoTag(value)
+
+  def AppendInt64(self, field_number, value):
+    """Appends a 64-bit integer to our buffer, varint-encoded."""
+    self.AppendTag(field_number, wire_format.WIRETYPE_VARINT)
+    self.AppendInt64NoTag(value)
+
+  def AppendUInt32(self, field_number, unsigned_value):
+    """Appends an unsigned 32-bit integer to our buffer, varint-encoded."""
+    self.AppendTag(field_number, wire_format.WIRETYPE_VARINT)
+    self.AppendUInt32NoTag(unsigned_value)
+
+  def AppendUInt64(self, field_number, unsigned_value):
+    """Appends an unsigned 64-bit integer to our buffer, varint-encoded."""
+    self.AppendTag(field_number, wire_format.WIRETYPE_VARINT)
+    self.AppendUInt64NoTag(unsigned_value)
+
+  def AppendSInt32(self, field_number, value):
+    """Appends a 32-bit integer to our buffer, zigzag-encoded and then
+    varint-encoded.
+    """
+    self.AppendTag(field_number, wire_format.WIRETYPE_VARINT)
+    self.AppendSInt32NoTag(value)
+
+  def AppendSInt64(self, field_number, value):
+    """Appends a 64-bit integer to our buffer, zigzag-encoded and then
+    varint-encoded.
+    """
+    self.AppendTag(field_number, wire_format.WIRETYPE_VARINT)
+    self.AppendSInt64NoTag(value)
+
+  def AppendFixed32(self, field_number, unsigned_value):
+    """Appends an unsigned 32-bit integer to our buffer, in little-endian
+    byte-order.
+    """
+    self.AppendTag(field_number, wire_format.WIRETYPE_FIXED32)
+    self.AppendFixed32NoTag(unsigned_value)
+
+  def AppendFixed64(self, field_number, unsigned_value):
+    """Appends an unsigned 64-bit integer to our buffer, in little-endian
+    byte-order.
+    """
+    self.AppendTag(field_number, wire_format.WIRETYPE_FIXED64)
+    self.AppendFixed64NoTag(unsigned_value)
+
+  def AppendSFixed32(self, field_number, value):
+    """Appends a signed 32-bit integer to our buffer, in little-endian
+    byte-order.
+    """
+    self.AppendTag(field_number, wire_format.WIRETYPE_FIXED32)
+    self.AppendSFixed32NoTag(value)
+
+  def AppendSFixed64(self, field_number, value):
+    """Appends a signed 64-bit integer to our buffer, in little-endian
+    byte-order.
+    """
+    self.AppendTag(field_number, wire_format.WIRETYPE_FIXED64)
+    self.AppendSFixed64NoTag(value)
+
+  def AppendFloat(self, field_number, value):
+    """Appends a floating-point number to our buffer."""
+    self.AppendTag(field_number, wire_format.WIRETYPE_FIXED32)
+    self.AppendFloatNoTag(value)
+
+  def AppendDouble(self, field_number, value):
+    """Appends a double-precision floating-point number to our buffer."""
+    self.AppendTag(field_number, wire_format.WIRETYPE_FIXED64)
+    self.AppendDoubleNoTag(value)
+
+  def AppendBool(self, field_number, value):
+    """Appends a boolean to our buffer."""
+    self.AppendInt32(field_number, value)
+
+  def AppendEnum(self, field_number, value):
+    """Appends an enum value to our buffer."""
+    self.AppendInt32(field_number, value)
+
+  def AppendString(self, field_number, value):
+    """Appends a length-prefixed unicode string, encoded as UTF-8 to our buffer,
+    with the length varint-encoded.
+    """
+    self.AppendBytes(field_number, value.encode('utf-8'))
+
+  def AppendBytes(self, field_number, value):
+    """Appends a length-prefixed sequence of bytes to our buffer, with the
+    length varint-encoded.
+    """
+    self.AppendTag(field_number, wire_format.WIRETYPE_LENGTH_DELIMITED)
+    self._stream.AppendVarUInt32(len(value))
+    self._stream.AppendRawBytes(value)
+
+  # TODO(robinson): For AppendGroup() and AppendMessage(), we'd really like to
+  # avoid the extra string copy here.  We can do so if we widen the Message
+  # interface to be able to serialize to a stream in addition to a string.  The
+  # challenge when thinking ahead to the Python/C API implementation of Message
+  # is finding a stream-like Python thing to which we can write raw bytes
+  # from C.  I'm not sure such a thing exists(?).  (array.array is pretty much
+  # what we want, but it's not directly exposed in the Python/C API).
+
+  def AppendGroup(self, field_number, group):
+    """Appends a group to our buffer.
+    """
+    self.AppendTag(field_number, wire_format.WIRETYPE_START_GROUP)
+    self._stream.AppendRawBytes(group.SerializeToString())
+    self.AppendTag(field_number, wire_format.WIRETYPE_END_GROUP)
+
+  def AppendMessage(self, field_number, msg):
+    """Appends a nested message to our buffer.
+    """
+    self.AppendTag(field_number, wire_format.WIRETYPE_LENGTH_DELIMITED)
+    self._stream.AppendVarUInt32(msg.ByteSize())
+    self._stream.AppendRawBytes(msg.SerializeToString())
+
+  def AppendMessageSetItem(self, field_number, msg):
+    """Appends an item using the message set wire format.
+
+    The message set message looks like this:
+      message MessageSet {
+        repeated group Item = 1 {
+          required int32 type_id = 2;
+          required string message = 3;
+        }
+      }
+    """
+    self.AppendTag(1, wire_format.WIRETYPE_START_GROUP)
+    self.AppendInt32(2, field_number)
+    self.AppendMessage(3, msg)
+    self.AppendTag(1, wire_format.WIRETYPE_END_GROUP)
+
+  def AppendTag(self, field_number, wire_type):
+    """Appends a tag containing field number and wire type information."""
+    self._stream.AppendVarUInt32(wire_format.PackTag(field_number, wire_type))
diff --git a/python/google/protobuf/internal/encoder_test.py b/python/google/protobuf/internal/encoder_test.py
new file mode 100755
index 0000000..bf75ea8
--- /dev/null
+++ b/python/google/protobuf/internal/encoder_test.py
@@ -0,0 +1,286 @@
+#! /usr/bin/python
+#
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Test for google.protobuf.internal.encoder."""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+import struct
+import logging
+import unittest
+from google.protobuf.internal import wire_format
+from google.protobuf.internal import encoder
+from google.protobuf.internal import output_stream
+from google.protobuf import message
+import mox
+
+
+class EncoderTest(unittest.TestCase):
+
+  def setUp(self):
+    self.mox = mox.Mox()
+    self.encoder = encoder.Encoder()
+    self.mock_stream = self.mox.CreateMock(output_stream.OutputStream)
+    self.mock_message = self.mox.CreateMock(message.Message)
+    self.encoder._stream = self.mock_stream
+
+  def PackTag(self, field_number, wire_type):
+    return wire_format.PackTag(field_number, wire_type)
+
+  def AppendScalarTestHelper(self, test_name, encoder_method,
+                             expected_stream_method_name,
+                             wire_type, field_value,
+                             expected_value=None, expected_length=None,
+                             is_tag_test=True):
+    """Helper for testAppendScalars.
+
+    Calls one of the Encoder methods, and ensures that the Encoder
+    in turn makes the expected calls into its OutputStream.
+
+    Args:
+      test_name: Name of this test, used only for logging.
+      encoder_method: Callable on self.encoder. This is the Encoder
+        method we're testing.  If is_tag_test=True, the encoder method
+        accepts a field_number and field_value. if is_tag_test=False,
+        the encoder method accepts a field_value.
+      expected_stream_method_name: (string) Name of the OutputStream
+        method we expect Encoder to call to actually put the value
+        on the wire.
+      wire_type: The WIRETYPE_* constant we expect encoder to
+        use in the specified encoder_method.
+      field_value: The value we're trying to encode.  Passed
+        into encoder_method.
+      expected_value: The value we expect Encoder to pass into
+        the OutputStream method.  If None, we expect field_value
+        to pass through unmodified.
+      expected_length: The length we expect Encoder to pass to the
+        AppendVarUInt32 method. If None we expect the length of the
+        field_value.
+      is_tag_test: A Boolean.  If True (the default), we append the
+        the packed field number and wire_type to the stream before
+        the field value.
+    """
+    if expected_value is None:
+      expected_value = field_value
+
+    logging.info('Testing %s scalar output.\n'
+                 'Calling %r(%r), and expecting that to call the '
+                 'stream method %s(%r).' % (
+        test_name, encoder_method, field_value,
+        expected_stream_method_name, expected_value))
+
+    if is_tag_test:
+      field_number = 10
+      # Should first append the field number and type information.
+      self.mock_stream.AppendVarUInt32(self.PackTag(field_number, wire_type))
+      # If we're length-delimited, we should then append the length.
+      if wire_type == wire_format.WIRETYPE_LENGTH_DELIMITED:
+        if expected_length is None:
+          expected_length = len(field_value)
+        self.mock_stream.AppendVarUInt32(expected_length)
+
+    # Should then append the value itself.
+    # We have to use names instead of methods to work around some
+    # mox weirdness.  (ResetAll() is overzealous).
+    expected_stream_method = getattr(self.mock_stream,
+                                     expected_stream_method_name)
+    expected_stream_method(expected_value)
+
+    self.mox.ReplayAll()
+    if is_tag_test:
+      encoder_method(field_number, field_value)
+    else:
+      encoder_method(field_value)
+    self.mox.VerifyAll()
+    self.mox.ResetAll()
+
+  VAL = 1.125  # Perfectly representable as a float (no rounding error).
+  LITTLE_FLOAT_VAL = '\x00\x00\x90?'
+  LITTLE_DOUBLE_VAL = '\x00\x00\x00\x00\x00\x00\xf2?'
+
+  def testAppendScalars(self):
+    utf8_bytes = '\xd0\xa2\xd0\xb5\xd1\x81\xd1\x82'
+    utf8_string = unicode(utf8_bytes, 'utf-8')
+    scalar_tests = [
+        ['int32', self.encoder.AppendInt32, 'AppendVarint32',
+         wire_format.WIRETYPE_VARINT, 0],
+        ['int64', self.encoder.AppendInt64, 'AppendVarint64',
+         wire_format.WIRETYPE_VARINT, 0],
+        ['uint32', self.encoder.AppendUInt32, 'AppendVarUInt32',
+         wire_format.WIRETYPE_VARINT, 0],
+        ['uint64', self.encoder.AppendUInt64, 'AppendVarUInt64',
+         wire_format.WIRETYPE_VARINT, 0],
+        ['fixed32', self.encoder.AppendFixed32, 'AppendLittleEndian32',
+         wire_format.WIRETYPE_FIXED32, 0],
+        ['fixed64', self.encoder.AppendFixed64, 'AppendLittleEndian64',
+         wire_format.WIRETYPE_FIXED64, 0],
+        ['sfixed32', self.encoder.AppendSFixed32, 'AppendLittleEndian32',
+         wire_format.WIRETYPE_FIXED32, -1, 0xffffffff],
+        ['sfixed64', self.encoder.AppendSFixed64, 'AppendLittleEndian64',
+         wire_format.WIRETYPE_FIXED64, -1, 0xffffffffffffffff],
+        ['float', self.encoder.AppendFloat, 'AppendRawBytes',
+         wire_format.WIRETYPE_FIXED32, self.VAL, self.LITTLE_FLOAT_VAL],
+        ['double', self.encoder.AppendDouble, 'AppendRawBytes',
+         wire_format.WIRETYPE_FIXED64, self.VAL, self.LITTLE_DOUBLE_VAL],
+        ['bool', self.encoder.AppendBool, 'AppendVarint32',
+         wire_format.WIRETYPE_VARINT, False],
+        ['enum', self.encoder.AppendEnum, 'AppendVarint32',
+         wire_format.WIRETYPE_VARINT, 0],
+        ['string', self.encoder.AppendString, 'AppendRawBytes',
+         wire_format.WIRETYPE_LENGTH_DELIMITED,
+         "You're in a maze of twisty little passages, all alike."],
+        ['utf8-string', self.encoder.AppendString, 'AppendRawBytes',
+         wire_format.WIRETYPE_LENGTH_DELIMITED, utf8_string,
+         utf8_bytes, len(utf8_bytes)],
+        # We test zigzag encoding routines more extensively below.
+        ['sint32', self.encoder.AppendSInt32, 'AppendVarUInt32',
+         wire_format.WIRETYPE_VARINT, -1, 1],
+        ['sint64', self.encoder.AppendSInt64, 'AppendVarUInt64',
+         wire_format.WIRETYPE_VARINT, -1, 1],
+        ]
+    # Ensure that we're testing different Encoder methods and using
+    # different test names in all test cases above.
+    self.assertEqual(len(scalar_tests), len(set(t[0] for t in scalar_tests)))
+    self.assert_(len(scalar_tests) >= len(set(t[1] for t in scalar_tests)))
+    for args in scalar_tests:
+      self.AppendScalarTestHelper(*args)
+
+  def testAppendScalarsWithoutTags(self):
+    scalar_no_tag_tests = [
+        ['int32', self.encoder.AppendInt32NoTag, 'AppendVarint32', None, 0],
+        ['int64', self.encoder.AppendInt64NoTag, 'AppendVarint64', None, 0],
+        ['uint32', self.encoder.AppendUInt32NoTag, 'AppendVarUInt32', None, 0],
+        ['uint64', self.encoder.AppendUInt64NoTag, 'AppendVarUInt64', None, 0],
+        ['fixed32', self.encoder.AppendFixed32NoTag,
+         'AppendLittleEndian32', None, 0],
+        ['fixed64', self.encoder.AppendFixed64NoTag,
+         'AppendLittleEndian64', None, 0],
+        ['sfixed32', self.encoder.AppendSFixed32NoTag,
+         'AppendLittleEndian32', None, 0],
+        ['sfixed64', self.encoder.AppendSFixed64NoTag,
+         'AppendLittleEndian64', None, 0],
+        ['float', self.encoder.AppendFloatNoTag,
+         'AppendRawBytes', None, self.VAL, self.LITTLE_FLOAT_VAL],
+        ['double', self.encoder.AppendDoubleNoTag,
+         'AppendRawBytes', None, self.VAL, self.LITTLE_DOUBLE_VAL],
+        ['bool', self.encoder.AppendBoolNoTag, 'AppendVarint32', None, 0],
+        ['enum', self.encoder.AppendEnumNoTag, 'AppendVarint32', None, 0],
+        ['sint32', self.encoder.AppendSInt32NoTag,
+         'AppendVarUInt32', None, -1, 1],
+        ['sint64', self.encoder.AppendSInt64NoTag,
+         'AppendVarUInt64', None, -1, 1],
+    ]
+
+    self.assertEqual(len(scalar_no_tag_tests),
+                     len(set(t[0] for t in scalar_no_tag_tests)))
+    self.assert_(len(scalar_no_tag_tests) >=
+                 len(set(t[1] for t in scalar_no_tag_tests)))
+    for args in scalar_no_tag_tests:
+      # For no tag tests, the wire_type is not used, so we put in None.
+      self.AppendScalarTestHelper(is_tag_test=False, *args)
+
+  def testAppendGroup(self):
+    field_number = 23
+    # Should first append the start-group marker.
+    self.mock_stream.AppendVarUInt32(
+        self.PackTag(field_number, wire_format.WIRETYPE_START_GROUP))
+    # Should then serialize itself.
+    self.mock_message.SerializeToString().AndReturn('foo')
+    self.mock_stream.AppendRawBytes('foo')
+    # Should finally append the end-group marker.
+    self.mock_stream.AppendVarUInt32(
+        self.PackTag(field_number, wire_format.WIRETYPE_END_GROUP))
+
+    self.mox.ReplayAll()
+    self.encoder.AppendGroup(field_number, self.mock_message)
+    self.mox.VerifyAll()
+
+  def testAppendMessage(self):
+    field_number = 23
+    byte_size = 42
+    # Should first append the field number and type information.
+    self.mock_stream.AppendVarUInt32(
+        self.PackTag(field_number, wire_format.WIRETYPE_LENGTH_DELIMITED))
+    # Should then append its length.
+    self.mock_message.ByteSize().AndReturn(byte_size)
+    self.mock_stream.AppendVarUInt32(byte_size)
+    # Should then serialize itself to the encoder.
+    self.mock_message.SerializeToString().AndReturn('foo')
+    self.mock_stream.AppendRawBytes('foo')
+
+    self.mox.ReplayAll()
+    self.encoder.AppendMessage(field_number, self.mock_message)
+    self.mox.VerifyAll()
+
+  def testAppendMessageSetItem(self):
+    field_number = 23
+    byte_size = 42
+    # Should first append the field number and type information.
+    self.mock_stream.AppendVarUInt32(
+        self.PackTag(1, wire_format.WIRETYPE_START_GROUP))
+    self.mock_stream.AppendVarUInt32(
+        self.PackTag(2, wire_format.WIRETYPE_VARINT))
+    self.mock_stream.AppendVarint32(field_number)
+    self.mock_stream.AppendVarUInt32(
+        self.PackTag(3, wire_format.WIRETYPE_LENGTH_DELIMITED))
+    # Should then append its length.
+    self.mock_message.ByteSize().AndReturn(byte_size)
+    self.mock_stream.AppendVarUInt32(byte_size)
+    # Should then serialize itself to the encoder.
+    self.mock_message.SerializeToString().AndReturn('foo')
+    self.mock_stream.AppendRawBytes('foo')
+    self.mock_stream.AppendVarUInt32(
+        self.PackTag(1, wire_format.WIRETYPE_END_GROUP))
+
+    self.mox.ReplayAll()
+    self.encoder.AppendMessageSetItem(field_number, self.mock_message)
+    self.mox.VerifyAll()
+
+  def testAppendSFixed(self):
+    # Most of our bounds-checking is done in output_stream.py,
+    # but encoder.py is responsible for transforming signed
+    # fixed-width integers into unsigned ones, so we test here
+    # to ensure that we're not losing any entropy when we do
+    # that conversion.
+    field_number = 10
+    self.assertRaises(message.EncodeError, self.encoder.AppendSFixed32,
+        10, wire_format.UINT32_MAX + 1)
+    self.assertRaises(message.EncodeError, self.encoder.AppendSFixed32,
+        10, -(1 << 32))
+    self.assertRaises(message.EncodeError, self.encoder.AppendSFixed64,
+        10, wire_format.UINT64_MAX + 1)
+    self.assertRaises(message.EncodeError, self.encoder.AppendSFixed64,
+        10, -(1 << 64))
+
+
+if __name__ == '__main__':
+  unittest.main()
diff --git a/python/google/protobuf/internal/generator_test.py b/python/google/protobuf/internal/generator_test.py
new file mode 100755
index 0000000..11fcfa0
--- /dev/null
+++ b/python/google/protobuf/internal/generator_test.py
@@ -0,0 +1,100 @@
+#! /usr/bin/python
+#
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+# TODO(robinson): Flesh this out considerably.  We focused on reflection_test.py
+# first, since it's testing the subtler code, and since it provides decent
+# indirect testing of the protocol compiler output.
+
+"""Unittest that directly tests the output of the pure-Python protocol
+compiler.  See //net/proto2/internal/reflection_test.py for a test which
+further ensures that we can use Python protocol message objects as we expect.
+"""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+import unittest
+from google.protobuf import unittest_mset_pb2
+from google.protobuf import unittest_pb2
+
+
+class GeneratorTest(unittest.TestCase):
+
+  def testNestedMessageDescriptor(self):
+    field_name = 'optional_nested_message'
+    proto_type = unittest_pb2.TestAllTypes
+    self.assertEqual(
+        proto_type.NestedMessage.DESCRIPTOR,
+        proto_type.DESCRIPTOR.fields_by_name[field_name].message_type)
+
+  def testEnums(self):
+    # We test only module-level enums here.
+    # TODO(robinson): Examine descriptors directly to check
+    # enum descriptor output.
+    self.assertEqual(4, unittest_pb2.FOREIGN_FOO)
+    self.assertEqual(5, unittest_pb2.FOREIGN_BAR)
+    self.assertEqual(6, unittest_pb2.FOREIGN_BAZ)
+
+    proto = unittest_pb2.TestAllTypes()
+    self.assertEqual(1, proto.FOO)
+    self.assertEqual(1, unittest_pb2.TestAllTypes.FOO)
+    self.assertEqual(2, proto.BAR)
+    self.assertEqual(2, unittest_pb2.TestAllTypes.BAR)
+    self.assertEqual(3, proto.BAZ)
+    self.assertEqual(3, unittest_pb2.TestAllTypes.BAZ)
+
+  def testContainingTypeBehaviorForExtensions(self):
+    self.assertEqual(unittest_pb2.optional_int32_extension.containing_type,
+                     unittest_pb2.TestAllExtensions.DESCRIPTOR)
+    self.assertEqual(unittest_pb2.TestRequired.single.containing_type,
+                     unittest_pb2.TestAllExtensions.DESCRIPTOR)
+
+  def testExtensionScope(self):
+    self.assertEqual(unittest_pb2.optional_int32_extension.extension_scope,
+                     None)
+    self.assertEqual(unittest_pb2.TestRequired.single.extension_scope,
+                     unittest_pb2.TestRequired.DESCRIPTOR)
+
+  def testIsExtension(self):
+    self.assertTrue(unittest_pb2.optional_int32_extension.is_extension)
+    self.assertTrue(unittest_pb2.TestRequired.single.is_extension)
+
+    message_descriptor = unittest_pb2.TestRequired.DESCRIPTOR
+    non_extension_descriptor = message_descriptor.fields_by_name['a']
+    self.assertTrue(not non_extension_descriptor.is_extension)
+
+  def testOptions(self):
+    proto = unittest_mset_pb2.TestMessageSet()
+    self.assertTrue(proto.DESCRIPTOR.GetOptions().message_set_wire_format)
+
+
+if __name__ == '__main__':
+  unittest.main()
diff --git a/python/google/protobuf/internal/input_stream.py b/python/google/protobuf/internal/input_stream.py
new file mode 100755
index 0000000..7bda17e
--- /dev/null
+++ b/python/google/protobuf/internal/input_stream.py
@@ -0,0 +1,338 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""InputStream is the primitive interface for reading bits from the wire.
+
+All protocol buffer deserialization can be expressed in terms of
+the InputStream primitives provided here.
+"""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+import array
+import struct
+from google.protobuf import message
+from google.protobuf.internal import wire_format
+
+
+# Note that much of this code is ported from //net/proto/ProtocolBuffer, and
+# that the interface is strongly inspired by CodedInputStream from the C++
+# proto2 implementation.
+
+
+class InputStreamBuffer(object):
+
+  """Contains all logic for reading bits, and dealing with stream position.
+
+  If an InputStream method ever raises an exception, the stream is left
+  in an indeterminate state and is not safe for further use.
+  """
+
+  def __init__(self, s):
+    # What we really want is something like array('B', s), where elements we
+    # read from the array are already given to us as one-byte integers.  BUT
+    # using array() instead of buffer() would force full string copies to result
+    # from each GetSubBuffer() call.
+    #
+    # So, if the N serialized bytes of a single protocol buffer object are
+    # split evenly between 2 child messages, and so on recursively, using
+    # array('B', s) instead of buffer() would incur an additional N*logN bytes
+    # copied during deserialization.
+    #
+    # The higher constant overhead of having to ord() for every byte we read
+    # from the buffer in _ReadVarintHelper() could definitely lead to worse
+    # performance in many real-world scenarios, even if the asymptotic
+    # complexity is better.  However, our real answer is that the mythical
+    # Python/C extension module output mode for the protocol compiler will
+    # be blazing-fast and will eliminate most use of this class anyway.
+    self._buffer = buffer(s)
+    self._pos = 0
+
+  def EndOfStream(self):
+    """Returns true iff we're at the end of the stream.
+    If this returns true, then a call to any other InputStream method
+    will raise an exception.
+    """
+    return self._pos >= len(self._buffer)
+
+  def Position(self):
+    """Returns the current position in the stream, or equivalently, the
+    number of bytes read so far.
+    """
+    return self._pos
+
+  def GetSubBuffer(self, size=None):
+    """Returns a sequence-like object that represents a portion of our
+    underlying sequence.
+
+    Position 0 in the returned object corresponds to self.Position()
+    in this stream.
+
+    If size is specified, then the returned object ends after the
+    next "size" bytes in this stream.  If size is not specified,
+    then the returned object ends at the end of this stream.
+
+    We guarantee that the returned object R supports the Python buffer
+    interface (and thus that the call buffer(R) will work).
+
+    Note that the returned buffer is read-only.
+
+    The intended use for this method is for nested-message and nested-group
+    deserialization, where we want to make a recursive MergeFromString()
+    call on the portion of the original sequence that contains the serialized
+    nested message.  (And we'd like to do so without making unnecessary string
+    copies).
+
+    REQUIRES: size is nonnegative.
+    """
+    # Note that buffer() doesn't perform any actual string copy.
+    if size is None:
+      return buffer(self._buffer, self._pos)
+    else:
+      if size < 0:
+        raise message.DecodeError('Negative size %d' % size)
+      return buffer(self._buffer, self._pos, size)
+
+  def SkipBytes(self, num_bytes):
+    """Skip num_bytes bytes ahead, or go to the end of the stream, whichever
+    comes first.
+
+    REQUIRES: num_bytes is nonnegative.
+    """
+    if num_bytes < 0:
+      raise message.DecodeError('Negative num_bytes %d' % num_bytes)
+    self._pos += num_bytes
+    self._pos = min(self._pos, len(self._buffer))
+
+  def ReadBytes(self, size):
+    """Reads up to 'size' bytes from the stream, stopping early
+    only if we reach the end of the stream.  Returns the bytes read
+    as a string.
+    """
+    if size < 0:
+      raise message.DecodeError('Negative size %d' % size)
+    s = (self._buffer[self._pos : self._pos + size])
+    self._pos += len(s)  # Only advance by the number of bytes actually read.
+    return s
+
+  def ReadLittleEndian32(self):
+    """Interprets the next 4 bytes of the stream as a little-endian
+    encoded, unsiged 32-bit integer, and returns that integer.
+    """
+    try:
+      i = struct.unpack(wire_format.FORMAT_UINT32_LITTLE_ENDIAN,
+                        self._buffer[self._pos : self._pos + 4])
+      self._pos += 4
+      return i[0]  # unpack() result is a 1-element tuple.
+    except struct.error, e:
+      raise message.DecodeError(e)
+
+  def ReadLittleEndian64(self):
+    """Interprets the next 8 bytes of the stream as a little-endian
+    encoded, unsiged 64-bit integer, and returns that integer.
+    """
+    try:
+      i = struct.unpack(wire_format.FORMAT_UINT64_LITTLE_ENDIAN,
+                        self._buffer[self._pos : self._pos + 8])
+      self._pos += 8
+      return i[0]  # unpack() result is a 1-element tuple.
+    except struct.error, e:
+      raise message.DecodeError(e)
+
+  def ReadVarint32(self):
+    """Reads a varint from the stream, interprets this varint
+    as a signed, 32-bit integer, and returns the integer.
+    """
+    i = self.ReadVarint64()
+    if not wire_format.INT32_MIN <= i <= wire_format.INT32_MAX:
+      raise message.DecodeError('Value out of range for int32: %d' % i)
+    return int(i)
+
+  def ReadVarUInt32(self):
+    """Reads a varint from the stream, interprets this varint
+    as an unsigned, 32-bit integer, and returns the integer.
+    """
+    i = self.ReadVarUInt64()
+    if i > wire_format.UINT32_MAX:
+      raise message.DecodeError('Value out of range for uint32: %d' % i)
+    return i
+
+  def ReadVarint64(self):
+    """Reads a varint from the stream, interprets this varint
+    as a signed, 64-bit integer, and returns the integer.
+    """
+    i = self.ReadVarUInt64()
+    if i > wire_format.INT64_MAX:
+      i -= (1 << 64)
+    return i
+
+  def ReadVarUInt64(self):
+    """Reads a varint from the stream, interprets this varint
+    as an unsigned, 64-bit integer, and returns the integer.
+    """
+    i = self._ReadVarintHelper()
+    if not 0 <= i <= wire_format.UINT64_MAX:
+      raise message.DecodeError('Value out of range for uint64: %d' % i)
+    return i
+
+  def _ReadVarintHelper(self):
+    """Helper for the various varint-reading methods above.
+    Reads an unsigned, varint-encoded integer from the stream and
+    returns this integer.
+
+    Does no bounds checking except to ensure that we read at most as many bytes
+    as could possibly be present in a varint-encoded 64-bit number.
+    """
+    result = 0
+    shift = 0
+    while 1:
+      if shift >= 64:
+        raise message.DecodeError('Too many bytes when decoding varint.')
+      try:
+        b = ord(self._buffer[self._pos])
+      except IndexError:
+        raise message.DecodeError('Truncated varint.')
+      self._pos += 1
+      result |= ((b & 0x7f) << shift)
+      shift += 7
+      if not (b & 0x80):
+        return result
+
+
+class InputStreamArray(object):
+
+  """Contains all logic for reading bits, and dealing with stream position.
+
+  If an InputStream method ever raises an exception, the stream is left
+  in an indeterminate state and is not safe for further use.
+
+  This alternative to InputStreamBuffer is used in environments where buffer()
+  is unavailble, such as Google App Engine.
+  """
+
+  def __init__(self, s):
+    self._buffer = array.array('B', s)
+    self._pos = 0
+
+  def EndOfStream(self):
+    return self._pos >= len(self._buffer)
+
+  def Position(self):
+    return self._pos
+
+  def GetSubBuffer(self, size=None):
+    if size is None:
+      return self._buffer[self._pos : ].tostring()
+    else:
+      if size < 0:
+        raise message.DecodeError('Negative size %d' % size)
+      return self._buffer[self._pos : self._pos + size].tostring()
+
+  def SkipBytes(self, num_bytes):
+    if num_bytes < 0:
+      raise message.DecodeError('Negative num_bytes %d' % num_bytes)
+    self._pos += num_bytes
+    self._pos = min(self._pos, len(self._buffer))
+
+  def ReadBytes(self, size):
+    if size < 0:
+      raise message.DecodeError('Negative size %d' % size)
+    s = self._buffer[self._pos : self._pos + size].tostring()
+    self._pos += len(s)  # Only advance by the number of bytes actually read.
+    return s
+
+  def ReadLittleEndian32(self):
+    try:
+      i = struct.unpack(wire_format.FORMAT_UINT32_LITTLE_ENDIAN,
+                        self._buffer[self._pos : self._pos + 4])
+      self._pos += 4
+      return i[0]  # unpack() result is a 1-element tuple.
+    except struct.error, e:
+      raise message.DecodeError(e)
+
+  def ReadLittleEndian64(self):
+    try:
+      i = struct.unpack(wire_format.FORMAT_UINT64_LITTLE_ENDIAN,
+                        self._buffer[self._pos : self._pos + 8])
+      self._pos += 8
+      return i[0]  # unpack() result is a 1-element tuple.
+    except struct.error, e:
+      raise message.DecodeError(e)
+
+  def ReadVarint32(self):
+    i = self.ReadVarint64()
+    if not wire_format.INT32_MIN <= i <= wire_format.INT32_MAX:
+      raise message.DecodeError('Value out of range for int32: %d' % i)
+    return int(i)
+
+  def ReadVarUInt32(self):
+    i = self.ReadVarUInt64()
+    if i > wire_format.UINT32_MAX:
+      raise message.DecodeError('Value out of range for uint32: %d' % i)
+    return i
+
+  def ReadVarint64(self):
+    i = self.ReadVarUInt64()
+    if i > wire_format.INT64_MAX:
+      i -= (1 << 64)
+    return i
+
+  def ReadVarUInt64(self):
+    i = self._ReadVarintHelper()
+    if not 0 <= i <= wire_format.UINT64_MAX:
+      raise message.DecodeError('Value out of range for uint64: %d' % i)
+    return i
+
+  def _ReadVarintHelper(self):
+    result = 0
+    shift = 0
+    while 1:
+      if shift >= 64:
+        raise message.DecodeError('Too many bytes when decoding varint.')
+      try:
+        b = self._buffer[self._pos]
+      except IndexError:
+        raise message.DecodeError('Truncated varint.')
+      self._pos += 1
+      result |= ((b & 0x7f) << shift)
+      shift += 7
+      if not (b & 0x80):
+        return result
+
+
+try:
+  buffer('')
+  InputStream = InputStreamBuffer
+except NotImplementedError:
+  # Google App Engine: dev_appserver.py
+  InputStream = InputStreamArray
+except RuntimeError:
+  # Google App Engine: production
+  InputStream = InputStreamArray
diff --git a/python/google/protobuf/internal/input_stream_test.py b/python/google/protobuf/internal/input_stream_test.py
new file mode 100755
index 0000000..ecec7f7
--- /dev/null
+++ b/python/google/protobuf/internal/input_stream_test.py
@@ -0,0 +1,314 @@
+#! /usr/bin/python
+#
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Test for google.protobuf.internal.input_stream."""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+import unittest
+from google.protobuf import message
+from google.protobuf.internal import wire_format
+from google.protobuf.internal import input_stream
+
+
+class InputStreamBufferTest(unittest.TestCase):
+
+  def setUp(self):
+    self.__original_input_stream = input_stream.InputStream
+    input_stream.InputStream = input_stream.InputStreamBuffer
+
+  def tearDown(self):
+    input_stream.InputStream = self.__original_input_stream
+
+  def testEndOfStream(self):
+    stream = input_stream.InputStream('abcd')
+    self.assertFalse(stream.EndOfStream())
+    self.assertEqual('abcd', stream.ReadBytes(10))
+    self.assertTrue(stream.EndOfStream())
+
+  def testPosition(self):
+    stream = input_stream.InputStream('abcd')
+    self.assertEqual(0, stream.Position())
+    self.assertEqual(0, stream.Position())  # No side-effects.
+    stream.ReadBytes(1)
+    self.assertEqual(1, stream.Position())
+    stream.ReadBytes(1)
+    self.assertEqual(2, stream.Position())
+    stream.ReadBytes(10)
+    self.assertEqual(4, stream.Position())  # Can't go past end of stream.
+
+  def testGetSubBuffer(self):
+    stream = input_stream.InputStream('abcd')
+    # Try leaving out the size.
+    self.assertEqual('abcd', str(stream.GetSubBuffer()))
+    stream.SkipBytes(1)
+    # GetSubBuffer() always starts at current size.
+    self.assertEqual('bcd', str(stream.GetSubBuffer()))
+    # Try 0-size.
+    self.assertEqual('', str(stream.GetSubBuffer(0)))
+    # Negative sizes should raise an error.
+    self.assertRaises(message.DecodeError, stream.GetSubBuffer, -1)
+    # Positive sizes should work as expected.
+    self.assertEqual('b', str(stream.GetSubBuffer(1)))
+    self.assertEqual('bc', str(stream.GetSubBuffer(2)))
+    # Sizes longer than remaining bytes in the buffer should
+    # return the whole remaining buffer.
+    self.assertEqual('bcd', str(stream.GetSubBuffer(1000)))
+
+  def testSkipBytes(self):
+    stream = input_stream.InputStream('')
+    # Skipping bytes when at the end of stream
+    # should have no effect.
+    stream.SkipBytes(0)
+    stream.SkipBytes(1)
+    stream.SkipBytes(2)
+    self.assertTrue(stream.EndOfStream())
+    self.assertEqual(0, stream.Position())
+
+    # Try skipping within a stream.
+    stream = input_stream.InputStream('abcd')
+    self.assertEqual(0, stream.Position())
+    stream.SkipBytes(1)
+    self.assertEqual(1, stream.Position())
+    stream.SkipBytes(10)  # Can't skip past the end.
+    self.assertEqual(4, stream.Position())
+
+    # Ensure that a negative skip raises an exception.
+    stream = input_stream.InputStream('abcd')
+    stream.SkipBytes(1)
+    self.assertRaises(message.DecodeError, stream.SkipBytes, -1)
+
+  def testReadBytes(self):
+    s = 'abcd'
+    # Also test going past the total stream length.
+    for i in range(len(s) + 10):
+      stream = input_stream.InputStream(s)
+      self.assertEqual(s[:i], stream.ReadBytes(i))
+      self.assertEqual(min(i, len(s)), stream.Position())
+    stream = input_stream.InputStream(s)
+    self.assertRaises(message.DecodeError, stream.ReadBytes, -1)
+
+  def EnsureFailureOnEmptyStream(self, input_stream_method):
+    """Helper for integer-parsing tests below.
+    Ensures that the given InputStream method raises a DecodeError
+    if called on a stream with no bytes remaining.
+    """
+    stream = input_stream.InputStream('')
+    self.assertRaises(message.DecodeError, input_stream_method, stream)
+
+  def testReadLittleEndian32(self):
+    self.EnsureFailureOnEmptyStream(input_stream.InputStream.ReadLittleEndian32)
+    s = ''
+    # Read 0.
+    s += '\x00\x00\x00\x00'
+    # Read 1.
+    s += '\x01\x00\x00\x00'
+    # Read a bunch of different bytes.
+    s += '\x01\x02\x03\x04'
+    # Read max unsigned 32-bit int.
+    s += '\xff\xff\xff\xff'
+    # Try a read with fewer than 4 bytes left in the stream.
+    s += '\x00\x00\x00'
+    stream = input_stream.InputStream(s)
+    self.assertEqual(0, stream.ReadLittleEndian32())
+    self.assertEqual(4, stream.Position())
+    self.assertEqual(1, stream.ReadLittleEndian32())
+    self.assertEqual(8, stream.Position())
+    self.assertEqual(0x04030201, stream.ReadLittleEndian32())
+    self.assertEqual(12, stream.Position())
+    self.assertEqual(wire_format.UINT32_MAX, stream.ReadLittleEndian32())
+    self.assertEqual(16, stream.Position())
+    self.assertRaises(message.DecodeError, stream.ReadLittleEndian32)
+
+  def testReadLittleEndian64(self):
+    self.EnsureFailureOnEmptyStream(input_stream.InputStream.ReadLittleEndian64)
+    s = ''
+    # Read 0.
+    s += '\x00\x00\x00\x00\x00\x00\x00\x00'
+    # Read 1.
+    s += '\x01\x00\x00\x00\x00\x00\x00\x00'
+    # Read a bunch of different bytes.
+    s += '\x01\x02\x03\x04\x05\x06\x07\x08'
+    # Read max unsigned 64-bit int.
+    s += '\xff\xff\xff\xff\xff\xff\xff\xff'
+    # Try a read with fewer than 8 bytes left in the stream.
+    s += '\x00\x00\x00'
+    stream = input_stream.InputStream(s)
+    self.assertEqual(0, stream.ReadLittleEndian64())
+    self.assertEqual(8, stream.Position())
+    self.assertEqual(1, stream.ReadLittleEndian64())
+    self.assertEqual(16, stream.Position())
+    self.assertEqual(0x0807060504030201, stream.ReadLittleEndian64())
+    self.assertEqual(24, stream.Position())
+    self.assertEqual(wire_format.UINT64_MAX, stream.ReadLittleEndian64())
+    self.assertEqual(32, stream.Position())
+    self.assertRaises(message.DecodeError, stream.ReadLittleEndian64)
+
+  def ReadVarintSuccessTestHelper(self, varints_and_ints, read_method):
+    """Helper for tests below that test successful reads of various varints.
+
+    Args:
+      varints_and_ints: Iterable of (str, integer) pairs, where the string
+        gives the wire encoding and the integer gives the value we expect
+        to be returned by the read_method upon encountering this string.
+      read_method: Unbound InputStream method that is capable of reading
+        the encoded strings provided in the first elements of varints_and_ints.
+    """
+    s = ''.join(s for s, i in varints_and_ints)
+    stream = input_stream.InputStream(s)
+    expected_pos = 0
+    self.assertEqual(expected_pos, stream.Position())
+    for s, expected_int in varints_and_ints:
+      self.assertEqual(expected_int, read_method(stream))
+      expected_pos += len(s)
+      self.assertEqual(expected_pos, stream.Position())
+
+  def testReadVarint32Success(self):
+    varints_and_ints = [
+        ('\x00', 0),
+        ('\x01', 1),
+        ('\x7f', 127),
+        ('\x80\x01', 128),
+        ('\xff\xff\xff\xff\xff\xff\xff\xff\xff\x01', -1),
+        ('\xff\xff\xff\xff\x07', wire_format.INT32_MAX),
+        ('\x80\x80\x80\x80\xf8\xff\xff\xff\xff\x01', wire_format.INT32_MIN),
+        ]
+    self.ReadVarintSuccessTestHelper(varints_and_ints,
+                                     input_stream.InputStream.ReadVarint32)
+
+  def testReadVarint32Failure(self):
+    self.EnsureFailureOnEmptyStream(input_stream.InputStream.ReadVarint32)
+
+    # Try and fail to read INT32_MAX + 1.
+    s = '\x80\x80\x80\x80\x08'
+    stream = input_stream.InputStream(s)
+    self.assertRaises(message.DecodeError, stream.ReadVarint32)
+
+    # Try and fail to read INT32_MIN - 1.
+    s = '\xfe\xff\xff\xff\xf7\xff\xff\xff\xff\x01'
+    stream = input_stream.InputStream(s)
+    self.assertRaises(message.DecodeError, stream.ReadVarint32)
+
+    # Try and fail to read something that looks like
+    # a varint with more than 10 bytes.
+    s = '\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x00'
+    stream = input_stream.InputStream(s)
+    self.assertRaises(message.DecodeError, stream.ReadVarint32)
+
+  def testReadVarUInt32Success(self):
+    varints_and_ints = [
+        ('\x00', 0),
+        ('\x01', 1),
+        ('\x7f', 127),
+        ('\x80\x01', 128),
+        ('\xff\xff\xff\xff\x0f', wire_format.UINT32_MAX),
+        ]
+    self.ReadVarintSuccessTestHelper(varints_and_ints,
+                                     input_stream.InputStream.ReadVarUInt32)
+
+  def testReadVarUInt32Failure(self):
+    self.EnsureFailureOnEmptyStream(input_stream.InputStream.ReadVarUInt32)
+    # Try and fail to read UINT32_MAX + 1
+    s = '\x80\x80\x80\x80\x10'
+    stream = input_stream.InputStream(s)
+    self.assertRaises(message.DecodeError, stream.ReadVarUInt32)
+
+    # Try and fail to read something that looks like
+    # a varint with more than 10 bytes.
+    s = '\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x00'
+    stream = input_stream.InputStream(s)
+    self.assertRaises(message.DecodeError, stream.ReadVarUInt32)
+
+  def testReadVarint64Success(self):
+    varints_and_ints = [
+        ('\x00', 0),
+        ('\x01', 1),
+        ('\xff\xff\xff\xff\xff\xff\xff\xff\xff\x01', -1),
+        ('\x7f', 127),
+        ('\x80\x01', 128),
+        ('\xff\xff\xff\xff\xff\xff\xff\xff\x7f', wire_format.INT64_MAX),
+        ('\x80\x80\x80\x80\x80\x80\x80\x80\x80\x01', wire_format.INT64_MIN),
+        ]
+    self.ReadVarintSuccessTestHelper(varints_and_ints,
+                                     input_stream.InputStream.ReadVarint64)
+
+  def testReadVarint64Failure(self):
+    self.EnsureFailureOnEmptyStream(input_stream.InputStream.ReadVarint64)
+    # Try and fail to read something with the mythical 64th bit set.
+    s = '\x80\x80\x80\x80\x80\x80\x80\x80\x80\x02'
+    stream = input_stream.InputStream(s)
+    self.assertRaises(message.DecodeError, stream.ReadVarint64)
+
+    # Try and fail to read something that looks like
+    # a varint with more than 10 bytes.
+    s = '\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x00'
+    stream = input_stream.InputStream(s)
+    self.assertRaises(message.DecodeError, stream.ReadVarint64)
+
+  def testReadVarUInt64Success(self):
+    varints_and_ints = [
+        ('\x00', 0),
+        ('\x01', 1),
+        ('\x7f', 127),
+        ('\x80\x01', 128),
+        ('\x80\x80\x80\x80\x80\x80\x80\x80\x80\x01', 1 << 63),
+        ]
+    self.ReadVarintSuccessTestHelper(varints_and_ints,
+                                     input_stream.InputStream.ReadVarUInt64)
+
+  def testReadVarUInt64Failure(self):
+    self.EnsureFailureOnEmptyStream(input_stream.InputStream.ReadVarUInt64)
+    # Try and fail to read something with the mythical 64th bit set.
+    s = '\x80\x80\x80\x80\x80\x80\x80\x80\x80\x02'
+    stream = input_stream.InputStream(s)
+    self.assertRaises(message.DecodeError, stream.ReadVarUInt64)
+
+    # Try and fail to read something that looks like
+    # a varint with more than 10 bytes.
+    s = '\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x00'
+    stream = input_stream.InputStream(s)
+    self.assertRaises(message.DecodeError, stream.ReadVarUInt64)
+
+
+class InputStreamArrayTest(InputStreamBufferTest):
+
+  def setUp(self):
+    # Test InputStreamArray against the same tests in InputStreamBuffer
+    self.__original_input_stream = input_stream.InputStream
+    input_stream.InputStream = input_stream.InputStreamArray
+
+  def tearDown(self):
+    input_stream.InputStream = self.__original_input_stream
+
+
+if __name__ == '__main__':
+  unittest.main()
diff --git a/python/google/protobuf/internal/message_listener.py b/python/google/protobuf/internal/message_listener.py
new file mode 100755
index 0000000..4397895
--- /dev/null
+++ b/python/google/protobuf/internal/message_listener.py
@@ -0,0 +1,69 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Defines a listener interface for observing certain
+state transitions on Message objects.
+
+Also defines a null implementation of this interface.
+"""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+
+class MessageListener(object):
+
+  """Listens for transitions to nonempty and for invalidations of cached
+  byte sizes.  Meant to be registered via Message._SetListener().
+  """
+
+  def TransitionToNonempty(self):
+    """Called the *first* time that this message becomes nonempty.
+    Implementations are free (but not required) to call this method multiple
+    times after the message has become nonempty.
+    """
+    raise NotImplementedError
+
+  def ByteSizeDirty(self):
+    """Called *every* time the cached byte size value
+    for this object is invalidated (transitions from being
+    "clean" to "dirty").
+    """
+    raise NotImplementedError
+
+
+class NullMessageListener(object):
+
+  """No-op MessageListener implementation."""
+
+  def TransitionToNonempty(self):
+    pass
+
+  def ByteSizeDirty(self):
+    pass
diff --git a/python/google/protobuf/internal/message_test.py b/python/google/protobuf/internal/message_test.py
new file mode 100755
index 0000000..df344cf
--- /dev/null
+++ b/python/google/protobuf/internal/message_test.py
@@ -0,0 +1,53 @@
+#! /usr/bin/python
+#
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Tests python protocol buffers against the golden message."""
+
+__author__ = 'gps@google.com (Gregory P. Smith)'
+
+import unittest
+from google.protobuf import unittest_import_pb2
+from google.protobuf import unittest_pb2
+from google.protobuf.internal import test_util
+
+
+class MessageTest(test_util.GoldenMessageTestCase):
+
+  def testGoldenMessage(self):
+    golden_data = test_util.GoldenFile('golden_message').read()
+    golden_message = unittest_pb2.TestAllTypes()
+    golden_message.ParseFromString(golden_data)
+    self.ExpectAllFieldsSet(golden_message)
+
+
+if __name__ == '__main__':
+  unittest.main()
diff --git a/python/google/protobuf/internal/more_extensions.proto b/python/google/protobuf/internal/more_extensions.proto
new file mode 100644
index 0000000..e2d9701
--- /dev/null
+++ b/python/google/protobuf/internal/more_extensions.proto
@@ -0,0 +1,58 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: robinson@google.com (Will Robinson)
+
+
+package google.protobuf.internal;
+
+
+message TopLevelMessage {
+  optional ExtendedMessage submessage = 1;
+}
+
+
+message ExtendedMessage {
+  extensions 1 to max;
+}
+
+
+message ForeignMessage {
+  optional int32 foreign_message_int = 1;
+}
+
+
+extend ExtendedMessage {
+  optional int32 optional_int_extension = 1;
+  optional ForeignMessage optional_message_extension = 2;
+
+  repeated int32 repeated_int_extension = 3;
+  repeated ForeignMessage repeated_message_extension = 4;
+}
diff --git a/python/google/protobuf/internal/more_messages.proto b/python/google/protobuf/internal/more_messages.proto
new file mode 100644
index 0000000..c701b44
--- /dev/null
+++ b/python/google/protobuf/internal/more_messages.proto
@@ -0,0 +1,51 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// http://code.google.com/p/protobuf/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: robinson@google.com (Will Robinson)
+
+
+package google.protobuf.internal;
+
+// A message where tag numbers are listed out of order, to allow us to test our
+// canonicalization of serialized output, which should always be in tag order.
+// We also mix in some extensions for extra fun.
+message OutOfOrderFields {
+  optional   sint32 optional_sint32   =  5;
+  extensions 4 to 4;
+  optional   uint32 optional_uint32   =  3;
+  extensions 2 to 2;
+  optional    int32 optional_int32    =  1;
+};
+
+
+extend OutOfOrderFields {
+  optional   uint64 optional_uint64   =  4;
+  optional    int64 optional_int64    =  2;
+}
diff --git a/python/google/protobuf/internal/output_stream.py b/python/google/protobuf/internal/output_stream.py
new file mode 100755
index 0000000..6c2d6f6
--- /dev/null
+++ b/python/google/protobuf/internal/output_stream.py
@@ -0,0 +1,125 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""OutputStream is the primitive interface for sticking bits on the wire.
+
+All protocol buffer serialization can be expressed in terms of
+the OutputStream primitives provided here.
+"""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+import array
+import struct
+from google.protobuf import message
+from google.protobuf.internal import wire_format
+
+
+
+# Note that much of this code is ported from //net/proto/ProtocolBuffer, and
+# that the interface is strongly inspired by CodedOutputStream from the C++
+# proto2 implementation.
+
+
+class OutputStream(object):
+
+  """Contains all logic for writing bits, and ToString() to get the result."""
+
+  def __init__(self):
+    self._buffer = array.array('B')
+
+  def AppendRawBytes(self, raw_bytes):
+    """Appends raw_bytes to our internal buffer."""
+    self._buffer.fromstring(raw_bytes)
+
+  def AppendLittleEndian32(self, unsigned_value):
+    """Appends an unsigned 32-bit integer to the internal buffer,
+    in little-endian byte order.
+    """
+    if not 0 <= unsigned_value <= wire_format.UINT32_MAX:
+      raise message.EncodeError(
+          'Unsigned 32-bit out of range: %d' % unsigned_value)
+    self._buffer.fromstring(struct.pack(
+        wire_format.FORMAT_UINT32_LITTLE_ENDIAN, unsigned_value))
+
+  def AppendLittleEndian64(self, unsigned_value):
+    """Appends an unsigned 64-bit integer to the internal buffer,
+    in little-endian byte order.
+    """
+    if not 0 <= unsigned_value <= wire_format.UINT64_MAX:
+      raise message.EncodeError(
+          'Unsigned 64-bit out of range: %d' % unsigned_value)
+    self._buffer.fromstring(struct.pack(
+        wire_format.FORMAT_UINT64_LITTLE_ENDIAN, unsigned_value))
+
+  def AppendVarint32(self, value):
+    """Appends a signed 32-bit integer to the internal buffer,
+    encoded as a varint.  (Note that a negative varint32 will
+    always require 10 bytes of space.)
+    """
+    if not wire_format.INT32_MIN <= value <= wire_format.INT32_MAX:
+      raise message.EncodeError('Value out of range: %d' % value)
+    self.AppendVarint64(value)
+
+  def AppendVarUInt32(self, value):
+    """Appends an unsigned 32-bit integer to the internal buffer,
+    encoded as a varint.
+    """
+    if not 0 <= value <= wire_format.UINT32_MAX:
+      raise message.EncodeError('Value out of range: %d' % value)
+    self.AppendVarUInt64(value)
+
+  def AppendVarint64(self, value):
+    """Appends a signed 64-bit integer to the internal buffer,
+    encoded as a varint.
+    """
+    if not wire_format.INT64_MIN <= value <= wire_format.INT64_MAX:
+      raise message.EncodeError('Value out of range: %d' % value)
+    if value < 0:
+      value += (1 << 64)
+    self.AppendVarUInt64(value)
+
+  def AppendVarUInt64(self, unsigned_value):
+    """Appends an unsigned 64-bit integer to the internal buffer,
+    encoded as a varint.
+    """
+    if not 0 <= unsigned_value <= wire_format.UINT64_MAX:
+      raise message.EncodeError('Value out of range: %d' % unsigned_value)
+    while True:
+      bits = unsigned_value & 0x7f
+      unsigned_value >>= 7
+      if not unsigned_value:
+        self._buffer.append(bits)
+        break
+      self._buffer.append(0x80|bits)
+
+  def ToString(self):
+    """Returns a string containing the bytes in our internal buffer."""
+    return self._buffer.tostring()
diff --git a/python/google/protobuf/internal/output_stream_test.py b/python/google/protobuf/internal/output_stream_test.py
new file mode 100755
index 0000000..df92eec
--- /dev/null
+++ b/python/google/protobuf/internal/output_stream_test.py
@@ -0,0 +1,178 @@
+#! /usr/bin/python
+#
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Test for google.protobuf.internal.output_stream."""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+import unittest
+from google.protobuf import message
+from google.protobuf.internal import output_stream
+from google.protobuf.internal import wire_format
+
+
+class OutputStreamTest(unittest.TestCase):
+
+  def setUp(self):
+    self.stream = output_stream.OutputStream()
+
+  def testAppendRawBytes(self):
+    # Empty string.
+    self.stream.AppendRawBytes('')
+    self.assertEqual('', self.stream.ToString())
+
+    # Nonempty string.
+    self.stream.AppendRawBytes('abc')
+    self.assertEqual('abc', self.stream.ToString())
+
+    # Ensure that we're actually appending.
+    self.stream.AppendRawBytes('def')
+    self.assertEqual('abcdef', self.stream.ToString())
+
+  def AppendNumericTestHelper(self, append_fn, values_and_strings):
+    """For each (value, expected_string) pair in values_and_strings,
+    calls an OutputStream.Append*(value) method on an OutputStream and ensures
+    that the string written to that stream matches expected_string.
+
+    Args:
+      append_fn: Unbound OutputStream method that takes an integer or
+        long value as input.
+      values_and_strings: Iterable of (value, expected_string) pairs.
+    """
+    for conversion in (int, long):
+      for value, string in values_and_strings:
+        stream = output_stream.OutputStream()
+        expected_string = ''
+        append_fn(stream, conversion(value))
+        expected_string += string
+        self.assertEqual(expected_string, stream.ToString())
+
+  def AppendOverflowTestHelper(self, append_fn, value):
+    """Calls an OutputStream.Append*(value) method and asserts
+    that the method raises message.EncodeError.
+
+    Args:
+      append_fn: Unbound OutputStream method that takes an integer or
+        long value as input.
+      value: Value to pass to append_fn which should cause an
+        message.EncodeError.
+    """
+    stream = output_stream.OutputStream()
+    self.assertRaises(message.EncodeError, append_fn, stream, value)
+
+  def testAppendLittleEndian32(self):
+    append_fn = output_stream.OutputStream.AppendLittleEndian32
+    values_and_expected_strings = [
+        (0, '\x00\x00\x00\x00'),
+        (1, '\x01\x00\x00\x00'),
+        ((1 << 32) - 1, '\xff\xff\xff\xff'),
+        ]
+    self.AppendNumericTestHelper(append_fn, values_and_expected_strings)
+
+    self.AppendOverflowTestHelper(append_fn, 1 << 32)
+    self.AppendOverflowTestHelper(append_fn, -1)
+
+  def testAppendLittleEndian64(self):
+    append_fn = output_stream.OutputStream.AppendLittleEndian64
+    values_and_expected_strings = [
+        (0, '\x00\x00\x00\x00\x00\x00\x00\x00'),
+        (1, '\x01\x00\x00\x00\x00\x00\x00\x00'),
+        ((1 << 64) - 1, '\xff\xff\xff\xff\xff\xff\xff\xff'),
+        ]
+    self.AppendNumericTestHelper(append_fn, values_and_expected_strings)
+
+    self.AppendOverflowTestHelper(append_fn, 1 << 64)
+    self.AppendOverflowTestHelper(append_fn, -1)
+
+  def testAppendVarint32(self):
+    append_fn = output_stream.OutputStream.AppendVarint32
+    values_and_expected_strings = [
+        (0, '\x00'),
+        (1, '\x01'),
+        (127, '\x7f'),
+        (128, '\x80\x01'),
+        (-1, '\xff\xff\xff\xff\xff\xff\xff\xff\xff\x01'),
+        (wire_format.INT32_MAX, '\xff\xff\xff\xff\x07'),
+        (wire_format.INT32_MIN, '\x80\x80\x80\x80\xf8\xff\xff\xff\xff\x01'),
+        ]
+    self.AppendNumericTestHelper(append_fn, values_and_expected_strings)
+
+    self.AppendOverflowTestHelper(append_fn, wire_format.INT32_MAX + 1)
+    self.AppendOverflowTestHelper(append_fn, wire_format.INT32_MIN - 1)
+
+  def testAppendVarUInt32(self):
+    append_fn = output_stream.OutputStream.AppendVarUInt32
+    values_and_expected_strings = [
+        (0, '\x00'),
+        (1, '\x01'),
+        (127, '\x7f'),
+        (128, '\x80\x01'),
+        (wire_format.UINT32_MAX, '\xff\xff\xff\xff\x0f'),
+        ]
+    self.AppendNumericTestHelper(append_fn, values_and_expected_strings)
+
+    self.AppendOverflowTestHelper(append_fn, -1)
+    self.AppendOverflowTestHelper(append_fn, wire_format.UINT32_MAX + 1)
+
+  def testAppendVarint64(self):
+    append_fn = output_stream.OutputStream.AppendVarint64
+    values_and_expected_strings = [
+        (0, '\x00'),
+        (1, '\x01'),
+        (127, '\x7f'),
+        (128, '\x80\x01'),
+        (-1, '\xff\xff\xff\xff\xff\xff\xff\xff\xff\x01'),
+        (wire_format.INT64_MAX, '\xff\xff\xff\xff\xff\xff\xff\xff\x7f'),
+        (wire_format.INT64_MIN, '\x80\x80\x80\x80\x80\x80\x80\x80\x80\x01'),
+        ]
+    self.AppendNumericTestHelper(append_fn, values_and_expected_strings)
+
+    self.AppendOverflowTestHelper(append_fn, wire_format.INT64_MAX + 1)
+    self.AppendOverflowTestHelper(append_fn, wire_format.INT64_MIN - 1)
+
+  def testAppendVarUInt64(self):
+    append_fn = output_stream.OutputStream.AppendVarUInt64
+    values_and_expected_strings = [
+        (0, '\x00'),
+        (1, '\x01'),
+        (127, '\x7f'),
+        (128, '\x80\x01'),
+        (wire_format.UINT64_MAX, '\xff\xff\xff\xff\xff\xff\xff\xff\xff\x01'),
+        ]
+    self.AppendNumericTestHelper(append_fn, values_and_expected_strings)
+
+    self.AppendOverflowTestHelper(append_fn, -1)
+    self.AppendOverflowTestHelper(append_fn, wire_format.UINT64_MAX + 1)
+
+
+if __name__ == '__main__':
+  unittest.main()
diff --git a/python/google/protobuf/internal/reflection_test.py b/python/google/protobuf/internal/reflection_test.py
new file mode 100755
index 0000000..8610177
--- /dev/null
+++ b/python/google/protobuf/internal/reflection_test.py
@@ -0,0 +1,1976 @@
+#! /usr/bin/python
+# -*- coding: utf-8 -*-
+#
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Unittest for reflection.py, which also indirectly tests the output of the
+pure-Python protocol compiler.
+"""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+import operator
+
+import unittest
+# TODO(robinson): When we split this test in two, only some of these imports
+# will be necessary in each test.
+from google.protobuf import unittest_import_pb2
+from google.protobuf import unittest_mset_pb2
+from google.protobuf import unittest_pb2
+from google.protobuf import descriptor_pb2
+from google.protobuf import descriptor
+from google.protobuf import message
+from google.protobuf import reflection
+from google.protobuf.internal import more_extensions_pb2
+from google.protobuf.internal import more_messages_pb2
+from google.protobuf.internal import wire_format
+from google.protobuf.internal import test_util
+from google.protobuf.internal import decoder
+
+
+class ReflectionTest(unittest.TestCase):
+
+  def assertIs(self, values, others):
+    self.assertEqual(len(values), len(others))
+    for i in range(len(values)):
+      self.assertTrue(values[i] is others[i])
+
+  def testSimpleHasBits(self):
+    # Test a scalar.
+    proto = unittest_pb2.TestAllTypes()
+    self.assertTrue(not proto.HasField('optional_int32'))
+    self.assertEqual(0, proto.optional_int32)
+    # HasField() shouldn't be true if all we've done is
+    # read the default value.
+    self.assertTrue(not proto.HasField('optional_int32'))
+    proto.optional_int32 = 1
+    # Setting a value however *should* set the "has" bit.
+    self.assertTrue(proto.HasField('optional_int32'))
+    proto.ClearField('optional_int32')
+    # And clearing that value should unset the "has" bit.
+    self.assertTrue(not proto.HasField('optional_int32'))
+
+  def testHasBitsWithSinglyNestedScalar(self):
+    # Helper used to test foreign messages and groups.
+    #
+    # composite_field_name should be the name of a non-repeated
+    # composite (i.e., foreign or group) field in TestAllTypes,
+    # and scalar_field_name should be the name of an integer-valued
+    # scalar field within that composite.
+    #
+    # I never thought I'd miss C++ macros and templates so much. :(
+    # This helper is semantically just:
+    #
+    #   assert proto.composite_field.scalar_field == 0
+    #   assert not proto.composite_field.HasField('scalar_field')
+    #   assert not proto.HasField('composite_field')
+    #
+    #   proto.composite_field.scalar_field = 10
+    #   old_composite_field = proto.composite_field
+    #
+    #   assert proto.composite_field.scalar_field == 10
+    #   assert proto.composite_field.HasField('scalar_field')
+    #   assert proto.HasField('composite_field')
+    #
+    #   proto.ClearField('composite_field')
+    #
+    #   assert not proto.composite_field.HasField('scalar_field')
+    #   assert not proto.HasField('composite_field')
+    #   assert proto.composite_field.scalar_field == 0
+    #
+    #   # Now ensure that ClearField('composite_field') disconnected
+    #   # the old field object from the object tree...
+    #   assert old_composite_field is not proto.composite_field
+    #   old_composite_field.scalar_field = 20
+    #   assert not proto.composite_field.HasField('scalar_field')
+    #   assert not proto.HasField('composite_field')
+    def TestCompositeHasBits(composite_field_name, scalar_field_name):
+      proto = unittest_pb2.TestAllTypes()
+      # First, check that we can get the scalar value, and see that it's the
+      # default (0), but that proto.HasField('omposite') and
+      # proto.composite.HasField('scalar') will still return False.
+      composite_field = getattr(proto, composite_field_name)
+      original_scalar_value = getattr(composite_field, scalar_field_name)
+      self.assertEqual(0, original_scalar_value)
+      # Assert that the composite object does not "have" the scalar.
+      self.assertTrue(not composite_field.HasField(scalar_field_name))
+      # Assert that proto does not "have" the composite field.
+      self.assertTrue(not proto.HasField(composite_field_name))
+
+      # Now set the scalar within the composite field.  Ensure that the setting
+      # is reflected, and that proto.HasField('composite') and
+      # proto.composite.HasField('scalar') now both return True.
+      new_val = 20
+      setattr(composite_field, scalar_field_name, new_val)
+      self.assertEqual(new_val, getattr(composite_field, scalar_field_name))
+      # Hold on to a reference to the current composite_field object.
+      old_composite_field = composite_field
+      # Assert that the has methods now return true.
+      self.assertTrue(composite_field.HasField(scalar_field_name))
+      self.assertTrue(proto.HasField(composite_field_name))
+
+      # Now call the clear method...
+      proto.ClearField(composite_field_name)
+
+      # ...and ensure that the "has" bits are all back to False...
+      composite_field = getattr(proto, composite_field_name)
+      self.assertTrue(not composite_field.HasField(scalar_field_name))
+      self.assertTrue(not proto.HasField(composite_field_name))
+      # ...and ensure that the scalar field has returned to its default.
+      self.assertEqual(0, getattr(composite_field, scalar_field_name))
+
+      # Finally, ensure that modifications to the old composite field object
+      # don't have any effect on the parent.
+      #
+      # (NOTE that when we clear the composite field in the parent, we actually
+      # don't recursively clear down the tree.  Instead, we just disconnect the
+      # cleared composite from the tree.)
+      self.assertTrue(old_composite_field is not composite_field)
+      setattr(old_composite_field, scalar_field_name, new_val)
+      self.assertTrue(not composite_field.HasField(scalar_field_name))
+      self.assertTrue(not proto.HasField(composite_field_name))
+      self.assertEqual(0, getattr(composite_field, scalar_field_name))
+
+    # Test simple, single-level nesting when we set a scalar.
+    TestCompositeHasBits('optionalgroup', 'a')
+    TestCompositeHasBits('optional_nested_message', 'bb')
+    TestCompositeHasBits('optional_foreign_message', 'c')
+    TestCompositeHasBits('optional_import_message', 'd')
+
+  def testReferencesToNestedMessage(self):
+    proto = unittest_pb2.TestAllTypes()
+    nested = proto.optional_nested_message
+    del proto
+    # A previous version had a bug where this would raise an exception when
+    # hitting a now-dead weak reference.
+    nested.bb = 23
+
+  def testDisconnectingNestedMessageBeforeSettingField(self):
+    proto = unittest_pb2.TestAllTypes()
+    nested = proto.optional_nested_message
+    proto.ClearField('optional_nested_message')  # Should disconnect from parent
+    self.assertTrue(nested is not proto.optional_nested_message)
+    nested.bb = 23
+    self.assertTrue(not proto.HasField('optional_nested_message'))
+    self.assertEqual(0, proto.optional_nested_message.bb)
+
+  def testHasBitsWhenModifyingRepeatedFields(self):
+    # Test nesting when we add an element to a repeated field in a submessage.
+    proto = unittest_pb2.TestNestedMessageHasBits()
+    proto.optional_nested_message.nestedmessage_repeated_int32.append(5)
+    self.assertEqual(
+        [5], proto.optional_nested_message.nestedmessage_repeated_int32)
+    self.assertTrue(proto.HasField('optional_nested_message'))
+
+    # Do the same test, but with a repeated composite field within the
+    # submessage.
+    proto.ClearField('optional_nested_message')
+    self.assertTrue(not proto.HasField('optional_nested_message'))
+    proto.optional_nested_message.nestedmessage_repeated_foreignmessage.add()
+    self.assertTrue(proto.HasField('optional_nested_message'))
+
+  def testHasBitsForManyLevelsOfNesting(self):
+    # Test nesting many levels deep.
+    recursive_proto = unittest_pb2.TestMutualRecursionA()
+    self.assertTrue(not recursive_proto.HasField('bb'))
+    self.assertEqual(0, recursive_proto.bb.a.bb.a.bb.optional_int32)
+    self.assertTrue(not recursive_proto.HasField('bb'))
+    recursive_proto.bb.a.bb.a.bb.optional_int32 = 5
+    self.assertEqual(5, recursive_proto.bb.a.bb.a.bb.optional_int32)
+    self.assertTrue(recursive_proto.HasField('bb'))
+    self.assertTrue(recursive_proto.bb.HasField('a'))
+    self.assertTrue(recursive_proto.bb.a.HasField('bb'))
+    self.assertTrue(recursive_proto.bb.a.bb.HasField('a'))
+    self.assertTrue(recursive_proto.bb.a.bb.a.HasField('bb'))
+    self.assertTrue(not recursive_proto.bb.a.bb.a.bb.HasField('a'))
+    self.assertTrue(recursive_proto.bb.a.bb.a.bb.HasField('optional_int32'))
+
+  def testSingularListFields(self):
+    proto = unittest_pb2.TestAllTypes()
+    proto.optional_fixed32 = 1
+    proto.optional_int32 = 5
+    proto.optional_string = 'foo'
+    self.assertEqual(
+      [ (proto.DESCRIPTOR.fields_by_name['optional_int32'  ], 5),
+        (proto.DESCRIPTOR.fields_by_name['optional_fixed32'], 1),
+        (proto.DESCRIPTOR.fields_by_name['optional_string' ], 'foo') ],
+      proto.ListFields())
+
+  def testRepeatedListFields(self):
+    proto = unittest_pb2.TestAllTypes()
+    proto.repeated_fixed32.append(1)
+    proto.repeated_int32.append(5)
+    proto.repeated_int32.append(11)
+    proto.repeated_string.extend(['foo', 'bar'])
+    proto.repeated_string.extend([])
+    proto.repeated_string.append('baz')
+    proto.repeated_string.extend(str(x) for x in xrange(2))
+    proto.optional_int32 = 21
+    self.assertEqual(
+      [ (proto.DESCRIPTOR.fields_by_name['optional_int32'  ], 21),
+        (proto.DESCRIPTOR.fields_by_name['repeated_int32'  ], [5, 11]),
+        (proto.DESCRIPTOR.fields_by_name['repeated_fixed32'], [1]),
+        (proto.DESCRIPTOR.fields_by_name['repeated_string' ],
+          ['foo', 'bar', 'baz', '0', '1']) ],
+      proto.ListFields())
+
+  def testSingularListExtensions(self):
+    proto = unittest_pb2.TestAllExtensions()
+    proto.Extensions[unittest_pb2.optional_fixed32_extension] = 1
+    proto.Extensions[unittest_pb2.optional_int32_extension  ] = 5
+    proto.Extensions[unittest_pb2.optional_string_extension ] = 'foo'
+    self.assertEqual(
+      [ (unittest_pb2.optional_int32_extension  , 5),
+        (unittest_pb2.optional_fixed32_extension, 1),
+        (unittest_pb2.optional_string_extension , 'foo') ],
+      proto.ListFields())
+
+  def testRepeatedListExtensions(self):
+    proto = unittest_pb2.TestAllExtensions()
+    proto.Extensions[unittest_pb2.repeated_fixed32_extension].append(1)
+    proto.Extensions[unittest_pb2.repeated_int32_extension  ].append(5)
+    proto.Extensions[unittest_pb2.repeated_int32_extension  ].append(11)
+    proto.Extensions[unittest_pb2.repeated_string_extension ].append('foo')
+    proto.Extensions[unittest_pb2.repeated_string_extension ].append('bar')
+    proto.Extensions[unittest_pb2.repeated_string_extension ].append('baz')
+    proto.Extensions[unittest_pb2.optional_int32_extension  ] = 21
+    self.assertEqual(
+      [ (unittest_pb2.optional_int32_extension  , 21),
+        (unittest_pb2.repeated_int32_extension  , [5, 11]),
+        (unittest_pb2.repeated_fixed32_extension, [1]),
+        (unittest_pb2.repeated_string_extension , ['foo', 'bar', 'baz']) ],
+      proto.ListFields())
+
+  def testListFieldsAndExtensions(self):
+    proto = unittest_pb2.TestFieldOrderings()
+    test_util.SetAllFieldsAndExtensions(proto)
+    unittest_pb2.my_extension_int
+    self.assertEqual(
+      [ (proto.DESCRIPTOR.fields_by_name['my_int'   ], 1),
+        (unittest_pb2.my_extension_int               , 23),
+        (proto.DESCRIPTOR.fields_by_name['my_string'], 'foo'),
+        (unittest_pb2.my_extension_string            , 'bar'),
+        (proto.DESCRIPTOR.fields_by_name['my_float' ], 1.0) ],
+      proto.ListFields())
+
+  def testDefaultValues(self):
+    proto = unittest_pb2.TestAllTypes()
+    self.assertEqual(0, proto.optional_int32)
+    self.assertEqual(0, proto.optional_int64)
+    self.assertEqual(0, proto.optional_uint32)
+    self.assertEqual(0, proto.optional_uint64)
+    self.assertEqual(0, proto.optional_sint32)
+    self.assertEqual(0, proto.optional_sint64)
+    self.assertEqual(0, proto.optional_fixed32)
+    self.assertEqual(0, proto.optional_fixed64)
+    self.assertEqual(0, proto.optional_sfixed32)
+    self.assertEqual(0, proto.optional_sfixed64)
+    self.assertEqual(0.0, proto.optional_float)
+    self.assertEqual(0.0, proto.optional_double)
+    self.assertEqual(False, proto.optional_bool)
+    self.assertEqual('', proto.optional_string)
+    self.assertEqual('', proto.optional_bytes)
+
+    self.assertEqual(41, proto.default_int32)
+    self.assertEqual(42, proto.default_int64)
+    self.assertEqual(43, proto.default_uint32)
+    self.assertEqual(44, proto.default_uint64)
+    self.assertEqual(-45, proto.default_sint32)
+    self.assertEqual(46, proto.default_sint64)
+    self.assertEqual(47, proto.default_fixed32)
+    self.assertEqual(48, proto.default_fixed64)
+    self.assertEqual(49, proto.default_sfixed32)
+    self.assertEqual(-50, proto.default_sfixed64)
+    self.assertEqual(51.5, proto.default_float)
+    self.assertEqual(52e3, proto.default_double)
+    self.assertEqual(True, proto.default_bool)
+    self.assertEqual('hello', proto.default_string)
+    self.assertEqual('world', proto.default_bytes)
+    self.assertEqual(unittest_pb2.TestAllTypes.BAR, proto.default_nested_enum)
+    self.assertEqual(unittest_pb2.FOREIGN_BAR, proto.default_foreign_enum)
+    self.assertEqual(unittest_import_pb2.IMPORT_BAR,
+                     proto.default_import_enum)
+
+    proto = unittest_pb2.TestExtremeDefaultValues()
+    self.assertEqual(u'\u1234', proto.utf8_string)
+
+  def testHasFieldWithUnknownFieldName(self):
+    proto = unittest_pb2.TestAllTypes()
+    self.assertRaises(ValueError, proto.HasField, 'nonexistent_field')
+
+  def testClearFieldWithUnknownFieldName(self):
+    proto = unittest_pb2.TestAllTypes()
+    self.assertRaises(ValueError, proto.ClearField, 'nonexistent_field')
+
+  def testDisallowedAssignments(self):
+    # It's illegal to assign values directly to repeated fields
+    # or to nonrepeated composite fields.  Ensure that this fails.
+    proto = unittest_pb2.TestAllTypes()
+    # Repeated fields.
+    self.assertRaises(AttributeError, setattr, proto, 'repeated_int32', 10)
+    # Lists shouldn't work, either.
+    self.assertRaises(AttributeError, setattr, proto, 'repeated_int32', [10])
+    # Composite fields.
+    self.assertRaises(AttributeError, setattr, proto,
+                      'optional_nested_message', 23)
+    # Assignment to a repeated nested message field without specifying
+    # the index in the array of nested messages.
+    self.assertRaises(AttributeError, setattr, proto.repeated_nested_message,
+                      'bb', 34)
+    # Assignment to an attribute of a repeated field.
+    self.assertRaises(AttributeError, setattr, proto.repeated_float,
+                      'some_attribute', 34)
+    # proto.nonexistent_field = 23 should fail as well.
+    self.assertRaises(AttributeError, setattr, proto, 'nonexistent_field', 23)
+
+  # TODO(robinson): Add type-safety check for enums.
+  def testSingleScalarTypeSafety(self):
+    proto = unittest_pb2.TestAllTypes()
+    self.assertRaises(TypeError, setattr, proto, 'optional_int32', 1.1)
+    self.assertRaises(TypeError, setattr, proto, 'optional_int32', 'foo')
+    self.assertRaises(TypeError, setattr, proto, 'optional_string', 10)
+    self.assertRaises(TypeError, setattr, proto, 'optional_bytes', 10)
+
+  def testSingleScalarBoundsChecking(self):
+    def TestMinAndMaxIntegers(field_name, expected_min, expected_max):
+      pb = unittest_pb2.TestAllTypes()
+      setattr(pb, field_name, expected_min)
+      setattr(pb, field_name, expected_max)
+      self.assertRaises(ValueError, setattr, pb, field_name, expected_min - 1)
+      self.assertRaises(ValueError, setattr, pb, field_name, expected_max + 1)
+
+    TestMinAndMaxIntegers('optional_int32', -(1 << 31), (1 << 31) - 1)
+    TestMinAndMaxIntegers('optional_uint32', 0, 0xffffffff)
+    TestMinAndMaxIntegers('optional_int64', -(1 << 63), (1 << 63) - 1)
+    TestMinAndMaxIntegers('optional_uint64', 0, 0xffffffffffffffff)
+    TestMinAndMaxIntegers('optional_nested_enum', -(1 << 31), (1 << 31) - 1)
+
+  def testRepeatedScalarTypeSafety(self):
+    proto = unittest_pb2.TestAllTypes()
+    self.assertRaises(TypeError, proto.repeated_int32.append, 1.1)
+    self.assertRaises(TypeError, proto.repeated_int32.append, 'foo')
+    self.assertRaises(TypeError, proto.repeated_string, 10)
+    self.assertRaises(TypeError, proto.repeated_bytes, 10)
+
+    proto.repeated_int32.append(10)
+    proto.repeated_int32[0] = 23
+    self.assertRaises(IndexError, proto.repeated_int32.__setitem__, 500, 23)
+    self.assertRaises(TypeError, proto.repeated_int32.__setitem__, 0, 'abc')
+
+  def testSingleScalarGettersAndSetters(self):
+    proto = unittest_pb2.TestAllTypes()
+    self.assertEqual(0, proto.optional_int32)
+    proto.optional_int32 = 1
+    self.assertEqual(1, proto.optional_int32)
+    # TODO(robinson): Test all other scalar field types.
+
+  def testSingleScalarClearField(self):
+    proto = unittest_pb2.TestAllTypes()
+    # Should be allowed to clear something that's not there (a no-op).
+    proto.ClearField('optional_int32')
+    proto.optional_int32 = 1
+    self.assertTrue(proto.HasField('optional_int32'))
+    proto.ClearField('optional_int32')
+    self.assertEqual(0, proto.optional_int32)
+    self.assertTrue(not proto.HasField('optional_int32'))
+    # TODO(robinson): Test all other scalar field types.
+
+  def testEnums(self):
+    proto = unittest_pb2.TestAllTypes()
+    self.assertEqual(1, proto.FOO)
+    self.assertEqual(1, unittest_pb2.TestAllTypes.FOO)
+    self.assertEqual(2, proto.BAR)
+    self.assertEqual(2, unittest_pb2.TestAllTypes.BAR)
+    self.assertEqual(3, proto.BAZ)
+    self.assertEqual(3, unittest_pb2.TestAllTypes.BAZ)
+
+  def testRepeatedScalars(self):
+    proto = unittest_pb2.TestAllTypes()
+
+    self.assertTrue(not proto.repeated_int32)
+    self.assertEqual(0, len(proto.repeated_int32))
+    proto.repeated_int32.append(5)
+    proto.repeated_int32.append(10)
+    proto.repeated_int32.append(15)
+    self.assertTrue(proto.repeated_int32)
+    self.assertEqual(3, len(proto.repeated_int32))
+
+    self.assertEqual([5, 10, 15], proto.repeated_int32)
+
+    # Test single retrieval.
+    self.assertEqual(5, proto.repeated_int32[0])
+    self.assertEqual(15, proto.repeated_int32[-1])
+    # Test out-of-bounds indices.
+    self.assertRaises(IndexError, proto.repeated_int32.__getitem__, 1234)
+    self.assertRaises(IndexError, proto.repeated_int32.__getitem__, -1234)
+    # Test incorrect types passed to __getitem__.
+    self.assertRaises(TypeError, proto.repeated_int32.__getitem__, 'foo')
+    self.assertRaises(TypeError, proto.repeated_int32.__getitem__, None)
+
+    # Test single assignment.
+    proto.repeated_int32[1] = 20
+    self.assertEqual([5, 20, 15], proto.repeated_int32)
+
+    # Test insertion.
+    proto.repeated_int32.insert(1, 25)
+    self.assertEqual([5, 25, 20, 15], proto.repeated_int32)
+
+    # Test slice retrieval.
+    proto.repeated_int32.append(30)
+    self.assertEqual([25, 20, 15], proto.repeated_int32[1:4])
+    self.assertEqual([5, 25, 20, 15, 30], proto.repeated_int32[:])
+
+    # Test slice assignment with an iterator
+    proto.repeated_int32[1:4] = (i for i in xrange(3))
+    self.assertEqual([5, 0, 1, 2, 30], proto.repeated_int32)
+
+    # Test slice assignment.
+    proto.repeated_int32[1:4] = [35, 40, 45]
+    self.assertEqual([5, 35, 40, 45, 30], proto.repeated_int32)
+
+    # Test that we can use the field as an iterator.
+    result = []
+    for i in proto.repeated_int32:
+      result.append(i)
+    self.assertEqual([5, 35, 40, 45, 30], result)
+
+    # Test single deletion.
+    del proto.repeated_int32[2]
+    self.assertEqual([5, 35, 45, 30], proto.repeated_int32)
+
+    # Test slice deletion.
+    del proto.repeated_int32[2:]
+    self.assertEqual([5, 35], proto.repeated_int32)
+
+    # Test clearing.
+    proto.ClearField('repeated_int32')
+    self.assertTrue(not proto.repeated_int32)
+    self.assertEqual(0, len(proto.repeated_int32))
+
+  def testRepeatedScalarsRemove(self):
+    proto = unittest_pb2.TestAllTypes()
+
+    self.assertTrue(not proto.repeated_int32)
+    self.assertEqual(0, len(proto.repeated_int32))
+    proto.repeated_int32.append(5)
+    proto.repeated_int32.append(10)
+    proto.repeated_int32.append(5)
+    proto.repeated_int32.append(5)
+
+    self.assertEqual(4, len(proto.repeated_int32))
+    proto.repeated_int32.remove(5)
+    self.assertEqual(3, len(proto.repeated_int32))
+    self.assertEqual(10, proto.repeated_int32[0])
+    self.assertEqual(5, proto.repeated_int32[1])
+    self.assertEqual(5, proto.repeated_int32[2])
+
+    proto.repeated_int32.remove(5)
+    self.assertEqual(2, len(proto.repeated_int32))
+    self.assertEqual(10, proto.repeated_int32[0])
+    self.assertEqual(5, proto.repeated_int32[1])
+
+    proto.repeated_int32.remove(10)
+    self.assertEqual(1, len(proto.repeated_int32))
+    self.assertEqual(5, proto.repeated_int32[0])
+
+    # Remove a non-existent element.
+    self.assertRaises(ValueError, proto.repeated_int32.remove, 123)
+
+  def testRepeatedComposites(self):
+    proto = unittest_pb2.TestAllTypes()
+    self.assertTrue(not proto.repeated_nested_message)
+    self.assertEqual(0, len(proto.repeated_nested_message))
+    m0 = proto.repeated_nested_message.add()
+    m1 = proto.repeated_nested_message.add()
+    self.assertTrue(proto.repeated_nested_message)
+    self.assertEqual(2, len(proto.repeated_nested_message))
+    self.assertIs([m0, m1], proto.repeated_nested_message)
+    self.assertTrue(isinstance(m0, unittest_pb2.TestAllTypes.NestedMessage))
+
+    # Test out-of-bounds indices.
+    self.assertRaises(IndexError, proto.repeated_nested_message.__getitem__,
+                      1234)
+    self.assertRaises(IndexError, proto.repeated_nested_message.__getitem__,
+                      -1234)
+
+    # Test incorrect types passed to __getitem__.
+    self.assertRaises(TypeError, proto.repeated_nested_message.__getitem__,
+                      'foo')
+    self.assertRaises(TypeError, proto.repeated_nested_message.__getitem__,
+                      None)
+
+    # Test slice retrieval.
+    m2 = proto.repeated_nested_message.add()
+    m3 = proto.repeated_nested_message.add()
+    m4 = proto.repeated_nested_message.add()
+    self.assertIs([m1, m2, m3], proto.repeated_nested_message[1:4])
+    self.assertIs([m0, m1, m2, m3, m4], proto.repeated_nested_message[:])
+
+    # Test that we can use the field as an iterator.
+    result = []
+    for i in proto.repeated_nested_message:
+      result.append(i)
+    self.assertIs([m0, m1, m2, m3, m4], result)
+
+    # Test single deletion.
+    del proto.repeated_nested_message[2]
+    self.assertIs([m0, m1, m3, m4], proto.repeated_nested_message)
+
+    # Test slice deletion.
+    del proto.repeated_nested_message[2:]
+    self.assertIs([m0, m1], proto.repeated_nested_message)
+
+    # Test clearing.
+    proto.ClearField('repeated_nested_message')
+    self.assertTrue(not proto.repeated_nested_message)
+    self.assertEqual(0, len(proto.repeated_nested_message))
+
+  def testHandWrittenReflection(self):
+    # TODO(robinson): We probably need a better way to specify
+    # protocol types by hand.  But then again, this isn't something
+    # we expect many people to do.  Hmm.
+    FieldDescriptor = descriptor.FieldDescriptor
+    foo_field_descriptor = FieldDescriptor(
+        name='foo_field', full_name='MyProto.foo_field',
+        index=0, number=1, type=FieldDescriptor.TYPE_INT64,
+        cpp_type=FieldDescriptor.CPPTYPE_INT64,
+        label=FieldDescriptor.LABEL_OPTIONAL, default_value=0,
+        containing_type=None, message_type=None, enum_type=None,
+        is_extension=False, extension_scope=None,
+        options=descriptor_pb2.FieldOptions())
+    mydescriptor = descriptor.Descriptor(
+        name='MyProto', full_name='MyProto', filename='ignored',
+        containing_type=None, nested_types=[], enum_types=[],
+        fields=[foo_field_descriptor], extensions=[],
+        options=descriptor_pb2.MessageOptions())
+    class MyProtoClass(message.Message):
+      DESCRIPTOR = mydescriptor
+      __metaclass__ = reflection.GeneratedProtocolMessageType
+    myproto_instance = MyProtoClass()
+    self.assertEqual(0, myproto_instance.foo_field)
+    self.assertTrue(not myproto_instance.HasField('foo_field'))
+    myproto_instance.foo_field = 23
+    self.assertEqual(23, myproto_instance.foo_field)
+    self.assertTrue(myproto_instance.HasField('foo_field'))
+
+  def testTopLevelExtensionsForOptionalScalar(self):
+    extendee_proto = unittest_pb2.TestAllExtensions()
+    extension = unittest_pb2.optional_int32_extension
+    self.assertTrue(not extendee_proto.HasExtension(extension))
+    self.assertEqual(0, extendee_proto.Extensions[extension])
+    # As with normal scalar fields, just doing a read doesn't actually set the
+    # "has" bit.
+    self.assertTrue(not extendee_proto.HasExtension(extension))
+    # Actually set the thing.
+    extendee_proto.Extensions[extension] = 23
+    self.assertEqual(23, extendee_proto.Extensions[extension])
+    self.assertTrue(extendee_proto.HasExtension(extension))
+    # Ensure that clearing works as well.
+    extendee_proto.ClearExtension(extension)
+    self.assertEqual(0, extendee_proto.Extensions[extension])
+    self.assertTrue(not extendee_proto.HasExtension(extension))
+
+  def testTopLevelExtensionsForRepeatedScalar(self):
+    extendee_proto = unittest_pb2.TestAllExtensions()
+    extension = unittest_pb2.repeated_string_extension
+    self.assertEqual(0, len(extendee_proto.Extensions[extension]))
+    extendee_proto.Extensions[extension].append('foo')
+    self.assertEqual(['foo'], extendee_proto.Extensions[extension])
+    string_list = extendee_proto.Extensions[extension]
+    extendee_proto.ClearExtension(extension)
+    self.assertEqual(0, len(extendee_proto.Extensions[extension]))
+    self.assertTrue(string_list is not extendee_proto.Extensions[extension])
+    # Shouldn't be allowed to do Extensions[extension] = 'a'
+    self.assertRaises(TypeError, operator.setitem, extendee_proto.Extensions,
+                      extension, 'a')
+
+  def testTopLevelExtensionsForOptionalMessage(self):
+    extendee_proto = unittest_pb2.TestAllExtensions()
+    extension = unittest_pb2.optional_foreign_message_extension
+    self.assertTrue(not extendee_proto.HasExtension(extension))
+    self.assertEqual(0, extendee_proto.Extensions[extension].c)
+    # As with normal (non-extension) fields, merely reading from the
+    # thing shouldn't set the "has" bit.
+    self.assertTrue(not extendee_proto.HasExtension(extension))
+    extendee_proto.Extensions[extension].c = 23
+    self.assertEqual(23, extendee_proto.Extensions[extension].c)
+    self.assertTrue(extendee_proto.HasExtension(extension))
+    # Save a reference here.
+    foreign_message = extendee_proto.Extensions[extension]
+    extendee_proto.ClearExtension(extension)
+    self.assertTrue(foreign_message is not extendee_proto.Extensions[extension])
+    # Setting a field on foreign_message now shouldn't set
+    # any "has" bits on extendee_proto.
+    foreign_message.c = 42
+    self.assertEqual(42, foreign_message.c)
+    self.assertTrue(foreign_message.HasField('c'))
+    self.assertTrue(not extendee_proto.HasExtension(extension))
+    # Shouldn't be allowed to do Extensions[extension] = 'a'
+    self.assertRaises(TypeError, operator.setitem, extendee_proto.Extensions,
+                      extension, 'a')
+
+  def testTopLevelExtensionsForRepeatedMessage(self):
+    extendee_proto = unittest_pb2.TestAllExtensions()
+    extension = unittest_pb2.repeatedgroup_extension
+    self.assertEqual(0, len(extendee_proto.Extensions[extension]))
+    group = extendee_proto.Extensions[extension].add()
+    group.a = 23
+    self.assertEqual(23, extendee_proto.Extensions[extension][0].a)
+    group.a = 42
+    self.assertEqual(42, extendee_proto.Extensions[extension][0].a)
+    group_list = extendee_proto.Extensions[extension]
+    extendee_proto.ClearExtension(extension)
+    self.assertEqual(0, len(extendee_proto.Extensions[extension]))
+    self.assertTrue(group_list is not extendee_proto.Extensions[extension])
+    # Shouldn't be allowed to do Extensions[extension] = 'a'
+    self.assertRaises(TypeError, operator.setitem, extendee_proto.Extensions,
+                      extension, 'a')
+
+  def testNestedExtensions(self):
+    extendee_proto = unittest_pb2.TestAllExtensions()
+    extension = unittest_pb2.TestRequired.single
+
+    # We just test the non-repeated case.
+    self.assertTrue(not extendee_proto.HasExtension(extension))
+    required = extendee_proto.Extensions[extension]
+    self.assertEqual(0, required.a)
+    self.assertTrue(not extendee_proto.HasExtension(extension))
+    required.a = 23
+    self.assertEqual(23, extendee_proto.Extensions[extension].a)
+    self.assertTrue(extendee_proto.HasExtension(extension))
+    extendee_proto.ClearExtension(extension)
+    self.assertTrue(required is not extendee_proto.Extensions[extension])
+    self.assertTrue(not extendee_proto.HasExtension(extension))
+
+  # If message A directly contains message B, and
+  # a.HasField('b') is currently False, then mutating any
+  # extension in B should change a.HasField('b') to True
+  # (and so on up the object tree).
+  def testHasBitsForAncestorsOfExtendedMessage(self):
+    # Optional scalar extension.
+    toplevel = more_extensions_pb2.TopLevelMessage()
+    self.assertTrue(not toplevel.HasField('submessage'))
+    self.assertEqual(0, toplevel.submessage.Extensions[
+        more_extensions_pb2.optional_int_extension])
+    self.assertTrue(not toplevel.HasField('submessage'))
+    toplevel.submessage.Extensions[
+        more_extensions_pb2.optional_int_extension] = 23
+    self.assertEqual(23, toplevel.submessage.Extensions[
+        more_extensions_pb2.optional_int_extension])
+    self.assertTrue(toplevel.HasField('submessage'))
+
+    # Repeated scalar extension.
+    toplevel = more_extensions_pb2.TopLevelMessage()
+    self.assertTrue(not toplevel.HasField('submessage'))
+    self.assertEqual([], toplevel.submessage.Extensions[
+        more_extensions_pb2.repeated_int_extension])
+    self.assertTrue(not toplevel.HasField('submessage'))
+    toplevel.submessage.Extensions[
+        more_extensions_pb2.repeated_int_extension].append(23)
+    self.assertEqual([23], toplevel.submessage.Extensions[
+        more_extensions_pb2.repeated_int_extension])
+    self.assertTrue(toplevel.HasField('submessage'))
+
+    # Optional message extension.
+    toplevel = more_extensions_pb2.TopLevelMessage()
+    self.assertTrue(not toplevel.HasField('submessage'))
+    self.assertEqual(0, toplevel.submessage.Extensions[
+        more_extensions_pb2.optional_message_extension].foreign_message_int)
+    self.assertTrue(not toplevel.HasField('submessage'))
+    toplevel.submessage.Extensions[
+        more_extensions_pb2.optional_message_extension].foreign_message_int = 23
+    self.assertEqual(23, toplevel.submessage.Extensions[
+        more_extensions_pb2.optional_message_extension].foreign_message_int)
+    self.assertTrue(toplevel.HasField('submessage'))
+
+    # Repeated message extension.
+    toplevel = more_extensions_pb2.TopLevelMessage()
+    self.assertTrue(not toplevel.HasField('submessage'))
+    self.assertEqual(0, len(toplevel.submessage.Extensions[
+        more_extensions_pb2.repeated_message_extension]))
+    self.assertTrue(not toplevel.HasField('submessage'))
+    foreign = toplevel.submessage.Extensions[
+        more_extensions_pb2.repeated_message_extension].add()
+    self.assertTrue(foreign is toplevel.submessage.Extensions[
+        more_extensions_pb2.repeated_message_extension][0])
+    self.assertTrue(toplevel.HasField('submessage'))
+
+  def testDisconnectionAfterClearingEmptyMessage(self):
+    toplevel = more_extensions_pb2.TopLevelMessage()
+    extendee_proto = toplevel.submessage
+    extension = more_extensions_pb2.optional_message_extension
+    extension_proto = extendee_proto.Extensions[extension]
+    extendee_proto.ClearExtension(extension)
+    extension_proto.foreign_message_int = 23
+
+    self.assertTrue(not toplevel.HasField('submessage'))
+    self.assertTrue(extension_proto is not extendee_proto.Extensions[extension])
+
+  def testExtensionFailureModes(self):
+    extendee_proto = unittest_pb2.TestAllExtensions()
+
+    # Try non-extension-handle arguments to HasExtension,
+    # ClearExtension(), and Extensions[]...
+    self.assertRaises(KeyError, extendee_proto.HasExtension, 1234)
+    self.assertRaises(KeyError, extendee_proto.ClearExtension, 1234)
+    self.assertRaises(KeyError, extendee_proto.Extensions.__getitem__, 1234)
+    self.assertRaises(KeyError, extendee_proto.Extensions.__setitem__, 1234, 5)
+
+    # Try something that *is* an extension handle, just not for
+    # this message...
+    unknown_handle = more_extensions_pb2.optional_int_extension
+    self.assertRaises(KeyError, extendee_proto.HasExtension,
+                      unknown_handle)
+    self.assertRaises(KeyError, extendee_proto.ClearExtension,
+                      unknown_handle)
+    self.assertRaises(KeyError, extendee_proto.Extensions.__getitem__,
+                      unknown_handle)
+    self.assertRaises(KeyError, extendee_proto.Extensions.__setitem__,
+                      unknown_handle, 5)
+
+    # Try call HasExtension() with a valid handle, but for a
+    # *repeated* field.  (Just as with non-extension repeated
+    # fields, Has*() isn't supported for extension repeated fields).
+    self.assertRaises(KeyError, extendee_proto.HasExtension,
+                      unittest_pb2.repeated_string_extension)
+
+  def testStaticParseFrom(self):
+    proto1 = unittest_pb2.TestAllTypes()
+    test_util.SetAllFields(proto1)
+
+    string1 = proto1.SerializeToString()
+    proto2 = unittest_pb2.TestAllTypes.FromString(string1)
+
+    # Messages should be equal.
+    self.assertEqual(proto2, proto1)
+
+  def testMergeFromSingularField(self):
+    # Test merge with just a singular field.
+    proto1 = unittest_pb2.TestAllTypes()
+    proto1.optional_int32 = 1
+
+    proto2 = unittest_pb2.TestAllTypes()
+    # This shouldn't get overwritten.
+    proto2.optional_string = 'value'
+
+    proto2.MergeFrom(proto1)
+    self.assertEqual(1, proto2.optional_int32)
+    self.assertEqual('value', proto2.optional_string)
+
+  def testMergeFromRepeatedField(self):
+    # Test merge with just a repeated field.
+    proto1 = unittest_pb2.TestAllTypes()
+    proto1.repeated_int32.append(1)
+    proto1.repeated_int32.append(2)
+
+    proto2 = unittest_pb2.TestAllTypes()
+    proto2.repeated_int32.append(0)
+    proto2.MergeFrom(proto1)
+
+    self.assertEqual(0, proto2.repeated_int32[0])
+    self.assertEqual(1, proto2.repeated_int32[1])
+    self.assertEqual(2, proto2.repeated_int32[2])
+
+  def testMergeFromOptionalGroup(self):
+    # Test merge with an optional group.
+    proto1 = unittest_pb2.TestAllTypes()
+    proto1.optionalgroup.a = 12
+    proto2 = unittest_pb2.TestAllTypes()
+    proto2.MergeFrom(proto1)
+    self.assertEqual(12, proto2.optionalgroup.a)
+
+  def testMergeFromRepeatedNestedMessage(self):
+    # Test merge with a repeated nested message.
+    proto1 = unittest_pb2.TestAllTypes()
+    m = proto1.repeated_nested_message.add()
+    m.bb = 123
+    m = proto1.repeated_nested_message.add()
+    m.bb = 321
+
+    proto2 = unittest_pb2.TestAllTypes()
+    m = proto2.repeated_nested_message.add()
+    m.bb = 999
+    proto2.MergeFrom(proto1)
+    self.assertEqual(999, proto2.repeated_nested_message[0].bb)
+    self.assertEqual(123, proto2.repeated_nested_message[1].bb)
+    self.assertEqual(321, proto2.repeated_nested_message[2].bb)
+
+  def testMergeFromAllFields(self):
+    # With all fields set.
+    proto1 = unittest_pb2.TestAllTypes()
+    test_util.SetAllFields(proto1)
+    proto2 = unittest_pb2.TestAllTypes()
+    proto2.MergeFrom(proto1)
+
+    # Messages should be equal.
+    self.assertEqual(proto2, proto1)
+
+    # Serialized string should be equal too.
+    string1 = proto1.SerializeToString()
+    string2 = proto2.SerializeToString()
+    self.assertEqual(string1, string2)
+
+  def testMergeFromExtensionsSingular(self):
+    proto1 = unittest_pb2.TestAllExtensions()
+    proto1.Extensions[unittest_pb2.optional_int32_extension] = 1
+
+    proto2 = unittest_pb2.TestAllExtensions()
+    proto2.MergeFrom(proto1)
+    self.assertEqual(
+        1, proto2.Extensions[unittest_pb2.optional_int32_extension])
+
+  def testMergeFromExtensionsRepeated(self):
+    proto1 = unittest_pb2.TestAllExtensions()
+    proto1.Extensions[unittest_pb2.repeated_int32_extension].append(1)
+    proto1.Extensions[unittest_pb2.repeated_int32_extension].append(2)
+
+    proto2 = unittest_pb2.TestAllExtensions()
+    proto2.Extensions[unittest_pb2.repeated_int32_extension].append(0)
+    proto2.MergeFrom(proto1)
+    self.assertEqual(
+        3, len(proto2.Extensions[unittest_pb2.repeated_int32_extension]))
+    self.assertEqual(
+        0, proto2.Extensions[unittest_pb2.repeated_int32_extension][0])
+    self.assertEqual(
+        1, proto2.Extensions[unittest_pb2.repeated_int32_extension][1])
+    self.assertEqual(
+        2, proto2.Extensions[unittest_pb2.repeated_int32_extension][2])
+
+  def testMergeFromExtensionsNestedMessage(self):
+    proto1 = unittest_pb2.TestAllExtensions()
+    ext1 = proto1.Extensions[
+        unittest_pb2.repeated_nested_message_extension]
+    m = ext1.add()
+    m.bb = 222
+    m = ext1.add()
+    m.bb = 333
+
+    proto2 = unittest_pb2.TestAllExtensions()
+    ext2 = proto2.Extensions[
+        unittest_pb2.repeated_nested_message_extension]
+    m = ext2.add()
+    m.bb = 111
+
+    proto2.MergeFrom(proto1)
+    ext2 = proto2.Extensions[
+        unittest_pb2.repeated_nested_message_extension]
+    self.assertEqual(3, len(ext2))
+    self.assertEqual(111, ext2[0].bb)
+    self.assertEqual(222, ext2[1].bb)
+    self.assertEqual(333, ext2[2].bb)
+
+  def testCopyFromSingularField(self):
+    # Test copy with just a singular field.
+    proto1 = unittest_pb2.TestAllTypes()
+    proto1.optional_int32 = 1
+    proto1.optional_string = 'important-text'
+
+    proto2 = unittest_pb2.TestAllTypes()
+    proto2.optional_string = 'value'
+
+    proto2.CopyFrom(proto1)
+    self.assertEqual(1, proto2.optional_int32)
+    self.assertEqual('important-text', proto2.optional_string)
+
+  def testCopyFromRepeatedField(self):
+    # Test copy with a repeated field.
+    proto1 = unittest_pb2.TestAllTypes()
+    proto1.repeated_int32.append(1)
+    proto1.repeated_int32.append(2)
+
+    proto2 = unittest_pb2.TestAllTypes()
+    proto2.repeated_int32.append(0)
+    proto2.CopyFrom(proto1)
+
+    self.assertEqual(1, proto2.repeated_int32[0])
+    self.assertEqual(2, proto2.repeated_int32[1])
+
+  def testCopyFromAllFields(self):
+    # With all fields set.
+    proto1 = unittest_pb2.TestAllTypes()
+    test_util.SetAllFields(proto1)
+    proto2 = unittest_pb2.TestAllTypes()
+    proto2.CopyFrom(proto1)
+
+    # Messages should be equal.
+    self.assertEqual(proto2, proto1)
+
+    # Serialized string should be equal too.
+    string1 = proto1.SerializeToString()
+    string2 = proto2.SerializeToString()
+    self.assertEqual(string1, string2)
+
+  def testCopyFromSelf(self):
+    proto1 = unittest_pb2.TestAllTypes()
+    proto1.repeated_int32.append(1)
+    proto1.optional_int32 = 2
+    proto1.optional_string = 'important-text'
+
+    proto1.CopyFrom(proto1)
+    self.assertEqual(1, proto1.repeated_int32[0])
+    self.assertEqual(2, proto1.optional_int32)
+    self.assertEqual('important-text', proto1.optional_string)
+
+  def testClear(self):
+    proto = unittest_pb2.TestAllTypes()
+    test_util.SetAllFields(proto)
+    # Clear the message.
+    proto.Clear()
+    self.assertEquals(proto.ByteSize(), 0)
+    empty_proto = unittest_pb2.TestAllTypes()
+    self.assertEquals(proto, empty_proto)
+
+    # Test if extensions which were set are cleared.
+    proto = unittest_pb2.TestAllExtensions()
+    test_util.SetAllExtensions(proto)
+    # Clear the message.
+    proto.Clear()
+    self.assertEquals(proto.ByteSize(), 0)
+    empty_proto = unittest_pb2.TestAllExtensions()
+    self.assertEquals(proto, empty_proto)
+
+  def testIsInitialized(self):
+    # Trivial cases - all optional fields and extensions.
+    proto = unittest_pb2.TestAllTypes()
+    self.assertTrue(proto.IsInitialized())
+    proto = unittest_pb2.TestAllExtensions()
+    self.assertTrue(proto.IsInitialized())
+
+    # The case of uninitialized required fields.
+    proto = unittest_pb2.TestRequired()
+    self.assertFalse(proto.IsInitialized())
+    proto.a = proto.b = proto.c = 2
+    self.assertTrue(proto.IsInitialized())
+
+    # The case of uninitialized submessage.
+    proto = unittest_pb2.TestRequiredForeign()
+    self.assertTrue(proto.IsInitialized())
+    proto.optional_message.a = 1
+    self.assertFalse(proto.IsInitialized())
+    proto.optional_message.b = 0
+    proto.optional_message.c = 0
+    self.assertTrue(proto.IsInitialized())
+
+    # Uninitialized repeated submessage.
+    message1 = proto.repeated_message.add()
+    self.assertFalse(proto.IsInitialized())
+    message1.a = message1.b = message1.c = 0
+    self.assertTrue(proto.IsInitialized())
+
+    # Uninitialized repeated group in an extension.
+    proto = unittest_pb2.TestAllExtensions()
+    extension = unittest_pb2.TestRequired.multi
+    message1 = proto.Extensions[extension].add()
+    message2 = proto.Extensions[extension].add()
+    self.assertFalse(proto.IsInitialized())
+    message1.a = 1
+    message1.b = 1
+    message1.c = 1
+    self.assertFalse(proto.IsInitialized())
+    message2.a = 2
+    message2.b = 2
+    message2.c = 2
+    self.assertTrue(proto.IsInitialized())
+
+    # Uninitialized nonrepeated message in an extension.
+    proto = unittest_pb2.TestAllExtensions()
+    extension = unittest_pb2.TestRequired.single
+    proto.Extensions[extension].a = 1
+    self.assertFalse(proto.IsInitialized())
+    proto.Extensions[extension].b = 2
+    proto.Extensions[extension].c = 3
+    self.assertTrue(proto.IsInitialized())
+
+  def testStringUTF8Encoding(self):
+    proto = unittest_pb2.TestAllTypes()
+
+    # Assignment of a unicode object to a field of type 'bytes' is not allowed.
+    self.assertRaises(TypeError,
+                      setattr, proto, 'optional_bytes', u'unicode object')
+
+    # Check that the default value is of python's 'unicode' type.
+    self.assertEqual(type(proto.optional_string), unicode)
+
+    proto.optional_string = unicode('Testing')
+    self.assertEqual(proto.optional_string, str('Testing'))
+
+    # Assign a value of type 'str' which can be encoded in UTF-8.
+    proto.optional_string = str('Testing')
+    self.assertEqual(proto.optional_string, unicode('Testing'))
+
+    # Values of type 'str' are also accepted as long as they can be encoded in
+    # UTF-8.
+    self.assertEqual(type(proto.optional_string), str)
+
+    # Try to assign a 'str' value which contains bytes that aren't 7-bit ASCII.
+    self.assertRaises(ValueError,
+                      setattr, proto, 'optional_string', str('a\x80a'))
+    # Assign a 'str' object which contains a UTF-8 encoded string.
+    self.assertRaises(ValueError,
+                      setattr, proto, 'optional_string', 'Тест')
+    # No exception thrown.
+    proto.optional_string = 'abc'
+
+  def testStringUTF8Serialization(self):
+    proto = unittest_mset_pb2.TestMessageSet()
+    extension_message = unittest_mset_pb2.TestMessageSetExtension2
+    extension = extension_message.message_set_extension
+
+    test_utf8 = u'Тест'
+    test_utf8_bytes = test_utf8.encode('utf-8')
+
+    # 'Test' in another language, using UTF-8 charset.
+    proto.Extensions[extension].str = test_utf8
+
+    # Serialize using the MessageSet wire format (this is specified in the
+    # .proto file).
+    serialized = proto.SerializeToString()
+
+    # Check byte size.
+    self.assertEqual(proto.ByteSize(), len(serialized))
+
+    raw = unittest_mset_pb2.RawMessageSet()
+    raw.MergeFromString(serialized)
+
+    message2 = unittest_mset_pb2.TestMessageSetExtension2()
+
+    self.assertEqual(1, len(raw.item))
+    # Check that the type_id is the same as the tag ID in the .proto file.
+    self.assertEqual(raw.item[0].type_id, 1547769)
+
+    # Check the actually bytes on the wire.
+    self.assertTrue(
+        raw.item[0].message.endswith(test_utf8_bytes))
+    message2.MergeFromString(raw.item[0].message)
+
+    self.assertEqual(type(message2.str), unicode)
+    self.assertEqual(message2.str, test_utf8)
+
+    # How about if the bytes on the wire aren't a valid UTF-8 encoded string.
+    bytes = raw.item[0].message.replace(
+        test_utf8_bytes, len(test_utf8_bytes) * '\xff')
+    self.assertRaises(UnicodeDecodeError, message2.MergeFromString, bytes)
+
+
+#  Since we had so many tests for protocol buffer equality, we broke these out
+#  into separate TestCase classes.
+
+
+class TestAllTypesEqualityTest(unittest.TestCase):
+
+  def setUp(self):
+    self.first_proto = unittest_pb2.TestAllTypes()
+    self.second_proto = unittest_pb2.TestAllTypes()
+
+  def testSelfEquality(self):
+    self.assertEqual(self.first_proto, self.first_proto)
+
+  def testEmptyProtosEqual(self):
+    self.assertEqual(self.first_proto, self.second_proto)
+
+
+class FullProtosEqualityTest(unittest.TestCase):
+
+  """Equality tests using completely-full protos as a starting point."""
+
+  def setUp(self):
+    self.first_proto = unittest_pb2.TestAllTypes()
+    self.second_proto = unittest_pb2.TestAllTypes()
+    test_util.SetAllFields(self.first_proto)
+    test_util.SetAllFields(self.second_proto)
+
+  def testNoneNotEqual(self):
+    self.assertNotEqual(self.first_proto, None)
+    self.assertNotEqual(None, self.second_proto)
+
+  def testNotEqualToOtherMessage(self):
+    third_proto = unittest_pb2.TestRequired()
+    self.assertNotEqual(self.first_proto, third_proto)
+    self.assertNotEqual(third_proto, self.second_proto)
+
+  def testAllFieldsFilledEquality(self):
+    self.assertEqual(self.first_proto, self.second_proto)
+
+  def testNonRepeatedScalar(self):
+    # Nonrepeated scalar field change should cause inequality.
+    self.first_proto.optional_int32 += 1
+    self.assertNotEqual(self.first_proto, self.second_proto)
+    # ...as should clearing a field.
+    self.first_proto.ClearField('optional_int32')
+    self.assertNotEqual(self.first_proto, self.second_proto)
+
+  def testNonRepeatedComposite(self):
+    # Change a nonrepeated composite field.
+    self.first_proto.optional_nested_message.bb += 1
+    self.assertNotEqual(self.first_proto, self.second_proto)
+    self.first_proto.optional_nested_message.bb -= 1
+    self.assertEqual(self.first_proto, self.second_proto)
+    # Clear a field in the nested message.
+    self.first_proto.optional_nested_message.ClearField('bb')
+    self.assertNotEqual(self.first_proto, self.second_proto)
+    self.first_proto.optional_nested_message.bb = (
+        self.second_proto.optional_nested_message.bb)
+    self.assertEqual(self.first_proto, self.second_proto)
+    # Remove the nested message entirely.
+    self.first_proto.ClearField('optional_nested_message')
+    self.assertNotEqual(self.first_proto, self.second_proto)
+
+  def testRepeatedScalar(self):
+    # Change a repeated scalar field.
+    self.first_proto.repeated_int32.append(5)
+    self.assertNotEqual(self.first_proto, self.second_proto)
+    self.first_proto.ClearField('repeated_int32')
+    self.assertNotEqual(self.first_proto, self.second_proto)
+
+  def testRepeatedComposite(self):
+    # Change value within a repeated composite field.
+    self.first_proto.repeated_nested_message[0].bb += 1
+    self.assertNotEqual(self.first_proto, self.second_proto)
+    self.first_proto.repeated_nested_message[0].bb -= 1
+    self.assertEqual(self.first_proto, self.second_proto)
+    # Add a value to a repeated composite field.
+    self.first_proto.repeated_nested_message.add()
+    self.assertNotEqual(self.first_proto, self.second_proto)
+    self.second_proto.repeated_nested_message.add()
+    self.assertEqual(self.first_proto, self.second_proto)
+
+  def testNonRepeatedScalarHasBits(self):
+    # Ensure that we test "has" bits as well as value for
+    # nonrepeated scalar field.
+    self.first_proto.ClearField('optional_int32')
+    self.second_proto.optional_int32 = 0
+    self.assertNotEqual(self.first_proto, self.second_proto)
+
+  def testNonRepeatedCompositeHasBits(self):
+    # Ensure that we test "has" bits as well as value for
+    # nonrepeated composite field.
+    self.first_proto.ClearField('optional_nested_message')
+    self.second_proto.optional_nested_message.ClearField('bb')
+    self.assertNotEqual(self.first_proto, self.second_proto)
+    # TODO(robinson): Replace next two lines with method
+    # to set the "has" bit without changing the value,
+    # if/when such a method exists.
+    self.first_proto.optional_nested_message.bb = 0
+    self.first_proto.optional_nested_message.ClearField('bb')
+    self.assertEqual(self.first_proto, self.second_proto)
+
+
+class ExtensionEqualityTest(unittest.TestCase):
+
+  def testExtensionEquality(self):
+    first_proto = unittest_pb2.TestAllExtensions()
+    second_proto = unittest_pb2.TestAllExtensions()
+    self.assertEqual(first_proto, second_proto)
+    test_util.SetAllExtensions(first_proto)
+    self.assertNotEqual(first_proto, second_proto)
+    test_util.SetAllExtensions(second_proto)
+    self.assertEqual(first_proto, second_proto)
+
+    # Ensure that we check value equality.
+    first_proto.Extensions[unittest_pb2.optional_int32_extension] += 1
+    self.assertNotEqual(first_proto, second_proto)
+    first_proto.Extensions[unittest_pb2.optional_int32_extension] -= 1
+    self.assertEqual(first_proto, second_proto)
+
+    # Ensure that we also look at "has" bits.
+    first_proto.ClearExtension(unittest_pb2.optional_int32_extension)
+    second_proto.Extensions[unittest_pb2.optional_int32_extension] = 0
+    self.assertNotEqual(first_proto, second_proto)
+    first_proto.Extensions[unittest_pb2.optional_int32_extension] = 0
+    self.assertEqual(first_proto, second_proto)
+
+    # Ensure that differences in cached values
+    # don't matter if "has" bits are both false.
+    first_proto = unittest_pb2.TestAllExtensions()
+    second_proto = unittest_pb2.TestAllExtensions()
+    self.assertEqual(
+        0, first_proto.Extensions[unittest_pb2.optional_int32_extension])
+    self.assertEqual(first_proto, second_proto)
+
+
+class MutualRecursionEqualityTest(unittest.TestCase):
+
+  def testEqualityWithMutualRecursion(self):
+    first_proto = unittest_pb2.TestMutualRecursionA()
+    second_proto = unittest_pb2.TestMutualRecursionA()
+    self.assertEqual(first_proto, second_proto)
+    first_proto.bb.a.bb.optional_int32 = 23
+    self.assertNotEqual(first_proto, second_proto)
+    second_proto.bb.a.bb.optional_int32 = 23
+    self.assertEqual(first_proto, second_proto)
+
+
+class ByteSizeTest(unittest.TestCase):
+
+  def setUp(self):
+    self.proto = unittest_pb2.TestAllTypes()
+    self.extended_proto = more_extensions_pb2.ExtendedMessage()
+    self.packed_proto = unittest_pb2.TestPackedTypes()
+    self.packed_extended_proto = unittest_pb2.TestPackedExtensions()
+
+  def Size(self):
+    return self.proto.ByteSize()
+
+  def testEmptyMessage(self):
+    self.assertEqual(0, self.proto.ByteSize())
+
+  def testVarints(self):
+    def Test(i, expected_varint_size):
+      self.proto.Clear()
+      self.proto.optional_int64 = i
+      # Add one to the varint size for the tag info
+      # for tag 1.
+      self.assertEqual(expected_varint_size + 1, self.Size())
+    Test(0, 1)
+    Test(1, 1)
+    for i, num_bytes in zip(range(7, 63, 7), range(1, 10000)):
+      Test((1 << i) - 1, num_bytes)
+    Test(-1, 10)
+    Test(-2, 10)
+    Test(-(1 << 63), 10)
+
+  def testStrings(self):
+    self.proto.optional_string = ''
+    # Need one byte for tag info (tag #14), and one byte for length.
+    self.assertEqual(2, self.Size())
+
+    self.proto.optional_string = 'abc'
+    # Need one byte for tag info (tag #14), and one byte for length.
+    self.assertEqual(2 + len(self.proto.optional_string), self.Size())
+
+    self.proto.optional_string = 'x' * 128
+    # Need one byte for tag info (tag #14), and TWO bytes for length.
+    self.assertEqual(3 + len(self.proto.optional_string), self.Size())
+
+  def testOtherNumerics(self):
+    self.proto.optional_fixed32 = 1234
+    # One byte for tag and 4 bytes for fixed32.
+    self.assertEqual(5, self.Size())
+    self.proto = unittest_pb2.TestAllTypes()
+
+    self.proto.optional_fixed64 = 1234
+    # One byte for tag and 8 bytes for fixed64.
+    self.assertEqual(9, self.Size())
+    self.proto = unittest_pb2.TestAllTypes()
+
+    self.proto.optional_float = 1.234
+    # One byte for tag and 4 bytes for float.
+    self.assertEqual(5, self.Size())
+    self.proto = unittest_pb2.TestAllTypes()
+
+    self.proto.optional_double = 1.234
+    # One byte for tag and 8 bytes for float.
+    self.assertEqual(9, self.Size())
+    self.proto = unittest_pb2.TestAllTypes()
+
+    self.proto.optional_sint32 = 64
+    # One byte for tag and 2 bytes for zig-zag-encoded 64.
+    self.assertEqual(3, self.Size())
+    self.proto = unittest_pb2.TestAllTypes()
+
+  def testComposites(self):
+    # 3 bytes.
+    self.proto.optional_nested_message.bb = (1 << 14)
+    # Plus one byte for bb tag.
+    # Plus 1 byte for optional_nested_message serialized size.
+    # Plus two bytes for optional_nested_message tag.
+    self.assertEqual(3 + 1 + 1 + 2, self.Size())
+
+  def testGroups(self):
+    # 4 bytes.
+    self.proto.optionalgroup.a = (1 << 21)
+    # Plus two bytes for |a| tag.
+    # Plus 2 * two bytes for START_GROUP and END_GROUP tags.
+    self.assertEqual(4 + 2 + 2*2, self.Size())
+
+  def testRepeatedScalars(self):
+    self.proto.repeated_int32.append(10)  # 1 byte.
+    self.proto.repeated_int32.append(128)  # 2 bytes.
+    # Also need 2 bytes for each entry for tag.
+    self.assertEqual(1 + 2 + 2*2, self.Size())
+
+  def testRepeatedScalarsExtend(self):
+    self.proto.repeated_int32.extend([10, 128])  # 3 bytes.
+    # Also need 2 bytes for each entry for tag.
+    self.assertEqual(1 + 2 + 2*2, self.Size())
+
+  def testRepeatedScalarsRemove(self):
+    self.proto.repeated_int32.append(10)  # 1 byte.
+    self.proto.repeated_int32.append(128)  # 2 bytes.
+    # Also need 2 bytes for each entry for tag.
+    self.assertEqual(1 + 2 + 2*2, self.Size())
+    self.proto.repeated_int32.remove(128)
+    self.assertEqual(1 + 2, self.Size())
+
+  def testRepeatedComposites(self):
+    # Empty message.  2 bytes tag plus 1 byte length.
+    foreign_message_0 = self.proto.repeated_nested_message.add()
+    # 2 bytes tag plus 1 byte length plus 1 byte bb tag 1 byte int.
+    foreign_message_1 = self.proto.repeated_nested_message.add()
+    foreign_message_1.bb = 7
+    self.assertEqual(2 + 1 + 2 + 1 + 1 + 1, self.Size())
+
+  def testRepeatedCompositesDelete(self):
+    # Empty message.  2 bytes tag plus 1 byte length.
+    foreign_message_0 = self.proto.repeated_nested_message.add()
+    # 2 bytes tag plus 1 byte length plus 1 byte bb tag 1 byte int.
+    foreign_message_1 = self.proto.repeated_nested_message.add()
+    foreign_message_1.bb = 9
+    self.assertEqual(2 + 1 + 2 + 1 + 1 + 1, self.Size())
+
+    # 2 bytes tag plus 1 byte length plus 1 byte bb tag 1 byte int.
+    del self.proto.repeated_nested_message[0]
+    self.assertEqual(2 + 1 + 1 + 1, self.Size())
+
+    # Now add a new message.
+    foreign_message_2 = self.proto.repeated_nested_message.add()
+    foreign_message_2.bb = 12
+
+    # 2 bytes tag plus 1 byte length plus 1 byte bb tag 1 byte int.
+    # 2 bytes tag plus 1 byte length plus 1 byte bb tag 1 byte int.
+    self.assertEqual(2 + 1 + 1 + 1 + 2 + 1 + 1 + 1, self.Size())
+
+    # 2 bytes tag plus 1 byte length plus 1 byte bb tag 1 byte int.
+    del self.proto.repeated_nested_message[1]
+    self.assertEqual(2 + 1 + 1 + 1, self.Size())
+
+    del self.proto.repeated_nested_message[0]
+    self.assertEqual(0, self.Size())
+
+  def testRepeatedGroups(self):
+    # 2-byte START_GROUP plus 2-byte END_GROUP.
+    group_0 = self.proto.repeatedgroup.add()
+    # 2-byte START_GROUP plus 2-byte |a| tag + 1-byte |a|
+    # plus 2-byte END_GROUP.
+    group_1 = self.proto.repeatedgroup.add()
+    group_1.a =  7
+    self.assertEqual(2 + 2 + 2 + 2 + 1 + 2, self.Size())
+
+  def testExtensions(self):
+    proto = unittest_pb2.TestAllExtensions()
+    self.assertEqual(0, proto.ByteSize())
+    extension = unittest_pb2.optional_int32_extension  # Field #1, 1 byte.
+    proto.Extensions[extension] = 23
+    # 1 byte for tag, 1 byte for value.
+    self.assertEqual(2, proto.ByteSize())
+
+  def testCacheInvalidationForNonrepeatedScalar(self):
+    # Test non-extension.
+    self.proto.optional_int32 = 1
+    self.assertEqual(2, self.proto.ByteSize())
+    self.proto.optional_int32 = 128
+    self.assertEqual(3, self.proto.ByteSize())
+    self.proto.ClearField('optional_int32')
+    self.assertEqual(0, self.proto.ByteSize())
+
+    # Test within extension.
+    extension = more_extensions_pb2.optional_int_extension
+    self.extended_proto.Extensions[extension] = 1
+    self.assertEqual(2, self.extended_proto.ByteSize())
+    self.extended_proto.Extensions[extension] = 128
+    self.assertEqual(3, self.extended_proto.ByteSize())
+    self.extended_proto.ClearExtension(extension)
+    self.assertEqual(0, self.extended_proto.ByteSize())
+
+  def testCacheInvalidationForRepeatedScalar(self):
+    # Test non-extension.
+    self.proto.repeated_int32.append(1)
+    self.assertEqual(3, self.proto.ByteSize())
+    self.proto.repeated_int32.append(1)
+    self.assertEqual(6, self.proto.ByteSize())
+    self.proto.repeated_int32[1] = 128
+    self.assertEqual(7, self.proto.ByteSize())
+    self.proto.ClearField('repeated_int32')
+    self.assertEqual(0, self.proto.ByteSize())
+
+    # Test within extension.
+    extension = more_extensions_pb2.repeated_int_extension
+    repeated = self.extended_proto.Extensions[extension]
+    repeated.append(1)
+    self.assertEqual(2, self.extended_proto.ByteSize())
+    repeated.append(1)
+    self.assertEqual(4, self.extended_proto.ByteSize())
+    repeated[1] = 128
+    self.assertEqual(5, self.extended_proto.ByteSize())
+    self.extended_proto.ClearExtension(extension)
+    self.assertEqual(0, self.extended_proto.ByteSize())
+
+  def testCacheInvalidationForNonrepeatedMessage(self):
+    # Test non-extension.
+    self.proto.optional_foreign_message.c = 1
+    self.assertEqual(5, self.proto.ByteSize())
+    self.proto.optional_foreign_message.c = 128
+    self.assertEqual(6, self.proto.ByteSize())
+    self.proto.optional_foreign_message.ClearField('c')
+    self.assertEqual(3, self.proto.ByteSize())
+    self.proto.ClearField('optional_foreign_message')
+    self.assertEqual(0, self.proto.ByteSize())
+    child = self.proto.optional_foreign_message
+    self.proto.ClearField('optional_foreign_message')
+    child.c = 128
+    self.assertEqual(0, self.proto.ByteSize())
+
+    # Test within extension.
+    extension = more_extensions_pb2.optional_message_extension
+    child = self.extended_proto.Extensions[extension]
+    self.assertEqual(0, self.extended_proto.ByteSize())
+    child.foreign_message_int = 1
+    self.assertEqual(4, self.extended_proto.ByteSize())
+    child.foreign_message_int = 128
+    self.assertEqual(5, self.extended_proto.ByteSize())
+    self.extended_proto.ClearExtension(extension)
+    self.assertEqual(0, self.extended_proto.ByteSize())
+
+  def testCacheInvalidationForRepeatedMessage(self):
+    # Test non-extension.
+    child0 = self.proto.repeated_foreign_message.add()
+    self.assertEqual(3, self.proto.ByteSize())
+    self.proto.repeated_foreign_message.add()
+    self.assertEqual(6, self.proto.ByteSize())
+    child0.c = 1
+    self.assertEqual(8, self.proto.ByteSize())
+    self.proto.ClearField('repeated_foreign_message')
+    self.assertEqual(0, self.proto.ByteSize())
+
+    # Test within extension.
+    extension = more_extensions_pb2.repeated_message_extension
+    child_list = self.extended_proto.Extensions[extension]
+    child0 = child_list.add()
+    self.assertEqual(2, self.extended_proto.ByteSize())
+    child_list.add()
+    self.assertEqual(4, self.extended_proto.ByteSize())
+    child0.foreign_message_int = 1
+    self.assertEqual(6, self.extended_proto.ByteSize())
+    child0.ClearField('foreign_message_int')
+    self.assertEqual(4, self.extended_proto.ByteSize())
+    self.extended_proto.ClearExtension(extension)
+    self.assertEqual(0, self.extended_proto.ByteSize())
+
+  def testPackedRepeatedScalars(self):
+    self.assertEqual(0, self.packed_proto.ByteSize())
+
+    self.packed_proto.packed_int32.append(10)   # 1 byte.
+    self.packed_proto.packed_int32.append(128)  # 2 bytes.
+    # The tag is 2 bytes (the field number is 90), and the varint
+    # storing the length is 1 byte.
+    int_size = 1 + 2 + 3
+    self.assertEqual(int_size, self.packed_proto.ByteSize())
+
+    self.packed_proto.packed_double.append(4.2)   # 8 bytes
+    self.packed_proto.packed_double.append(3.25)  # 8 bytes
+    # 2 more tag bytes, 1 more length byte.
+    double_size = 8 + 8 + 3
+    self.assertEqual(int_size+double_size, self.packed_proto.ByteSize())
+
+    self.packed_proto.ClearField('packed_int32')
+    self.assertEqual(double_size, self.packed_proto.ByteSize())
+
+  def testPackedExtensions(self):
+    self.assertEqual(0, self.packed_extended_proto.ByteSize())
+    extension = self.packed_extended_proto.Extensions[
+        unittest_pb2.packed_fixed32_extension]
+    extension.extend([1, 2, 3, 4])   # 16 bytes
+    # Tag is 3 bytes.
+    self.assertEqual(19, self.packed_extended_proto.ByteSize())
+
+
+# TODO(robinson): We need cross-language serialization consistency tests.
+# Issues to be sure to cover include:
+#   * Handling of unrecognized tags ("uninterpreted_bytes").
+#   * Handling of MessageSets.
+#   * Consistent ordering of tags in the wire format,
+#     including ordering between extensions and non-extension
+#     fields.
+#   * Consistent serialization of negative numbers, especially
+#     negative int32s.
+#   * Handling of empty submessages (with and without "has"
+#     bits set).
+
+class SerializationTest(unittest.TestCase):
+
+  def testSerializeEmtpyMessage(self):
+    first_proto = unittest_pb2.TestAllTypes()
+    second_proto = unittest_pb2.TestAllTypes()
+    serialized = first_proto.SerializeToString()
+    self.assertEqual(first_proto.ByteSize(), len(serialized))
+    second_proto.MergeFromString(serialized)
+    self.assertEqual(first_proto, second_proto)
+
+  def testSerializeAllFields(self):
+    first_proto = unittest_pb2.TestAllTypes()
+    second_proto = unittest_pb2.TestAllTypes()
+    test_util.SetAllFields(first_proto)
+    serialized = first_proto.SerializeToString()
+    self.assertEqual(first_proto.ByteSize(), len(serialized))
+    second_proto.MergeFromString(serialized)
+    self.assertEqual(first_proto, second_proto)
+
+  def testSerializeAllExtensions(self):
+    first_proto = unittest_pb2.TestAllExtensions()
+    second_proto = unittest_pb2.TestAllExtensions()
+    test_util.SetAllExtensions(first_proto)
+    serialized = first_proto.SerializeToString()
+    second_proto.MergeFromString(serialized)
+    self.assertEqual(first_proto, second_proto)
+
+  def testCanonicalSerializationOrder(self):
+    proto = more_messages_pb2.OutOfOrderFields()
+    # These are also their tag numbers.  Even though we're setting these in
+    # reverse-tag order AND they're listed in reverse tag-order in the .proto
+    # file, they should nonetheless be serialized in tag order.
+    proto.optional_sint32 = 5
+    proto.Extensions[more_messages_pb2.optional_uint64] = 4
+    proto.optional_uint32 = 3
+    proto.Extensions[more_messages_pb2.optional_int64] = 2
+    proto.optional_int32 = 1
+    serialized = proto.SerializeToString()
+    self.assertEqual(proto.ByteSize(), len(serialized))
+    d = decoder.Decoder(serialized)
+    ReadTag = d.ReadFieldNumberAndWireType
+    self.assertEqual((1, wire_format.WIRETYPE_VARINT), ReadTag())
+    self.assertEqual(1, d.ReadInt32())
+    self.assertEqual((2, wire_format.WIRETYPE_VARINT), ReadTag())
+    self.assertEqual(2, d.ReadInt64())
+    self.assertEqual((3, wire_format.WIRETYPE_VARINT), ReadTag())
+    self.assertEqual(3, d.ReadUInt32())
+    self.assertEqual((4, wire_format.WIRETYPE_VARINT), ReadTag())
+    self.assertEqual(4, d.ReadUInt64())
+    self.assertEqual((5, wire_format.WIRETYPE_VARINT), ReadTag())
+    self.assertEqual(5, d.ReadSInt32())
+
+  def testCanonicalSerializationOrderSameAsCpp(self):
+    # Copy of the same test we use for C++.
+    proto = unittest_pb2.TestFieldOrderings()
+    test_util.SetAllFieldsAndExtensions(proto)
+    serialized = proto.SerializeToString()
+    test_util.ExpectAllFieldsAndExtensionsInOrder(serialized)
+
+  def testMergeFromStringWhenFieldsAlreadySet(self):
+    first_proto = unittest_pb2.TestAllTypes()
+    first_proto.repeated_string.append('foobar')
+    first_proto.optional_int32 = 23
+    first_proto.optional_nested_message.bb = 42
+    serialized = first_proto.SerializeToString()
+
+    second_proto = unittest_pb2.TestAllTypes()
+    second_proto.repeated_string.append('baz')
+    second_proto.optional_int32 = 100
+    second_proto.optional_nested_message.bb = 999
+
+    second_proto.MergeFromString(serialized)
+    # Ensure that we append to repeated fields.
+    self.assertEqual(['baz', 'foobar'], list(second_proto.repeated_string))
+    # Ensure that we overwrite nonrepeatd scalars.
+    self.assertEqual(23, second_proto.optional_int32)
+    # Ensure that we recursively call MergeFromString() on
+    # submessages.
+    self.assertEqual(42, second_proto.optional_nested_message.bb)
+
+  def testMessageSetWireFormat(self):
+    proto = unittest_mset_pb2.TestMessageSet()
+    extension_message1 = unittest_mset_pb2.TestMessageSetExtension1
+    extension_message2 = unittest_mset_pb2.TestMessageSetExtension2
+    extension1 = extension_message1.message_set_extension
+    extension2 = extension_message2.message_set_extension
+    proto.Extensions[extension1].i = 123
+    proto.Extensions[extension2].str = 'foo'
+
+    # Serialize using the MessageSet wire format (this is specified in the
+    # .proto file).
+    serialized = proto.SerializeToString()
+
+    raw = unittest_mset_pb2.RawMessageSet()
+    self.assertEqual(False,
+                     raw.DESCRIPTOR.GetOptions().message_set_wire_format)
+    raw.MergeFromString(serialized)
+    self.assertEqual(2, len(raw.item))
+
+    message1 = unittest_mset_pb2.TestMessageSetExtension1()
+    message1.MergeFromString(raw.item[0].message)
+    self.assertEqual(123, message1.i)
+
+    message2 = unittest_mset_pb2.TestMessageSetExtension2()
+    message2.MergeFromString(raw.item[1].message)
+    self.assertEqual('foo', message2.str)
+
+    # Deserialize using the MessageSet wire format.
+    proto2 = unittest_mset_pb2.TestMessageSet()
+    proto2.MergeFromString(serialized)
+    self.assertEqual(123, proto2.Extensions[extension1].i)
+    self.assertEqual('foo', proto2.Extensions[extension2].str)
+
+    # Check byte size.
+    self.assertEqual(proto2.ByteSize(), len(serialized))
+    self.assertEqual(proto.ByteSize(), len(serialized))
+
+  def testMessageSetWireFormatUnknownExtension(self):
+    # Create a message using the message set wire format with an unknown
+    # message.
+    raw = unittest_mset_pb2.RawMessageSet()
+
+    # Add an item.
+    item = raw.item.add()
+    item.type_id = 1545008
+    extension_message1 = unittest_mset_pb2.TestMessageSetExtension1
+    message1 = unittest_mset_pb2.TestMessageSetExtension1()
+    message1.i = 12345
+    item.message = message1.SerializeToString()
+
+    # Add a second, unknown extension.
+    item = raw.item.add()
+    item.type_id = 1545009
+    extension_message1 = unittest_mset_pb2.TestMessageSetExtension1
+    message1 = unittest_mset_pb2.TestMessageSetExtension1()
+    message1.i = 12346
+    item.message = message1.SerializeToString()
+
+    # Add another unknown extension.
+    item = raw.item.add()
+    item.type_id = 1545010
+    message1 = unittest_mset_pb2.TestMessageSetExtension2()
+    message1.str = 'foo'
+    item.message = message1.SerializeToString()
+
+    serialized = raw.SerializeToString()
+
+    # Parse message using the message set wire format.
+    proto = unittest_mset_pb2.TestMessageSet()
+    proto.MergeFromString(serialized)
+
+    # Check that the message parsed well.
+    extension_message1 = unittest_mset_pb2.TestMessageSetExtension1
+    extension1 = extension_message1.message_set_extension
+    self.assertEquals(12345, proto.Extensions[extension1].i)
+
+  def testUnknownFields(self):
+    proto = unittest_pb2.TestAllTypes()
+    test_util.SetAllFields(proto)
+
+    serialized = proto.SerializeToString()
+
+    # The empty message should be parsable with all of the fields
+    # unknown.
+    proto2 = unittest_pb2.TestEmptyMessage()
+
+    # Parsing this message should succeed.
+    proto2.MergeFromString(serialized)
+
+    # Now test with a int64 field set.
+    proto = unittest_pb2.TestAllTypes()
+    proto.optional_int64 = 0x0fffffffffffffff
+    serialized = proto.SerializeToString()
+    # The empty message should be parsable with all of the fields
+    # unknown.
+    proto2 = unittest_pb2.TestEmptyMessage()
+    # Parsing this message should succeed.
+    proto2.MergeFromString(serialized)
+
+  def _CheckRaises(self, exc_class, callable_obj, exception):
+    """This method checks if the excpetion type and message are as expected."""
+    try:
+      callable_obj()
+    except exc_class, ex:
+      # Check if the exception message is the right one.
+      self.assertEqual(exception, str(ex))
+      return
+    else:
+      raise self.failureException('%s not raised' % str(exc_class))
+
+  def testSerializeUninitialized(self):
+    proto = unittest_pb2.TestRequired()
+    self._CheckRaises(
+        message.EncodeError,
+        proto.SerializeToString,
+        'Required field protobuf_unittest.TestRequired.a is not set.')
+    # Shouldn't raise exceptions.
+    partial = proto.SerializePartialToString()
+
+    proto.a = 1
+    self._CheckRaises(
+        message.EncodeError,
+        proto.SerializeToString,
+        'Required field protobuf_unittest.TestRequired.b is not set.')
+    # Shouldn't raise exceptions.
+    partial = proto.SerializePartialToString()
+
+    proto.b = 2
+    self._CheckRaises(
+        message.EncodeError,
+        proto.SerializeToString,
+        'Required field protobuf_unittest.TestRequired.c is not set.')
+    # Shouldn't raise exceptions.
+    partial = proto.SerializePartialToString()
+
+    proto.c = 3
+    serialized = proto.SerializeToString()
+    # Shouldn't raise exceptions.
+    partial = proto.SerializePartialToString()
+
+    proto2 = unittest_pb2.TestRequired()
+    proto2.MergeFromString(serialized)
+    self.assertEqual(1, proto2.a)
+    self.assertEqual(2, proto2.b)
+    self.assertEqual(3, proto2.c)
+    proto2.ParseFromString(partial)
+    self.assertEqual(1, proto2.a)
+    self.assertEqual(2, proto2.b)
+    self.assertEqual(3, proto2.c)
+
+  def testSerializeAllPackedFields(self):
+    first_proto = unittest_pb2.TestPackedTypes()
+    second_proto = unittest_pb2.TestPackedTypes()
+    test_util.SetAllPackedFields(first_proto)
+    serialized = first_proto.SerializeToString()
+    self.assertEqual(first_proto.ByteSize(), len(serialized))
+    bytes_read = second_proto.MergeFromString(serialized)
+    self.assertEqual(second_proto.ByteSize(), bytes_read)
+    self.assertEqual(first_proto, second_proto)
+
+  def testSerializeAllPackedExtensions(self):
+    first_proto = unittest_pb2.TestPackedExtensions()
+    second_proto = unittest_pb2.TestPackedExtensions()
+    test_util.SetAllPackedExtensions(first_proto)
+    serialized = first_proto.SerializeToString()
+    bytes_read = second_proto.MergeFromString(serialized)
+    self.assertEqual(second_proto.ByteSize(), bytes_read)
+    self.assertEqual(first_proto, second_proto)
+
+  def testMergePackedFromStringWhenSomeFieldsAlreadySet(self):
+    first_proto = unittest_pb2.TestPackedTypes()
+    first_proto.packed_int32.extend([1, 2])
+    first_proto.packed_double.append(3.0)
+    serialized = first_proto.SerializeToString()
+
+    second_proto = unittest_pb2.TestPackedTypes()
+    second_proto.packed_int32.append(3)
+    second_proto.packed_double.extend([1.0, 2.0])
+    second_proto.packed_sint32.append(4)
+
+    second_proto.MergeFromString(serialized)
+    self.assertEqual([3, 1, 2], second_proto.packed_int32)
+    self.assertEqual([1.0, 2.0, 3.0], second_proto.packed_double)
+    self.assertEqual([4], second_proto.packed_sint32)
+
+  def testPackedFieldsWireFormat(self):
+    proto = unittest_pb2.TestPackedTypes()
+    proto.packed_int32.extend([1, 2, 150, 3])  # 1 + 1 + 2 + 1 bytes
+    proto.packed_double.extend([1.0, 1000.0])  # 8 + 8 bytes
+    proto.packed_float.append(2.0)             # 4 bytes, will be before double
+    serialized = proto.SerializeToString()
+    self.assertEqual(proto.ByteSize(), len(serialized))
+    d = decoder.Decoder(serialized)
+    ReadTag = d.ReadFieldNumberAndWireType
+    self.assertEqual((90, wire_format.WIRETYPE_LENGTH_DELIMITED), ReadTag())
+    self.assertEqual(1+1+1+2, d.ReadInt32())
+    self.assertEqual(1, d.ReadInt32())
+    self.assertEqual(2, d.ReadInt32())
+    self.assertEqual(150, d.ReadInt32())
+    self.assertEqual(3, d.ReadInt32())
+    self.assertEqual((100, wire_format.WIRETYPE_LENGTH_DELIMITED), ReadTag())
+    self.assertEqual(4, d.ReadInt32())
+    self.assertEqual(2.0, d.ReadFloat())
+    self.assertEqual((101, wire_format.WIRETYPE_LENGTH_DELIMITED), ReadTag())
+    self.assertEqual(8+8, d.ReadInt32())
+    self.assertEqual(1.0, d.ReadDouble())
+    self.assertEqual(1000.0, d.ReadDouble())
+    self.assertTrue(d.EndOfStream())
+
+  def testFieldNumbers(self):
+    proto = unittest_pb2.TestAllTypes()
+    self.assertEqual(unittest_pb2.TestAllTypes.NestedMessage.BB_FIELD_NUMBER, 1)
+    self.assertEqual(unittest_pb2.TestAllTypes.OPTIONAL_INT32_FIELD_NUMBER, 1)
+    self.assertEqual(unittest_pb2.TestAllTypes.OPTIONALGROUP_FIELD_NUMBER, 16)
+    self.assertEqual(
+      unittest_pb2.TestAllTypes.OPTIONAL_NESTED_MESSAGE_FIELD_NUMBER, 18)
+    self.assertEqual(
+      unittest_pb2.TestAllTypes.OPTIONAL_NESTED_ENUM_FIELD_NUMBER, 21)
+    self.assertEqual(unittest_pb2.TestAllTypes.REPEATED_INT32_FIELD_NUMBER, 31)
+    self.assertEqual(unittest_pb2.TestAllTypes.REPEATEDGROUP_FIELD_NUMBER, 46)
+    self.assertEqual(
+      unittest_pb2.TestAllTypes.REPEATED_NESTED_MESSAGE_FIELD_NUMBER, 48)
+    self.assertEqual(
+      unittest_pb2.TestAllTypes.REPEATED_NESTED_ENUM_FIELD_NUMBER, 51)
+
+  def testExtensionFieldNumbers(self):
+    self.assertEqual(unittest_pb2.TestRequired.single.number, 1000)
+    self.assertEqual(unittest_pb2.TestRequired.SINGLE_FIELD_NUMBER, 1000)
+    self.assertEqual(unittest_pb2.TestRequired.multi.number, 1001)
+    self.assertEqual(unittest_pb2.TestRequired.MULTI_FIELD_NUMBER, 1001)
+    self.assertEqual(unittest_pb2.optional_int32_extension.number, 1)
+    self.assertEqual(unittest_pb2.OPTIONAL_INT32_EXTENSION_FIELD_NUMBER, 1)
+    self.assertEqual(unittest_pb2.optionalgroup_extension.number, 16)
+    self.assertEqual(unittest_pb2.OPTIONALGROUP_EXTENSION_FIELD_NUMBER, 16)
+    self.assertEqual(unittest_pb2.optional_nested_message_extension.number, 18)
+    self.assertEqual(
+      unittest_pb2.OPTIONAL_NESTED_MESSAGE_EXTENSION_FIELD_NUMBER, 18)
+    self.assertEqual(unittest_pb2.optional_nested_enum_extension.number, 21)
+    self.assertEqual(unittest_pb2.OPTIONAL_NESTED_ENUM_EXTENSION_FIELD_NUMBER,
+      21)
+    self.assertEqual(unittest_pb2.repeated_int32_extension.number, 31)
+    self.assertEqual(unittest_pb2.REPEATED_INT32_EXTENSION_FIELD_NUMBER, 31)
+    self.assertEqual(unittest_pb2.repeatedgroup_extension.number, 46)
+    self.assertEqual(unittest_pb2.REPEATEDGROUP_EXTENSION_FIELD_NUMBER, 46)
+    self.assertEqual(unittest_pb2.repeated_nested_message_extension.number, 48)
+    self.assertEqual(
+      unittest_pb2.REPEATED_NESTED_MESSAGE_EXTENSION_FIELD_NUMBER, 48)
+    self.assertEqual(unittest_pb2.repeated_nested_enum_extension.number, 51)
+    self.assertEqual(unittest_pb2.REPEATED_NESTED_ENUM_EXTENSION_FIELD_NUMBER,
+      51)
+
+  def testInitKwargs(self):
+    proto = unittest_pb2.TestAllTypes(
+        optional_int32=1,
+        optional_string='foo',
+        optional_bool=True,
+        optional_bytes='bar',
+        optional_nested_message=unittest_pb2.TestAllTypes.NestedMessage(bb=1),
+        optional_foreign_message=unittest_pb2.ForeignMessage(c=1),
+        optional_nested_enum=unittest_pb2.TestAllTypes.FOO,
+        optional_foreign_enum=unittest_pb2.FOREIGN_FOO,
+        repeated_int32=[1, 2, 3])
+    self.assertTrue(proto.IsInitialized())
+    self.assertTrue(proto.HasField('optional_int32'))
+    self.assertTrue(proto.HasField('optional_string'))
+    self.assertTrue(proto.HasField('optional_bool'))
+    self.assertTrue(proto.HasField('optional_bytes'))
+    self.assertTrue(proto.HasField('optional_nested_message'))
+    self.assertTrue(proto.HasField('optional_foreign_message'))
+    self.assertTrue(proto.HasField('optional_nested_enum'))
+    self.assertTrue(proto.HasField('optional_foreign_enum'))
+    self.assertEqual(1, proto.optional_int32)
+    self.assertEqual('foo', proto.optional_string)
+    self.assertEqual(True, proto.optional_bool)
+    self.assertEqual('bar', proto.optional_bytes)
+    self.assertEqual(1, proto.optional_nested_message.bb)
+    self.assertEqual(1, proto.optional_foreign_message.c)
+    self.assertEqual(unittest_pb2.TestAllTypes.FOO,
+                     proto.optional_nested_enum)
+    self.assertEqual(unittest_pb2.FOREIGN_FOO, proto.optional_foreign_enum)
+    self.assertEqual([1, 2, 3], proto.repeated_int32)
+
+  def testInitArgsUnknownFieldName(self):
+    def InitalizeEmptyMessageWithExtraKeywordArg():
+      unused_proto = unittest_pb2.TestEmptyMessage(unknown='unknown')
+    self._CheckRaises(ValueError,
+                      InitalizeEmptyMessageWithExtraKeywordArg,
+                      'Protocol message has no "unknown" field.')
+
+  def testInitRequiredKwargs(self):
+    proto = unittest_pb2.TestRequired(a=1, b=1, c=1)
+    self.assertTrue(proto.IsInitialized())
+    self.assertTrue(proto.HasField('a'))
+    self.assertTrue(proto.HasField('b'))
+    self.assertTrue(proto.HasField('c'))
+    self.assertTrue(not proto.HasField('dummy2'))
+    self.assertEqual(1, proto.a)
+    self.assertEqual(1, proto.b)
+    self.assertEqual(1, proto.c)
+
+  def testInitRequiredForeignKwargs(self):
+    proto = unittest_pb2.TestRequiredForeign(
+        optional_message=unittest_pb2.TestRequired(a=1, b=1, c=1))
+    self.assertTrue(proto.IsInitialized())
+    self.assertTrue(proto.HasField('optional_message'))
+    self.assertTrue(proto.optional_message.IsInitialized())
+    self.assertTrue(proto.optional_message.HasField('a'))
+    self.assertTrue(proto.optional_message.HasField('b'))
+    self.assertTrue(proto.optional_message.HasField('c'))
+    self.assertTrue(not proto.optional_message.HasField('dummy2'))
+    self.assertEqual(unittest_pb2.TestRequired(a=1, b=1, c=1),
+                     proto.optional_message)
+    self.assertEqual(1, proto.optional_message.a)
+    self.assertEqual(1, proto.optional_message.b)
+    self.assertEqual(1, proto.optional_message.c)
+
+  def testInitRepeatedKwargs(self):
+    proto = unittest_pb2.TestAllTypes(repeated_int32=[1, 2, 3])
+    self.assertTrue(proto.IsInitialized())
+    self.assertEqual(1, proto.repeated_int32[0])
+    self.assertEqual(2, proto.repeated_int32[1])
+    self.assertEqual(3, proto.repeated_int32[2])
+
+
+class OptionsTest(unittest.TestCase):
+
+  def testMessageOptions(self):
+    proto = unittest_mset_pb2.TestMessageSet()
+    self.assertEqual(True,
+                     proto.DESCRIPTOR.GetOptions().message_set_wire_format)
+    proto = unittest_pb2.TestAllTypes()
+    self.assertEqual(False,
+                     proto.DESCRIPTOR.GetOptions().message_set_wire_format)
+
+  def testPackedOptions(self):
+    proto = unittest_pb2.TestAllTypes()
+    proto.optional_int32 = 1
+    proto.optional_double = 3.0
+    for field_descriptor, _ in proto.ListFields():
+      self.assertEqual(False, field_descriptor.GetOptions().packed)
+
+    proto = unittest_pb2.TestPackedTypes()
+    proto.packed_int32.append(1)
+    proto.packed_double.append(3.0)
+    for field_descriptor, _ in proto.ListFields():
+      self.assertEqual(True, field_descriptor.GetOptions().packed)
+      self.assertEqual(reflection._FieldDescriptor.LABEL_REPEATED,
+                       field_descriptor.label)
+
+
+class UtilityTest(unittest.TestCase):
+
+  def testImergeSorted(self):
+    ImergeSorted = reflection._ImergeSorted
+    # Various types of emptiness.
+    self.assertEqual([], list(ImergeSorted()))
+    self.assertEqual([], list(ImergeSorted([])))
+    self.assertEqual([], list(ImergeSorted([], [])))
+
+    # One nonempty list.
+    self.assertEqual([1, 2, 3], list(ImergeSorted([1, 2, 3])))
+    self.assertEqual([1, 2, 3], list(ImergeSorted([1, 2, 3], [])))
+    self.assertEqual([1, 2, 3], list(ImergeSorted([], [1, 2, 3])))
+
+    # Merging some nonempty lists together.
+    self.assertEqual([1, 2, 3], list(ImergeSorted([1, 3], [2])))
+    self.assertEqual([1, 2, 3], list(ImergeSorted([1], [3], [2])))
+    self.assertEqual([1, 2, 3], list(ImergeSorted([1], [3], [2], [])))
+
+    # Elements repeated across component iterators.
+    self.assertEqual([1, 2, 2, 3, 3],
+                     list(ImergeSorted([1, 2], [3], [2, 3])))
+
+    # Elements repeated within an iterator.
+    self.assertEqual([1, 2, 2, 3, 3],
+                     list(ImergeSorted([1, 2, 2], [3], [3])))
+
+
+if __name__ == '__main__':
+  unittest.main()
diff --git a/python/google/protobuf/internal/service_reflection_test.py b/python/google/protobuf/internal/service_reflection_test.py
new file mode 100755
index 0000000..e04f825
--- /dev/null
+++ b/python/google/protobuf/internal/service_reflection_test.py
@@ -0,0 +1,136 @@
+#! /usr/bin/python
+#
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Tests for google.protobuf.internal.service_reflection."""
+
+__author__ = 'petar@google.com (Petar Petrov)'
+
+import unittest
+from google.protobuf import unittest_pb2
+from google.protobuf import service_reflection
+from google.protobuf import service
+
+
+class FooUnitTest(unittest.TestCase):
+
+  def testService(self):
+    class MockRpcChannel(service.RpcChannel):
+      def CallMethod(self, method, controller, request, response, callback):
+        self.method = method
+        self.controller = controller
+        self.request = request
+        callback(response)
+
+    class MockRpcController(service.RpcController):
+      def SetFailed(self, msg):
+        self.failure_message = msg
+
+    self.callback_response = None
+
+    class MyService(unittest_pb2.TestService):
+      pass
+
+    self.callback_response = None
+
+    def MyCallback(response):
+      self.callback_response = response
+
+    rpc_controller = MockRpcController()
+    channel = MockRpcChannel()
+    srvc = MyService()
+    srvc.Foo(rpc_controller, unittest_pb2.FooRequest(), MyCallback)
+    self.assertEqual('Method Foo not implemented.',
+                     rpc_controller.failure_message)
+    self.assertEqual(None, self.callback_response)
+
+    rpc_controller.failure_message = None
+
+    service_descriptor = unittest_pb2.TestService.GetDescriptor()
+    srvc.CallMethod(service_descriptor.methods[1], rpc_controller,
+                    unittest_pb2.BarRequest(), MyCallback)
+    self.assertEqual('Method Bar not implemented.',
+                     rpc_controller.failure_message)
+    self.assertEqual(None, self.callback_response)
+    
+    class MyServiceImpl(unittest_pb2.TestService):
+      def Foo(self, rpc_controller, request, done):
+        self.foo_called = True
+      def Bar(self, rpc_controller, request, done):
+        self.bar_called = True
+
+    srvc = MyServiceImpl()
+    rpc_controller.failure_message = None
+    srvc.Foo(rpc_controller, unittest_pb2.FooRequest(), MyCallback)
+    self.assertEqual(None, rpc_controller.failure_message)
+    self.assertEqual(True, srvc.foo_called)
+
+    rpc_controller.failure_message = None
+    srvc.CallMethod(service_descriptor.methods[1], rpc_controller,
+                    unittest_pb2.BarRequest(), MyCallback)
+    self.assertEqual(None, rpc_controller.failure_message)
+    self.assertEqual(True, srvc.bar_called)
+
+  def testServiceStub(self):
+    class MockRpcChannel(service.RpcChannel):
+      def CallMethod(self, method, controller, request,
+                     response_class, callback):
+        self.method = method
+        self.controller = controller
+        self.request = request
+        callback(response_class())
+
+    self.callback_response = None
+
+    def MyCallback(response):
+      self.callback_response = response
+
+    channel = MockRpcChannel()
+    stub = unittest_pb2.TestService_Stub(channel)
+    rpc_controller = 'controller'
+    request = 'request'
+
+    # GetDescriptor now static, still works as instance method for compatability
+    self.assertEqual(unittest_pb2.TestService_Stub.GetDescriptor(),
+                     stub.GetDescriptor())
+
+    # Invoke method.
+    stub.Foo(rpc_controller, request, MyCallback)
+
+    self.assertTrue(isinstance(self.callback_response,
+                               unittest_pb2.FooResponse))
+    self.assertEqual(request, channel.request)
+    self.assertEqual(rpc_controller, channel.controller)
+    self.assertEqual(stub.GetDescriptor().methods[0], channel.method)
+
+
+if __name__ == '__main__':
+  unittest.main()
diff --git a/python/google/protobuf/internal/test_util.py b/python/google/protobuf/internal/test_util.py
new file mode 100755
index 0000000..1a0da55
--- /dev/null
+++ b/python/google/protobuf/internal/test_util.py
@@ -0,0 +1,612 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Utilities for Python proto2 tests.
+
+This is intentionally modeled on C++ code in
+//net/proto2/internal/test_util.*.
+"""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+import os.path
+
+import unittest
+from google.protobuf import unittest_import_pb2
+from google.protobuf import unittest_pb2
+
+
+def SetAllFields(message):
+  """Sets every field in the message to a unique value.
+
+  Args:
+    message: A unittest_pb2.TestAllTypes instance.
+  """
+
+  #
+  # Optional fields.
+  #
+
+  message.optional_int32    = 101
+  message.optional_int64    = 102
+  message.optional_uint32   = 103
+  message.optional_uint64   = 104
+  message.optional_sint32   = 105
+  message.optional_sint64   = 106
+  message.optional_fixed32  = 107
+  message.optional_fixed64  = 108
+  message.optional_sfixed32 = 109
+  message.optional_sfixed64 = 110
+  message.optional_float    = 111
+  message.optional_double   = 112
+  message.optional_bool     = True
+  # TODO(robinson): Firmly spec out and test how
+  # protos interact with unicode.  One specific example:
+  # what happens if we change the literal below to
+  # u'115'?  What *should* happen?  Still some discussion
+  # to finish with Kenton about bytes vs. strings
+  # and forcing everything to be utf8. :-/
+  message.optional_string   = '115'
+  message.optional_bytes    = '116'
+
+  message.optionalgroup.a = 117
+  message.optional_nested_message.bb = 118
+  message.optional_foreign_message.c = 119
+  message.optional_import_message.d = 120
+
+  message.optional_nested_enum = unittest_pb2.TestAllTypes.BAZ
+  message.optional_foreign_enum = unittest_pb2.FOREIGN_BAZ
+  message.optional_import_enum = unittest_import_pb2.IMPORT_BAZ
+
+  message.optional_string_piece = '124'
+  message.optional_cord = '125'
+
+  #
+  # Repeated fields.
+  #
+
+  message.repeated_int32.append(201)
+  message.repeated_int64.append(202)
+  message.repeated_uint32.append(203)
+  message.repeated_uint64.append(204)
+  message.repeated_sint32.append(205)
+  message.repeated_sint64.append(206)
+  message.repeated_fixed32.append(207)
+  message.repeated_fixed64.append(208)
+  message.repeated_sfixed32.append(209)
+  message.repeated_sfixed64.append(210)
+  message.repeated_float.append(211)
+  message.repeated_double.append(212)
+  message.repeated_bool.append(True)
+  message.repeated_string.append('215')
+  message.repeated_bytes.append('216')
+
+  message.repeatedgroup.add().a = 217
+  message.repeated_nested_message.add().bb = 218
+  message.repeated_foreign_message.add().c = 219
+  message.repeated_import_message.add().d = 220
+
+  message.repeated_nested_enum.append(unittest_pb2.TestAllTypes.BAR)
+  message.repeated_foreign_enum.append(unittest_pb2.FOREIGN_BAR)
+  message.repeated_import_enum.append(unittest_import_pb2.IMPORT_BAR)
+
+  message.repeated_string_piece.append('224')
+  message.repeated_cord.append('225')
+
+  # Add a second one of each field.
+  message.repeated_int32.append(301)
+  message.repeated_int64.append(302)
+  message.repeated_uint32.append(303)
+  message.repeated_uint64.append(304)
+  message.repeated_sint32.append(305)
+  message.repeated_sint64.append(306)
+  message.repeated_fixed32.append(307)
+  message.repeated_fixed64.append(308)
+  message.repeated_sfixed32.append(309)
+  message.repeated_sfixed64.append(310)
+  message.repeated_float.append(311)
+  message.repeated_double.append(312)
+  message.repeated_bool.append(False)
+  message.repeated_string.append('315')
+  message.repeated_bytes.append('316')
+
+  message.repeatedgroup.add().a = 317
+  message.repeated_nested_message.add().bb = 318
+  message.repeated_foreign_message.add().c = 319
+  message.repeated_import_message.add().d = 320
+
+  message.repeated_nested_enum.append(unittest_pb2.TestAllTypes.BAZ)
+  message.repeated_foreign_enum.append(unittest_pb2.FOREIGN_BAZ)
+  message.repeated_import_enum.append(unittest_import_pb2.IMPORT_BAZ)
+
+  message.repeated_string_piece.append('324')
+  message.repeated_cord.append('325')
+
+  #
+  # Fields that have defaults.
+  #
+
+  message.default_int32 = 401
+  message.default_int64 = 402
+  message.default_uint32 = 403
+  message.default_uint64 = 404
+  message.default_sint32 = 405
+  message.default_sint64 = 406
+  message.default_fixed32 = 407
+  message.default_fixed64 = 408
+  message.default_sfixed32 = 409
+  message.default_sfixed64 = 410
+  message.default_float = 411
+  message.default_double = 412
+  message.default_bool = False
+  message.default_string = '415'
+  message.default_bytes = '416'
+
+  message.default_nested_enum = unittest_pb2.TestAllTypes.FOO
+  message.default_foreign_enum = unittest_pb2.FOREIGN_FOO
+  message.default_import_enum = unittest_import_pb2.IMPORT_FOO
+
+  message.default_string_piece = '424'
+  message.default_cord = '425'
+
+
+def SetAllExtensions(message):
+  """Sets every extension in the message to a unique value.
+
+  Args:
+    message: A unittest_pb2.TestAllExtensions instance.
+  """
+
+  extensions = message.Extensions
+  pb2 = unittest_pb2
+  import_pb2 = unittest_import_pb2
+
+  #
+  # Optional fields.
+  #
+
+  extensions[pb2.optional_int32_extension] = 101
+  extensions[pb2.optional_int64_extension] = 102
+  extensions[pb2.optional_uint32_extension] = 103
+  extensions[pb2.optional_uint64_extension] = 104
+  extensions[pb2.optional_sint32_extension] = 105
+  extensions[pb2.optional_sint64_extension] = 106
+  extensions[pb2.optional_fixed32_extension] = 107
+  extensions[pb2.optional_fixed64_extension] = 108
+  extensions[pb2.optional_sfixed32_extension] = 109
+  extensions[pb2.optional_sfixed64_extension] = 110
+  extensions[pb2.optional_float_extension] = 111
+  extensions[pb2.optional_double_extension] = 112
+  extensions[pb2.optional_bool_extension] = True
+  extensions[pb2.optional_string_extension] = '115'
+  extensions[pb2.optional_bytes_extension] = '116'
+
+  extensions[pb2.optionalgroup_extension].a = 117
+  extensions[pb2.optional_nested_message_extension].bb = 118
+  extensions[pb2.optional_foreign_message_extension].c = 119
+  extensions[pb2.optional_import_message_extension].d = 120
+
+  extensions[pb2.optional_nested_enum_extension] = pb2.TestAllTypes.BAZ
+  extensions[pb2.optional_nested_enum_extension] = pb2.TestAllTypes.BAZ
+  extensions[pb2.optional_foreign_enum_extension] = pb2.FOREIGN_BAZ
+  extensions[pb2.optional_import_enum_extension] = import_pb2.IMPORT_BAZ
+
+  extensions[pb2.optional_string_piece_extension] = '124'
+  extensions[pb2.optional_cord_extension] = '125'
+
+  #
+  # Repeated fields.
+  #
+
+  extensions[pb2.repeated_int32_extension].append(201)
+  extensions[pb2.repeated_int64_extension].append(202)
+  extensions[pb2.repeated_uint32_extension].append(203)
+  extensions[pb2.repeated_uint64_extension].append(204)
+  extensions[pb2.repeated_sint32_extension].append(205)
+  extensions[pb2.repeated_sint64_extension].append(206)
+  extensions[pb2.repeated_fixed32_extension].append(207)
+  extensions[pb2.repeated_fixed64_extension].append(208)
+  extensions[pb2.repeated_sfixed32_extension].append(209)
+  extensions[pb2.repeated_sfixed64_extension].append(210)
+  extensions[pb2.repeated_float_extension].append(211)
+  extensions[pb2.repeated_double_extension].append(212)
+  extensions[pb2.repeated_bool_extension].append(True)
+  extensions[pb2.repeated_string_extension].append('215')
+  extensions[pb2.repeated_bytes_extension].append('216')
+
+  extensions[pb2.repeatedgroup_extension].add().a = 217
+  extensions[pb2.repeated_nested_message_extension].add().bb = 218
+  extensions[pb2.repeated_foreign_message_extension].add().c = 219
+  extensions[pb2.repeated_import_message_extension].add().d = 220
+
+  extensions[pb2.repeated_nested_enum_extension].append(pb2.TestAllTypes.BAR)
+  extensions[pb2.repeated_foreign_enum_extension].append(pb2.FOREIGN_BAR)
+  extensions[pb2.repeated_import_enum_extension].append(import_pb2.IMPORT_BAR)
+
+  extensions[pb2.repeated_string_piece_extension].append('224')
+  extensions[pb2.repeated_cord_extension].append('225')
+
+  # Append a second one of each field.
+  extensions[pb2.repeated_int32_extension].append(301)
+  extensions[pb2.repeated_int64_extension].append(302)
+  extensions[pb2.repeated_uint32_extension].append(303)
+  extensions[pb2.repeated_uint64_extension].append(304)
+  extensions[pb2.repeated_sint32_extension].append(305)
+  extensions[pb2.repeated_sint64_extension].append(306)
+  extensions[pb2.repeated_fixed32_extension].append(307)
+  extensions[pb2.repeated_fixed64_extension].append(308)
+  extensions[pb2.repeated_sfixed32_extension].append(309)
+  extensions[pb2.repeated_sfixed64_extension].append(310)
+  extensions[pb2.repeated_float_extension].append(311)
+  extensions[pb2.repeated_double_extension].append(312)
+  extensions[pb2.repeated_bool_extension].append(False)
+  extensions[pb2.repeated_string_extension].append('315')
+  extensions[pb2.repeated_bytes_extension].append('316')
+
+  extensions[pb2.repeatedgroup_extension].add().a = 317
+  extensions[pb2.repeated_nested_message_extension].add().bb = 318
+  extensions[pb2.repeated_foreign_message_extension].add().c = 319
+  extensions[pb2.repeated_import_message_extension].add().d = 320
+
+  extensions[pb2.repeated_nested_enum_extension].append(pb2.TestAllTypes.BAZ)
+  extensions[pb2.repeated_foreign_enum_extension].append(pb2.FOREIGN_BAZ)
+  extensions[pb2.repeated_import_enum_extension].append(import_pb2.IMPORT_BAZ)
+
+  extensions[pb2.repeated_string_piece_extension].append('324')
+  extensions[pb2.repeated_cord_extension].append('325')
+
+  #
+  # Fields with defaults.
+  #
+
+  extensions[pb2.default_int32_extension] = 401
+  extensions[pb2.default_int64_extension] = 402
+  extensions[pb2.default_uint32_extension] = 403
+  extensions[pb2.default_uint64_extension] = 404
+  extensions[pb2.default_sint32_extension] = 405
+  extensions[pb2.default_sint64_extension] = 406
+  extensions[pb2.default_fixed32_extension] = 407
+  extensions[pb2.default_fixed64_extension] = 408
+  extensions[pb2.default_sfixed32_extension] = 409
+  extensions[pb2.default_sfixed64_extension] = 410
+  extensions[pb2.default_float_extension] = 411
+  extensions[pb2.default_double_extension] = 412
+  extensions[pb2.default_bool_extension] = False
+  extensions[pb2.default_string_extension] = '415'
+  extensions[pb2.default_bytes_extension] = '416'
+
+  extensions[pb2.default_nested_enum_extension] = pb2.TestAllTypes.FOO
+  extensions[pb2.default_foreign_enum_extension] = pb2.FOREIGN_FOO
+  extensions[pb2.default_import_enum_extension] = import_pb2.IMPORT_FOO
+
+  extensions[pb2.default_string_piece_extension] = '424'
+  extensions[pb2.default_cord_extension] = '425'
+
+
+def SetAllFieldsAndExtensions(message):
+  """Sets every field and extension in the message to a unique value.
+
+  Args:
+    message: A unittest_pb2.TestAllExtensions message.
+  """
+  message.my_int = 1
+  message.my_string = 'foo'
+  message.my_float = 1.0
+  message.Extensions[unittest_pb2.my_extension_int] = 23
+  message.Extensions[unittest_pb2.my_extension_string] = 'bar'
+
+
+def ExpectAllFieldsAndExtensionsInOrder(serialized):
+  """Ensures that serialized is the serialization we expect for a message
+  filled with SetAllFieldsAndExtensions().  (Specifically, ensures that the
+  serialization is in canonical, tag-number order).
+  """
+  my_extension_int = unittest_pb2.my_extension_int
+  my_extension_string = unittest_pb2.my_extension_string
+  expected_strings = []
+  message = unittest_pb2.TestFieldOrderings()
+  message.my_int = 1  # Field 1.
+  expected_strings.append(message.SerializeToString())
+  message.Clear()
+  message.Extensions[my_extension_int] = 23  # Field 5.
+  expected_strings.append(message.SerializeToString())
+  message.Clear()
+  message.my_string = 'foo'  # Field 11.
+  expected_strings.append(message.SerializeToString())
+  message.Clear()
+  message.Extensions[my_extension_string] = 'bar'  # Field 50.
+  expected_strings.append(message.SerializeToString())
+  message.Clear()
+  message.my_float = 1.0
+  expected_strings.append(message.SerializeToString())
+  message.Clear()
+  expected = ''.join(expected_strings)
+
+  if expected != serialized:
+    raise ValueError('Expected %r, found %r' % (expected, serialized))
+
+
+class GoldenMessageTestCase(unittest.TestCase):
+  """This adds methods to TestCase useful for verifying our Golden Message."""
+
+  def ExpectAllFieldsSet(self, message):
+    """Check all fields for correct values have after Set*Fields() is called."""
+    self.assertTrue(message.HasField('optional_int32'))
+    self.assertTrue(message.HasField('optional_int64'))
+    self.assertTrue(message.HasField('optional_uint32'))
+    self.assertTrue(message.HasField('optional_uint64'))
+    self.assertTrue(message.HasField('optional_sint32'))
+    self.assertTrue(message.HasField('optional_sint64'))
+    self.assertTrue(message.HasField('optional_fixed32'))
+    self.assertTrue(message.HasField('optional_fixed64'))
+    self.assertTrue(message.HasField('optional_sfixed32'))
+    self.assertTrue(message.HasField('optional_sfixed64'))
+    self.assertTrue(message.HasField('optional_float'))
+    self.assertTrue(message.HasField('optional_double'))
+    self.assertTrue(message.HasField('optional_bool'))
+    self.assertTrue(message.HasField('optional_string'))
+    self.assertTrue(message.HasField('optional_bytes'))
+
+    self.assertTrue(message.HasField('optionalgroup'))
+    self.assertTrue(message.HasField('optional_nested_message'))
+    self.assertTrue(message.HasField('optional_foreign_message'))
+    self.assertTrue(message.HasField('optional_import_message'))
+
+    self.assertTrue(message.optionalgroup.HasField('a'))
+    self.assertTrue(message.optional_nested_message.HasField('bb'))
+    self.assertTrue(message.optional_foreign_message.HasField('c'))
+    self.assertTrue(message.optional_import_message.HasField('d'))
+
+    self.assertTrue(message.HasField('optional_nested_enum'))
+    self.assertTrue(message.HasField('optional_foreign_enum'))
+    self.assertTrue(message.HasField('optional_import_enum'))
+
+    self.assertTrue(message.HasField('optional_string_piece'))
+    self.assertTrue(message.HasField('optional_cord'))
+
+    self.assertEqual(101, message.optional_int32)
+    self.assertEqual(102, message.optional_int64)
+    self.assertEqual(103, message.optional_uint32)
+    self.assertEqual(104, message.optional_uint64)
+    self.assertEqual(105, message.optional_sint32)
+    self.assertEqual(106, message.optional_sint64)
+    self.assertEqual(107, message.optional_fixed32)
+    self.assertEqual(108, message.optional_fixed64)
+    self.assertEqual(109, message.optional_sfixed32)
+    self.assertEqual(110, message.optional_sfixed64)
+    self.assertEqual(111, message.optional_float)
+    self.assertEqual(112, message.optional_double)
+    self.assertEqual(True, message.optional_bool)
+    self.assertEqual('115', message.optional_string)
+    self.assertEqual('116', message.optional_bytes)
+
+    self.assertEqual(117, message.optionalgroup.a);
+    self.assertEqual(118, message.optional_nested_message.bb)
+    self.assertEqual(119, message.optional_foreign_message.c)
+    self.assertEqual(120, message.optional_import_message.d)
+
+    self.assertEqual(unittest_pb2.TestAllTypes.BAZ,
+                     message.optional_nested_enum)
+    self.assertEqual(unittest_pb2.FOREIGN_BAZ, message.optional_foreign_enum)
+    self.assertEqual(unittest_import_pb2.IMPORT_BAZ,
+                     message.optional_import_enum)
+
+    # -----------------------------------------------------------------
+
+    self.assertEqual(2, len(message.repeated_int32))
+    self.assertEqual(2, len(message.repeated_int64))
+    self.assertEqual(2, len(message.repeated_uint32))
+    self.assertEqual(2, len(message.repeated_uint64))
+    self.assertEqual(2, len(message.repeated_sint32))
+    self.assertEqual(2, len(message.repeated_sint64))
+    self.assertEqual(2, len(message.repeated_fixed32))
+    self.assertEqual(2, len(message.repeated_fixed64))
+    self.assertEqual(2, len(message.repeated_sfixed32))
+    self.assertEqual(2, len(message.repeated_sfixed64))
+    self.assertEqual(2, len(message.repeated_float))
+    self.assertEqual(2, len(message.repeated_double))
+    self.assertEqual(2, len(message.repeated_bool))
+    self.assertEqual(2, len(message.repeated_string))
+    self.assertEqual(2, len(message.repeated_bytes))
+
+    self.assertEqual(2, len(message.repeatedgroup))
+    self.assertEqual(2, len(message.repeated_nested_message))
+    self.assertEqual(2, len(message.repeated_foreign_message))
+    self.assertEqual(2, len(message.repeated_import_message))
+    self.assertEqual(2, len(message.repeated_nested_enum))
+    self.assertEqual(2, len(message.repeated_foreign_enum))
+    self.assertEqual(2, len(message.repeated_import_enum))
+
+    self.assertEqual(2, len(message.repeated_string_piece))
+    self.assertEqual(2, len(message.repeated_cord))
+
+    self.assertEqual(201, message.repeated_int32[0])
+    self.assertEqual(202, message.repeated_int64[0])
+    self.assertEqual(203, message.repeated_uint32[0])
+    self.assertEqual(204, message.repeated_uint64[0])
+    self.assertEqual(205, message.repeated_sint32[0])
+    self.assertEqual(206, message.repeated_sint64[0])
+    self.assertEqual(207, message.repeated_fixed32[0])
+    self.assertEqual(208, message.repeated_fixed64[0])
+    self.assertEqual(209, message.repeated_sfixed32[0])
+    self.assertEqual(210, message.repeated_sfixed64[0])
+    self.assertEqual(211, message.repeated_float[0])
+    self.assertEqual(212, message.repeated_double[0])
+    self.assertEqual(True, message.repeated_bool[0])
+    self.assertEqual('215', message.repeated_string[0])
+    self.assertEqual('216', message.repeated_bytes[0])
+
+    self.assertEqual(217, message.repeatedgroup[0].a)
+    self.assertEqual(218, message.repeated_nested_message[0].bb)
+    self.assertEqual(219, message.repeated_foreign_message[0].c)
+    self.assertEqual(220, message.repeated_import_message[0].d)
+
+    self.assertEqual(unittest_pb2.TestAllTypes.BAR,
+                     message.repeated_nested_enum[0])
+    self.assertEqual(unittest_pb2.FOREIGN_BAR,
+                     message.repeated_foreign_enum[0])
+    self.assertEqual(unittest_import_pb2.IMPORT_BAR,
+                     message.repeated_import_enum[0])
+
+    self.assertEqual(301, message.repeated_int32[1])
+    self.assertEqual(302, message.repeated_int64[1])
+    self.assertEqual(303, message.repeated_uint32[1])
+    self.assertEqual(304, message.repeated_uint64[1])
+    self.assertEqual(305, message.repeated_sint32[1])
+    self.assertEqual(306, message.repeated_sint64[1])
+    self.assertEqual(307, message.repeated_fixed32[1])
+    self.assertEqual(308, message.repeated_fixed64[1])
+    self.assertEqual(309, message.repeated_sfixed32[1])
+    self.assertEqual(310, message.repeated_sfixed64[1])
+    self.assertEqual(311, message.repeated_float[1])
+    self.assertEqual(312, message.repeated_double[1])
+    self.assertEqual(False, message.repeated_bool[1])
+    self.assertEqual('315', message.repeated_string[1])
+    self.assertEqual('316', message.repeated_bytes[1])
+
+    self.assertEqual(317, message.repeatedgroup[1].a)
+    self.assertEqual(318, message.repeated_nested_message[1].bb)
+    self.assertEqual(319, message.repeated_foreign_message[1].c)
+    self.assertEqual(320, message.repeated_import_message[1].d)
+
+    self.assertEqual(unittest_pb2.TestAllTypes.BAZ,
+                     message.repeated_nested_enum[1])
+    self.assertEqual(unittest_pb2.FOREIGN_BAZ,
+                     message.repeated_foreign_enum[1])
+    self.assertEqual(unittest_import_pb2.IMPORT_BAZ,
+                     message.repeated_import_enum[1])
+
+    # -----------------------------------------------------------------
+
+    self.assertTrue(message.HasField('default_int32'))
+    self.assertTrue(message.HasField('default_int64'))
+    self.assertTrue(message.HasField('default_uint32'))
+    self.assertTrue(message.HasField('default_uint64'))
+    self.assertTrue(message.HasField('default_sint32'))
+    self.assertTrue(message.HasField('default_sint64'))
+    self.assertTrue(message.HasField('default_fixed32'))
+    self.assertTrue(message.HasField('default_fixed64'))
+    self.assertTrue(message.HasField('default_sfixed32'))
+    self.assertTrue(message.HasField('default_sfixed64'))
+    self.assertTrue(message.HasField('default_float'))
+    self.assertTrue(message.HasField('default_double'))
+    self.assertTrue(message.HasField('default_bool'))
+    self.assertTrue(message.HasField('default_string'))
+    self.assertTrue(message.HasField('default_bytes'))
+
+    self.assertTrue(message.HasField('default_nested_enum'))
+    self.assertTrue(message.HasField('default_foreign_enum'))
+    self.assertTrue(message.HasField('default_import_enum'))
+
+    self.assertEqual(401, message.default_int32)
+    self.assertEqual(402, message.default_int64)
+    self.assertEqual(403, message.default_uint32)
+    self.assertEqual(404, message.default_uint64)
+    self.assertEqual(405, message.default_sint32)
+    self.assertEqual(406, message.default_sint64)
+    self.assertEqual(407, message.default_fixed32)
+    self.assertEqual(408, message.default_fixed64)
+    self.assertEqual(409, message.default_sfixed32)
+    self.assertEqual(410, message.default_sfixed64)
+    self.assertEqual(411, message.default_float)
+    self.assertEqual(412, message.default_double)
+    self.assertEqual(False, message.default_bool)
+    self.assertEqual('415', message.default_string)
+    self.assertEqual('416', message.default_bytes)
+
+    self.assertEqual(unittest_pb2.TestAllTypes.FOO, message.default_nested_enum)
+    self.assertEqual(unittest_pb2.FOREIGN_FOO, message.default_foreign_enum)
+    self.assertEqual(unittest_import_pb2.IMPORT_FOO,
+                     message.default_import_enum)
+
+def GoldenFile(filename):
+  """Finds the given golden file and returns a file object representing it."""
+
+  # Search up the directory tree looking for the C++ protobuf source code.
+  path = '.'
+  while os.path.exists(path):
+    if os.path.exists(os.path.join(path, 'src/google/protobuf')):
+      # Found it.  Load the golden file from the testdata directory.
+      full_path = os.path.join(path, 'src/google/protobuf/testdata', filename)
+      return open(full_path, 'rb')
+    path = os.path.join(path, '..')
+
+  raise RuntimeError(
+    'Could not find golden files.  This test must be run from within the '
+    'protobuf source package so that it can read test data files from the '
+    'C++ source tree.')
+
+
+def SetAllPackedFields(message):
+  """Sets every field in the message to a unique value.
+
+  Args:
+    message: A unittest_pb2.TestPackedTypes instance.
+  """
+  message.packed_int32.extend([101, 102])
+  message.packed_int64.extend([103, 104])
+  message.packed_uint32.extend([105, 106])
+  message.packed_uint64.extend([107, 108])
+  message.packed_sint32.extend([109, 110])
+  message.packed_sint64.extend([111, 112])
+  message.packed_fixed32.extend([113, 114])
+  message.packed_fixed64.extend([115, 116])
+  message.packed_sfixed32.extend([117, 118])
+  message.packed_sfixed64.extend([119, 120])
+  message.packed_float.extend([121.0, 122.0])
+  message.packed_double.extend([122.0, 123.0])
+  message.packed_bool.extend([True, False])
+  message.packed_enum.extend([unittest_pb2.FOREIGN_FOO,
+                              unittest_pb2.FOREIGN_BAR])
+
+
+def SetAllPackedExtensions(message):
+  """Sets every extension in the message to a unique value.
+
+  Args:
+    message: A unittest_pb2.TestPackedExtensions instance.
+  """
+  extensions = message.Extensions
+  pb2 = unittest_pb2
+
+  extensions[pb2.packed_int32_extension].append(101)
+  extensions[pb2.packed_int64_extension].append(102)
+  extensions[pb2.packed_uint32_extension].append(103)
+  extensions[pb2.packed_uint64_extension].append(104)
+  extensions[pb2.packed_sint32_extension].append(105)
+  extensions[pb2.packed_sint64_extension].append(106)
+  extensions[pb2.packed_fixed32_extension].append(107)
+  extensions[pb2.packed_fixed64_extension].append(108)
+  extensions[pb2.packed_sfixed32_extension].append(109)
+  extensions[pb2.packed_sfixed64_extension].append(110)
+  extensions[pb2.packed_float_extension].append(111.0)
+  extensions[pb2.packed_double_extension].append(112.0)
+  extensions[pb2.packed_bool_extension].append(True)
+  extensions[pb2.packed_enum_extension].append(pb2.FOREIGN_BAZ)
diff --git a/python/google/protobuf/internal/text_format_test.py b/python/google/protobuf/internal/text_format_test.py
new file mode 100755
index 0000000..0cf2718
--- /dev/null
+++ b/python/google/protobuf/internal/text_format_test.py
@@ -0,0 +1,397 @@
+#! /usr/bin/python
+#
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Test for google.protobuf.text_format."""
+
+__author__ = 'kenton@google.com (Kenton Varda)'
+
+import difflib
+
+import unittest
+from google.protobuf import text_format
+from google.protobuf.internal import test_util
+from google.protobuf import unittest_pb2
+from google.protobuf import unittest_mset_pb2
+
+
+class TextFormatTest(test_util.GoldenMessageTestCase):
+  def ReadGolden(self, golden_filename):
+    f = test_util.GoldenFile(golden_filename)
+    golden_lines = f.readlines()
+    f.close()
+    return golden_lines
+
+  def CompareToGoldenFile(self, text, golden_filename):
+    golden_lines = self.ReadGolden(golden_filename)
+    self.CompareToGoldenLines(text, golden_lines)
+
+  def CompareToGoldenText(self, text, golden_text):
+    self.CompareToGoldenLines(text, golden_text.splitlines(1))
+
+  def CompareToGoldenLines(self, text, golden_lines):
+    actual_lines = text.splitlines(1)
+    self.assertEqual(golden_lines, actual_lines,
+      "Text doesn't match golden.  Diff:\n" +
+      ''.join(difflib.ndiff(golden_lines, actual_lines)))
+
+  def testPrintAllFields(self):
+    message = unittest_pb2.TestAllTypes()
+    test_util.SetAllFields(message)
+    self.CompareToGoldenFile(
+      self.RemoveRedundantZeros(text_format.MessageToString(message)),
+      'text_format_unittest_data.txt')
+
+  def testPrintAllExtensions(self):
+    message = unittest_pb2.TestAllExtensions()
+    test_util.SetAllExtensions(message)
+    self.CompareToGoldenFile(
+      self.RemoveRedundantZeros(text_format.MessageToString(message)),
+      'text_format_unittest_extensions_data.txt')
+
+  def testPrintMessageSet(self):
+    message = unittest_mset_pb2.TestMessageSetContainer()
+    ext1 = unittest_mset_pb2.TestMessageSetExtension1.message_set_extension
+    ext2 = unittest_mset_pb2.TestMessageSetExtension2.message_set_extension
+    message.message_set.Extensions[ext1].i = 23
+    message.message_set.Extensions[ext2].str = 'foo'
+    self.CompareToGoldenText(text_format.MessageToString(message),
+      'message_set {\n'
+      '  [protobuf_unittest.TestMessageSetExtension1] {\n'
+      '    i: 23\n'
+      '  }\n'
+      '  [protobuf_unittest.TestMessageSetExtension2] {\n'
+      '    str: \"foo\"\n'
+      '  }\n'
+      '}\n')
+
+  def testPrintExotic(self):
+    message = unittest_pb2.TestAllTypes()
+    message.repeated_int64.append(-9223372036854775808);
+    message.repeated_uint64.append(18446744073709551615);
+    message.repeated_double.append(123.456);
+    message.repeated_double.append(1.23e22);
+    message.repeated_double.append(1.23e-18);
+    message.repeated_string.append('\000\001\a\b\f\n\r\t\v\\\'\"');
+    self.CompareToGoldenText(
+      self.RemoveRedundantZeros(text_format.MessageToString(message)),
+      'repeated_int64: -9223372036854775808\n'
+      'repeated_uint64: 18446744073709551615\n'
+      'repeated_double: 123.456\n'
+      'repeated_double: 1.23e+22\n'
+      'repeated_double: 1.23e-18\n'
+      'repeated_string: '
+        '\"\\000\\001\\007\\010\\014\\n\\r\\t\\013\\\\\\\'\\\"\"\n')
+
+  def testMessageToString(self):
+    message = unittest_pb2.ForeignMessage()
+    message.c = 123
+    self.assertEqual('c: 123\n', str(message))
+
+  def RemoveRedundantZeros(self, text):
+    # Some platforms print 1e+5 as 1e+005.  This is fine, but we need to remove
+    # these zeros in order to match the golden file.
+    return text.replace('e+0','e+').replace('e+0','e+') \
+               .replace('e-0','e-').replace('e-0','e-')
+
+  def testMergeGolden(self):
+    golden_text = '\n'.join(self.ReadGolden('text_format_unittest_data.txt'))
+    parsed_message = unittest_pb2.TestAllTypes()
+    text_format.Merge(golden_text, parsed_message)
+
+    message = unittest_pb2.TestAllTypes()
+    test_util.SetAllFields(message)
+    self.assertEquals(message, parsed_message)
+
+  def testMergeGoldenExtensions(self):
+    golden_text = '\n'.join(self.ReadGolden(
+        'text_format_unittest_extensions_data.txt'))
+    parsed_message = unittest_pb2.TestAllExtensions()
+    text_format.Merge(golden_text, parsed_message)
+
+    message = unittest_pb2.TestAllExtensions()
+    test_util.SetAllExtensions(message)
+    self.assertEquals(message, parsed_message)
+
+  def testMergeAllFields(self):
+    message = unittest_pb2.TestAllTypes()
+    test_util.SetAllFields(message)
+    ascii_text = text_format.MessageToString(message)
+
+    parsed_message = unittest_pb2.TestAllTypes()
+    text_format.Merge(ascii_text, parsed_message)
+    self.assertEqual(message, parsed_message)
+    self.ExpectAllFieldsSet(message)
+
+  def testMergeAllExtensions(self):
+    message = unittest_pb2.TestAllExtensions()
+    test_util.SetAllExtensions(message)
+    ascii_text = text_format.MessageToString(message)
+
+    parsed_message = unittest_pb2.TestAllExtensions()
+    text_format.Merge(ascii_text, parsed_message)
+    self.assertEqual(message, parsed_message)
+
+  def testMergeMessageSet(self):
+    message = unittest_pb2.TestAllTypes()
+    text = ('repeated_uint64: 1\n'
+            'repeated_uint64: 2\n')
+    text_format.Merge(text, message)
+    self.assertEqual(1, message.repeated_uint64[0])
+    self.assertEqual(2, message.repeated_uint64[1])
+
+    message = unittest_mset_pb2.TestMessageSetContainer()
+    text = ('message_set {\n'
+            '  [protobuf_unittest.TestMessageSetExtension1] {\n'
+            '    i: 23\n'
+            '  }\n'
+            '  [protobuf_unittest.TestMessageSetExtension2] {\n'
+            '    str: \"foo\"\n'
+            '  }\n'
+            '}\n')
+    text_format.Merge(text, message)
+    ext1 = unittest_mset_pb2.TestMessageSetExtension1.message_set_extension
+    ext2 = unittest_mset_pb2.TestMessageSetExtension2.message_set_extension
+    self.assertEquals(23, message.message_set.Extensions[ext1].i)
+    self.assertEquals('foo', message.message_set.Extensions[ext2].str)
+
+  def testMergeExotic(self):
+    message = unittest_pb2.TestAllTypes()
+    text = ('repeated_int64: -9223372036854775808\n'
+            'repeated_uint64: 18446744073709551615\n'
+            'repeated_double: 123.456\n'
+            'repeated_double: 1.23e+22\n'
+            'repeated_double: 1.23e-18\n'
+            'repeated_string: \n'
+            '\"\\000\\001\\007\\010\\014\\n\\r\\t\\013\\\\\\\'\\\"\"\n')
+    text_format.Merge(text, message)
+
+    self.assertEqual(-9223372036854775808, message.repeated_int64[0])
+    self.assertEqual(18446744073709551615, message.repeated_uint64[0])
+    self.assertEqual(123.456, message.repeated_double[0])
+    self.assertEqual(1.23e22, message.repeated_double[1])
+    self.assertEqual(1.23e-18, message.repeated_double[2])
+    self.assertEqual(
+        '\000\001\a\b\f\n\r\t\v\\\'\"', message.repeated_string[0])
+
+  def testMergeUnknownField(self):
+    message = unittest_pb2.TestAllTypes()
+    text = 'unknown_field: 8\n'
+    self.assertRaisesWithMessage(
+        text_format.ParseError,
+        ('1:1 : Message type "protobuf_unittest.TestAllTypes" has no field named '
+         '"unknown_field".'),
+        text_format.Merge, text, message)
+
+  def testMergeBadExtension(self):
+    message = unittest_pb2.TestAllTypes()
+    text = '[unknown_extension]: 8\n'
+    self.assertRaisesWithMessage(
+        text_format.ParseError,
+        '1:2 : Extension "unknown_extension" not registered.',
+        text_format.Merge, text, message)
+
+  def testMergeGroupNotClosed(self):
+    message = unittest_pb2.TestAllTypes()
+    text = 'RepeatedGroup: <'
+    self.assertRaisesWithMessage(
+        text_format.ParseError, '1:16 : Expected ">".',
+        text_format.Merge, text, message)
+
+    text = 'RepeatedGroup: {'
+    self.assertRaisesWithMessage(
+        text_format.ParseError, '1:16 : Expected "}".',
+        text_format.Merge, text, message)
+
+  def testMergeBadEnumValue(self):
+    message = unittest_pb2.TestAllTypes()
+    text = 'optional_nested_enum: BARR'
+    self.assertRaisesWithMessage(
+        text_format.ParseError,
+        ('1:23 : Enum type "protobuf_unittest.TestAllTypes.NestedEnum" '
+         'has no value named BARR.'),
+        text_format.Merge, text, message)
+
+    message = unittest_pb2.TestAllTypes()
+    text = 'optional_nested_enum: 100'
+    self.assertRaisesWithMessage(
+        text_format.ParseError,
+        ('1:23 : Enum type "protobuf_unittest.TestAllTypes.NestedEnum" '
+         'has no value with number 100.'),
+        text_format.Merge, text, message)
+
+  def assertRaisesWithMessage(self, e_class, e, func, *args, **kwargs):
+    """Same as assertRaises, but also compares the exception message."""
+    if hasattr(e_class, '__name__'):
+      exc_name = e_class.__name__
+    else:
+      exc_name = str(e_class)
+
+    try:
+      func(*args, **kwargs)
+    except e_class, expr:
+      if str(expr) != e:
+        msg = '%s raised, but with wrong message: "%s" instead of "%s"'
+        raise self.failureException(msg % (exc_name,
+                                           str(expr).encode('string_escape'),
+                                           e.encode('string_escape')))
+      return
+    else:
+      raise self.failureException('%s not raised' % exc_name)
+
+
+class TokenizerTest(unittest.TestCase):
+
+  def testSimpleTokenCases(self):
+    text = ('identifier1:"string1"\n     \n\n'
+            'identifier2 : \n \n123  \n  identifier3 :\'string\'\n'
+            'identifiER_4 : 1.1e+2 ID5:-0.23 ID6:\'aaaa\\\'bbbb\'\n'
+            'ID7 : "aa\\"bb"\n\n\n\n ID8: {A:inf B:-inf C:true D:false}\n'
+            'ID9: 22 ID10: -111111111111111111 ID11: -22\n'
+            'ID12: 2222222222222222222')
+    tokenizer = text_format._Tokenizer(text)
+    methods = [(tokenizer.ConsumeIdentifier, 'identifier1'),
+               ':',
+               (tokenizer.ConsumeString, 'string1'),
+               (tokenizer.ConsumeIdentifier, 'identifier2'),
+               ':',
+               (tokenizer.ConsumeInt32, 123),
+               (tokenizer.ConsumeIdentifier, 'identifier3'),
+               ':',
+               (tokenizer.ConsumeString, 'string'),
+               (tokenizer.ConsumeIdentifier, 'identifiER_4'),
+               ':',
+               (tokenizer.ConsumeFloat, 1.1e+2),
+               (tokenizer.ConsumeIdentifier, 'ID5'),
+               ':',
+               (tokenizer.ConsumeFloat, -0.23),
+               (tokenizer.ConsumeIdentifier, 'ID6'),
+               ':',
+               (tokenizer.ConsumeString, 'aaaa\'bbbb'),
+               (tokenizer.ConsumeIdentifier, 'ID7'),
+               ':',
+               (tokenizer.ConsumeString, 'aa\"bb'),
+               (tokenizer.ConsumeIdentifier, 'ID8'),
+               ':',
+               '{',
+               (tokenizer.ConsumeIdentifier, 'A'),
+               ':',
+               (tokenizer.ConsumeFloat, float('inf')),
+               (tokenizer.ConsumeIdentifier, 'B'),
+               ':',
+               (tokenizer.ConsumeFloat, float('-inf')),
+               (tokenizer.ConsumeIdentifier, 'C'),
+               ':',
+               (tokenizer.ConsumeBool, True),
+               (tokenizer.ConsumeIdentifier, 'D'),
+               ':',
+               (tokenizer.ConsumeBool, False),
+               '}',
+               (tokenizer.ConsumeIdentifier, 'ID9'),
+               ':',
+               (tokenizer.ConsumeUint32, 22),
+               (tokenizer.ConsumeIdentifier, 'ID10'),
+               ':',
+               (tokenizer.ConsumeInt64, -111111111111111111),
+               (tokenizer.ConsumeIdentifier, 'ID11'),
+               ':',
+               (tokenizer.ConsumeInt32, -22),
+               (tokenizer.ConsumeIdentifier, 'ID12'),
+               ':',
+               (tokenizer.ConsumeUint64, 2222222222222222222)]
+
+    i = 0
+    while not tokenizer.AtEnd():
+      m = methods[i]
+      if type(m) == str:
+        token = tokenizer.token
+        self.assertEqual(token, m)
+        tokenizer.NextToken()
+      else:
+        self.assertEqual(m[1], m[0]())
+      i += 1
+
+  def testConsumeIntegers(self):
+    # This test only tests the failures in the integer parsing methods as well
+    # as the '0' special cases.
+    int64_max = (1 << 63) - 1
+    uint32_max = (1 << 32) - 1
+    text = '-1 %d %d' % (uint32_max + 1, int64_max + 1)
+    tokenizer = text_format._Tokenizer(text)
+    self.assertRaises(text_format.ParseError, tokenizer.ConsumeUint32)
+    self.assertRaises(text_format.ParseError, tokenizer.ConsumeUint64)
+    self.assertEqual(-1, tokenizer.ConsumeInt32())
+
+    self.assertRaises(text_format.ParseError, tokenizer.ConsumeUint32)
+    self.assertRaises(text_format.ParseError, tokenizer.ConsumeInt32)
+    self.assertEqual(uint32_max + 1, tokenizer.ConsumeInt64())
+
+    self.assertRaises(text_format.ParseError, tokenizer.ConsumeInt64)
+    self.assertEqual(int64_max + 1, tokenizer.ConsumeUint64())
+    self.assertTrue(tokenizer.AtEnd())
+
+    text = '-0 -0 0 0'
+    tokenizer = text_format._Tokenizer(text)
+    self.assertEqual(0, tokenizer.ConsumeUint32())
+    self.assertEqual(0, tokenizer.ConsumeUint64())
+    self.assertEqual(0, tokenizer.ConsumeUint32())
+    self.assertEqual(0, tokenizer.ConsumeUint64())
+    self.assertTrue(tokenizer.AtEnd())
+
+  def testConsumeByteString(self):
+    text = '"string1\''
+    tokenizer = text_format._Tokenizer(text)
+    self.assertRaises(text_format.ParseError, tokenizer.ConsumeByteString)
+
+    text = 'string1"'
+    tokenizer = text_format._Tokenizer(text)
+    self.assertRaises(text_format.ParseError, tokenizer.ConsumeByteString)
+
+    text = '\n"\\xt"'
+    tokenizer = text_format._Tokenizer(text)
+    self.assertRaises(text_format.ParseError, tokenizer.ConsumeByteString)
+
+    text = '\n"\\"'
+    tokenizer = text_format._Tokenizer(text)
+    self.assertRaises(text_format.ParseError, tokenizer.ConsumeByteString)
+
+    text = '\n"\\x"'
+    tokenizer = text_format._Tokenizer(text)
+    self.assertRaises(text_format.ParseError, tokenizer.ConsumeByteString)
+
+  def testConsumeBool(self):
+    text = 'not-a-bool'
+    tokenizer = text_format._Tokenizer(text)
+    self.assertRaises(text_format.ParseError, tokenizer.ConsumeBool)
+
+
+if __name__ == '__main__':
+  unittest.main()
diff --git a/python/google/protobuf/internal/type_checkers.py b/python/google/protobuf/internal/type_checkers.py
new file mode 100755
index 0000000..a3bc57f
--- /dev/null
+++ b/python/google/protobuf/internal/type_checkers.py
@@ -0,0 +1,287 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Provides type checking routines.
+
+This module defines type checking utilities in the forms of dictionaries:
+
+VALUE_CHECKERS: A dictionary of field types and a value validation object.
+TYPE_TO_BYTE_SIZE_FN: A dictionary with field types and a size computing
+  function.
+TYPE_TO_SERIALIZE_METHOD: A dictionary with field types and serialization
+  function.
+FIELD_TYPE_TO_WIRE_TYPE: A dictionary with field typed and their
+  coresponding wire types.
+TYPE_TO_DESERIALIZE_METHOD: A dictionary with field types and deserialization
+  function.
+"""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+from google.protobuf.internal import decoder
+from google.protobuf.internal import encoder
+from google.protobuf.internal import wire_format
+from google.protobuf import descriptor
+
+_FieldDescriptor = descriptor.FieldDescriptor
+
+
+def GetTypeChecker(cpp_type, field_type):
+  """Returns a type checker for a message field of the specified types.
+
+  Args:
+    cpp_type: C++ type of the field (see descriptor.py).
+    field_type: Protocol message field type (see descriptor.py).
+
+  Returns:
+    An instance of TypeChecker which can be used to verify the types
+    of values assigned to a field of the specified type.
+  """
+  if (cpp_type == _FieldDescriptor.CPPTYPE_STRING and
+      field_type == _FieldDescriptor.TYPE_STRING):
+    return UnicodeValueChecker()
+  return _VALUE_CHECKERS[cpp_type]
+
+
+# None of the typecheckers below make any attempt to guard against people
+# subclassing builtin types and doing weird things.  We're not trying to
+# protect against malicious clients here, just people accidentally shooting
+# themselves in the foot in obvious ways.
+
+class TypeChecker(object):
+
+  """Type checker used to catch type errors as early as possible
+  when the client is setting scalar fields in protocol messages.
+  """
+
+  def __init__(self, *acceptable_types):
+    self._acceptable_types = acceptable_types
+
+  def CheckValue(self, proposed_value):
+    if not isinstance(proposed_value, self._acceptable_types):
+      message = ('%.1024r has type %s, but expected one of: %s' %
+                 (proposed_value, type(proposed_value), self._acceptable_types))
+      raise TypeError(message)
+
+
+# IntValueChecker and its subclasses perform integer type-checks
+# and bounds-checks.
+class IntValueChecker(object):
+
+  """Checker used for integer fields.  Performs type-check and range check."""
+
+  def CheckValue(self, proposed_value):
+    if not isinstance(proposed_value, (int, long)):
+      message = ('%.1024r has type %s, but expected one of: %s' %
+                 (proposed_value, type(proposed_value), (int, long)))
+      raise TypeError(message)
+    if not self._MIN <= proposed_value <= self._MAX:
+      raise ValueError('Value out of range: %d' % proposed_value)
+
+
+class UnicodeValueChecker(object):
+
+  """Checker used for string fields."""
+
+  def CheckValue(self, proposed_value):
+    if not isinstance(proposed_value, (str, unicode)):
+      message = ('%.1024r has type %s, but expected one of: %s' %
+                 (proposed_value, type(proposed_value), (str, unicode)))
+      raise TypeError(message)
+
+    # If the value is of type 'str' make sure that it is in 7-bit ASCII
+    # encoding.
+    if isinstance(proposed_value, str):
+      try:
+        unicode(proposed_value, 'ascii')
+      except UnicodeDecodeError:
+        raise ValueError('%.1024r has type str, but isn\'t in 7-bit ASCII '
+                         'encoding. Non-ASCII strings must be converted to '
+                         'unicode objects before being added.' %
+                         (proposed_value))
+
+
+class Int32ValueChecker(IntValueChecker):
+  # We're sure to use ints instead of longs here since comparison may be more
+  # efficient.
+  _MIN = -2147483648
+  _MAX = 2147483647
+
+
+class Uint32ValueChecker(IntValueChecker):
+  _MIN = 0
+  _MAX = (1 << 32) - 1
+
+
+class Int64ValueChecker(IntValueChecker):
+  _MIN = -(1 << 63)
+  _MAX = (1 << 63) - 1
+
+
+class Uint64ValueChecker(IntValueChecker):
+  _MIN = 0
+  _MAX = (1 << 64) - 1
+
+
+# Type-checkers for all scalar CPPTYPEs.
+_VALUE_CHECKERS = {
+    _FieldDescriptor.CPPTYPE_INT32: Int32ValueChecker(),
+    _FieldDescriptor.CPPTYPE_INT64: Int64ValueChecker(),
+    _FieldDescriptor.CPPTYPE_UINT32: Uint32ValueChecker(),
+    _FieldDescriptor.CPPTYPE_UINT64: Uint64ValueChecker(),
+    _FieldDescriptor.CPPTYPE_DOUBLE: TypeChecker(
+        float, int, long),
+    _FieldDescriptor.CPPTYPE_FLOAT: TypeChecker(
+        float, int, long),
+    _FieldDescriptor.CPPTYPE_BOOL: TypeChecker(bool, int),
+    _FieldDescriptor.CPPTYPE_ENUM: Int32ValueChecker(),
+    _FieldDescriptor.CPPTYPE_STRING: TypeChecker(str),
+    }
+
+
+# Map from field type to a function F, such that F(field_num, value)
+# gives the total byte size for a value of the given type.  This
+# byte size includes tag information and any other additional space
+# associated with serializing "value".
+TYPE_TO_BYTE_SIZE_FN = {
+    _FieldDescriptor.TYPE_DOUBLE: wire_format.DoubleByteSize,
+    _FieldDescriptor.TYPE_FLOAT: wire_format.FloatByteSize,
+    _FieldDescriptor.TYPE_INT64: wire_format.Int64ByteSize,
+    _FieldDescriptor.TYPE_UINT64: wire_format.UInt64ByteSize,
+    _FieldDescriptor.TYPE_INT32: wire_format.Int32ByteSize,
+    _FieldDescriptor.TYPE_FIXED64: wire_format.Fixed64ByteSize,
+    _FieldDescriptor.TYPE_FIXED32: wire_format.Fixed32ByteSize,
+    _FieldDescriptor.TYPE_BOOL: wire_format.BoolByteSize,
+    _FieldDescriptor.TYPE_STRING: wire_format.StringByteSize,
+    _FieldDescriptor.TYPE_GROUP: wire_format.GroupByteSize,
+    _FieldDescriptor.TYPE_MESSAGE: wire_format.MessageByteSize,
+    _FieldDescriptor.TYPE_BYTES: wire_format.BytesByteSize,
+    _FieldDescriptor.TYPE_UINT32: wire_format.UInt32ByteSize,
+    _FieldDescriptor.TYPE_ENUM: wire_format.EnumByteSize,
+    _FieldDescriptor.TYPE_SFIXED32: wire_format.SFixed32ByteSize,
+    _FieldDescriptor.TYPE_SFIXED64: wire_format.SFixed64ByteSize,
+    _FieldDescriptor.TYPE_SINT32: wire_format.SInt32ByteSize,
+    _FieldDescriptor.TYPE_SINT64: wire_format.SInt64ByteSize
+    }
+
+
+# Maps from field type to an unbound Encoder method F, such that
+# F(encoder, field_number, value) will append the serialization
+# of a value of this type to the encoder.
+_Encoder = encoder.Encoder
+TYPE_TO_SERIALIZE_METHOD = {
+    _FieldDescriptor.TYPE_DOUBLE: _Encoder.AppendDouble,
+    _FieldDescriptor.TYPE_FLOAT: _Encoder.AppendFloat,
+    _FieldDescriptor.TYPE_INT64: _Encoder.AppendInt64,
+    _FieldDescriptor.TYPE_UINT64: _Encoder.AppendUInt64,
+    _FieldDescriptor.TYPE_INT32: _Encoder.AppendInt32,
+    _FieldDescriptor.TYPE_FIXED64: _Encoder.AppendFixed64,
+    _FieldDescriptor.TYPE_FIXED32: _Encoder.AppendFixed32,
+    _FieldDescriptor.TYPE_BOOL: _Encoder.AppendBool,
+    _FieldDescriptor.TYPE_STRING: _Encoder.AppendString,
+    _FieldDescriptor.TYPE_GROUP: _Encoder.AppendGroup,
+    _FieldDescriptor.TYPE_MESSAGE: _Encoder.AppendMessage,
+    _FieldDescriptor.TYPE_BYTES: _Encoder.AppendBytes,
+    _FieldDescriptor.TYPE_UINT32: _Encoder.AppendUInt32,
+    _FieldDescriptor.TYPE_ENUM: _Encoder.AppendEnum,
+    _FieldDescriptor.TYPE_SFIXED32: _Encoder.AppendSFixed32,
+    _FieldDescriptor.TYPE_SFIXED64: _Encoder.AppendSFixed64,
+    _FieldDescriptor.TYPE_SINT32: _Encoder.AppendSInt32,
+    _FieldDescriptor.TYPE_SINT64: _Encoder.AppendSInt64,
+    }
+
+
+TYPE_TO_NOTAG_SERIALIZE_METHOD = {
+    _FieldDescriptor.TYPE_DOUBLE: _Encoder.AppendDoubleNoTag,
+    _FieldDescriptor.TYPE_FLOAT: _Encoder.AppendFloatNoTag,
+    _FieldDescriptor.TYPE_INT64: _Encoder.AppendInt64NoTag,
+    _FieldDescriptor.TYPE_UINT64: _Encoder.AppendUInt64NoTag,
+    _FieldDescriptor.TYPE_INT32: _Encoder.AppendInt32NoTag,
+    _FieldDescriptor.TYPE_FIXED64: _Encoder.AppendFixed64NoTag,
+    _FieldDescriptor.TYPE_FIXED32: _Encoder.AppendFixed32NoTag,
+    _FieldDescriptor.TYPE_BOOL: _Encoder.AppendBoolNoTag,
+    _FieldDescriptor.TYPE_UINT32: _Encoder.AppendUInt32NoTag,
+    _FieldDescriptor.TYPE_ENUM: _Encoder.AppendEnumNoTag,
+    _FieldDescriptor.TYPE_SFIXED32: _Encoder.AppendSFixed32NoTag,
+    _FieldDescriptor.TYPE_SFIXED64: _Encoder.AppendSFixed64NoTag,
+    _FieldDescriptor.TYPE_SINT32: _Encoder.AppendSInt32NoTag,
+    _FieldDescriptor.TYPE_SINT64: _Encoder.AppendSInt64NoTag,
+    }
+
+# Maps from field type to expected wiretype.
+FIELD_TYPE_TO_WIRE_TYPE = {
+    _FieldDescriptor.TYPE_DOUBLE: wire_format.WIRETYPE_FIXED64,
+    _FieldDescriptor.TYPE_FLOAT: wire_format.WIRETYPE_FIXED32,
+    _FieldDescriptor.TYPE_INT64: wire_format.WIRETYPE_VARINT,
+    _FieldDescriptor.TYPE_UINT64: wire_format.WIRETYPE_VARINT,
+    _FieldDescriptor.TYPE_INT32: wire_format.WIRETYPE_VARINT,
+    _FieldDescriptor.TYPE_FIXED64: wire_format.WIRETYPE_FIXED64,
+    _FieldDescriptor.TYPE_FIXED32: wire_format.WIRETYPE_FIXED32,
+    _FieldDescriptor.TYPE_BOOL: wire_format.WIRETYPE_VARINT,
+    _FieldDescriptor.TYPE_STRING:
+      wire_format.WIRETYPE_LENGTH_DELIMITED,
+    _FieldDescriptor.TYPE_GROUP: wire_format.WIRETYPE_START_GROUP,
+    _FieldDescriptor.TYPE_MESSAGE:
+      wire_format.WIRETYPE_LENGTH_DELIMITED,
+    _FieldDescriptor.TYPE_BYTES:
+      wire_format.WIRETYPE_LENGTH_DELIMITED,
+    _FieldDescriptor.TYPE_UINT32: wire_format.WIRETYPE_VARINT,
+    _FieldDescriptor.TYPE_ENUM: wire_format.WIRETYPE_VARINT,
+    _FieldDescriptor.TYPE_SFIXED32: wire_format.WIRETYPE_FIXED32,
+    _FieldDescriptor.TYPE_SFIXED64: wire_format.WIRETYPE_FIXED64,
+    _FieldDescriptor.TYPE_SINT32: wire_format.WIRETYPE_VARINT,
+    _FieldDescriptor.TYPE_SINT64: wire_format.WIRETYPE_VARINT,
+    }
+
+
+# Maps from field type to an unbound Decoder method F,
+# such that F(decoder) will read a field of the requested type.
+#
+# Note that Message and Group are intentionally missing here.
+# They're handled by _RecursivelyMerge().
+_Decoder = decoder.Decoder
+TYPE_TO_DESERIALIZE_METHOD = {
+    _FieldDescriptor.TYPE_DOUBLE: _Decoder.ReadDouble,
+    _FieldDescriptor.TYPE_FLOAT: _Decoder.ReadFloat,
+    _FieldDescriptor.TYPE_INT64: _Decoder.ReadInt64,
+    _FieldDescriptor.TYPE_UINT64: _Decoder.ReadUInt64,
+    _FieldDescriptor.TYPE_INT32: _Decoder.ReadInt32,
+    _FieldDescriptor.TYPE_FIXED64: _Decoder.ReadFixed64,
+    _FieldDescriptor.TYPE_FIXED32: _Decoder.ReadFixed32,
+    _FieldDescriptor.TYPE_BOOL: _Decoder.ReadBool,
+    _FieldDescriptor.TYPE_STRING: _Decoder.ReadString,
+    _FieldDescriptor.TYPE_BYTES: _Decoder.ReadBytes,
+    _FieldDescriptor.TYPE_UINT32: _Decoder.ReadUInt32,
+    _FieldDescriptor.TYPE_ENUM: _Decoder.ReadEnum,
+    _FieldDescriptor.TYPE_SFIXED32: _Decoder.ReadSFixed32,
+    _FieldDescriptor.TYPE_SFIXED64: _Decoder.ReadSFixed64,
+    _FieldDescriptor.TYPE_SINT32: _Decoder.ReadSInt32,
+    _FieldDescriptor.TYPE_SINT64: _Decoder.ReadSInt64,
+    }
diff --git a/python/google/protobuf/internal/wire_format.py b/python/google/protobuf/internal/wire_format.py
new file mode 100755
index 0000000..da6464d
--- /dev/null
+++ b/python/google/protobuf/internal/wire_format.py
@@ -0,0 +1,247 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Constants and static functions to support protocol buffer wire format."""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+import struct
+from google.protobuf import message
+
+
+TAG_TYPE_BITS = 3  # Number of bits used to hold type info in a proto tag.
+_TAG_TYPE_MASK = (1 << TAG_TYPE_BITS) - 1  # 0x7
+
+# These numbers identify the wire type of a protocol buffer value.
+# We use the least-significant TAG_TYPE_BITS bits of the varint-encoded
+# tag-and-type to store one of these WIRETYPE_* constants.
+# These values must match WireType enum in //net/proto2/public/wire_format.h.
+WIRETYPE_VARINT = 0
+WIRETYPE_FIXED64 = 1
+WIRETYPE_LENGTH_DELIMITED = 2
+WIRETYPE_START_GROUP = 3
+WIRETYPE_END_GROUP = 4
+WIRETYPE_FIXED32 = 5
+_WIRETYPE_MAX = 5
+
+
+# Bounds for various integer types.
+INT32_MAX = int((1 << 31) - 1)
+INT32_MIN = int(-(1 << 31))
+UINT32_MAX = (1 << 32) - 1
+
+INT64_MAX = (1 << 63) - 1
+INT64_MIN = -(1 << 63)
+UINT64_MAX = (1 << 64) - 1
+
+# "struct" format strings that will encode/decode the specified formats.
+FORMAT_UINT32_LITTLE_ENDIAN = '<I'
+FORMAT_UINT64_LITTLE_ENDIAN = '<Q'
+FORMAT_FLOAT_LITTLE_ENDIAN = '<f'
+FORMAT_DOUBLE_LITTLE_ENDIAN = '<d'
+
+
+# We'll have to provide alternate implementations of AppendLittleEndian*() on
+# any architectures where these checks fail.
+if struct.calcsize(FORMAT_UINT32_LITTLE_ENDIAN) != 4:
+  raise AssertionError('Format "I" is not a 32-bit number.')
+if struct.calcsize(FORMAT_UINT64_LITTLE_ENDIAN) != 8:
+  raise AssertionError('Format "Q" is not a 64-bit number.')
+
+
+def PackTag(field_number, wire_type):
+  """Returns an unsigned 32-bit integer that encodes the field number and
+  wire type information in standard protocol message wire format.
+
+  Args:
+    field_number: Expected to be an integer in the range [1, 1 << 29)
+    wire_type: One of the WIRETYPE_* constants.
+  """
+  if not 0 <= wire_type <= _WIRETYPE_MAX:
+    raise message.EncodeError('Unknown wire type: %d' % wire_type)
+  return (field_number << TAG_TYPE_BITS) | wire_type
+
+
+def UnpackTag(tag):
+  """The inverse of PackTag().  Given an unsigned 32-bit number,
+  returns a (field_number, wire_type) tuple.
+  """
+  return (tag >> TAG_TYPE_BITS), (tag & _TAG_TYPE_MASK)
+
+
+def ZigZagEncode(value):
+  """ZigZag Transform:  Encodes signed integers so that they can be
+  effectively used with varint encoding.  See wire_format.h for
+  more details.
+  """
+  if value >= 0:
+    return value << 1
+  return (value << 1) ^ (~0)
+
+
+def ZigZagDecode(value):
+  """Inverse of ZigZagEncode()."""
+  if not value & 0x1:
+    return value >> 1
+  return (value >> 1) ^ (~0)
+
+
+
+# The *ByteSize() functions below return the number of bytes required to
+# serialize "field number + type" information and then serialize the value.
+
+
+def Int32ByteSize(field_number, int32):
+  return Int64ByteSize(field_number, int32)
+
+
+def Int32ByteSizeNoTag(int32):
+  return _VarUInt64ByteSizeNoTag(0xffffffffffffffff & int32)
+
+
+def Int64ByteSize(field_number, int64):
+  # Have to convert to uint before calling UInt64ByteSize().
+  return UInt64ByteSize(field_number, 0xffffffffffffffff & int64)
+
+
+def UInt32ByteSize(field_number, uint32):
+  return UInt64ByteSize(field_number, uint32)
+
+
+def UInt64ByteSize(field_number, uint64):
+  return TagByteSize(field_number) + _VarUInt64ByteSizeNoTag(uint64)
+
+
+def SInt32ByteSize(field_number, int32):
+  return UInt32ByteSize(field_number, ZigZagEncode(int32))
+
+
+def SInt64ByteSize(field_number, int64):
+  return UInt64ByteSize(field_number, ZigZagEncode(int64))
+
+
+def Fixed32ByteSize(field_number, fixed32):
+  return TagByteSize(field_number) + 4
+
+
+def Fixed64ByteSize(field_number, fixed64):
+  return TagByteSize(field_number) + 8
+
+
+def SFixed32ByteSize(field_number, sfixed32):
+  return TagByteSize(field_number) + 4
+
+
+def SFixed64ByteSize(field_number, sfixed64):
+  return TagByteSize(field_number) + 8
+
+
+def FloatByteSize(field_number, flt):
+  return TagByteSize(field_number) + 4
+
+
+def DoubleByteSize(field_number, double):
+  return TagByteSize(field_number) + 8
+
+
+def BoolByteSize(field_number, b):
+  return TagByteSize(field_number) + 1
+
+
+def EnumByteSize(field_number, enum):
+  return UInt32ByteSize(field_number, enum)
+
+
+def StringByteSize(field_number, string):
+  return BytesByteSize(field_number, string.encode('utf-8'))
+
+
+def BytesByteSize(field_number, b):
+  return (TagByteSize(field_number)
+          + _VarUInt64ByteSizeNoTag(len(b))
+          + len(b))
+
+
+def GroupByteSize(field_number, message):
+  return (2 * TagByteSize(field_number)  # START and END group.
+          + message.ByteSize())
+
+
+def MessageByteSize(field_number, message):
+  return (TagByteSize(field_number)
+          + _VarUInt64ByteSizeNoTag(message.ByteSize())
+          + message.ByteSize())
+
+
+def MessageSetItemByteSize(field_number, msg):
+  # First compute the sizes of the tags.
+  # There are 2 tags for the beginning and ending of the repeated group, that
+  # is field number 1, one with field number 2 (type_id) and one with field
+  # number 3 (message).
+  total_size = (2 * TagByteSize(1) + TagByteSize(2) + TagByteSize(3))
+
+  # Add the number of bytes for type_id.
+  total_size += _VarUInt64ByteSizeNoTag(field_number)
+
+  message_size = msg.ByteSize()
+
+  # The number of bytes for encoding the length of the message.
+  total_size += _VarUInt64ByteSizeNoTag(message_size)
+
+  # The size of the message.
+  total_size += message_size
+  return total_size
+
+
+def TagByteSize(field_number):
+  """Returns the bytes required to serialize a tag with this field number."""
+  # Just pass in type 0, since the type won't affect the tag+type size.
+  return _VarUInt64ByteSizeNoTag(PackTag(field_number, 0))
+
+
+# Private helper function for the *ByteSize() functions above.
+
+def _VarUInt64ByteSizeNoTag(uint64):
+  """Returns the number of bytes required to serialize a single varint
+  using boundary value comparisons. (unrolled loop optimization -WPierce)
+  uint64 must be unsigned.
+  """
+  if uint64 <= 0x7f: return 1
+  if uint64 <= 0x3fff: return 2
+  if uint64 <= 0x1fffff: return 3
+  if uint64 <= 0xfffffff: return 4
+  if uint64 <= 0x7ffffffff: return 5
+  if uint64 <= 0x3ffffffffff: return 6
+  if uint64 <= 0x1ffffffffffff: return 7
+  if uint64 <= 0xffffffffffffff: return 8
+  if uint64 <= 0x7fffffffffffffff: return 9
+  if uint64 > UINT64_MAX:
+    raise message.EncodeError('Value out of range: %d' % uint64)
+  return 10
diff --git a/python/google/protobuf/internal/wire_format_test.py b/python/google/protobuf/internal/wire_format_test.py
new file mode 100755
index 0000000..7600778
--- /dev/null
+++ b/python/google/protobuf/internal/wire_format_test.py
@@ -0,0 +1,253 @@
+#! /usr/bin/python
+#
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Test for google.protobuf.internal.wire_format."""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+import unittest
+from google.protobuf import message
+from google.protobuf.internal import wire_format
+
+
+class WireFormatTest(unittest.TestCase):
+
+  def testPackTag(self):
+    field_number = 0xabc
+    tag_type = 2
+    self.assertEqual((field_number << 3) | tag_type,
+                     wire_format.PackTag(field_number, tag_type))
+    PackTag = wire_format.PackTag
+    # Number too high.
+    self.assertRaises(message.EncodeError, PackTag, field_number, 6)
+    # Number too low.
+    self.assertRaises(message.EncodeError, PackTag, field_number, -1)
+
+  def testUnpackTag(self):
+    # Test field numbers that will require various varint sizes.
+    for expected_field_number in (1, 15, 16, 2047, 2048):
+      for expected_wire_type in range(6):  # Highest-numbered wiretype is 5.
+        field_number, wire_type = wire_format.UnpackTag(
+            wire_format.PackTag(expected_field_number, expected_wire_type))
+        self.assertEqual(expected_field_number, field_number)
+        self.assertEqual(expected_wire_type, wire_type)
+
+    self.assertRaises(TypeError, wire_format.UnpackTag, None)
+    self.assertRaises(TypeError, wire_format.UnpackTag, 'abc')
+    self.assertRaises(TypeError, wire_format.UnpackTag, 0.0)
+    self.assertRaises(TypeError, wire_format.UnpackTag, object())
+
+  def testZigZagEncode(self):
+    Z = wire_format.ZigZagEncode
+    self.assertEqual(0, Z(0))
+    self.assertEqual(1, Z(-1))
+    self.assertEqual(2, Z(1))
+    self.assertEqual(3, Z(-2))
+    self.assertEqual(4, Z(2))
+    self.assertEqual(0xfffffffe, Z(0x7fffffff))
+    self.assertEqual(0xffffffff, Z(-0x80000000))
+    self.assertEqual(0xfffffffffffffffe, Z(0x7fffffffffffffff))
+    self.assertEqual(0xffffffffffffffff, Z(-0x8000000000000000))
+
+    self.assertRaises(TypeError, Z, None)
+    self.assertRaises(TypeError, Z, 'abcd')
+    self.assertRaises(TypeError, Z, 0.0)
+    self.assertRaises(TypeError, Z, object())
+
+  def testZigZagDecode(self):
+    Z = wire_format.ZigZagDecode
+    self.assertEqual(0, Z(0))
+    self.assertEqual(-1, Z(1))
+    self.assertEqual(1, Z(2))
+    self.assertEqual(-2, Z(3))
+    self.assertEqual(2, Z(4))
+    self.assertEqual(0x7fffffff, Z(0xfffffffe))
+    self.assertEqual(-0x80000000, Z(0xffffffff))
+    self.assertEqual(0x7fffffffffffffff, Z(0xfffffffffffffffe))
+    self.assertEqual(-0x8000000000000000, Z(0xffffffffffffffff))
+
+    self.assertRaises(TypeError, Z, None)
+    self.assertRaises(TypeError, Z, 'abcd')
+    self.assertRaises(TypeError, Z, 0.0)
+    self.assertRaises(TypeError, Z, object())
+
+  def NumericByteSizeTestHelper(self, byte_size_fn, value, expected_value_size):
+    # Use field numbers that cause various byte sizes for the tag information.
+    for field_number, tag_bytes in ((15, 1), (16, 2), (2047, 2), (2048, 3)):
+      expected_size = expected_value_size + tag_bytes
+      actual_size = byte_size_fn(field_number, value)
+      self.assertEqual(expected_size, actual_size,
+                       'byte_size_fn: %s, field_number: %d, value: %r\n'
+                       'Expected: %d, Actual: %d'% (
+          byte_size_fn, field_number, value, expected_size, actual_size))
+
+  def testByteSizeFunctions(self):
+    # Test all numeric *ByteSize() functions.
+    NUMERIC_ARGS = [
+        # Int32ByteSize().
+        [wire_format.Int32ByteSize, 0, 1],
+        [wire_format.Int32ByteSize, 127, 1],
+        [wire_format.Int32ByteSize, 128, 2],
+        [wire_format.Int32ByteSize, -1, 10],
+        # Int64ByteSize().
+        [wire_format.Int64ByteSize, 0, 1],
+        [wire_format.Int64ByteSize, 127, 1],
+        [wire_format.Int64ByteSize, 128, 2],
+        [wire_format.Int64ByteSize, -1, 10],
+        # UInt32ByteSize().
+        [wire_format.UInt32ByteSize, 0, 1],
+        [wire_format.UInt32ByteSize, 127, 1],
+        [wire_format.UInt32ByteSize, 128, 2],
+        [wire_format.UInt32ByteSize, wire_format.UINT32_MAX, 5],
+        # UInt64ByteSize().
+        [wire_format.UInt64ByteSize, 0, 1],
+        [wire_format.UInt64ByteSize, 127, 1],
+        [wire_format.UInt64ByteSize, 128, 2],
+        [wire_format.UInt64ByteSize, wire_format.UINT64_MAX, 10],
+        # SInt32ByteSize().
+        [wire_format.SInt32ByteSize, 0, 1],
+        [wire_format.SInt32ByteSize, -1, 1],
+        [wire_format.SInt32ByteSize, 1, 1],
+        [wire_format.SInt32ByteSize, -63, 1],
+        [wire_format.SInt32ByteSize, 63, 1],
+        [wire_format.SInt32ByteSize, -64, 1],
+        [wire_format.SInt32ByteSize, 64, 2],
+        # SInt64ByteSize().
+        [wire_format.SInt64ByteSize, 0, 1],
+        [wire_format.SInt64ByteSize, -1, 1],
+        [wire_format.SInt64ByteSize, 1, 1],
+        [wire_format.SInt64ByteSize, -63, 1],
+        [wire_format.SInt64ByteSize, 63, 1],
+        [wire_format.SInt64ByteSize, -64, 1],
+        [wire_format.SInt64ByteSize, 64, 2],
+        # Fixed32ByteSize().
+        [wire_format.Fixed32ByteSize, 0, 4],
+        [wire_format.Fixed32ByteSize, wire_format.UINT32_MAX, 4],
+        # Fixed64ByteSize().
+        [wire_format.Fixed64ByteSize, 0, 8],
+        [wire_format.Fixed64ByteSize, wire_format.UINT64_MAX, 8],
+        # SFixed32ByteSize().
+        [wire_format.SFixed32ByteSize, 0, 4],
+        [wire_format.SFixed32ByteSize, wire_format.INT32_MIN, 4],
+        [wire_format.SFixed32ByteSize, wire_format.INT32_MAX, 4],
+        # SFixed64ByteSize().
+        [wire_format.SFixed64ByteSize, 0, 8],
+        [wire_format.SFixed64ByteSize, wire_format.INT64_MIN, 8],
+        [wire_format.SFixed64ByteSize, wire_format.INT64_MAX, 8],
+        # FloatByteSize().
+        [wire_format.FloatByteSize, 0.0, 4],
+        [wire_format.FloatByteSize, 1000000000.0, 4],
+        [wire_format.FloatByteSize, -1000000000.0, 4],
+        # DoubleByteSize().
+        [wire_format.DoubleByteSize, 0.0, 8],
+        [wire_format.DoubleByteSize, 1000000000.0, 8],
+        [wire_format.DoubleByteSize, -1000000000.0, 8],
+        # BoolByteSize().
+        [wire_format.BoolByteSize, False, 1],
+        [wire_format.BoolByteSize, True, 1],
+        # EnumByteSize().
+        [wire_format.EnumByteSize, 0, 1],
+        [wire_format.EnumByteSize, 127, 1],
+        [wire_format.EnumByteSize, 128, 2],
+        [wire_format.EnumByteSize, wire_format.UINT32_MAX, 5],
+        ]
+    for args in NUMERIC_ARGS:
+      self.NumericByteSizeTestHelper(*args)
+
+    # Test strings and bytes.
+    for byte_size_fn in (wire_format.StringByteSize, wire_format.BytesByteSize):
+      # 1 byte for tag, 1 byte for length, 3 bytes for contents.
+      self.assertEqual(5, byte_size_fn(10, 'abc'))
+      # 2 bytes for tag, 1 byte for length, 3 bytes for contents.
+      self.assertEqual(6, byte_size_fn(16, 'abc'))
+      # 2 bytes for tag, 2 bytes for length, 128 bytes for contents.
+      self.assertEqual(132, byte_size_fn(16, 'a' * 128))
+
+    # Test UTF-8 string byte size calculation.
+    # 1 byte for tag, 1 byte for length, 8 bytes for content.
+    self.assertEqual(10, wire_format.StringByteSize(
+        5, unicode('\xd0\xa2\xd0\xb5\xd1\x81\xd1\x82', 'utf-8')))
+
+    class MockMessage(object):
+      def __init__(self, byte_size):
+        self.byte_size = byte_size
+      def ByteSize(self):
+        return self.byte_size
+
+    message_byte_size = 10
+    mock_message = MockMessage(byte_size=message_byte_size)
+    # Test groups.
+    # (2 * 1) bytes for begin and end tags, plus message_byte_size.
+    self.assertEqual(2 + message_byte_size,
+                     wire_format.GroupByteSize(1, mock_message))
+    # (2 * 2) bytes for begin and end tags, plus message_byte_size.
+    self.assertEqual(4 + message_byte_size,
+                     wire_format.GroupByteSize(16, mock_message))
+
+    # Test messages.
+    # 1 byte for tag, plus 1 byte for length, plus contents.
+    self.assertEqual(2 + mock_message.byte_size,
+                     wire_format.MessageByteSize(1, mock_message))
+    # 2 bytes for tag, plus 1 byte for length, plus contents.
+    self.assertEqual(3 + mock_message.byte_size,
+                     wire_format.MessageByteSize(16, mock_message))
+    # 2 bytes for tag, plus 2 bytes for length, plus contents.
+    mock_message.byte_size = 128
+    self.assertEqual(4 + mock_message.byte_size,
+                     wire_format.MessageByteSize(16, mock_message))
+
+
+    # Test message set item byte size.
+    # 4 bytes for tags, plus 1 byte for length, plus 1 byte for type_id,
+    # plus contents.
+    mock_message.byte_size = 10
+    self.assertEqual(mock_message.byte_size + 6,
+                     wire_format.MessageSetItemByteSize(1, mock_message))
+
+    # 4 bytes for tags, plus 2 bytes for length, plus 1 byte for type_id,
+    # plus contents.
+    mock_message.byte_size = 128
+    self.assertEqual(mock_message.byte_size + 7,
+                     wire_format.MessageSetItemByteSize(1, mock_message))
+
+    # 4 bytes for tags, plus 2 bytes for length, plus 2 byte for type_id,
+    # plus contents.
+    self.assertEqual(mock_message.byte_size + 8,
+                     wire_format.MessageSetItemByteSize(128, mock_message))
+
+    # Too-long varint.
+    self.assertRaises(message.EncodeError,
+                      wire_format.UInt64ByteSize, 1, 1 << 128)
+
+
+if __name__ == '__main__':
+  unittest.main()
diff --git a/python/google/protobuf/message.py b/python/google/protobuf/message.py
new file mode 100755
index 0000000..9a88bdc
--- /dev/null
+++ b/python/google/protobuf/message.py
@@ -0,0 +1,245 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+# TODO(robinson): We should just make these methods all "pure-virtual" and move
+# all implementation out, into reflection.py for now.
+
+
+"""Contains an abstract base class for protocol messages."""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+
+class Error(Exception): pass
+class DecodeError(Error): pass
+class EncodeError(Error): pass
+
+
+class Message(object):
+
+  """Abstract base class for protocol messages.
+
+  Protocol message classes are almost always generated by the protocol
+  compiler.  These generated types subclass Message and implement the methods
+  shown below.
+
+  TODO(robinson): Link to an HTML document here.
+
+  TODO(robinson): Document that instances of this class will also
+  have an Extensions attribute with __getitem__ and __setitem__.
+  Again, not sure how to best convey this.
+
+  TODO(robinson): Document that the class must also have a static
+    RegisterExtension(extension_field) method.
+    Not sure how to best express at this point.
+  """
+
+  # TODO(robinson): Document these fields and methods.
+
+  __slots__ = []
+
+  DESCRIPTOR = None
+
+  def __eq__(self, other_msg):
+    raise NotImplementedError
+
+  def __ne__(self, other_msg):
+    # Can't just say self != other_msg, since that would infinitely recurse. :)
+    return not self == other_msg
+
+  def __str__(self):
+    raise NotImplementedError
+
+  def MergeFrom(self, other_msg):
+    """Merges the contents of the specified message into current message.
+
+    This method merges the contents of the specified message into the current
+    message. Singular fields that are set in the specified message overwrite
+    the corresponding fields in the current message. Repeated fields are
+    appended. Singular sub-messages and groups are recursively merged.
+
+    Args:
+      other_msg: Message to merge into the current message.
+    """
+    raise NotImplementedError
+
+  def CopyFrom(self, other_msg):
+    """Copies the content of the specified message into the current message.
+
+    The method clears the current message and then merges the specified
+    message using MergeFrom.
+
+    Args:
+      other_msg: Message to copy into the current one.
+    """
+    if self == other_msg:
+      return
+    self.Clear()
+    self.MergeFrom(other_msg)
+
+  def Clear(self):
+    """Clears all data that was set in the message."""
+    raise NotImplementedError
+
+  def IsInitialized(self):
+    """Checks if the message is initialized.
+
+    Returns:
+      The method returns True if the message is initialized (i.e. all of its
+      required fields are set).
+    """
+    raise NotImplementedError
+
+  # TODO(robinson): MergeFromString() should probably return None and be
+  # implemented in terms of a helper that returns the # of bytes read.  Our
+  # deserialization routines would use the helper when recursively
+  # deserializing, but the end user would almost always just want the no-return
+  # MergeFromString().
+
+  def MergeFromString(self, serialized):
+    """Merges serialized protocol buffer data into this message.
+
+    When we find a field in |serialized| that is already present
+    in this message:
+      - If it's a "repeated" field, we append to the end of our list.
+      - Else, if it's a scalar, we overwrite our field.
+      - Else, (it's a nonrepeated composite), we recursively merge
+        into the existing composite.
+
+    TODO(robinson): Document handling of unknown fields.
+
+    Args:
+      serialized: Any object that allows us to call buffer(serialized)
+        to access a string of bytes using the buffer interface.
+
+    TODO(robinson): When we switch to a helper, this will return None.
+
+    Returns:
+      The number of bytes read from |serialized|.
+      For non-group messages, this will always be len(serialized),
+      but for messages which are actually groups, this will
+      generally be less than len(serialized), since we must
+      stop when we reach an END_GROUP tag.  Note that if
+      we *do* stop because of an END_GROUP tag, the number
+      of bytes returned does not include the bytes
+      for the END_GROUP tag information.
+    """
+    raise NotImplementedError
+
+  def ParseFromString(self, serialized):
+    """Like MergeFromString(), except we clear the object first."""
+    self.Clear()
+    self.MergeFromString(serialized)
+
+  def SerializeToString(self):
+    """Serializes the protocol message to a binary string.
+
+    Returns:
+      A binary string representation of the message if all of the required
+      fields in the message are set (i.e. the message is initialized).
+
+    Raises:
+      message.EncodeError if the message isn't initialized.
+    """
+    raise NotImplementedError
+
+  def SerializePartialToString(self):
+    """Serializes the protocol message to a binary string.
+
+    This method is similar to SerializeToString but doesn't check if the
+    message is initialized.
+
+    Returns:
+      A string representation of the partial message.
+    """
+    raise NotImplementedError
+
+  # TODO(robinson): Decide whether we like these better
+  # than auto-generated has_foo() and clear_foo() methods
+  # on the instances themselves.  This way is less consistent
+  # with C++, but it makes reflection-type access easier and
+  # reduces the number of magically autogenerated things.
+  #
+  # TODO(robinson): Be sure to document (and test) exactly
+  # which field names are accepted here.  Are we case-sensitive?
+  # What do we do with fields that share names with Python keywords
+  # like 'lambda' and 'yield'?
+  #
+  # nnorwitz says:
+  # """
+  # Typically (in python), an underscore is appended to names that are
+  # keywords. So they would become lambda_ or yield_.
+  # """
+  def ListFields(self):
+    """Returns a list of (FieldDescriptor, value) tuples for all
+    fields in the message which are not empty.  A singular field is non-empty
+    if HasField() would return true, and a repeated field is non-empty if
+    it contains at least one element.  The fields are ordered by field
+    number"""
+    raise NotImplementedError
+
+  def HasField(self, field_name):
+    raise NotImplementedError
+
+  def ClearField(self, field_name):
+    raise NotImplementedError
+
+  def HasExtension(self, extension_handle):
+    raise NotImplementedError
+
+  def ClearExtension(self, extension_handle):
+    raise NotImplementedError
+
+  def ByteSize(self):
+    """Returns the serialized size of this message.
+    Recursively calls ByteSize() on all contained messages.
+    """
+    raise NotImplementedError
+
+  def _SetListener(self, message_listener):
+    """Internal method used by the protocol message implementation.
+    Clients should not call this directly.
+
+    Sets a listener that this message will call on certain state transitions.
+
+    The purpose of this method is to register back-edges from children to
+    parents at runtime, for the purpose of setting "has" bits and
+    byte-size-dirty bits in the parent and ancestor objects whenever a child or
+    descendant object is modified.
+
+    If the client wants to disconnect this Message from the object tree, she
+    explicitly sets callback to None.
+
+    If message_listener is None, unregisters any existing listener.  Otherwise,
+    message_listener must implement the MessageListener interface in
+    internal/message_listener.py, and we discard any listener registered
+    via a previous _SetListener() call.
+    """
+    raise NotImplementedError
diff --git a/python/google/protobuf/reflection.py b/python/google/protobuf/reflection.py
new file mode 100755
index 0000000..d65d8b6
--- /dev/null
+++ b/python/google/protobuf/reflection.py
@@ -0,0 +1,1661 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+# This code is meant to work on Python 2.4 and above only.
+#
+# TODO(robinson): Helpers for verbose, common checks like seeing if a
+# descriptor's cpp_type is CPPTYPE_MESSAGE.
+
+"""Contains a metaclass and helper functions used to create
+protocol message classes from Descriptor objects at runtime.
+
+Recall that a metaclass is the "type" of a class.
+(A class is to a metaclass what an instance is to a class.)
+
+In this case, we use the GeneratedProtocolMessageType metaclass
+to inject all the useful functionality into the classes
+output by the protocol compiler at compile-time.
+
+The upshot of all this is that the real implementation
+details for ALL pure-Python protocol buffers are *here in
+this file*.
+"""
+
+__author__ = 'robinson@google.com (Will Robinson)'
+
+import heapq
+import threading
+import weakref
+# We use "as" to avoid name collisions with variables.
+from google.protobuf.internal import containers
+from google.protobuf.internal import decoder
+from google.protobuf.internal import encoder
+from google.protobuf.internal import message_listener as message_listener_mod
+from google.protobuf.internal import type_checkers
+from google.protobuf.internal import wire_format
+from google.protobuf import descriptor as descriptor_mod
+from google.protobuf import message as message_mod
+from google.protobuf import text_format
+
+_FieldDescriptor = descriptor_mod.FieldDescriptor
+
+
+class GeneratedProtocolMessageType(type):
+
+  """Metaclass for protocol message classes created at runtime from Descriptors.
+
+  We add implementations for all methods described in the Message class.  We
+  also create properties to allow getting/setting all fields in the protocol
+  message.  Finally, we create slots to prevent users from accidentally
+  "setting" nonexistent fields in the protocol message, which then wouldn't get
+  serialized / deserialized properly.
+
+  The protocol compiler currently uses this metaclass to create protocol
+  message classes at runtime.  Clients can also manually create their own
+  classes at runtime, as in this example:
+
+  mydescriptor = Descriptor(.....)
+  class MyProtoClass(Message):
+    __metaclass__ = GeneratedProtocolMessageType
+    DESCRIPTOR = mydescriptor
+  myproto_instance = MyProtoClass()
+  myproto.foo_field = 23
+  ...
+  """
+
+  # Must be consistent with the protocol-compiler code in
+  # proto2/compiler/internal/generator.*.
+  _DESCRIPTOR_KEY = 'DESCRIPTOR'
+
+  def __new__(cls, name, bases, dictionary):
+    """Custom allocation for runtime-generated class types.
+
+    We override __new__ because this is apparently the only place
+    where we can meaningfully set __slots__ on the class we're creating(?).
+    (The interplay between metaclasses and slots is not very well-documented).
+
+    Args:
+      name: Name of the class (ignored, but required by the
+        metaclass protocol).
+      bases: Base classes of the class we're constructing.
+        (Should be message.Message).  We ignore this field, but
+        it's required by the metaclass protocol
+      dictionary: The class dictionary of the class we're
+        constructing.  dictionary[_DESCRIPTOR_KEY] must contain
+        a Descriptor object describing this protocol message
+        type.
+
+    Returns:
+      Newly-allocated class.
+    """
+    descriptor = dictionary[GeneratedProtocolMessageType._DESCRIPTOR_KEY]
+    _AddSlots(descriptor, dictionary)
+    _AddClassAttributesForNestedExtensions(descriptor, dictionary)
+    superclass = super(GeneratedProtocolMessageType, cls)
+    return superclass.__new__(cls, name, bases, dictionary)
+
+  def __init__(cls, name, bases, dictionary):
+    """Here we perform the majority of our work on the class.
+    We add enum getters, an __init__ method, implementations
+    of all Message methods, and properties for all fields
+    in the protocol type.
+
+    Args:
+      name: Name of the class (ignored, but required by the
+        metaclass protocol).
+      bases: Base classes of the class we're constructing.
+        (Should be message.Message).  We ignore this field, but
+        it's required by the metaclass protocol
+      dictionary: The class dictionary of the class we're
+        constructing.  dictionary[_DESCRIPTOR_KEY] must contain
+        a Descriptor object describing this protocol message
+        type.
+    """
+    descriptor = dictionary[GeneratedProtocolMessageType._DESCRIPTOR_KEY]
+    # We act as a "friend" class of the descriptor, setting
+    # its _concrete_class attribute the first time we use a
+    # given descriptor to initialize a concrete protocol message
+    # class.
+    concrete_class_attr_name = '_concrete_class'
+    if not hasattr(descriptor, concrete_class_attr_name):
+      setattr(descriptor, concrete_class_attr_name, cls)
+    cls._known_extensions = []
+    _AddEnumValues(descriptor, cls)
+    _AddInitMethod(descriptor, cls)
+    _AddPropertiesForFields(descriptor, cls)
+    _AddPropertiesForExtensions(descriptor, cls)
+    _AddStaticMethods(cls)
+    _AddMessageMethods(descriptor, cls)
+    _AddPrivateHelperMethods(cls)
+    superclass = super(GeneratedProtocolMessageType, cls)
+    superclass.__init__(name, bases, dictionary)
+
+
+# Stateless helpers for GeneratedProtocolMessageType below.
+# Outside clients should not access these directly.
+#
+# I opted not to make any of these methods on the metaclass, to make it more
+# clear that I'm not really using any state there and to keep clients from
+# thinking that they have direct access to these construction helpers.
+
+
+def _PropertyName(proto_field_name):
+  """Returns the name of the public property attribute which
+  clients can use to get and (in some cases) set the value
+  of a protocol message field.
+
+  Args:
+    proto_field_name: The protocol message field name, exactly
+      as it appears (or would appear) in a .proto file.
+  """
+  # TODO(robinson): Escape Python keywords (e.g., yield), and test this support.
+  # nnorwitz makes my day by writing:
+  # """
+  # FYI.  See the keyword module in the stdlib. This could be as simple as:
+  #
+  # if keyword.iskeyword(proto_field_name):
+  #   return proto_field_name + "_"
+  # return proto_field_name
+  # """
+  return proto_field_name
+
+
+def _ValueFieldName(proto_field_name):
+  """Returns the name of the (internal) instance attribute which objects
+  should use to store the current value for a given protocol message field.
+
+  Args:
+    proto_field_name: The protocol message field name, exactly
+      as it appears (or would appear) in a .proto file.
+  """
+  return '_value_' + proto_field_name
+
+
+def _HasFieldName(proto_field_name):
+  """Returns the name of the (internal) instance attribute which
+  objects should use to store a boolean telling whether this field
+  is explicitly set or not.
+
+  Args:
+    proto_field_name: The protocol message field name, exactly
+      as it appears (or would appear) in a .proto file.
+  """
+  return '_has_' + proto_field_name
+
+
+def _AddSlots(message_descriptor, dictionary):
+  """Adds a __slots__ entry to dictionary, containing the names of all valid
+  attributes for this message type.
+
+  Args:
+    message_descriptor: A Descriptor instance describing this message type.
+    dictionary: Class dictionary to which we'll add a '__slots__' entry.
+  """
+  field_names = [_ValueFieldName(f.name) for f in message_descriptor.fields]
+  field_names.extend(_HasFieldName(f.name) for f in message_descriptor.fields
+                     if f.label != _FieldDescriptor.LABEL_REPEATED)
+  field_names.extend(('Extensions',
+                      '_cached_byte_size',
+                      '_cached_byte_size_dirty',
+                      '_called_transition_to_nonempty',
+                      '_listener',
+                      '_lock', '__weakref__'))
+  dictionary['__slots__'] = field_names
+
+
+def _AddClassAttributesForNestedExtensions(descriptor, dictionary):
+  extension_dict = descriptor.extensions_by_name
+  for extension_name, extension_field in extension_dict.iteritems():
+    assert extension_name not in dictionary
+    dictionary[extension_name] = extension_field
+
+
+def _AddEnumValues(descriptor, cls):
+  """Sets class-level attributes for all enum fields defined in this message.
+
+  Args:
+    descriptor: Descriptor object for this message type.
+    cls: Class we're constructing for this message type.
+  """
+  for enum_type in descriptor.enum_types:
+    for enum_value in enum_type.values:
+      setattr(cls, enum_value.name, enum_value.number)
+
+
+def _DefaultValueForField(message, field):
+  """Returns a default value for a field.
+
+  Args:
+    message: Message instance containing this field, or a weakref proxy
+      of same.
+    field: FieldDescriptor object for this field.
+
+  Returns: A default value for this field.  May refer back to |message|
+    via a weak reference.
+  """
+  # TODO(robinson): Only the repeated fields need a reference to 'message' (so
+  # that they can set the 'has' bit on the containing Message when someone
+  # append()s a value).  We could special-case this, and avoid an extra
+  # function call on __init__() and Clear() for non-repeated fields.
+
+  # TODO(robinson): Find a better place for the default value assertion in this
+  # function.  No need to repeat them every time the client calls Clear('foo').
+  # (We should probably just assert these things once and as early as possible,
+  # by tightening checking in the descriptor classes.)
+  if field.label == _FieldDescriptor.LABEL_REPEATED:
+    if field.default_value != []:
+      raise ValueError('Repeated field default value not empty list: %s' % (
+          field.default_value))
+    listener = _Listener(message, None)
+    if field.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
+      # We can't look at _concrete_class yet since it might not have
+      # been set.  (Depends on order in which we initialize the classes).
+      return containers.RepeatedCompositeFieldContainer(
+          listener, field.message_type)
+    else:
+      return containers.RepeatedScalarFieldContainer(
+          listener, type_checkers.GetTypeChecker(field.cpp_type, field.type))
+
+  if field.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
+    assert field.default_value is None
+
+  return field.default_value
+
+
+def _AddInitMethod(message_descriptor, cls):
+  """Adds an __init__ method to cls."""
+  fields = message_descriptor.fields
+  def init(self, **kwargs):
+    self._cached_byte_size = 0
+    self._cached_byte_size_dirty = False
+    self._listener = message_listener_mod.NullMessageListener()
+    self._called_transition_to_nonempty = False
+    # TODO(robinson): We should only create a lock if we really need one
+    # in this class.
+    self._lock = threading.Lock()
+    for field in fields:
+      default_value = _DefaultValueForField(self, field)
+      python_field_name = _ValueFieldName(field.name)
+      setattr(self, python_field_name, default_value)
+      if field.label != _FieldDescriptor.LABEL_REPEATED:
+        setattr(self, _HasFieldName(field.name), False)
+    self.Extensions = _ExtensionDict(self, cls._known_extensions)
+    for field_name, field_value in kwargs.iteritems():
+      field = _GetFieldByName(message_descriptor, field_name)
+      _MergeFieldOrExtension(self, field, field_value)
+
+  init.__module__ = None
+  init.__doc__ = None
+  cls.__init__ = init
+
+
+def _GetFieldByName(message_descriptor, field_name):
+  """Returns a field descriptor by field name.
+
+  Args:
+    message_descriptor: A Descriptor describing all fields in message.
+    field_name: The name of the field to retrieve.
+  Returns:
+    The field descriptor associated with the field name.
+  """
+  try:
+    return message_descriptor.fields_by_name[field_name]
+  except KeyError:
+    raise ValueError('Protocol message has no "%s" field.' % field_name)
+
+
+def _AddPropertiesForFields(descriptor, cls):
+  """Adds properties for all fields in this protocol message type."""
+  for field in descriptor.fields:
+    _AddPropertiesForField(field, cls)
+
+
+def _AddPropertiesForField(field, cls):
+  """Adds a public property for a protocol message field.
+  Clients can use this property to get and (in the case
+  of non-repeated scalar fields) directly set the value
+  of a protocol message field.
+
+  Args:
+    field: A FieldDescriptor for this field.
+    cls: The class we're constructing.
+  """
+  # Catch it if we add other types that we should
+  # handle specially here.
+  assert _FieldDescriptor.MAX_CPPTYPE == 10
+
+  constant_name = field.name.upper() + "_FIELD_NUMBER"
+  setattr(cls, constant_name, field.number)
+
+  if field.label == _FieldDescriptor.LABEL_REPEATED:
+    _AddPropertiesForRepeatedField(field, cls)
+  elif field.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
+    _AddPropertiesForNonRepeatedCompositeField(field, cls)
+  else:
+    _AddPropertiesForNonRepeatedScalarField(field, cls)
+
+
+def _AddPropertiesForRepeatedField(field, cls):
+  """Adds a public property for a "repeated" protocol message field.  Clients
+  can use this property to get the value of the field, which will be either a
+  _RepeatedScalarFieldContainer or _RepeatedCompositeFieldContainer (see
+  below).
+
+  Note that when clients add values to these containers, we perform
+  type-checking in the case of repeated scalar fields, and we also set any
+  necessary "has" bits as a side-effect.
+
+  Args:
+    field: A FieldDescriptor for this field.
+    cls: The class we're constructing.
+  """
+  proto_field_name = field.name
+  python_field_name = _ValueFieldName(proto_field_name)
+  property_name = _PropertyName(proto_field_name)
+
+  def getter(self):
+    return getattr(self, python_field_name)
+  getter.__module__ = None
+  getter.__doc__ = 'Getter for %s.' % proto_field_name
+
+  # We define a setter just so we can throw an exception with a more
+  # helpful error message.
+  def setter(self, new_value):
+    raise AttributeError('Assignment not allowed to repeated field '
+                         '"%s" in protocol message object.' % proto_field_name)
+
+  doc = 'Magic attribute generated for "%s" proto field.' % proto_field_name
+  setattr(cls, property_name, property(getter, setter, doc=doc))
+
+
+def _AddPropertiesForNonRepeatedScalarField(field, cls):
+  """Adds a public property for a nonrepeated, scalar protocol message field.
+  Clients can use this property to get and directly set the value of the field.
+  Note that when the client sets the value of a field by using this property,
+  all necessary "has" bits are set as a side-effect, and we also perform
+  type-checking.
+
+  Args:
+    field: A FieldDescriptor for this field.
+    cls: The class we're constructing.
+  """
+  proto_field_name = field.name
+  python_field_name = _ValueFieldName(proto_field_name)
+  has_field_name = _HasFieldName(proto_field_name)
+  property_name = _PropertyName(proto_field_name)
+  type_checker = type_checkers.GetTypeChecker(field.cpp_type, field.type)
+
+  def getter(self):
+    return getattr(self, python_field_name)
+  getter.__module__ = None
+  getter.__doc__ = 'Getter for %s.' % proto_field_name
+  def setter(self, new_value):
+    type_checker.CheckValue(new_value)
+    setattr(self, has_field_name, True)
+    self._MarkByteSizeDirty()
+    self._MaybeCallTransitionToNonemptyCallback()
+    setattr(self, python_field_name, new_value)
+  setter.__module__ = None
+  setter.__doc__ = 'Setter for %s.' % proto_field_name
+
+  # Add a property to encapsulate the getter/setter.
+  doc = 'Magic attribute generated for "%s" proto field.' % proto_field_name
+  setattr(cls, property_name, property(getter, setter, doc=doc))
+
+
+def _AddPropertiesForNonRepeatedCompositeField(field, cls):
+  """Adds a public property for a nonrepeated, composite protocol message field.
+  A composite field is a "group" or "message" field.
+
+  Clients can use this property to get the value of the field, but cannot
+  assign to the property directly.
+
+  Args:
+    field: A FieldDescriptor for this field.
+    cls: The class we're constructing.
+  """
+  # TODO(robinson): Remove duplication with similar method
+  # for non-repeated scalars.
+  proto_field_name = field.name
+  python_field_name = _ValueFieldName(proto_field_name)
+  has_field_name = _HasFieldName(proto_field_name)
+  property_name = _PropertyName(proto_field_name)
+  message_type = field.message_type
+
+  def getter(self):
+    # TODO(robinson): Appropriately scary note about double-checked locking.
+    field_value = getattr(self, python_field_name)
+    if field_value is None:
+      self._lock.acquire()
+      try:
+        field_value = getattr(self, python_field_name)
+        if field_value is None:
+          field_class = message_type._concrete_class
+          field_value = field_class()
+          field_value._SetListener(_Listener(self, has_field_name))
+          setattr(self, python_field_name, field_value)
+      finally:
+        self._lock.release()
+    return field_value
+  getter.__module__ = None
+  getter.__doc__ = 'Getter for %s.' % proto_field_name
+
+  # We define a setter just so we can throw an exception with a more
+  # helpful error message.
+  def setter(self, new_value):
+    raise AttributeError('Assignment not allowed to composite field '
+                         '"%s" in protocol message object.' % proto_field_name)
+
+  # Add a property to encapsulate the getter.
+  doc = 'Magic attribute generated for "%s" proto field.' % proto_field_name
+  setattr(cls, property_name, property(getter, setter, doc=doc))
+
+
+def _AddPropertiesForExtensions(descriptor, cls):
+  """Adds properties for all fields in this protocol message type."""
+  extension_dict = descriptor.extensions_by_name
+  for extension_name, extension_field in extension_dict.iteritems():
+    constant_name = extension_name.upper() + "_FIELD_NUMBER"
+    setattr(cls, constant_name, extension_field.number)
+
+
+def _AddStaticMethods(cls):
+  # TODO(robinson): This probably needs to be thread-safe(?)
+  def RegisterExtension(extension_handle):
+    extension_handle.containing_type = cls.DESCRIPTOR
+    cls._known_extensions.append(extension_handle)
+  cls.RegisterExtension = staticmethod(RegisterExtension)
+
+  def FromString(s):
+    message = cls()
+    message.MergeFromString(s)
+    return message
+  cls.FromString = staticmethod(FromString)
+
+
+def _AddListFieldsMethod(message_descriptor, cls):
+  """Helper for _AddMessageMethods()."""
+
+  # Ensure that we always list in ascending field-number order.
+  # For non-extension fields, we can do the sort once, here, at import-time.
+  # For extensions, we sort on each ListFields() call, though
+  # we could do better if we have to.
+  fields = sorted(message_descriptor.fields, key=lambda f: f.number)
+  has_field_names = (_HasFieldName(f.name) for f in fields)
+  value_field_names = (_ValueFieldName(f.name) for f in fields)
+  triplets = zip(has_field_names, value_field_names, fields)
+
+  def ListFields(self):
+    # We need to list all extension and non-extension fields
+    # together, in sorted order by field number.
+
+    # Step 0: Get an iterator over all "set" non-extension fields,
+    # sorted by field number.
+    # This iterator yields (field_number, field_descriptor, value) tuples.
+    def SortedSetFieldsIter():
+      # Note that triplets is already sorted by field number.
+      for has_field_name, value_field_name, field_descriptor in triplets:
+        if field_descriptor.label == _FieldDescriptor.LABEL_REPEATED:
+          value = getattr(self, _ValueFieldName(field_descriptor.name))
+          if len(value) > 0:
+            yield (field_descriptor.number, field_descriptor, value)
+        elif getattr(self, _HasFieldName(field_descriptor.name)):
+          value = getattr(self, _ValueFieldName(field_descriptor.name))
+          yield (field_descriptor.number, field_descriptor, value)
+    sorted_fields = SortedSetFieldsIter()
+
+    # Step 1: Get an iterator over all "set" extension fields,
+    # sorted by field number.
+    # This iterator ALSO yields (field_number, field_descriptor, value) tuples.
+    # TODO(robinson): It's not necessary to repeat this with each
+    # serialization call.  We can do better.
+    sorted_extension_fields = sorted(
+        [(f.number, f, v) for f, v in self.Extensions._ListSetExtensions()])
+
+    # Step 2: Create a composite iterator that merges the extension-
+    # and non-extension fields, and that still yields fields in
+    # sorted order.
+    all_set_fields = _ImergeSorted(sorted_fields, sorted_extension_fields)
+
+    # Step 3: Strip off the field numbers and return.
+    return [field[1:] for field in all_set_fields]
+
+  cls.ListFields = ListFields
+
+def _AddHasFieldMethod(cls):
+  """Helper for _AddMessageMethods()."""
+  def HasField(self, field_name):
+    try:
+      return getattr(self, _HasFieldName(field_name))
+    except AttributeError:
+      raise ValueError('Protocol message has no "%s" field.' % field_name)
+  cls.HasField = HasField
+
+
+def _AddClearFieldMethod(cls):
+  """Helper for _AddMessageMethods()."""
+  def ClearField(self, field_name):
+    field = _GetFieldByName(self.DESCRIPTOR, field_name)
+    proto_field_name = field.name
+    python_field_name = _ValueFieldName(proto_field_name)
+    has_field_name = _HasFieldName(proto_field_name)
+    default_value = _DefaultValueForField(self, field)
+    if field.label == _FieldDescriptor.LABEL_REPEATED:
+      self._MarkByteSizeDirty()
+    else:
+      if field.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
+        old_field_value = getattr(self, python_field_name)
+        if old_field_value is not None:
+          # Snip the old object out of the object tree.
+          old_field_value._SetListener(None)
+      if getattr(self, has_field_name):
+        setattr(self, has_field_name, False)
+        # Set dirty bit on ourself and parents only if
+        # we're actually changing state.
+        self._MarkByteSizeDirty()
+    setattr(self, python_field_name, default_value)
+  cls.ClearField = ClearField
+
+
+def _AddClearExtensionMethod(cls):
+  """Helper for _AddMessageMethods()."""
+  def ClearExtension(self, extension_handle):
+    self.Extensions._ClearExtension(extension_handle)
+  cls.ClearExtension = ClearExtension
+
+
+def _AddClearMethod(cls):
+  """Helper for _AddMessageMethods()."""
+  def Clear(self):
+    # Clear fields.
+    fields = self.DESCRIPTOR.fields
+    for field in fields:
+      self.ClearField(field.name)
+    # Clear extensions.
+    extensions = self.Extensions._ListSetExtensions()
+    for extension in extensions:
+      self.ClearExtension(extension[0])
+  cls.Clear = Clear
+
+
+def _AddHasExtensionMethod(cls):
+  """Helper for _AddMessageMethods()."""
+  def HasExtension(self, extension_handle):
+    return self.Extensions._HasExtension(extension_handle)
+  cls.HasExtension = HasExtension
+
+
+def _AddEqualsMethod(message_descriptor, cls):
+  """Helper for _AddMessageMethods()."""
+  def __eq__(self, other):
+    if (not isinstance(other, message_mod.Message) or
+        other.DESCRIPTOR != self.DESCRIPTOR):
+      return False
+
+    if self is other:
+      return True
+
+    # Compare all fields contained directly in this message.
+    for field_descriptor in message_descriptor.fields:
+      label = field_descriptor.label
+      property_name = _PropertyName(field_descriptor.name)
+      # Non-repeated field equality requires matching "has" bits as well
+      # as having an equal value.
+      if label != _FieldDescriptor.LABEL_REPEATED:
+        self_has = self.HasField(property_name)
+        other_has = other.HasField(property_name)
+        if self_has != other_has:
+          return False
+        if not self_has:
+          # If the "has" bit for this field is False, we must stop here.
+          # Otherwise we will recurse forever on recursively-defined protos.
+          continue
+      if getattr(self, property_name) != getattr(other, property_name):
+        return False
+
+    # Compare the extensions present in both messages.
+    return self.Extensions == other.Extensions
+  cls.__eq__ = __eq__
+
+
+def _AddStrMethod(message_descriptor, cls):
+  """Helper for _AddMessageMethods()."""
+  def __str__(self):
+    return text_format.MessageToString(self)
+  cls.__str__ = __str__
+
+
+def _AddSetListenerMethod(cls):
+  """Helper for _AddMessageMethods()."""
+  def SetListener(self, listener):
+    if listener is None:
+      self._listener = message_listener_mod.NullMessageListener()
+    else:
+      self._listener = listener
+  cls._SetListener = SetListener
+
+
+def _BytesForNonRepeatedElement(value, field_number, field_type):
+  """Returns the number of bytes needed to serialize a non-repeated element.
+  The returned byte count includes space for tag information and any
+  other additional space associated with serializing value.
+
+  Args:
+    value: Value we're serializing.
+    field_number: Field number of this value.  (Since the field number
+      is stored as part of a varint-encoded tag, this has an impact
+      on the total bytes required to serialize the value).
+    field_type: The type of the field.  One of the TYPE_* constants
+      within FieldDescriptor.
+  """
+  try:
+    fn = type_checkers.TYPE_TO_BYTE_SIZE_FN[field_type]
+    return fn(field_number, value)
+  except KeyError:
+    raise message_mod.EncodeError('Unrecognized field type: %d' % field_type)
+
+
+def _AddByteSizeMethod(message_descriptor, cls):
+  """Helper for _AddMessageMethods()."""
+
+  def BytesForField(message, field, value):
+    """Returns the number of bytes required to serialize a single field
+    in message.  The field may be repeated or not, composite or not.
+
+    Args:
+      message: The Message instance containing a field of the given type.
+      field: A FieldDescriptor describing the field of interest.
+      value: The value whose byte size we're interested in.
+
+    Returns: The number of bytes required to serialize the current value
+      of "field" in "message", including space for tags and any other
+      necessary information.
+    """
+
+    if _MessageSetField(field):
+      return wire_format.MessageSetItemByteSize(field.number, value)
+
+    field_number, field_type = field.number, field.type
+
+    # Repeated fields.
+    if field.label == _FieldDescriptor.LABEL_REPEATED:
+      elements = value
+    else:
+      elements = [value]
+
+    if field.GetOptions().packed:
+      content_size = _ContentBytesForPackedField(message, field, elements)
+      if content_size:
+        tag_size = wire_format.TagByteSize(field_number)
+        length_size = wire_format.Int32ByteSizeNoTag(content_size)
+        return tag_size + length_size + content_size
+      else:
+        return 0
+    else:
+      return sum(_BytesForNonRepeatedElement(element, field_number, field_type)
+                 for element in elements)
+
+  def _ContentBytesForPackedField(self, field, value):
+    """Returns the number of bytes required to serialize the actual
+    content of a packed field (not including the tag or the encoding
+    of the length.
+
+    Args:
+      self: The Message instance containing a field of the given type.
+      field: A FieldDescriptor describing the field of interest.
+      value: The value whose byte size we're interested in.
+
+    Returns: The number of bytes required to serialize the current value
+      of the packed "field" in "message", excluding space for tags and the
+      length encoding.
+    """
+    size = sum(_BytesForNonRepeatedElement(element, field.number, field.type)
+               for element in value)
+    # In the packed case, there are no per element tags.
+    return size - wire_format.TagByteSize(field.number) * len(value)
+
+  fields = message_descriptor.fields
+  has_field_names = (_HasFieldName(f.name) for f in fields)
+  zipped = zip(has_field_names, fields)
+
+  def ByteSize(self):
+    if not self._cached_byte_size_dirty:
+      return self._cached_byte_size
+
+    size = 0
+    # Hardcoded fields first.
+    for has_field_name, field in zipped:
+      if (field.label == _FieldDescriptor.LABEL_REPEATED
+          or getattr(self, has_field_name)):
+        value = getattr(self, _ValueFieldName(field.name))
+        size += BytesForField(self, field, value)
+    # Extensions next.
+    for field, value in self.Extensions._ListSetExtensions():
+      size += BytesForField(self, field, value)
+
+    self._cached_byte_size = size
+    self._cached_byte_size_dirty = False
+    return size
+
+  cls._ContentBytesForPackedField = _ContentBytesForPackedField
+  cls.ByteSize = ByteSize
+
+
+def _MessageSetField(field_descriptor):
+  """Checks if a field should be serialized using the message set wire format.
+
+  Args:
+    field_descriptor: Descriptor of the field.
+
+  Returns:
+    True if the field should be serialized using the message set wire format,
+    false otherwise.
+  """
+  return (field_descriptor.is_extension and
+          field_descriptor.label != _FieldDescriptor.LABEL_REPEATED and
+          field_descriptor.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE and
+          field_descriptor.containing_type.GetOptions().message_set_wire_format)
+
+
+def _SerializeValueToEncoder(value, field_number, field_descriptor, encoder):
+  """Appends the serialization of a single value to encoder.
+
+  Args:
+    value: Value to serialize.
+    field_number: Field number of this value.
+    field_descriptor: Descriptor of the field to serialize.
+    encoder: encoder.Encoder object to which we should serialize this value.
+  """
+  if _MessageSetField(field_descriptor):
+    encoder.AppendMessageSetItem(field_number, value)
+    return
+
+  try:
+    method = type_checkers.TYPE_TO_SERIALIZE_METHOD[field_descriptor.type]
+    method(encoder, field_number, value)
+  except KeyError:
+    raise message_mod.EncodeError('Unrecognized field type: %d' %
+                                  field_descriptor.type)
+
+
+def _ImergeSorted(*streams):
+  """Merges N sorted iterators into a single sorted iterator.
+  Each element in streams must be an iterable that yields
+  its elements in sorted order, and the elements contained
+  in each stream must all be comparable.
+
+  There may be repeated elements in the component streams or
+  across the streams; the repeated elements will all be repeated
+  in the merged iterator as well.
+
+  I believe that the heapq module at HEAD in the Python
+  sources has a method like this, but for now we roll our own.
+  """
+  iters = [iter(stream) for stream in streams]
+  heap = []
+  for index, it in enumerate(iters):
+    try:
+      heap.append((it.next(), index))
+    except StopIteration:
+      pass
+  heapq.heapify(heap)
+
+  while heap:
+    smallest_value, idx = heap[0]
+    yield smallest_value
+    try:
+      next_element = iters[idx].next()
+      heapq.heapreplace(heap, (next_element, idx))
+    except StopIteration:
+      heapq.heappop(heap)
+
+
+def _AddSerializeToStringMethod(message_descriptor, cls):
+  """Helper for _AddMessageMethods()."""
+
+  def SerializeToString(self):
+    # Check if the message has all of its required fields set.
+    errors = []
+    if not _InternalIsInitialized(self, errors):
+      raise message_mod.EncodeError('\n'.join(errors))
+    return self.SerializePartialToString()
+  cls.SerializeToString = SerializeToString
+
+
+def _AddSerializePartialToStringMethod(message_descriptor, cls):
+  """Helper for _AddMessageMethods()."""
+  Encoder = encoder.Encoder
+
+  def SerializePartialToString(self):
+    encoder = Encoder()
+    # We need to serialize all extension and non-extension fields
+    # together, in sorted order by field number.
+    for field_descriptor, field_value in self.ListFields():
+      if field_descriptor.label == _FieldDescriptor.LABEL_REPEATED:
+        repeated_value = field_value
+      else:
+        repeated_value = [field_value]
+      if field_descriptor.GetOptions().packed:
+        # First, write the field number and WIRETYPE_LENGTH_DELIMITED.
+        field_number = field_descriptor.number
+        encoder.AppendTag(field_number, wire_format.WIRETYPE_LENGTH_DELIMITED)
+        # Next, write the number of bytes.
+        content_bytes = self._ContentBytesForPackedField(
+            field_descriptor, field_value)
+        encoder.AppendInt32NoTag(content_bytes)
+        # Finally, write the actual values.
+        try:
+          method = type_checkers.TYPE_TO_NOTAG_SERIALIZE_METHOD[
+              field_descriptor.type]
+          for value in repeated_value:
+            method(encoder, value)
+        except KeyError:
+          raise message_mod.EncodeError('Unrecognized field type: %d' %
+                                        field_descriptor.type)
+      else:
+        for element in repeated_value:
+          _SerializeValueToEncoder(element, field_descriptor.number,
+                                   field_descriptor, encoder)
+    return encoder.ToString()
+
+  cls.SerializePartialToString = SerializePartialToString
+
+
+def _WireTypeForFieldType(field_type):
+  """Given a field type, returns the expected wire type."""
+  try:
+    return type_checkers.FIELD_TYPE_TO_WIRE_TYPE[field_type]
+  except KeyError:
+    raise message_mod.DecodeError('Unknown field type: %d' % field_type)
+
+
+def _WireTypeForField(field_descriptor):
+  """Given a field descriptor, returns the expected wire type."""
+  if field_descriptor.GetOptions().packed:
+    return wire_format.WIRETYPE_LENGTH_DELIMITED
+  else:
+    return _WireTypeForFieldType(field_descriptor.type)
+
+
+def _RecursivelyMerge(field_number, field_type, decoder, message):
+  """Decodes a message from decoder into message.
+  message is either a group or a nested message within some containing
+  protocol message.  If it's a group, we use the group protocol to
+  deserialize, and if it's a nested message, we use the nested-message
+  protocol.
+
+  Args:
+    field_number: The field number of message in its enclosing protocol buffer.
+    field_type: The field type of message.  Must be either TYPE_MESSAGE
+      or TYPE_GROUP.
+    decoder: Decoder to read from.
+    message: Message to deserialize into.
+  """
+  if field_type == _FieldDescriptor.TYPE_MESSAGE:
+    decoder.ReadMessageInto(message)
+  elif field_type == _FieldDescriptor.TYPE_GROUP:
+    decoder.ReadGroupInto(field_number, message)
+  else:
+    raise message_mod.DecodeError('Unexpected field type: %d' % field_type)
+
+
+def _DeserializeScalarFromDecoder(field_type, decoder):
+  """Deserializes a scalar of the requested type from decoder.  field_type must
+  be a scalar (non-group, non-message) FieldDescriptor.FIELD_* constant.
+  """
+  try:
+    method = type_checkers.TYPE_TO_DESERIALIZE_METHOD[field_type]
+    return method(decoder)
+  except KeyError:
+    raise message_mod.DecodeError('Unrecognized field type: %d' % field_type)
+
+
+def _SkipField(field_number, wire_type, decoder):
+  """Skips a field with the specified wire type.
+
+  Args:
+    field_number: Tag number of the field to skip.
+    wire_type: Wire type of the field to skip.
+    decoder: Decoder used to deserialize the messsage. It must be positioned
+      just after reading the the tag and wire type of the field.
+  """
+  if wire_type == wire_format.WIRETYPE_VARINT:
+    decoder.ReadUInt64()
+  elif wire_type == wire_format.WIRETYPE_FIXED64:
+    decoder.ReadFixed64()
+  elif wire_type == wire_format.WIRETYPE_LENGTH_DELIMITED:
+    decoder.SkipBytes(decoder.ReadInt32())
+  elif wire_type == wire_format.WIRETYPE_START_GROUP:
+    _SkipGroup(field_number, decoder)
+  elif wire_type == wire_format.WIRETYPE_END_GROUP:
+    pass
+  elif wire_type == wire_format.WIRETYPE_FIXED32:
+    decoder.ReadFixed32()
+  else:
+    raise message_mod.DecodeError('Unexpected wire type: %d' % wire_type)
+
+
+def _SkipGroup(group_number, decoder):
+  """Skips a nested group from the decoder.
+
+  Args:
+    group_number: Tag number of the group to skip.
+    decoder: Decoder used to deserialize the message. It must be positioned
+      exactly at the beginning of the message that should be skipped.
+  """
+  while True:
+    field_number, wire_type = decoder.ReadFieldNumberAndWireType()
+    if (wire_type == wire_format.WIRETYPE_END_GROUP and
+        field_number == group_number):
+      return
+    _SkipField(field_number, wire_type, decoder)
+
+
+def _DeserializeMessageSetItem(message, decoder):
+  """Deserializes a message using the message set wire format.
+
+  Args:
+    message: Message to be parsed to.
+    decoder: The decoder to be used to deserialize encoded data. Note that the
+      decoder should be positioned just after reading the START_GROUP tag that
+      began the messageset item.
+  """
+  field_number, wire_type = decoder.ReadFieldNumberAndWireType()
+  if wire_type != wire_format.WIRETYPE_VARINT or field_number != 2:
+    raise message_mod.DecodeError(
+        'Incorrect message set wire format. '
+        'wire_type: %d, field_number: %d' % (wire_type, field_number))
+
+  type_id = decoder.ReadInt32()
+  field_number, wire_type = decoder.ReadFieldNumberAndWireType()
+  if wire_type != wire_format.WIRETYPE_LENGTH_DELIMITED or field_number != 3:
+    raise message_mod.DecodeError(
+        'Incorrect message set wire format. '
+        'wire_type: %d, field_number: %d' % (wire_type, field_number))
+
+  extension_dict = message.Extensions
+  extensions_by_number = extension_dict._AllExtensionsByNumber()
+  if type_id not in extensions_by_number:
+    _SkipField(field_number, wire_type, decoder)
+    return
+
+  field_descriptor = extensions_by_number[type_id]
+  value = extension_dict[field_descriptor]
+  decoder.ReadMessageInto(value)
+  # Read the END_GROUP tag.
+  field_number, wire_type = decoder.ReadFieldNumberAndWireType()
+  if wire_type != wire_format.WIRETYPE_END_GROUP or field_number != 1:
+    raise message_mod.DecodeError(
+        'Incorrect message set wire format. '
+        'wire_type: %d, field_number: %d' % (wire_type, field_number))
+
+
+def _DeserializeOneEntity(message_descriptor, message, decoder):
+  """Deserializes the next wire entity from decoder into message.
+
+  The next wire entity is either a scalar or a nested message, an
+  element in a repeated field (the wire encoding in this case is the
+  same), or a packed repeated field (in this case, the entire repeated
+  field is read by a single call to _DeserializeOneEntity).
+
+  Args:
+    message_descriptor: A Descriptor instance describing all fields
+      in message.
+    message: The Message instance into which we're decoding our fields.
+    decoder: The Decoder we're using to deserialize encoded data.
+
+  Returns: The number of bytes read from decoder during this method.
+  """
+  initial_position = decoder.Position()
+  field_number, wire_type = decoder.ReadFieldNumberAndWireType()
+  extension_dict = message.Extensions
+  extensions_by_number = extension_dict._AllExtensionsByNumber()
+  if field_number in message_descriptor.fields_by_number:
+    # Non-extension field.
+    field_descriptor = message_descriptor.fields_by_number[field_number]
+    value = getattr(message, _PropertyName(field_descriptor.name))
+    def nonextension_setter_fn(scalar):
+      setattr(message, _PropertyName(field_descriptor.name), scalar)
+    scalar_setter_fn = nonextension_setter_fn
+  elif field_number in extensions_by_number:
+    # Extension field.
+    field_descriptor = extensions_by_number[field_number]
+    value = extension_dict[field_descriptor]
+    def extension_setter_fn(scalar):
+      extension_dict[field_descriptor] = scalar
+    scalar_setter_fn = extension_setter_fn
+  elif wire_type == wire_format.WIRETYPE_END_GROUP:
+    # We assume we're being parsed as the group that's ended.
+    return 0
+  elif (wire_type == wire_format.WIRETYPE_START_GROUP and
+        field_number == 1 and
+        message_descriptor.GetOptions().message_set_wire_format):
+    # A Message Set item.
+    _DeserializeMessageSetItem(message, decoder)
+    return decoder.Position() - initial_position
+  else:
+    _SkipField(field_number, wire_type, decoder)
+    return decoder.Position() - initial_position
+
+  # If we reach this point, we've identified the field as either
+  # hardcoded or extension, and set |field_descriptor|, |scalar_setter_fn|,
+  # and |value| appropriately.  Now actually deserialize the thing.
+  #
+  # field_descriptor: Describes the field we're deserializing.
+  # value: The value currently stored in the field to deserialize.
+  #   Used only if the field is composite and/or repeated.
+  # scalar_setter_fn: A function F such that F(scalar) will
+  #   set a nonrepeated scalar value for this field.  Used only
+  #   if this field is a nonrepeated scalar.
+
+  field_number = field_descriptor.number
+  expected_wire_type = _WireTypeForField(field_descriptor)
+  if wire_type != expected_wire_type:
+    # Need to fill in uninterpreted_bytes.  Work for the next CL.
+    raise RuntimeError('TODO(robinson): Wiretype mismatches not handled.')
+
+  property_name = _PropertyName(field_descriptor.name)
+  label = field_descriptor.label
+  field_type = field_descriptor.type
+  cpp_type = field_descriptor.cpp_type
+
+  # Nonrepeated scalar.  Just set the field directly.
+  if (label != _FieldDescriptor.LABEL_REPEATED
+      and cpp_type != _FieldDescriptor.CPPTYPE_MESSAGE):
+    scalar_setter_fn(_DeserializeScalarFromDecoder(field_type, decoder))
+    return decoder.Position() - initial_position
+
+  # Nonrepeated composite.  Recursively deserialize.
+  if label != _FieldDescriptor.LABEL_REPEATED:
+    composite = value
+    _RecursivelyMerge(field_number, field_type, decoder, composite)
+    return decoder.Position() - initial_position
+
+  # Now we know we're dealing with a repeated field of some kind.
+  element_list = value
+
+  if cpp_type != _FieldDescriptor.CPPTYPE_MESSAGE:
+    # Repeated scalar.
+    if not field_descriptor.GetOptions().packed:
+      element_list.append(_DeserializeScalarFromDecoder(field_type, decoder))
+      return decoder.Position() - initial_position
+    else:
+      # Packed repeated field.
+      length = _DeserializeScalarFromDecoder(
+          _FieldDescriptor.TYPE_INT32, decoder)
+      content_start = decoder.Position()
+      while decoder.Position() - content_start < length:
+        element_list.append(_DeserializeScalarFromDecoder(field_type, decoder))
+      return decoder.Position() - initial_position
+  else:
+    # Repeated composite.
+    composite = element_list.add()
+    _RecursivelyMerge(field_number, field_type, decoder, composite)
+    return decoder.Position() - initial_position
+
+
+def _FieldOrExtensionValues(message, field_or_extension):
+  """Retrieves the list of values for the specified field or extension.
+
+  The target field or extension can be optional, required or repeated, but it
+  must have value(s) set. The assumption is that the target field or extension
+  is set (e.g. _HasFieldOrExtension holds true).
+
+  Args:
+    message: Message which contains the target field or extension.
+    field_or_extension: Field or extension for which the list of values is
+      required. Must be an instance of FieldDescriptor.
+
+  Returns:
+    A list of values for the specified field or extension. This list will only
+    contain a single element if the field is non-repeated.
+  """
+  if field_or_extension.is_extension:
+    value = message.Extensions[field_or_extension]
+  else:
+    value = getattr(message, _ValueFieldName(field_or_extension.name))
+  if field_or_extension.label != _FieldDescriptor.LABEL_REPEATED:
+    return [value]
+  else:
+    # In this case value is a list or repeated values.
+    return value
+
+
+def _HasFieldOrExtension(message, field_or_extension):
+  """Checks if a message has the specified field or extension set.
+
+  The field or extension specified can be optional, required or repeated. If
+  it is repeated, this function returns True. Otherwise it checks the has bit
+  of the field or extension.
+
+  Args:
+    message: Message which contains the target field or extension.
+    field_or_extension: Field or extension to check. This must be a
+      FieldDescriptor instance.
+
+  Returns:
+    True if the message has a value set for the specified field or extension,
+    or if the field or extension is repeated.
+  """
+  if field_or_extension.label == _FieldDescriptor.LABEL_REPEATED:
+    return True
+  if field_or_extension.is_extension:
+    return message.HasExtension(field_or_extension)
+  else:
+    return message.HasField(field_or_extension.name)
+
+
+def _IsFieldOrExtensionInitialized(message, field, errors=None):
+  """Checks if a message field or extension is initialized.
+
+  Args:
+    message: The message which contains the field or extension.
+    field: Field or extension to check. This must be a FieldDescriptor instance.
+    errors: Errors will be appended to it, if set to a meaningful value.
+
+  Returns:
+    True if the field/extension can be considered initialized.
+  """
+  # If the field is required and is not set, it isn't initialized.
+  if field.label == _FieldDescriptor.LABEL_REQUIRED:
+    if not _HasFieldOrExtension(message, field):
+      if errors is not None:
+        errors.append('Required field %s is not set.' % field.full_name)
+      return False
+
+  # If the field is optional and is not set, or if it
+  # isn't a submessage then the field is initialized.
+  if field.label == _FieldDescriptor.LABEL_OPTIONAL:
+    if not _HasFieldOrExtension(message, field):
+      return True
+  if field.cpp_type != _FieldDescriptor.CPPTYPE_MESSAGE:
+    return True
+
+  # The field is set and is either a single or a repeated submessage.
+  messages = _FieldOrExtensionValues(message, field)
+  # If all submessages in this field are initialized, the field is
+  # considered initialized.
+  for message in messages:
+    if not _InternalIsInitialized(message, errors):
+      return False
+  return True
+
+
+def _InternalIsInitialized(message, errors=None):
+  """Checks if all required fields of a message are set.
+
+  Args:
+    message: The message to check.
+    errors: If set, initialization errors will be appended to it.
+
+  Returns:
+    True iff the specified message has all required fields set.
+  """
+  fields_and_extensions = []
+  fields_and_extensions.extend(message.DESCRIPTOR.fields)
+  fields_and_extensions.extend(
+      [extension[0] for extension in message.Extensions._ListSetExtensions()])
+  for field_or_extension in fields_and_extensions:
+    if not _IsFieldOrExtensionInitialized(message, field_or_extension, errors):
+      return False
+  return True
+
+
+def _AddMergeFromStringMethod(message_descriptor, cls):
+  """Helper for _AddMessageMethods()."""
+  Decoder = decoder.Decoder
+  def MergeFromString(self, serialized):
+    decoder = Decoder(serialized)
+    byte_count = 0
+    while not decoder.EndOfStream():
+      bytes_read = _DeserializeOneEntity(message_descriptor, self, decoder)
+      if not bytes_read:
+        break
+      byte_count += bytes_read
+    return byte_count
+  cls.MergeFromString = MergeFromString
+
+
+def _AddIsInitializedMethod(cls):
+  """Adds the IsInitialized method to the protocol message class."""
+  cls.IsInitialized = _InternalIsInitialized
+
+
+def _MergeFieldOrExtension(destination_msg, field, value):
+  """Merges a specified message field into another message."""
+  property_name = _PropertyName(field.name)
+  is_extension = field.is_extension
+
+  if not is_extension:
+    destination = getattr(destination_msg, property_name)
+  elif (field.label == _FieldDescriptor.LABEL_REPEATED or
+        field.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE):
+    destination = destination_msg.Extensions[field]
+
+  # Case 1 - a composite field.
+  if field.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
+    if field.label == _FieldDescriptor.LABEL_REPEATED:
+      for v in value:
+        destination.add().MergeFrom(v)
+    else:
+      destination.MergeFrom(value)
+    return
+
+  # Case 2 - a repeated field.
+  if field.label == _FieldDescriptor.LABEL_REPEATED:
+    for v in value:
+      destination.append(v)
+    return
+
+  # Case 3 - a singular field.
+  if is_extension:
+    destination_msg.Extensions[field] = value
+  else:
+    setattr(destination_msg, property_name, value)
+
+
+def _AddMergeFromMethod(cls):
+  def MergeFrom(self, msg):
+    assert msg is not self
+    for field in msg.ListFields():
+      _MergeFieldOrExtension(self, field[0], field[1])
+  cls.MergeFrom = MergeFrom
+
+
+def _AddMessageMethods(message_descriptor, cls):
+  """Adds implementations of all Message methods to cls."""
+  _AddListFieldsMethod(message_descriptor, cls)
+  _AddHasFieldMethod(cls)
+  _AddClearFieldMethod(cls)
+  _AddClearExtensionMethod(cls)
+  _AddClearMethod(cls)
+  _AddHasExtensionMethod(cls)
+  _AddEqualsMethod(message_descriptor, cls)
+  _AddStrMethod(message_descriptor, cls)
+  _AddSetListenerMethod(cls)
+  _AddByteSizeMethod(message_descriptor, cls)
+  _AddSerializeToStringMethod(message_descriptor, cls)
+  _AddSerializePartialToStringMethod(message_descriptor, cls)
+  _AddMergeFromStringMethod(message_descriptor, cls)
+  _AddIsInitializedMethod(cls)
+  _AddMergeFromMethod(cls)
+
+
+def _AddPrivateHelperMethods(cls):
+  """Adds implementation of private helper methods to cls."""
+
+  def MaybeCallTransitionToNonemptyCallback(self):
+    """Calls self._listener.TransitionToNonempty() the first time this
+    method is called.  On all subsequent calls, this is a no-op.
+    """
+    if not self._called_transition_to_nonempty:
+      self._listener.TransitionToNonempty()
+      self._called_transition_to_nonempty = True
+  cls._MaybeCallTransitionToNonemptyCallback = (
+      MaybeCallTransitionToNonemptyCallback)
+
+  def MarkByteSizeDirty(self):
+    """Sets the _cached_byte_size_dirty bit to true,
+    and propagates this to our listener iff this was a state change.
+    """
+    if not self._cached_byte_size_dirty:
+      self._cached_byte_size_dirty = True
+      self._listener.ByteSizeDirty()
+  cls._MarkByteSizeDirty = MarkByteSizeDirty
+
+
+class _Listener(object):
+
+  """MessageListener implementation that a parent message registers with its
+  child message.
+
+  In order to support semantics like:
+
+    foo.bar.baz = 23
+    assert foo.HasField('bar')
+
+  ...child objects must have back references to their parents.
+  This helper class is at the heart of this support.
+  """
+
+  def __init__(self, parent_message, has_field_name):
+    """Args:
+      parent_message: The message whose _MaybeCallTransitionToNonemptyCallback()
+        and _MarkByteSizeDirty() methods we should call when we receive
+        TransitionToNonempty() and ByteSizeDirty() messages.
+      has_field_name: The name of the "has" field that we should set in
+        the parent message when we receive a TransitionToNonempty message,
+        or None if there's no "has" field to set.  (This will be the case
+        for child objects in "repeated" fields).
+    """
+    # This listener establishes a back reference from a child (contained) object
+    # to its parent (containing) object.  We make this a weak reference to avoid
+    # creating cyclic garbage when the client finishes with the 'parent' object
+    # in the tree.
+    if isinstance(parent_message, weakref.ProxyType):
+      self._parent_message_weakref = parent_message
+    else:
+      self._parent_message_weakref = weakref.proxy(parent_message)
+    self._has_field_name = has_field_name
+
+  def TransitionToNonempty(self):
+    try:
+      if self._has_field_name is not None:
+        setattr(self._parent_message_weakref, self._has_field_name, True)
+      # Propagate the signal to our parents iff this is the first field set.
+      self._parent_message_weakref._MaybeCallTransitionToNonemptyCallback()
+    except ReferenceError:
+      # We can get here if a client has kept a reference to a child object,
+      # and is now setting a field on it, but the child's parent has been
+      # garbage-collected.  This is not an error.
+      pass
+
+  def ByteSizeDirty(self):
+    try:
+      self._parent_message_weakref._MarkByteSizeDirty()
+    except ReferenceError:
+      # Same as above.
+      pass
+
+
+# TODO(robinson): Move elsewhere?  This file is getting pretty ridiculous...
+# TODO(robinson): Unify error handling of "unknown extension" crap.
+# TODO(robinson): There's so much similarity between the way that
+# extensions behave and the way that normal fields behave that it would
+# be really nice to unify more code.  It's not immediately obvious
+# how to do this, though, and I'd rather get the full functionality
+# implemented (and, crucially, get all the tests and specs fleshed out
+# and passing), and then come back to this thorny unification problem.
+# TODO(robinson): Support iteritems()-style iteration over all
+# extensions with the "has" bits turned on?
+class _ExtensionDict(object):
+
+  """Dict-like container for supporting an indexable "Extensions"
+  field on proto instances.
+
+  Note that in all cases we expect extension handles to be
+  FieldDescriptors.
+  """
+
+  class _ExtensionListener(object):
+
+    """Adapts an _ExtensionDict to behave as a MessageListener."""
+
+    def __init__(self, extension_dict, handle_id):
+      self._extension_dict = extension_dict
+      self._handle_id = handle_id
+
+    def TransitionToNonempty(self):
+      self._extension_dict._SubmessageTransitionedToNonempty(self._handle_id)
+
+    def ByteSizeDirty(self):
+      self._extension_dict._SubmessageByteSizeBecameDirty()
+
+  # TODO(robinson): Somewhere, we need to blow up if people
+  # try to register two extensions with the same field number.
+  # (And we need a test for this of course).
+
+  def __init__(self, extended_message, known_extensions):
+    """extended_message: Message instance for which we are the Extensions dict.
+      known_extensions: Iterable of known extension handles.
+        These must be FieldDescriptors.
+    """
+    # We keep a weak reference to extended_message, since
+    # it has a reference to this instance in turn.
+    self._extended_message = weakref.proxy(extended_message)
+    # We make a deep copy of known_extensions to avoid any
+    # thread-safety concerns, since the argument passed in
+    # is the global (class-level) dict of known extensions for
+    # this type of message, which could be modified at any time
+    # via a RegisterExtension() call.
+    #
+    # This dict maps from handle id to handle (a FieldDescriptor).
+    #
+    # XXX
+    # TODO(robinson): This isn't good enough.  The client could
+    # instantiate an object in module A, then afterward import
+    # module B and pass the instance to B.Foo().  If B imports
+    # an extender of this proto and then tries to use it, B
+    # will get a KeyError, even though the extension *is* registered
+    # at the time of use.
+    # XXX
+    self._known_extensions = dict((id(e), e) for e in known_extensions)
+    # Read lock around self._values, which may be modified by multiple
+    # concurrent readers in the conceptually "const" __getitem__ method.
+    # So, we grab this lock in every "read-only" method to ensure
+    # that concurrent read access is safe without external locking.
+    self._lock = threading.Lock()
+    # Maps from extension handle ID to current value of that extension.
+    self._values = {}
+    # Maps from extension handle ID to a boolean "has" bit, but only
+    # for non-repeated extension fields.
+    keys = (id for id, extension in self._known_extensions.iteritems()
+            if extension.label != _FieldDescriptor.LABEL_REPEATED)
+    self._has_bits = dict.fromkeys(keys, False)
+
+    self._extensions_by_number = dict(
+        (f.number, f) for f in self._known_extensions.itervalues())
+
+    self._extensions_by_name = {}
+    for extension in self._known_extensions.itervalues():
+      if (extension.containing_type.GetOptions().message_set_wire_format and
+          extension.type == descriptor_mod.FieldDescriptor.TYPE_MESSAGE and
+          extension.message_type == extension.extension_scope and
+          extension.label == descriptor_mod.FieldDescriptor.LABEL_OPTIONAL):
+        extension_name = extension.message_type.full_name
+      else:
+        extension_name = extension.full_name
+      self._extensions_by_name[extension_name] = extension
+
+  def __getitem__(self, extension_handle):
+    """Returns the current value of the given extension handle."""
+    # We don't care as much about keeping critical sections short in the
+    # extension support, since it's presumably much less of a common case.
+    self._lock.acquire()
+    try:
+      handle_id = id(extension_handle)
+      if handle_id not in self._known_extensions:
+        raise KeyError('Extension not known to this class')
+      if handle_id not in self._values:
+        self._AddMissingHandle(extension_handle, handle_id)
+      return self._values[handle_id]
+    finally:
+      self._lock.release()
+
+  def __eq__(self, other):
+    # We have to grab read locks since we're accessing _values
+    # in a "const" method.  See the comment in the constructor.
+    if self is other:
+      return True
+    self._lock.acquire()
+    try:
+      other._lock.acquire()
+      try:
+        if self._has_bits != other._has_bits:
+          return False
+        # If there's a "has" bit, then only compare values where it is true.
+        for k, v in self._values.iteritems():
+          if self._has_bits.get(k, False) and v != other._values[k]:
+            return False
+        return True
+      finally:
+        other._lock.release()
+    finally:
+      self._lock.release()
+
+  def __ne__(self, other):
+    return not self == other
+
+  # Note that this is only meaningful for non-repeated, scalar extension
+  # fields.  Note also that we may have to call
+  # MaybeCallTransitionToNonemptyCallback() when we do successfully set a field
+  # this way, to set any necssary "has" bits in the ancestors of the extended
+  # message.
+  def __setitem__(self, extension_handle, value):
+    """If extension_handle specifies a non-repeated, scalar extension
+    field, sets the value of that field.
+    """
+    handle_id = id(extension_handle)
+    if handle_id not in self._known_extensions:
+      raise KeyError('Extension not known to this class')
+    field = extension_handle  # Just shorten the name.
+    if (field.label == _FieldDescriptor.LABEL_OPTIONAL
+        and field.cpp_type != _FieldDescriptor.CPPTYPE_MESSAGE):
+      # It's slightly wasteful to lookup the type checker each time,
+      # but we expect this to be a vanishingly uncommon case anyway.
+      type_checker = type_checkers.GetTypeChecker(field.cpp_type, field.type)
+      type_checker.CheckValue(value)
+      self._values[handle_id] = value
+      self._has_bits[handle_id] = True
+      self._extended_message._MarkByteSizeDirty()
+      self._extended_message._MaybeCallTransitionToNonemptyCallback()
+    else:
+      raise TypeError('Extension is repeated and/or a composite type.')
+
+  def _AddMissingHandle(self, extension_handle, handle_id):
+    """Helper internal to ExtensionDict."""
+    # Special handling for non-repeated message extensions, which (like
+    # normal fields of this kind) are initialized lazily.
+    # REQUIRES: _lock already held.
+    cpp_type = extension_handle.cpp_type
+    label = extension_handle.label
+    if (cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE
+        and label != _FieldDescriptor.LABEL_REPEATED):
+      self._AddMissingNonRepeatedCompositeHandle(extension_handle, handle_id)
+    else:
+      self._values[handle_id] = _DefaultValueForField(
+          self._extended_message, extension_handle)
+
+  def _AddMissingNonRepeatedCompositeHandle(self, extension_handle, handle_id):
+    """Helper internal to ExtensionDict."""
+    # REQUIRES: _lock already held.
+    value = extension_handle.message_type._concrete_class()
+    value._SetListener(_ExtensionDict._ExtensionListener(self, handle_id))
+    self._values[handle_id] = value
+
+  def _SubmessageTransitionedToNonempty(self, handle_id):
+    """Called when a submessage with a given handle id first transitions to
+    being nonempty.  Called by _ExtensionListener.
+    """
+    assert handle_id in self._has_bits
+    self._has_bits[handle_id] = True
+    self._extended_message._MaybeCallTransitionToNonemptyCallback()
+
+  def _SubmessageByteSizeBecameDirty(self):
+    """Called whenever a submessage's cached byte size becomes invalid
+    (goes from being "clean" to being "dirty").  Called by _ExtensionListener.
+    """
+    self._extended_message._MarkByteSizeDirty()
+
+  # We may wish to widen the public interface of Message.Extensions
+  # to expose some of this private functionality in the future.
+  # For now, we make all this functionality module-private and just
+  # implement what we need for serialization/deserialization,
+  # HasField()/ClearField(), etc.
+
+  def _HasExtension(self, extension_handle):
+    """Method for internal use by this module.
+    Returns true iff we "have" this extension in the sense of the
+    "has" bit being set.
+    """
+    handle_id = id(extension_handle)
+    # Note that this is different from the other checks.
+    if handle_id not in self._has_bits:
+      raise KeyError('Extension not known to this class, or is repeated field.')
+    return self._has_bits[handle_id]
+
+  # Intentionally pretty similar to ClearField() above.
+  def _ClearExtension(self, extension_handle):
+    """Method for internal use by this module.
+    Clears the specified extension, unsetting its "has" bit.
+    """
+    handle_id = id(extension_handle)
+    if handle_id not in self._known_extensions:
+      raise KeyError('Extension not known to this class')
+    default_value = _DefaultValueForField(self._extended_message,
+                                          extension_handle)
+    if extension_handle.label == _FieldDescriptor.LABEL_REPEATED:
+      self._extended_message._MarkByteSizeDirty()
+    else:
+      cpp_type = extension_handle.cpp_type
+      if cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
+        if handle_id in self._values:
+          # Future modifications to this object shouldn't set any
+          # "has" bits here.
+          self._values[handle_id]._SetListener(None)
+      if self._has_bits[handle_id]:
+        self._has_bits[handle_id] = False
+        self._extended_message._MarkByteSizeDirty()
+    if handle_id in self._values:
+      del self._values[handle_id]
+
+  def _ListSetExtensions(self):
+    """Method for internal use by this module.
+
+    Returns an sequence of all extensions that are currently "set"
+    in this extension dict.  A "set" extension is a repeated extension,
+    or a non-repeated extension with its "has" bit set.
+
+    The returned sequence contains (field_descriptor, value) pairs,
+    where value is the current value of the extension with the given
+    field descriptor.
+
+    The sequence values are in arbitrary order.
+    """
+    self._lock.acquire()  # Read-only methods must lock around self._values.
+    try:
+      set_extensions = []
+      for handle_id, value in self._values.iteritems():
+        handle = self._known_extensions[handle_id]
+        if (handle.label == _FieldDescriptor.LABEL_REPEATED
+            or self._has_bits[handle_id]):
+          set_extensions.append((handle, value))
+      return set_extensions
+    finally:
+      self._lock.release()
+
+  def _AllExtensionsByNumber(self):
+    """Method for internal use by this module.
+
+    Returns: A dict mapping field_number to (handle, field_descriptor),
+      for *all* registered extensions for this dict.
+    """
+    return self._extensions_by_number
+
+  def _FindExtensionByName(self, name):
+    """Tries to find a known extension with the specified name.
+
+    Args:
+      name: Extension full name.
+
+    Returns:
+      Extension field descriptor.
+    """
+    return self._extensions_by_name.get(name, None)
diff --git a/python/google/protobuf/service.py b/python/google/protobuf/service.py
new file mode 100755
index 0000000..dd136c9
--- /dev/null
+++ b/python/google/protobuf/service.py
@@ -0,0 +1,222 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Declares the RPC service interfaces.
+
+This module declares the abstract interfaces underlying proto2 RPC
+services.  These are intended to be independent of any particular RPC
+implementation, so that proto2 services can be used on top of a variety
+of implementations.
+"""
+
+__author__ = 'petar@google.com (Petar Petrov)'
+
+
+class RpcException(Exception):
+  """Exception raised on failed blocking RPC method call."""
+  pass
+
+
+class Service(object):
+
+  """Abstract base interface for protocol-buffer-based RPC services.
+
+  Services themselves are abstract classes (implemented either by servers or as
+  stubs), but they subclass this base interface. The methods of this
+  interface can be used to call the methods of the service without knowing
+  its exact type at compile time (analogous to the Message interface).
+  """
+
+  def GetDescriptor():
+    """Retrieves this service's descriptor."""
+    raise NotImplementedError
+
+  def CallMethod(self, method_descriptor, rpc_controller,
+                 request, done):
+    """Calls a method of the service specified by method_descriptor.
+
+    If "done" is None then the call is blocking and the response
+    message will be returned directly.  Otherwise the call is asynchronous
+    and "done" will later be called with the response value.
+
+    In the blocking case, RpcException will be raised on error.
+
+    Preconditions:
+    * method_descriptor.service == GetDescriptor
+    * request is of the exact same classes as returned by
+      GetRequestClass(method).
+    * After the call has started, the request must not be modified.
+    * "rpc_controller" is of the correct type for the RPC implementation being
+      used by this Service.  For stubs, the "correct type" depends on the
+      RpcChannel which the stub is using.
+
+    Postconditions:
+    * "done" will be called when the method is complete.  This may be
+      before CallMethod() returns or it may be at some point in the future.
+    * If the RPC failed, the response value passed to "done" will be None.
+      Further details about the failure can be found by querying the
+      RpcController.
+    """
+    raise NotImplementedError
+
+  def GetRequestClass(self, method_descriptor):
+    """Returns the class of the request message for the specified method.
+
+    CallMethod() requires that the request is of a particular subclass of
+    Message. GetRequestClass() gets the default instance of this required
+    type.
+
+    Example:
+      method = service.GetDescriptor().FindMethodByName("Foo")
+      request = stub.GetRequestClass(method)()
+      request.ParseFromString(input)
+      service.CallMethod(method, request, callback)
+    """
+    raise NotImplementedError
+
+  def GetResponseClass(self, method_descriptor):
+    """Returns the class of the response message for the specified method.
+
+    This method isn't really needed, as the RpcChannel's CallMethod constructs
+    the response protocol message. It's provided anyway in case it is useful
+    for the caller to know the response type in advance.
+    """
+    raise NotImplementedError
+
+
+class RpcController(object):
+
+  """An RpcController mediates a single method call.
+
+  The primary purpose of the controller is to provide a way to manipulate
+  settings specific to the RPC implementation and to find out about RPC-level
+  errors. The methods provided by the RpcController interface are intended
+  to be a "least common denominator" set of features which we expect all
+  implementations to support.  Specific implementations may provide more
+  advanced features (e.g. deadline propagation).
+  """
+
+  # Client-side methods below
+
+  def Reset(self):
+    """Resets the RpcController to its initial state.
+
+    After the RpcController has been reset, it may be reused in
+    a new call. Must not be called while an RPC is in progress.
+    """
+    raise NotImplementedError
+
+  def Failed(self):
+    """Returns true if the call failed.
+
+    After a call has finished, returns true if the call failed.  The possible
+    reasons for failure depend on the RPC implementation.  Failed() must not
+    be called before a call has finished.  If Failed() returns true, the
+    contents of the response message are undefined.
+    """
+    raise NotImplementedError
+
+  def ErrorText(self):
+    """If Failed is true, returns a human-readable description of the error."""
+    raise NotImplementedError
+
+  def StartCancel(self):
+    """Initiate cancellation.
+
+    Advises the RPC system that the caller desires that the RPC call be
+    canceled.  The RPC system may cancel it immediately, may wait awhile and
+    then cancel it, or may not even cancel the call at all.  If the call is
+    canceled, the "done" callback will still be called and the RpcController
+    will indicate that the call failed at that time.
+    """
+    raise NotImplementedError
+
+  # Server-side methods below
+
+  def SetFailed(self, reason):
+    """Sets a failure reason.
+
+    Causes Failed() to return true on the client side.  "reason" will be
+    incorporated into the message returned by ErrorText().  If you find
+    you need to return machine-readable information about failures, you
+    should incorporate it into your response protocol buffer and should
+    NOT call SetFailed().
+    """
+    raise NotImplementedError
+
+  def IsCanceled(self):
+    """Checks if the client cancelled the RPC.
+
+    If true, indicates that the client canceled the RPC, so the server may
+    as well give up on replying to it.  The server should still call the
+    final "done" callback.
+    """
+    raise NotImplementedError
+
+  def NotifyOnCancel(self, callback):
+    """Sets a callback to invoke on cancel.
+
+    Asks that the given callback be called when the RPC is canceled.  The
+    callback will always be called exactly once.  If the RPC completes without
+    being canceled, the callback will be called after completion.  If the RPC
+    has already been canceled when NotifyOnCancel() is called, the callback
+    will be called immediately.
+
+    NotifyOnCancel() must be called no more than once per request.
+    """
+    raise NotImplementedError
+
+
+class RpcChannel(object):
+
+  """Abstract interface for an RPC channel.
+
+  An RpcChannel represents a communication line to a service which can be used
+  to call that service's methods.  The service may be running on another
+  machine. Normally, you should not use an RpcChannel directly, but instead
+  construct a stub {@link Service} wrapping it.  Example:
+
+  Example:
+    RpcChannel channel = rpcImpl.Channel("remotehost.example.com:1234")
+    RpcController controller = rpcImpl.Controller()
+    MyService service = MyService_Stub(channel)
+    service.MyMethod(controller, request, callback)
+  """
+
+  def CallMethod(self, method_descriptor, rpc_controller,
+                 request, response_class, done):
+    """Calls the method identified by the descriptor.
+
+    Call the given method of the remote service.  The signature of this
+    procedure looks the same as Service.CallMethod(), but the requirements
+    are less strict in one important way:  the request object doesn't have to
+    be of any specific class as long as its descriptor is method.input_type.
+    """
+    raise NotImplementedError
diff --git a/python/google/protobuf/service_reflection.py b/python/google/protobuf/service_reflection.py
new file mode 100755
index 0000000..851e83e
--- /dev/null
+++ b/python/google/protobuf/service_reflection.py
@@ -0,0 +1,284 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Contains metaclasses used to create protocol service and service stub
+classes from ServiceDescriptor objects at runtime.
+
+The GeneratedServiceType and GeneratedServiceStubType metaclasses are used to
+inject all useful functionality into the classes output by the protocol
+compiler at compile-time.
+"""
+
+__author__ = 'petar@google.com (Petar Petrov)'
+
+
+class GeneratedServiceType(type):
+
+  """Metaclass for service classes created at runtime from ServiceDescriptors.
+
+  Implementations for all methods described in the Service class are added here
+  by this class. We also create properties to allow getting/setting all fields
+  in the protocol message.
+
+  The protocol compiler currently uses this metaclass to create protocol service
+  classes at runtime. Clients can also manually create their own classes at
+  runtime, as in this example:
+
+  mydescriptor = ServiceDescriptor(.....)
+  class MyProtoService(service.Service):
+    __metaclass__ = GeneratedServiceType
+    DESCRIPTOR = mydescriptor
+  myservice_instance = MyProtoService()
+  ...
+  """
+
+  _DESCRIPTOR_KEY = 'DESCRIPTOR'
+
+  def __init__(cls, name, bases, dictionary):
+    """Creates a message service class.
+
+    Args:
+      name: Name of the class (ignored, but required by the metaclass
+        protocol).
+      bases: Base classes of the class being constructed.
+      dictionary: The class dictionary of the class being constructed.
+        dictionary[_DESCRIPTOR_KEY] must contain a ServiceDescriptor object
+        describing this protocol service type.
+    """
+    # Don't do anything if this class doesn't have a descriptor. This happens
+    # when a service class is subclassed.
+    if GeneratedServiceType._DESCRIPTOR_KEY not in dictionary:
+      return
+    descriptor = dictionary[GeneratedServiceType._DESCRIPTOR_KEY]
+    service_builder = _ServiceBuilder(descriptor)
+    service_builder.BuildService(cls)
+
+
+class GeneratedServiceStubType(GeneratedServiceType):
+
+  """Metaclass for service stubs created at runtime from ServiceDescriptors.
+
+  This class has similar responsibilities as GeneratedServiceType, except that
+  it creates the service stub classes.
+  """
+
+  _DESCRIPTOR_KEY = 'DESCRIPTOR'
+
+  def __init__(cls, name, bases, dictionary):
+    """Creates a message service stub class.
+
+    Args:
+      name: Name of the class (ignored, here).
+      bases: Base classes of the class being constructed.
+      dictionary: The class dictionary of the class being constructed.
+        dictionary[_DESCRIPTOR_KEY] must contain a ServiceDescriptor object
+        describing this protocol service type.
+    """
+    super(GeneratedServiceStubType, cls).__init__(name, bases, dictionary)
+    # Don't do anything if this class doesn't have a descriptor. This happens
+    # when a service stub is subclassed.
+    if GeneratedServiceStubType._DESCRIPTOR_KEY not in dictionary:
+      return
+    descriptor = dictionary[GeneratedServiceStubType._DESCRIPTOR_KEY]
+    service_stub_builder = _ServiceStubBuilder(descriptor)
+    service_stub_builder.BuildServiceStub(cls)
+
+
+class _ServiceBuilder(object):
+
+  """This class constructs a protocol service class using a service descriptor.
+
+  Given a service descriptor, this class constructs a class that represents
+  the specified service descriptor. One service builder instance constructs
+  exactly one service class. That means all instances of that class share the
+  same builder.
+  """
+
+  def __init__(self, service_descriptor):
+    """Initializes an instance of the service class builder.
+
+    Args:
+      service_descriptor: ServiceDescriptor to use when constructing the
+        service class.
+    """
+    self.descriptor = service_descriptor
+
+  def BuildService(self, cls):
+    """Constructs the service class.
+
+    Args:
+      cls: The class that will be constructed.
+    """
+
+    # CallMethod needs to operate with an instance of the Service class. This
+    # internal wrapper function exists only to be able to pass the service
+    # instance to the method that does the real CallMethod work.
+    def _WrapCallMethod(srvc, method_descriptor,
+                        rpc_controller, request, callback):
+      return self._CallMethod(srvc, method_descriptor,
+                       rpc_controller, request, callback)
+    self.cls = cls
+    cls.CallMethod = _WrapCallMethod
+    cls.GetDescriptor = staticmethod(lambda: self.descriptor)
+    cls.GetDescriptor.__doc__ = "Returns the service descriptor."
+    cls.GetRequestClass = self._GetRequestClass
+    cls.GetResponseClass = self._GetResponseClass
+    for method in self.descriptor.methods:
+      setattr(cls, method.name, self._GenerateNonImplementedMethod(method))
+
+  def _CallMethod(self, srvc, method_descriptor,
+                  rpc_controller, request, callback):
+    """Calls the method described by a given method descriptor.
+
+    Args:
+      srvc: Instance of the service for which this method is called.
+      method_descriptor: Descriptor that represent the method to call.
+      rpc_controller: RPC controller to use for this method's execution.
+      request: Request protocol message.
+      callback: A callback to invoke after the method has completed.
+    """
+    if method_descriptor.containing_service != self.descriptor:
+      raise RuntimeError(
+          'CallMethod() given method descriptor for wrong service type.')
+    method = getattr(srvc, method_descriptor.name)
+    return method(rpc_controller, request, callback)
+
+  def _GetRequestClass(self, method_descriptor):
+    """Returns the class of the request protocol message.
+
+    Args:
+      method_descriptor: Descriptor of the method for which to return the
+        request protocol message class.
+
+    Returns:
+      A class that represents the input protocol message of the specified
+      method.
+    """
+    if method_descriptor.containing_service != self.descriptor:
+      raise RuntimeError(
+          'GetRequestClass() given method descriptor for wrong service type.')
+    return method_descriptor.input_type._concrete_class
+
+  def _GetResponseClass(self, method_descriptor):
+    """Returns the class of the response protocol message.
+
+    Args:
+      method_descriptor: Descriptor of the method for which to return the
+        response protocol message class.
+
+    Returns:
+      A class that represents the output protocol message of the specified
+      method.
+    """
+    if method_descriptor.containing_service != self.descriptor:
+      raise RuntimeError(
+          'GetResponseClass() given method descriptor for wrong service type.')
+    return method_descriptor.output_type._concrete_class
+
+  def _GenerateNonImplementedMethod(self, method):
+    """Generates and returns a method that can be set for a service methods.
+
+    Args:
+      method: Descriptor of the service method for which a method is to be
+        generated.
+
+    Returns:
+      A method that can be added to the service class.
+    """
+    return lambda inst, rpc_controller, request, callback: (
+        self._NonImplementedMethod(method.name, rpc_controller, callback))
+
+  def _NonImplementedMethod(self, method_name, rpc_controller, callback):
+    """The body of all methods in the generated service class.
+
+    Args:
+      method_name: Name of the method being executed.
+      rpc_controller: RPC controller used to execute this method.
+      callback: A callback which will be invoked when the method finishes.
+    """
+    rpc_controller.SetFailed('Method %s not implemented.' % method_name)
+    callback(None)
+
+
+class _ServiceStubBuilder(object):
+
+  """Constructs a protocol service stub class using a service descriptor.
+
+  Given a service descriptor, this class constructs a suitable stub class.
+  A stub is just a type-safe wrapper around an RpcChannel which emulates a
+  local implementation of the service.
+
+  One service stub builder instance constructs exactly one class. It means all
+  instances of that class share the same service stub builder.
+  """
+
+  def __init__(self, service_descriptor):
+    """Initializes an instance of the service stub class builder.
+
+    Args:
+      service_descriptor: ServiceDescriptor to use when constructing the
+        stub class.
+    """
+    self.descriptor = service_descriptor
+
+  def BuildServiceStub(self, cls):
+    """Constructs the stub class.
+
+    Args:
+      cls: The class that will be constructed.
+    """
+
+    def _ServiceStubInit(stub, rpc_channel):
+      stub.rpc_channel = rpc_channel
+    self.cls = cls
+    cls.__init__ = _ServiceStubInit
+    for method in self.descriptor.methods:
+      setattr(cls, method.name, self._GenerateStubMethod(method))
+
+  def _GenerateStubMethod(self, method):
+    return (lambda inst, rpc_controller, request, callback=None:
+        self._StubMethod(inst, method, rpc_controller, request, callback))
+
+  def _StubMethod(self, stub, method_descriptor,
+                  rpc_controller, request, callback):
+    """The body of all service methods in the generated stub class.
+
+    Args:
+      stub: Stub instance.
+      method_descriptor: Descriptor of the invoked method.
+      rpc_controller: Rpc controller to execute the method.
+      request: Request protocol message.
+      callback: A callback to execute when the method finishes.
+    Returns:
+      Response message (in case of blocking call).
+    """
+    return stub.rpc_channel.CallMethod(
+        method_descriptor, rpc_controller, request,
+        method_descriptor.output_type._concrete_class, callback)
diff --git a/python/google/protobuf/text_format.py b/python/google/protobuf/text_format.py
new file mode 100755
index 0000000..1cddce6
--- /dev/null
+++ b/python/google/protobuf/text_format.py
@@ -0,0 +1,650 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# http://code.google.com/p/protobuf/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Contains routines for printing protocol messages in text format."""
+
+__author__ = 'kenton@google.com (Kenton Varda)'
+
+import cStringIO
+import re
+
+from collections import deque
+from google.protobuf.internal import type_checkers
+from google.protobuf import descriptor
+
+__all__ = [ 'MessageToString', 'PrintMessage', 'PrintField',
+            'PrintFieldValue', 'Merge' ]
+
+
+class ParseError(Exception):
+  """Thrown in case of ASCII parsing error."""
+
+
+def MessageToString(message):
+  out = cStringIO.StringIO()
+  PrintMessage(message, out)
+  result = out.getvalue()
+  out.close()
+  return result
+
+
+def PrintMessage(message, out, indent = 0):
+  for field, value in message.ListFields():
+    if field.label == descriptor.FieldDescriptor.LABEL_REPEATED:
+      for element in value:
+        PrintField(field, element, out, indent)
+    else:
+      PrintField(field, value, out, indent)
+
+
+def PrintField(field, value, out, indent = 0):
+  """Print a single field name/value pair.  For repeated fields, the value
+  should be a single element."""
+
+  out.write(' ' * indent);
+  if field.is_extension:
+    out.write('[')
+    if (field.containing_type.GetOptions().message_set_wire_format and
+        field.type == descriptor.FieldDescriptor.TYPE_MESSAGE and
+        field.message_type == field.extension_scope and
+        field.label == descriptor.FieldDescriptor.LABEL_OPTIONAL):
+      out.write(field.message_type.full_name)
+    else:
+      out.write(field.full_name)
+    out.write(']')
+  elif field.type == descriptor.FieldDescriptor.TYPE_GROUP:
+    # For groups, use the capitalized name.
+    out.write(field.message_type.name)
+  else:
+    out.write(field.name)
+
+  if field.cpp_type != descriptor.FieldDescriptor.CPPTYPE_MESSAGE:
+    # The colon is optional in this case, but our cross-language golden files
+    # don't include it.
+    out.write(': ')
+
+  PrintFieldValue(field, value, out, indent)
+  out.write('\n')
+
+
+def PrintFieldValue(field, value, out, indent = 0):
+  """Print a single field value (not including name).  For repeated fields,
+  the value should be a single element."""
+
+  if field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_MESSAGE:
+    out.write(' {\n')
+    PrintMessage(value, out, indent + 2)
+    out.write(' ' * indent + '}')
+  elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_ENUM:
+    out.write(field.enum_type.values_by_number[value].name)
+  elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_STRING:
+    out.write('\"')
+    out.write(_CEscape(value))
+    out.write('\"')
+  elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_BOOL:
+    if value:
+      out.write("true")
+    else:
+      out.write("false")
+  else:
+    out.write(str(value))
+
+
+def Merge(text, message):
+  """Merges an ASCII representation of a protocol message into a message.
+
+  Args:
+    text: Message ASCII representation.
+    message: A protocol buffer message to merge into.
+
+  Raises:
+    ParseError: On ASCII parsing problems.
+  """
+  tokenizer = _Tokenizer(text)
+  while not tokenizer.AtEnd():
+    _MergeField(tokenizer, message)
+
+
+def _MergeField(tokenizer, message):
+  """Merges a single protocol message field into a message.
+
+  Args:
+    tokenizer: A tokenizer to parse the field name and values.
+    message: A protocol message to record the data.
+
+  Raises:
+    ParseError: In case of ASCII parsing problems.
+  """
+  message_descriptor = message.DESCRIPTOR
+  if tokenizer.TryConsume('['):
+    name = [tokenizer.ConsumeIdentifier()]
+    while tokenizer.TryConsume('.'):
+      name.append(tokenizer.ConsumeIdentifier())
+    name = '.'.join(name)
+
+    field = message.Extensions._FindExtensionByName(name)
+    if not field:
+      raise tokenizer.ParseErrorPreviousToken(
+          'Extension "%s" not registered.' % name)
+    elif message_descriptor != field.containing_type:
+      raise tokenizer.ParseErrorPreviousToken(
+          'Extension "%s" does not extend message type "%s".' % (
+              name, message_descriptor.full_name))
+    tokenizer.Consume(']')
+  else:
+    name = tokenizer.ConsumeIdentifier()
+    field = message_descriptor.fields_by_name.get(name, None)
+
+    # Group names are expected to be capitalized as they appear in the
+    # .proto file, which actually matches their type names, not their field
+    # names.
+    if not field:
+      field = message_descriptor.fields_by_name.get(name.lower(), None)
+      if field and field.type != descriptor.FieldDescriptor.TYPE_GROUP:
+        field = None
+
+    if (field and field.type == descriptor.FieldDescriptor.TYPE_GROUP and
+        field.message_type.name != name):
+      field = None
+
+    if not field:
+      raise tokenizer.ParseErrorPreviousToken(
+          'Message type "%s" has no field named "%s".' % (
+              message_descriptor.full_name, name))
+
+  if field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_MESSAGE:
+    tokenizer.TryConsume(':')
+
+    if tokenizer.TryConsume('<'):
+      end_token = '>'
+    else:
+      tokenizer.Consume('{')
+      end_token = '}'
+
+    if field.label == descriptor.FieldDescriptor.LABEL_REPEATED:
+      if field.is_extension:
+        sub_message = message.Extensions[field].add()
+      else:
+        sub_message = getattr(message, field.name).add()
+    else:
+      if field.is_extension:
+        sub_message = message.Extensions[field]
+      else:
+        sub_message = getattr(message, field.name)
+
+    while not tokenizer.TryConsume(end_token):
+      if tokenizer.AtEnd():
+        raise tokenizer.ParseErrorPreviousToken('Expected "%s".' % (end_token))
+      _MergeField(tokenizer, sub_message)
+  else:
+    _MergeScalarField(tokenizer, message, field)
+
+
+def _MergeScalarField(tokenizer, message, field):
+  """Merges a single protocol message scalar field into a message.
+
+  Args:
+    tokenizer: A tokenizer to parse the field value.
+    message: A protocol message to record the data.
+    field: The descriptor of the field to be merged.
+
+  Raises:
+    ParseError: In case of ASCII parsing problems.
+    RuntimeError: On runtime errors.
+  """
+  tokenizer.Consume(':')
+  value = None
+
+  if field.type in (descriptor.FieldDescriptor.TYPE_INT32,
+                    descriptor.FieldDescriptor.TYPE_SINT32,
+                    descriptor.FieldDescriptor.TYPE_SFIXED32):
+    value = tokenizer.ConsumeInt32()
+  elif field.type in (descriptor.FieldDescriptor.TYPE_INT64,
+                      descriptor.FieldDescriptor.TYPE_SINT64,
+                      descriptor.FieldDescriptor.TYPE_SFIXED64):
+    value = tokenizer.ConsumeInt64()
+  elif field.type in (descriptor.FieldDescriptor.TYPE_UINT32,
+                      descriptor.FieldDescriptor.TYPE_FIXED32):
+    value = tokenizer.ConsumeUint32()
+  elif field.type in (descriptor.FieldDescriptor.TYPE_UINT64,
+                      descriptor.FieldDescriptor.TYPE_FIXED64):
+    value = tokenizer.ConsumeUint64()
+  elif field.type in (descriptor.FieldDescriptor.TYPE_FLOAT,
+                      descriptor.FieldDescriptor.TYPE_DOUBLE):
+    value = tokenizer.ConsumeFloat()
+  elif field.type == descriptor.FieldDescriptor.TYPE_BOOL:
+    value = tokenizer.ConsumeBool()
+  elif field.type == descriptor.FieldDescriptor.TYPE_STRING:
+    value = tokenizer.ConsumeString()
+  elif field.type == descriptor.FieldDescriptor.TYPE_BYTES:
+    value = tokenizer.ConsumeByteString()
+  elif field.type == descriptor.FieldDescriptor.TYPE_ENUM:
+    # Enum can be specified by a number (the enum value), or by
+    # a string literal (the enum name).
+    enum_descriptor = field.enum_type
+    if tokenizer.LookingAtInteger():
+      number = tokenizer.ConsumeInt32()
+      enum_value = enum_descriptor.values_by_number.get(number, None)
+      if enum_value is None:
+        raise tokenizer.ParseErrorPreviousToken(
+            'Enum type "%s" has no value with number %d.' % (
+                enum_descriptor.full_name, number))
+    else:
+      identifier = tokenizer.ConsumeIdentifier()
+      enum_value = enum_descriptor.values_by_name.get(identifier, None)
+      if enum_value is None:
+        raise tokenizer.ParseErrorPreviousToken(
+            'Enum type "%s" has no value named %s.' % (
+                enum_descriptor.full_name, identifier))
+    value = enum_value.number
+  else:
+    raise RuntimeError('Unknown field type %d' % field.type)
+
+  if field.label == descriptor.FieldDescriptor.LABEL_REPEATED:
+    if field.is_extension:
+      message.Extensions[field].append(value)
+    else:
+      getattr(message, field.name).append(value)
+  else:
+    if field.is_extension:
+      message.Extensions[field] = value
+    else:
+      setattr(message, field.name, value)
+
+
+class _Tokenizer(object):
+  """Protocol buffer ASCII representation tokenizer.
+
+  This class handles the lower level string parsing by splitting it into
+  meaningful tokens.
+
+  It was directly ported from the Java protocol buffer API.
+  """
+
+  _WHITESPACE = re.compile('(\\s|(#.*$))+', re.MULTILINE)
+  _TOKEN = re.compile(
+      '[a-zA-Z_][0-9a-zA-Z_+-]*|'           # an identifier
+      '[0-9+-][0-9a-zA-Z_.+-]*|'            # a number
+      '\"([^\"\n\\\\]|\\\\.)*(\"|\\\\?$)|'  # a double-quoted string
+      '\'([^\"\n\\\\]|\\\\.)*(\'|\\\\?$)')  # a single-quoted string
+  _IDENTIFIER = re.compile('\w+')
+  _INTEGER_CHECKERS = [type_checkers.Uint32ValueChecker(),
+                       type_checkers.Int32ValueChecker(),
+                       type_checkers.Uint64ValueChecker(),
+                       type_checkers.Int64ValueChecker()]
+  _FLOAT_INFINITY = re.compile('-?inf(inity)?f?', re.IGNORECASE)
+  _FLOAT_NAN = re.compile("nanf?", re.IGNORECASE)
+
+  def __init__(self, text_message):
+    self._text_message = text_message
+
+    self._position = 0
+    self._line = -1
+    self._column = 0
+    self._token_start = None
+    self.token = ''
+    self._lines = deque(text_message.split('\n'))
+    self._current_line = ''
+    self._previous_line = 0
+    self._previous_column = 0
+    self._SkipWhitespace()
+    self.NextToken()
+
+  def AtEnd(self):
+    """Checks the end of the text was reached.
+
+    Returns:
+      True iff the end was reached.
+    """
+    return not self._lines and not self._current_line
+
+  def _PopLine(self):
+    while not self._current_line:
+      if not self._lines:
+        self._current_line = ''
+        return
+      self._line += 1
+      self._column = 0
+      self._current_line = self._lines.popleft()
+
+  def _SkipWhitespace(self):
+    while True:
+      self._PopLine()
+      match = re.match(self._WHITESPACE, self._current_line)
+      if not match:
+        break
+      length = len(match.group(0))
+      self._current_line = self._current_line[length:]
+      self._column += length
+
+  def TryConsume(self, token):
+    """Tries to consume a given piece of text.
+
+    Args:
+      token: Text to consume.
+
+    Returns:
+      True iff the text was consumed.
+    """
+    if self.token == token:
+      self.NextToken()
+      return True
+    return False
+
+  def Consume(self, token):
+    """Consumes a piece of text.
+
+    Args:
+      token: Text to consume.
+
+    Raises:
+      ParseError: If the text couldn't be consumed.
+    """
+    if not self.TryConsume(token):
+      raise self._ParseError('Expected "%s".' % token)
+
+  def LookingAtInteger(self):
+    """Checks if the current token is an integer.
+
+    Returns:
+      True iff the current token is an integer.
+    """
+    if not self.token:
+      return False
+    c = self.token[0]
+    return (c >= '0' and c <= '9') or c == '-' or c == '+'
+
+  def ConsumeIdentifier(self):
+    """Consumes protocol message field identifier.
+
+    Returns:
+      Identifier string.
+
+    Raises:
+      ParseError: If an identifier couldn't be consumed.
+    """
+    result = self.token
+    if not re.match(self._IDENTIFIER, result):
+      raise self._ParseError('Expected identifier.')
+    self.NextToken()
+    return result
+
+  def ConsumeInt32(self):
+    """Consumes a signed 32bit integer number.
+
+    Returns:
+      The integer parsed.
+
+    Raises:
+      ParseError: If a signed 32bit integer couldn't be consumed.
+    """
+    try:
+      result = self._ParseInteger(self.token, is_signed=True, is_long=False)
+    except ValueError, e:
+      raise self._IntegerParseError(e)
+    self.NextToken()
+    return result
+
+  def ConsumeUint32(self):
+    """Consumes an unsigned 32bit integer number.
+
+    Returns:
+      The integer parsed.
+
+    Raises:
+      ParseError: If an unsigned 32bit integer couldn't be consumed.
+    """
+    try:
+      result = self._ParseInteger(self.token, is_signed=False, is_long=False)
+    except ValueError, e:
+      raise self._IntegerParseError(e)
+    self.NextToken()
+    return result
+
+  def ConsumeInt64(self):
+    """Consumes a signed 64bit integer number.
+
+    Returns:
+      The integer parsed.
+
+    Raises:
+      ParseError: If a signed 64bit integer couldn't be consumed.
+    """
+    try:
+      result = self._ParseInteger(self.token, is_signed=True, is_long=True)
+    except ValueError, e:
+      raise self._IntegerParseError(e)
+    self.NextToken()
+    return result
+
+  def ConsumeUint64(self):
+    """Consumes an unsigned 64bit integer number.
+
+    Returns:
+      The integer parsed.
+
+    Raises:
+      ParseError: If an unsigned 64bit integer couldn't be consumed.
+    """
+    try:
+      result = self._ParseInteger(self.token, is_signed=False, is_long=True)
+    except ValueError, e:
+      raise self._IntegerParseError(e)
+    self.NextToken()
+    return result
+
+  def ConsumeFloat(self):
+    """Consumes an floating point number.
+
+    Returns:
+      The number parsed.
+
+    Raises:
+      ParseError: If a floating point number couldn't be consumed.
+    """
+    text = self.token
+    if re.match(self._FLOAT_INFINITY, text):
+      self.NextToken()
+      if text.startswith('-'):
+        return float('-inf')
+      return float('inf')
+
+    if re.match(self._FLOAT_NAN, text):
+      self.NextToken()
+      return float('nan')
+
+    try:
+      result = float(text)
+    except ValueError, e:
+      raise self._FloatParseError(e)
+    self.NextToken()
+    return result
+
+  def ConsumeBool(self):
+    """Consumes a boolean value.
+
+    Returns:
+      The bool parsed.
+
+    Raises:
+      ParseError: If a boolean value couldn't be consumed.
+    """
+    if self.token == 'true':
+      self.NextToken()
+      return True
+    elif self.token == 'false':
+      self.NextToken()
+      return False
+    else:
+      raise self._ParseError('Expected "true" or "false".')
+
+  def ConsumeString(self):
+    """Consumes a string value.
+
+    Returns:
+      The string parsed.
+
+    Raises:
+      ParseError: If a string value couldn't be consumed.
+    """
+    return unicode(self.ConsumeByteString(), 'utf-8')
+
+  def ConsumeByteString(self):
+    """Consumes a byte array value.
+
+    Returns:
+      The array parsed (as a string).
+
+    Raises:
+      ParseError: If a byte array value couldn't be consumed.
+    """
+    text = self.token
+    if len(text) < 1 or text[0] not in ('\'', '"'):
+      raise self._ParseError('Exptected string.')
+
+    if len(text) < 2 or text[-1] != text[0]:
+      raise self._ParseError('String missing ending quote.')
+
+    try:
+      result = _CUnescape(text[1:-1])
+    except ValueError, e:
+      raise self._ParseError(str(e))
+    self.NextToken()
+    return result
+
+  def _ParseInteger(self, text, is_signed=False, is_long=False):
+    """Parses an integer.
+
+    Args:
+      text: The text to parse.
+      is_signed: True if a signed integer must be parsed.
+      is_long: True if a long integer must be parsed.
+
+    Returns:
+      The integer value.
+
+    Raises:
+      ValueError: Thrown Iff the text is not a valid integer.
+    """
+    pos = 0
+    if text.startswith('-'):
+      pos += 1
+
+    base = 10
+    if text.startswith('0x', pos) or text.startswith('0X', pos):
+      base = 16
+    elif text.startswith('0', pos):
+      base = 8
+
+    # Do the actual parsing. Exception handling is propagated to caller.
+    result = int(text, base)
+
+    # Check if the integer is sane. Exceptions handled by callers.
+    checker = self._INTEGER_CHECKERS[2 * int(is_long) + int(is_signed)]
+    checker.CheckValue(result)
+    return result
+
+  def ParseErrorPreviousToken(self, message):
+    """Creates and *returns* a ParseError for the previously read token.
+
+    Args:
+      message: A message to set for the exception.
+
+    Returns:
+      A ParseError instance.
+    """
+    return ParseError('%d:%d : %s' % (
+        self._previous_line + 1, self._previous_column + 1, message))
+
+  def _ParseError(self, message):
+    """Creates and *returns* a ParseError for the current token."""
+    return ParseError('%d:%d : %s' % (
+        self._line + 1, self._column + 1, message))
+
+  def _IntegerParseError(self, e):
+    return self._ParseError('Couldn\'t parse integer: ' + str(e))
+
+  def _FloatParseError(self, e):
+    return self._ParseError('Couldn\'t parse number: ' + str(e))
+
+  def NextToken(self):
+    """Reads the next meaningful token."""
+    self._previous_line = self._line
+    self._previous_column = self._column
+    if self.AtEnd():
+      self.token = ''
+      return
+    self._column += len(self.token)
+
+    # Make sure there is data to work on.
+    self._PopLine()
+
+    match = re.match(self._TOKEN, self._current_line)
+    if match:
+      token = match.group(0)
+      self._current_line = self._current_line[len(token):]
+      self.token = token
+    else:
+      self.token = self._current_line[0]
+      self._current_line = self._current_line[1:]
+    self._SkipWhitespace()
+
+
+# text.encode('string_escape') does not seem to satisfy our needs as it
+# encodes unprintable characters using two-digit hex escapes whereas our
+# C++ unescaping function allows hex escapes to be any length.  So,
+# "\0011".encode('string_escape') ends up being "\\x011", which will be
+# decoded in C++ as a single-character string with char code 0x11.
+def _CEscape(text):
+  def escape(c):
+    o = ord(c)
+    if o == 10: return r"\n"   # optional escape
+    if o == 13: return r"\r"   # optional escape
+    if o ==  9: return r"\t"   # optional escape
+    if o == 39: return r"\'"   # optional escape
+
+    if o == 34: return r'\"'   # necessary escape
+    if o == 92: return r"\\"   # necessary escape
+
+    if o >= 127 or o < 32: return "\\%03o" % o # necessary escapes
+    return c
+  return "".join([escape(c) for c in text])
+
+
+_CUNESCAPE_HEX = re.compile('\\\\x([0-9a-fA-F]{2}|[0-9a-f-A-F])')
+
+
+def _CUnescape(text):
+  def ReplaceHex(m):
+    return chr(int(m.group(0)[2:], 16))
+  # This is required because the 'string_escape' encoding doesn't
+  # allow single-digit hex escapes (like '\xf').
+  result = _CUNESCAPE_HEX.sub(ReplaceHex, text)
+  return result.decode('string_escape')
diff --git a/python/mox.py b/python/mox.py
new file mode 100755
index 0000000..ce80ba5
--- /dev/null
+++ b/python/mox.py
@@ -0,0 +1,1401 @@
+#!/usr/bin/python2.4
+#
+# Copyright 2008 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# This file is used for testing.  The original is at:
+#   http://code.google.com/p/pymox/
+
+"""Mox, an object-mocking framework for Python.
+
+Mox works in the record-replay-verify paradigm.  When you first create
+a mock object, it is in record mode.  You then programmatically set
+the expected behavior of the mock object (what methods are to be
+called on it, with what parameters, what they should return, and in
+what order).
+
+Once you have set up the expected mock behavior, you put it in replay
+mode.  Now the mock responds to method calls just as you told it to.
+If an unexpected method (or an expected method with unexpected
+parameters) is called, then an exception will be raised.
+
+Once you are done interacting with the mock, you need to verify that
+all the expected interactions occured.  (Maybe your code exited
+prematurely without calling some cleanup method!)  The verify phase
+ensures that every expected method was called; otherwise, an exception
+will be raised.
+
+Suggested usage / workflow:
+
+  # Create Mox factory
+  my_mox = Mox()
+
+  # Create a mock data access object
+  mock_dao = my_mox.CreateMock(DAOClass)
+
+  # Set up expected behavior
+  mock_dao.RetrievePersonWithIdentifier('1').AndReturn(person)
+  mock_dao.DeletePerson(person)
+
+  # Put mocks in replay mode
+  my_mox.ReplayAll()
+
+  # Inject mock object and run test
+  controller.SetDao(mock_dao)
+  controller.DeletePersonById('1')
+
+  # Verify all methods were called as expected
+  my_mox.VerifyAll()
+"""
+
+from collections import deque
+import re
+import types
+import unittest
+
+import stubout
+
+class Error(AssertionError):
+  """Base exception for this module."""
+
+  pass
+
+
+class ExpectedMethodCallsError(Error):
+  """Raised when Verify() is called before all expected methods have been called
+  """
+
+  def __init__(self, expected_methods):
+    """Init exception.
+
+    Args:
+      # expected_methods: A sequence of MockMethod objects that should have been
+      #   called.
+      expected_methods: [MockMethod]
+
+    Raises:
+      ValueError: if expected_methods contains no methods.
+    """
+
+    if not expected_methods:
+      raise ValueError("There must be at least one expected method")
+    Error.__init__(self)
+    self._expected_methods = expected_methods
+
+  def __str__(self):
+    calls = "\n".join(["%3d.  %s" % (i, m)
+                       for i, m in enumerate(self._expected_methods)])
+    return "Verify: Expected methods never called:\n%s" % (calls,)
+
+
+class UnexpectedMethodCallError(Error):
+  """Raised when an unexpected method is called.
+
+  This can occur if a method is called with incorrect parameters, or out of the
+  specified order.
+  """
+
+  def __init__(self, unexpected_method, expected):
+    """Init exception.
+
+    Args:
+      # unexpected_method: MockMethod that was called but was not at the head of
+      #   the expected_method queue.
+      # expected: MockMethod or UnorderedGroup the method should have
+      #   been in.
+      unexpected_method: MockMethod
+      expected: MockMethod or UnorderedGroup
+    """
+
+    Error.__init__(self)
+    self._unexpected_method = unexpected_method
+    self._expected = expected
+
+  def __str__(self):
+    return "Unexpected method call: %s.  Expecting: %s" % \
+      (self._unexpected_method, self._expected)
+
+
+class UnknownMethodCallError(Error):
+  """Raised if an unknown method is requested of the mock object."""
+
+  def __init__(self, unknown_method_name):
+    """Init exception.
+
+    Args:
+      # unknown_method_name: Method call that is not part of the mocked class's
+      #   public interface.
+      unknown_method_name: str
+    """
+
+    Error.__init__(self)
+    self._unknown_method_name = unknown_method_name
+
+  def __str__(self):
+    return "Method called is not a member of the object: %s" % \
+      self._unknown_method_name
+
+
+class Mox(object):
+  """Mox: a factory for creating mock objects."""
+
+  # A list of types that should be stubbed out with MockObjects (as
+  # opposed to MockAnythings).
+  _USE_MOCK_OBJECT = [types.ClassType, types.InstanceType, types.ModuleType,
+                      types.ObjectType, types.TypeType]
+
+  def __init__(self):
+    """Initialize a new Mox."""
+
+    self._mock_objects = []
+    self.stubs = stubout.StubOutForTesting()
+
+  def CreateMock(self, class_to_mock):
+    """Create a new mock object.
+
+    Args:
+      # class_to_mock: the class to be mocked
+      class_to_mock: class
+
+    Returns:
+      MockObject that can be used as the class_to_mock would be.
+    """
+
+    new_mock = MockObject(class_to_mock)
+    self._mock_objects.append(new_mock)
+    return new_mock
+
+  def CreateMockAnything(self):
+    """Create a mock that will accept any method calls.
+
+    This does not enforce an interface.
+    """
+
+    new_mock = MockAnything()
+    self._mock_objects.append(new_mock)
+    return new_mock
+
+  def ReplayAll(self):
+    """Set all mock objects to replay mode."""
+
+    for mock_obj in self._mock_objects:
+      mock_obj._Replay()
+
+
+  def VerifyAll(self):
+    """Call verify on all mock objects created."""
+
+    for mock_obj in self._mock_objects:
+      mock_obj._Verify()
+
+  def ResetAll(self):
+    """Call reset on all mock objects.  This does not unset stubs."""
+
+    for mock_obj in self._mock_objects:
+      mock_obj._Reset()
+
+  def StubOutWithMock(self, obj, attr_name, use_mock_anything=False):
+    """Replace a method, attribute, etc. with a Mock.
+
+    This will replace a class or module with a MockObject, and everything else
+    (method, function, etc) with a MockAnything.  This can be overridden to
+    always use a MockAnything by setting use_mock_anything to True.
+
+    Args:
+      obj: A Python object (class, module, instance, callable).
+      attr_name: str.  The name of the attribute to replace with a mock.
+      use_mock_anything: bool. True if a MockAnything should be used regardless
+        of the type of attribute.
+    """
+
+    attr_to_replace = getattr(obj, attr_name)
+    if type(attr_to_replace) in self._USE_MOCK_OBJECT and not use_mock_anything:
+      stub = self.CreateMock(attr_to_replace)
+    else:
+      stub = self.CreateMockAnything()
+
+    self.stubs.Set(obj, attr_name, stub)
+
+  def UnsetStubs(self):
+    """Restore stubs to their original state."""
+
+    self.stubs.UnsetAll()
+
+def Replay(*args):
+  """Put mocks into Replay mode.
+
+  Args:
+    # args is any number of mocks to put into replay mode.
+  """
+
+  for mock in args:
+    mock._Replay()
+
+
+def Verify(*args):
+  """Verify mocks.
+
+  Args:
+    # args is any number of mocks to be verified.
+  """
+
+  for mock in args:
+    mock._Verify()
+
+
+def Reset(*args):
+  """Reset mocks.
+
+  Args:
+    # args is any number of mocks to be reset.
+  """
+
+  for mock in args:
+    mock._Reset()
+
+
+class MockAnything:
+  """A mock that can be used to mock anything.
+
+  This is helpful for mocking classes that do not provide a public interface.
+  """
+
+  def __init__(self):
+    """ """
+    self._Reset()
+
+  def __getattr__(self, method_name):
+    """Intercept method calls on this object.
+
+     A new MockMethod is returned that is aware of the MockAnything's
+     state (record or replay).  The call will be recorded or replayed
+     by the MockMethod's __call__.
+
+    Args:
+      # method name: the name of the method being called.
+      method_name: str
+
+    Returns:
+      A new MockMethod aware of MockAnything's state (record or replay).
+    """
+
+    return self._CreateMockMethod(method_name)
+
+  def _CreateMockMethod(self, method_name):
+    """Create a new mock method call and return it.
+
+    Args:
+      # method name: the name of the method being called.
+      method_name: str
+
+    Returns:
+      A new MockMethod aware of MockAnything's state (record or replay).
+    """
+
+    return MockMethod(method_name, self._expected_calls_queue,
+                      self._replay_mode)
+
+  def __nonzero__(self):
+    """Return 1 for nonzero so the mock can be used as a conditional."""
+
+    return 1
+
+  def __eq__(self, rhs):
+    """Provide custom logic to compare objects."""
+
+    return (isinstance(rhs, MockAnything) and
+            self._replay_mode == rhs._replay_mode and
+            self._expected_calls_queue == rhs._expected_calls_queue)
+
+  def __ne__(self, rhs):
+    """Provide custom logic to compare objects."""
+
+    return not self == rhs
+
+  def _Replay(self):
+    """Start replaying expected method calls."""
+
+    self._replay_mode = True
+
+  def _Verify(self):
+    """Verify that all of the expected calls have been made.
+
+    Raises:
+      ExpectedMethodCallsError: if there are still more method calls in the
+        expected queue.
+    """
+
+    # If the list of expected calls is not empty, raise an exception
+    if self._expected_calls_queue:
+      # The last MultipleTimesGroup is not popped from the queue.
+      if (len(self._expected_calls_queue) == 1 and
+          isinstance(self._expected_calls_queue[0], MultipleTimesGroup) and
+          self._expected_calls_queue[0].IsSatisfied()):
+        pass
+      else:
+        raise ExpectedMethodCallsError(self._expected_calls_queue)
+
+  def _Reset(self):
+    """Reset the state of this mock to record mode with an empty queue."""
+
+    # Maintain a list of method calls we are expecting
+    self._expected_calls_queue = deque()
+
+    # Make sure we are in setup mode, not replay mode
+    self._replay_mode = False
+
+
+class MockObject(MockAnything, object):
+  """A mock object that simulates the public/protected interface of a class."""
+
+  def __init__(self, class_to_mock):
+    """Initialize a mock object.
+
+    This determines the methods and properties of the class and stores them.
+
+    Args:
+      # class_to_mock: class to be mocked
+      class_to_mock: class
+    """
+
+    # This is used to hack around the mixin/inheritance of MockAnything, which
+    # is not a proper object (it can be anything. :-)
+    MockAnything.__dict__['__init__'](self)
+
+    # Get a list of all the public and special methods we should mock.
+    self._known_methods = set()
+    self._known_vars = set()
+    self._class_to_mock = class_to_mock
+    for method in dir(class_to_mock):
+      if callable(getattr(class_to_mock, method)):
+        self._known_methods.add(method)
+      else:
+        self._known_vars.add(method)
+
+  def __getattr__(self, name):
+    """Intercept attribute request on this object.
+
+    If the attribute is a public class variable, it will be returned and not
+    recorded as a call.
+
+    If the attribute is not a variable, it is handled like a method
+    call. The method name is checked against the set of mockable
+    methods, and a new MockMethod is returned that is aware of the
+    MockObject's state (record or replay).  The call will be recorded
+    or replayed by the MockMethod's __call__.
+
+    Args:
+      # name: the name of the attribute being requested.
+      name: str
+
+    Returns:
+      Either a class variable or a new MockMethod that is aware of the state
+      of the mock (record or replay).
+
+    Raises:
+      UnknownMethodCallError if the MockObject does not mock the requested
+          method.
+    """
+
+    if name in self._known_vars:
+      return getattr(self._class_to_mock, name)
+
+    if name in self._known_methods:
+      return self._CreateMockMethod(name)
+
+    raise UnknownMethodCallError(name)
+
+  def __eq__(self, rhs):
+    """Provide custom logic to compare objects."""
+
+    return (isinstance(rhs, MockObject) and
+            self._class_to_mock == rhs._class_to_mock and
+            self._replay_mode == rhs._replay_mode and
+            self._expected_calls_queue == rhs._expected_calls_queue)
+
+  def __setitem__(self, key, value):
+    """Provide custom logic for mocking classes that support item assignment.
+
+    Args:
+      key: Key to set the value for.
+      value: Value to set.
+
+    Returns:
+      Expected return value in replay mode.  A MockMethod object for the
+      __setitem__ method that has already been called if not in replay mode.
+
+    Raises:
+      TypeError if the underlying class does not support item assignment.
+      UnexpectedMethodCallError if the object does not expect the call to
+        __setitem__.
+
+    """
+    setitem = self._class_to_mock.__dict__.get('__setitem__', None)
+
+    # Verify the class supports item assignment.
+    if setitem is None:
+      raise TypeError('object does not support item assignment')
+
+    # If we are in replay mode then simply call the mock __setitem__ method.
+    if self._replay_mode:
+      return MockMethod('__setitem__', self._expected_calls_queue,
+                        self._replay_mode)(key, value)
+
+
+    # Otherwise, create a mock method __setitem__.
+    return self._CreateMockMethod('__setitem__')(key, value)
+
+  def __getitem__(self, key):
+    """Provide custom logic for mocking classes that are subscriptable.
+
+    Args:
+      key: Key to return the value for.
+
+    Returns:
+      Expected return value in replay mode.  A MockMethod object for the
+      __getitem__ method that has already been called if not in replay mode.
+
+    Raises:
+      TypeError if the underlying class is not subscriptable.
+      UnexpectedMethodCallError if the object does not expect the call to
+        __setitem__.
+
+    """
+    getitem = self._class_to_mock.__dict__.get('__getitem__', None)
+
+    # Verify the class supports item assignment.
+    if getitem is None:
+      raise TypeError('unsubscriptable object')
+
+    # If we are in replay mode then simply call the mock __getitem__ method.
+    if self._replay_mode:
+      return MockMethod('__getitem__', self._expected_calls_queue,
+                        self._replay_mode)(key)
+
+
+    # Otherwise, create a mock method __getitem__.
+    return self._CreateMockMethod('__getitem__')(key)
+
+  def __call__(self, *params, **named_params):
+    """Provide custom logic for mocking classes that are callable."""
+
+    # Verify the class we are mocking is callable
+    callable = self._class_to_mock.__dict__.get('__call__', None)
+    if callable is None:
+      raise TypeError('Not callable')
+
+    # Because the call is happening directly on this object instead of a method,
+    # the call on the mock method is made right here
+    mock_method = self._CreateMockMethod('__call__')
+    return mock_method(*params, **named_params)
+
+  @property
+  def __class__(self):
+    """Return the class that is being mocked."""
+
+    return self._class_to_mock
+
+
+class MockMethod(object):
+  """Callable mock method.
+
+  A MockMethod should act exactly like the method it mocks, accepting parameters
+  and returning a value, or throwing an exception (as specified).  When this
+  method is called, it can optionally verify whether the called method (name and
+  signature) matches the expected method.
+  """
+
+  def __init__(self, method_name, call_queue, replay_mode):
+    """Construct a new mock method.
+
+    Args:
+      # method_name: the name of the method
+      # call_queue: deque of calls, verify this call against the head, or add
+      #     this call to the queue.
+      # replay_mode: False if we are recording, True if we are verifying calls
+      #     against the call queue.
+      method_name: str
+      call_queue: list or deque
+      replay_mode: bool
+    """
+
+    self._name = method_name
+    self._call_queue = call_queue
+    if not isinstance(call_queue, deque):
+      self._call_queue = deque(self._call_queue)
+    self._replay_mode = replay_mode
+
+    self._params = None
+    self._named_params = None
+    self._return_value = None
+    self._exception = None
+    self._side_effects = None
+
+  def __call__(self, *params, **named_params):
+    """Log parameters and return the specified return value.
+
+    If the Mock(Anything/Object) associated with this call is in record mode,
+    this MockMethod will be pushed onto the expected call queue.  If the mock
+    is in replay mode, this will pop a MockMethod off the top of the queue and
+    verify this call is equal to the expected call.
+
+    Raises:
+      UnexpectedMethodCall if this call is supposed to match an expected method
+        call and it does not.
+    """
+
+    self._params = params
+    self._named_params = named_params
+
+    if not self._replay_mode:
+      self._call_queue.append(self)
+      return self
+
+    expected_method = self._VerifyMethodCall()
+
+    if expected_method._side_effects:
+      expected_method._side_effects(*params, **named_params)
+
+    if expected_method._exception:
+      raise expected_method._exception
+
+    return expected_method._return_value
+
+  def __getattr__(self, name):
+    """Raise an AttributeError with a helpful message."""
+
+    raise AttributeError('MockMethod has no attribute "%s". '
+        'Did you remember to put your mocks in replay mode?' % name)
+
+  def _PopNextMethod(self):
+    """Pop the next method from our call queue."""
+    try:
+      return self._call_queue.popleft()
+    except IndexError:
+      raise UnexpectedMethodCallError(self, None)
+
+  def _VerifyMethodCall(self):
+    """Verify the called method is expected.
+
+    This can be an ordered method, or part of an unordered set.
+
+    Returns:
+      The expected mock method.
+
+    Raises:
+      UnexpectedMethodCall if the method called was not expected.
+    """
+
+    expected = self._PopNextMethod()
+
+    # Loop here, because we might have a MethodGroup followed by another
+    # group.
+    while isinstance(expected, MethodGroup):
+      expected, method = expected.MethodCalled(self)
+      if method is not None:
+        return method
+
+    # This is a mock method, so just check equality.
+    if expected != self:
+      raise UnexpectedMethodCallError(self, expected)
+
+    return expected
+
+  def __str__(self):
+    params = ', '.join(
+        [repr(p) for p in self._params or []] +
+        ['%s=%r' % x for x in sorted((self._named_params or {}).items())])
+    desc = "%s(%s) -> %r" % (self._name, params, self._return_value)
+    return desc
+
+  def __eq__(self, rhs):
+    """Test whether this MockMethod is equivalent to another MockMethod.
+
+    Args:
+      # rhs: the right hand side of the test
+      rhs: MockMethod
+    """
+
+    return (isinstance(rhs, MockMethod) and
+            self._name == rhs._name and
+            self._params == rhs._params and
+            self._named_params == rhs._named_params)
+
+  def __ne__(self, rhs):
+    """Test whether this MockMethod is not equivalent to another MockMethod.
+
+    Args:
+      # rhs: the right hand side of the test
+      rhs: MockMethod
+    """
+
+    return not self == rhs
+
+  def GetPossibleGroup(self):
+    """Returns a possible group from the end of the call queue or None if no
+    other methods are on the stack.
+    """
+
+    # Remove this method from the tail of the queue so we can add it to a group.
+    this_method = self._call_queue.pop()
+    assert this_method == self
+
+    # Determine if the tail of the queue is a group, or just a regular ordered
+    # mock method.
+    group = None
+    try:
+      group = self._call_queue[-1]
+    except IndexError:
+      pass
+
+    return group
+
+  def _CheckAndCreateNewGroup(self, group_name, group_class):
+    """Checks if the last method (a possible group) is an instance of our
+    group_class. Adds the current method to this group or creates a new one.
+
+    Args:
+
+      group_name: the name of the group.
+      group_class: the class used to create instance of this new group
+    """
+    group = self.GetPossibleGroup()
+
+    # If this is a group, and it is the correct group, add the method.
+    if isinstance(group, group_class) and group.group_name() == group_name:
+      group.AddMethod(self)
+      return self
+
+    # Create a new group and add the method.
+    new_group = group_class(group_name)
+    new_group.AddMethod(self)
+    self._call_queue.append(new_group)
+    return self
+
+  def InAnyOrder(self, group_name="default"):
+    """Move this method into a group of unordered calls.
+
+    A group of unordered calls must be defined together, and must be executed
+    in full before the next expected method can be called.  There can be
+    multiple groups that are expected serially, if they are given
+    different group names.  The same group name can be reused if there is a
+    standard method call, or a group with a different name, spliced between
+    usages.
+
+    Args:
+      group_name: the name of the unordered group.
+
+    Returns:
+      self
+    """
+    return self._CheckAndCreateNewGroup(group_name, UnorderedGroup)
+
+  def MultipleTimes(self, group_name="default"):
+    """Move this method into group of calls which may be called multiple times.
+
+    A group of repeating calls must be defined together, and must be executed in
+    full before the next expected mehtod can be called.
+
+    Args:
+      group_name: the name of the unordered group.
+
+    Returns:
+      self
+    """
+    return self._CheckAndCreateNewGroup(group_name, MultipleTimesGroup)
+
+  def AndReturn(self, return_value):
+    """Set the value to return when this method is called.
+
+    Args:
+      # return_value can be anything.
+    """
+
+    self._return_value = return_value
+    return return_value
+
+  def AndRaise(self, exception):
+    """Set the exception to raise when this method is called.
+
+    Args:
+      # exception: the exception to raise when this method is called.
+      exception: Exception
+    """
+
+    self._exception = exception
+
+  def WithSideEffects(self, side_effects):
+    """Set the side effects that are simulated when this method is called.
+
+    Args:
+      side_effects: A callable which modifies the parameters or other relevant
+        state which a given test case depends on.
+
+    Returns:
+      Self for chaining with AndReturn and AndRaise.
+    """
+    self._side_effects = side_effects
+    return self
+
+class Comparator:
+  """Base class for all Mox comparators.
+
+  A Comparator can be used as a parameter to a mocked method when the exact
+  value is not known.  For example, the code you are testing might build up a
+  long SQL string that is passed to your mock DAO. You're only interested that
+  the IN clause contains the proper primary keys, so you can set your mock
+  up as follows:
+
+  mock_dao.RunQuery(StrContains('IN (1, 2, 4, 5)')).AndReturn(mock_result)
+
+  Now whatever query is passed in must contain the string 'IN (1, 2, 4, 5)'.
+
+  A Comparator may replace one or more parameters, for example:
+  # return at most 10 rows
+  mock_dao.RunQuery(StrContains('SELECT'), 10)
+
+  or
+
+  # Return some non-deterministic number of rows
+  mock_dao.RunQuery(StrContains('SELECT'), IsA(int))
+  """
+
+  def equals(self, rhs):
+    """Special equals method that all comparators must implement.
+
+    Args:
+      rhs: any python object
+    """
+
+    raise NotImplementedError, 'method must be implemented by a subclass.'
+
+  def __eq__(self, rhs):
+    return self.equals(rhs)
+
+  def __ne__(self, rhs):
+    return not self.equals(rhs)
+
+
+class IsA(Comparator):
+  """This class wraps a basic Python type or class.  It is used to verify
+  that a parameter is of the given type or class.
+
+  Example:
+  mock_dao.Connect(IsA(DbConnectInfo))
+  """
+
+  def __init__(self, class_name):
+    """Initialize IsA
+
+    Args:
+      class_name: basic python type or a class
+    """
+
+    self._class_name = class_name
+
+  def equals(self, rhs):
+    """Check to see if the RHS is an instance of class_name.
+
+    Args:
+      # rhs: the right hand side of the test
+      rhs: object
+
+    Returns:
+      bool
+    """
+
+    try:
+      return isinstance(rhs, self._class_name)
+    except TypeError:
+      # Check raw types if there was a type error.  This is helpful for
+      # things like cStringIO.StringIO.
+      return type(rhs) == type(self._class_name)
+
+  def __repr__(self):
+    return str(self._class_name)
+
+class IsAlmost(Comparator):
+  """Comparison class used to check whether a parameter is nearly equal
+  to a given value.  Generally useful for floating point numbers.
+
+  Example mock_dao.SetTimeout((IsAlmost(3.9)))
+  """
+
+  def __init__(self, float_value, places=7):
+    """Initialize IsAlmost.
+
+    Args:
+      float_value: The value for making the comparison.
+      places: The number of decimal places to round to.
+    """
+
+    self._float_value = float_value
+    self._places = places
+
+  def equals(self, rhs):
+    """Check to see if RHS is almost equal to float_value
+
+    Args:
+      rhs: the value to compare to float_value
+
+    Returns:
+      bool
+    """
+
+    try:
+      return round(rhs-self._float_value, self._places) == 0
+    except TypeError:
+      # This is probably because either float_value or rhs is not a number.
+      return False
+
+  def __repr__(self):
+    return str(self._float_value)
+
+class StrContains(Comparator):
+  """Comparison class used to check whether a substring exists in a
+  string parameter.  This can be useful in mocking a database with SQL
+  passed in as a string parameter, for example.
+
+  Example:
+  mock_dao.RunQuery(StrContains('IN (1, 2, 4, 5)')).AndReturn(mock_result)
+  """
+
+  def __init__(self, search_string):
+    """Initialize.
+
+    Args:
+      # search_string: the string you are searching for
+      search_string: str
+    """
+
+    self._search_string = search_string
+
+  def equals(self, rhs):
+    """Check to see if the search_string is contained in the rhs string.
+
+    Args:
+      # rhs: the right hand side of the test
+      rhs: object
+
+    Returns:
+      bool
+    """
+
+    try:
+      return rhs.find(self._search_string) > -1
+    except Exception:
+      return False
+
+  def __repr__(self):
+    return '<str containing \'%s\'>' % self._search_string
+
+
+class Regex(Comparator):
+  """Checks if a string matches a regular expression.
+
+  This uses a given regular expression to determine equality.
+  """
+
+  def __init__(self, pattern, flags=0):
+    """Initialize.
+
+    Args:
+      # pattern is the regular expression to search for
+      pattern: str
+      # flags passed to re.compile function as the second argument
+      flags: int
+    """
+
+    self.regex = re.compile(pattern, flags=flags)
+
+  def equals(self, rhs):
+    """Check to see if rhs matches regular expression pattern.
+
+    Returns:
+      bool
+    """
+
+    return self.regex.search(rhs) is not None
+
+  def __repr__(self):
+    s = '<regular expression \'%s\'' % self.regex.pattern
+    if self.regex.flags:
+      s += ', flags=%d' % self.regex.flags
+    s += '>'
+    return s
+
+
+class In(Comparator):
+  """Checks whether an item (or key) is in a list (or dict) parameter.
+
+  Example:
+  mock_dao.GetUsersInfo(In('expectedUserName')).AndReturn(mock_result)
+  """
+
+  def __init__(self, key):
+    """Initialize.
+
+    Args:
+      # key is any thing that could be in a list or a key in a dict
+    """
+
+    self._key = key
+
+  def equals(self, rhs):
+    """Check to see whether key is in rhs.
+
+    Args:
+      rhs: dict
+
+    Returns:
+      bool
+    """
+
+    return self._key in rhs
+
+  def __repr__(self):
+    return '<sequence or map containing \'%s\'>' % self._key
+
+
+class ContainsKeyValue(Comparator):
+  """Checks whether a key/value pair is in a dict parameter.
+
+  Example:
+  mock_dao.UpdateUsers(ContainsKeyValue('stevepm', stevepm_user_info))
+  """
+
+  def __init__(self, key, value):
+    """Initialize.
+
+    Args:
+      # key: a key in a dict
+      # value: the corresponding value
+    """
+
+    self._key = key
+    self._value = value
+
+  def equals(self, rhs):
+    """Check whether the given key/value pair is in the rhs dict.
+
+    Returns:
+      bool
+    """
+
+    try:
+      return rhs[self._key] == self._value
+    except Exception:
+      return False
+
+  def __repr__(self):
+    return '<map containing the entry \'%s: %s\'>' % (self._key, self._value)
+
+
+class SameElementsAs(Comparator):
+  """Checks whether iterables contain the same elements (ignoring order).
+
+  Example:
+  mock_dao.ProcessUsers(SameElementsAs('stevepm', 'salomaki'))
+  """
+
+  def __init__(self, expected_seq):
+    """Initialize.
+
+    Args:
+      expected_seq: a sequence
+    """
+
+    self._expected_seq = expected_seq
+
+  def equals(self, actual_seq):
+    """Check to see whether actual_seq has same elements as expected_seq.
+
+    Args:
+      actual_seq: sequence
+
+    Returns:
+      bool
+    """
+
+    try:
+      expected = dict([(element, None) for element in self._expected_seq])
+      actual = dict([(element, None) for element in actual_seq])
+    except TypeError:
+      # Fall back to slower list-compare if any of the objects are unhashable.
+      expected = list(self._expected_seq)
+      actual = list(actual_seq)
+      expected.sort()
+      actual.sort()
+    return expected == actual
+
+  def __repr__(self):
+    return '<sequence with same elements as \'%s\'>' % self._expected_seq
+
+
+class And(Comparator):
+  """Evaluates one or more Comparators on RHS and returns an AND of the results.
+  """
+
+  def __init__(self, *args):
+    """Initialize.
+
+    Args:
+      *args: One or more Comparator
+    """
+
+    self._comparators = args
+
+  def equals(self, rhs):
+    """Checks whether all Comparators are equal to rhs.
+
+    Args:
+      # rhs: can be anything
+
+    Returns:
+      bool
+    """
+
+    for comparator in self._comparators:
+      if not comparator.equals(rhs):
+        return False
+
+    return True
+
+  def __repr__(self):
+    return '<AND %s>' % str(self._comparators)
+
+
+class Or(Comparator):
+  """Evaluates one or more Comparators on RHS and returns an OR of the results.
+  """
+
+  def __init__(self, *args):
+    """Initialize.
+
+    Args:
+      *args: One or more Mox comparators
+    """
+
+    self._comparators = args
+
+  def equals(self, rhs):
+    """Checks whether any Comparator is equal to rhs.
+
+    Args:
+      # rhs: can be anything
+
+    Returns:
+      bool
+    """
+
+    for comparator in self._comparators:
+      if comparator.equals(rhs):
+        return True
+
+    return False
+
+  def __repr__(self):
+    return '<OR %s>' % str(self._comparators)
+
+
+class Func(Comparator):
+  """Call a function that should verify the parameter passed in is correct.
+
+  You may need the ability to perform more advanced operations on the parameter
+  in order to validate it.  You can use this to have a callable validate any
+  parameter. The callable should return either True or False.
+
+
+  Example:
+
+  def myParamValidator(param):
+    # Advanced logic here
+    return True
+
+  mock_dao.DoSomething(Func(myParamValidator), true)
+  """
+
+  def __init__(self, func):
+    """Initialize.
+
+    Args:
+      func: callable that takes one parameter and returns a bool
+    """
+
+    self._func = func
+
+  def equals(self, rhs):
+    """Test whether rhs passes the function test.
+
+    rhs is passed into func.
+
+    Args:
+      rhs: any python object
+
+    Returns:
+      the result of func(rhs)
+    """
+
+    return self._func(rhs)
+
+  def __repr__(self):
+    return str(self._func)
+
+
+class IgnoreArg(Comparator):
+  """Ignore an argument.
+
+  This can be used when we don't care about an argument of a method call.
+
+  Example:
+  # Check if CastMagic is called with 3 as first arg and 'disappear' as third.
+  mymock.CastMagic(3, IgnoreArg(), 'disappear')
+  """
+
+  def equals(self, unused_rhs):
+    """Ignores arguments and returns True.
+
+    Args:
+      unused_rhs: any python object
+
+    Returns:
+      always returns True
+    """
+
+    return True
+
+  def __repr__(self):
+    return '<IgnoreArg>'
+
+
+class MethodGroup(object):
+  """Base class containing common behaviour for MethodGroups."""
+
+  def __init__(self, group_name):
+    self._group_name = group_name
+
+  def group_name(self):
+    return self._group_name
+
+  def __str__(self):
+    return '<%s "%s">' % (self.__class__.__name__, self._group_name)
+
+  def AddMethod(self, mock_method):
+    raise NotImplementedError
+
+  def MethodCalled(self, mock_method):
+    raise NotImplementedError
+
+  def IsSatisfied(self):
+    raise NotImplementedError
+
+class UnorderedGroup(MethodGroup):
+  """UnorderedGroup holds a set of method calls that may occur in any order.
+
+  This construct is helpful for non-deterministic events, such as iterating
+  over the keys of a dict.
+  """
+
+  def __init__(self, group_name):
+    super(UnorderedGroup, self).__init__(group_name)
+    self._methods = []
+
+  def AddMethod(self, mock_method):
+    """Add a method to this group.
+
+    Args:
+      mock_method: A mock method to be added to this group.
+    """
+
+    self._methods.append(mock_method)
+
+  def MethodCalled(self, mock_method):
+    """Remove a method call from the group.
+
+    If the method is not in the set, an UnexpectedMethodCallError will be
+    raised.
+
+    Args:
+      mock_method: a mock method that should be equal to a method in the group.
+
+    Returns:
+      The mock method from the group
+
+    Raises:
+      UnexpectedMethodCallError if the mock_method was not in the group.
+    """
+
+    # Check to see if this method exists, and if so, remove it from the set
+    # and return it.
+    for method in self._methods:
+      if method == mock_method:
+        # Remove the called mock_method instead of the method in the group.
+        # The called method will match any comparators when equality is checked
+        # during removal.  The method in the group could pass a comparator to
+        # another comparator during the equality check.
+        self._methods.remove(mock_method)
+
+        # If this group is not empty, put it back at the head of the queue.
+        if not self.IsSatisfied():
+          mock_method._call_queue.appendleft(self)
+
+        return self, method
+
+    raise UnexpectedMethodCallError(mock_method, self)
+
+  def IsSatisfied(self):
+    """Return True if there are not any methods in this group."""
+
+    return len(self._methods) == 0
+
+
+class MultipleTimesGroup(MethodGroup):
+  """MultipleTimesGroup holds methods that may be called any number of times.
+
+  Note: Each method must be called at least once.
+
+  This is helpful, if you don't know or care how many times a method is called.
+  """
+
+  def __init__(self, group_name):
+    super(MultipleTimesGroup, self).__init__(group_name)
+    self._methods = set()
+    self._methods_called = set()
+
+  def AddMethod(self, mock_method):
+    """Add a method to this group.
+
+    Args:
+      mock_method: A mock method to be added to this group.
+    """
+
+    self._methods.add(mock_method)
+
+  def MethodCalled(self, mock_method):
+    """Remove a method call from the group.
+
+    If the method is not in the set, an UnexpectedMethodCallError will be
+    raised.
+
+    Args:
+      mock_method: a mock method that should be equal to a method in the group.
+
+    Returns:
+      The mock method from the group
+
+    Raises:
+      UnexpectedMethodCallError if the mock_method was not in the group.
+    """
+
+    # Check to see if this method exists, and if so add it to the set of
+    # called methods.
+
+    for method in self._methods:
+      if method == mock_method:
+        self._methods_called.add(mock_method)
+        # Always put this group back on top of the queue, because we don't know
+        # when we are done.
+        mock_method._call_queue.appendleft(self)
+        return self, method
+
+    if self.IsSatisfied():
+      next_method = mock_method._PopNextMethod();
+      return next_method, None
+    else:
+      raise UnexpectedMethodCallError(mock_method, self)
+
+  def IsSatisfied(self):
+    """Return True if all methods in this group are called at least once."""
+    # NOTE(psycho): We can't use the simple set difference here because we want
+    # to match different parameters which are considered the same e.g. IsA(str)
+    # and some string. This solution is O(n^2) but n should be small.
+    tmp = self._methods.copy()
+    for called in self._methods_called:
+      for expected in tmp:
+        if called == expected:
+          tmp.remove(expected)
+          if not tmp:
+            return True
+          break
+    return False
+
+
+class MoxMetaTestBase(type):
+  """Metaclass to add mox cleanup and verification to every test.
+
+  As the mox unit testing class is being constructed (MoxTestBase or a
+  subclass), this metaclass will modify all test functions to call the
+  CleanUpMox method of the test class after they finish. This means that
+  unstubbing and verifying will happen for every test with no additional code,
+  and any failures will result in test failures as opposed to errors.
+  """
+
+  def __init__(cls, name, bases, d):
+    type.__init__(cls, name, bases, d)
+
+    # also get all the attributes from the base classes to account
+    # for a case when test class is not the immediate child of MoxTestBase
+    for base in bases:
+      for attr_name in dir(base):
+        d[attr_name] = getattr(base, attr_name)
+
+    for func_name, func in d.items():
+      if func_name.startswith('test') and callable(func):
+        setattr(cls, func_name, MoxMetaTestBase.CleanUpTest(cls, func))
+
+  @staticmethod
+  def CleanUpTest(cls, func):
+    """Adds Mox cleanup code to any MoxTestBase method.
+
+    Always unsets stubs after a test. Will verify all mocks for tests that
+    otherwise pass.
+
+    Args:
+      cls: MoxTestBase or subclass; the class whose test method we are altering.
+      func: method; the method of the MoxTestBase test class we wish to alter.
+
+    Returns:
+      The modified method.
+    """
+    def new_method(self, *args, **kwargs):
+      mox_obj = getattr(self, 'mox', None)
+      cleanup_mox = False
+      if mox_obj and isinstance(mox_obj, Mox):
+        cleanup_mox = True
+      try:
+        func(self, *args, **kwargs)
+      finally:
+        if cleanup_mox:
+          mox_obj.UnsetStubs()
+      if cleanup_mox:
+        mox_obj.VerifyAll()
+    new_method.__name__ = func.__name__
+    new_method.__doc__ = func.__doc__
+    new_method.__module__ = func.__module__
+    return new_method
+
+
+class MoxTestBase(unittest.TestCase):
+  """Convenience test class to make stubbing easier.
+
+  Sets up a "mox" attribute which is an instance of Mox - any mox tests will
+  want this. Also automatically unsets any stubs and verifies that all mock
+  methods have been called at the end of each test, eliminating boilerplate
+  code.
+  """
+
+  __metaclass__ = MoxMetaTestBase
+
+  def setUp(self):
+    self.mox = Mox()
diff --git a/python/setup.py b/python/setup.py
new file mode 100755
index 0000000..d2997da
--- /dev/null
+++ b/python/setup.py
@@ -0,0 +1,136 @@
+#! /usr/bin/python
+#
+# See README for usage instructions.
+
+# We must use setuptools, not distutils, because we need to use the
+# namespace_packages option for the "google" package.
+from ez_setup import use_setuptools
+use_setuptools()
+
+from setuptools import setup
+from distutils.spawn import find_executable
+import sys
+import os
+import subprocess
+
+maintainer_email = "protobuf@googlegroups.com"
+
+# Find the Protocol Compiler.
+if os.path.exists("../src/protoc"):
+  protoc = "../src/protoc"
+elif os.path.exists("../src/protoc.exe"):
+  protoc = "../src/protoc.exe"
+else:
+  protoc = find_executable("protoc")
+
+def generate_proto(source):
+  """Invokes the Protocol Compiler to generate a _pb2.py from the given
+  .proto file.  Does nothing if the output already exists and is newer than
+  the input."""
+
+  output = source.replace(".proto", "_pb2.py").replace("../src/", "")
+
+  if not os.path.exists(source):
+    print "Can't find required file: " + source
+    sys.exit(-1)
+
+  if (not os.path.exists(output) or
+      (os.path.exists(source) and
+       os.path.getmtime(source) > os.path.getmtime(output))):
+    print "Generating %s..." % output
+
+    if protoc == None:
+      sys.stderr.write(
+          "protoc is not installed nor found in ../src.  Please compile it "
+          "or install the binary package.\n")
+      sys.exit(-1)
+
+    protoc_command = [ protoc, "-I../src", "-I.", "--python_out=.", source ]
+    if subprocess.call(protoc_command) != 0:
+      sys.exit(-1)
+
+def MakeTestSuite():
+  # This is apparently needed on some systems to make sure that the tests
+  # work even if a previous version is already installed.
+  if 'google' in sys.modules:
+    del sys.modules['google']
+
+  generate_proto("../src/google/protobuf/unittest.proto")
+  generate_proto("../src/google/protobuf/unittest_import.proto")
+  generate_proto("../src/google/protobuf/unittest_mset.proto")
+  generate_proto("google/protobuf/internal/more_extensions.proto")
+  generate_proto("google/protobuf/internal/more_messages.proto")
+
+  import unittest
+  import google.protobuf.internal.generator_test     as generator_test
+  import google.protobuf.internal.decoder_test       as decoder_test
+  import google.protobuf.internal.descriptor_test    as descriptor_test
+  import google.protobuf.internal.encoder_test       as encoder_test
+  import google.protobuf.internal.input_stream_test  as input_stream_test
+  import google.protobuf.internal.output_stream_test as output_stream_test
+  import google.protobuf.internal.reflection_test    as reflection_test
+  import google.protobuf.internal.service_reflection_test \
+    as service_reflection_test
+  import google.protobuf.internal.text_format_test   as text_format_test
+  import google.protobuf.internal.wire_format_test   as wire_format_test
+
+  loader = unittest.defaultTestLoader
+  suite = unittest.TestSuite()
+  for test in [ generator_test,
+                decoder_test,
+                descriptor_test,
+                encoder_test,
+                input_stream_test,
+                output_stream_test,
+                reflection_test,
+                service_reflection_test,
+                text_format_test,
+                wire_format_test ]:
+    suite.addTest(loader.loadTestsFromModule(test))
+
+  return suite
+
+if __name__ == '__main__':
+  # TODO(kenton):  Integrate this into setuptools somehow?
+  if len(sys.argv) >= 2 and sys.argv[1] == "clean":
+    # Delete generated _pb2.py files and .pyc files in the code tree.
+    for (dirpath, dirnames, filenames) in os.walk("."):
+      for filename in filenames:
+        filepath = os.path.join(dirpath, filename)
+        if filepath.endswith("_pb2.py") or filepath.endswith(".pyc"):
+          os.remove(filepath)
+  else:
+    # Generate necessary .proto file if it doesn't exist.
+    # TODO(kenton):  Maybe we should hook this into a distutils command?
+    generate_proto("../src/google/protobuf/descriptor.proto")
+
+  setup(name = 'protobuf',
+        version = '2.2.0',
+        packages = [ 'google' ],
+        namespace_packages = [ 'google' ],
+        test_suite = 'setup.MakeTestSuite',
+        # Must list modules explicitly so that we don't install tests.
+        py_modules = [
+          'google.protobuf.internal.containers',
+          'google.protobuf.internal.decoder',
+          'google.protobuf.internal.encoder',
+          'google.protobuf.internal.input_stream',
+          'google.protobuf.internal.message_listener',
+          'google.protobuf.internal.output_stream',
+          'google.protobuf.internal.type_checkers',
+          'google.protobuf.internal.wire_format',
+          'google.protobuf.descriptor',
+          'google.protobuf.descriptor_pb2',
+          'google.protobuf.message',
+          'google.protobuf.reflection',
+          'google.protobuf.service',
+          'google.protobuf.service_reflection',
+          'google.protobuf.text_format' ],
+        url = 'http://code.google.com/p/protobuf/',
+        maintainer = maintainer_email,
+        maintainer_email = 'protobuf@googlegroups.com',
+        license = 'New BSD License',
+        description = 'Protocol Buffers',
+        long_description =
+          "Protocol Buffers are Google's data interchange format.",
+        )
diff --git a/python/stubout.py b/python/stubout.py
new file mode 100755
index 0000000..aee4f2d
--- /dev/null
+++ b/python/stubout.py
@@ -0,0 +1,140 @@
+#!/usr/bin/python2.4
+#
+# Copyright 2008 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# This file is used for testing.  The original is at:
+#   http://code.google.com/p/pymox/
+
+class StubOutForTesting:
+  """Sample Usage:
+     You want os.path.exists() to always return true during testing.
+
+     stubs = StubOutForTesting()
+     stubs.Set(os.path, 'exists', lambda x: 1)
+       ...
+     stubs.UnsetAll()
+
+     The above changes os.path.exists into a lambda that returns 1.  Once
+     the ... part of the code finishes, the UnsetAll() looks up the old value
+     of os.path.exists and restores it.
+
+  """
+  def __init__(self):
+    self.cache = []
+    self.stubs = []
+
+  def __del__(self):
+    self.SmartUnsetAll()
+    self.UnsetAll()
+
+  def SmartSet(self, obj, attr_name, new_attr):
+    """Replace obj.attr_name with new_attr. This method is smart and works
+       at the module, class, and instance level while preserving proper
+       inheritance. It will not stub out C types however unless that has been
+       explicitly allowed by the type.
+
+       This method supports the case where attr_name is a staticmethod or a
+       classmethod of obj.
+
+       Notes:
+      - If obj is an instance, then it is its class that will actually be
+        stubbed. Note that the method Set() does not do that: if obj is
+        an instance, it (and not its class) will be stubbed.
+      - The stubbing is using the builtin getattr and setattr. So, the __get__
+        and __set__ will be called when stubbing (TODO: A better idea would
+        probably be to manipulate obj.__dict__ instead of getattr() and
+        setattr()).
+
+       Raises AttributeError if the attribute cannot be found.
+    """
+    if (inspect.ismodule(obj) or
+        (not inspect.isclass(obj) and obj.__dict__.has_key(attr_name))):
+      orig_obj = obj
+      orig_attr = getattr(obj, attr_name)
+
+    else:
+      if not inspect.isclass(obj):
+        mro = list(inspect.getmro(obj.__class__))
+      else:
+        mro = list(inspect.getmro(obj))
+
+      mro.reverse()
+
+      orig_attr = None
+
+      for cls in mro:
+        try:
+          orig_obj = cls
+          orig_attr = getattr(obj, attr_name)
+        except AttributeError:
+          continue
+
+    if orig_attr is None:
+      raise AttributeError("Attribute not found.")
+
+    # Calling getattr() on a staticmethod transforms it to a 'normal' function.
+    # We need to ensure that we put it back as a staticmethod.
+    old_attribute = obj.__dict__.get(attr_name)
+    if old_attribute is not None and isinstance(old_attribute, staticmethod):
+      orig_attr = staticmethod(orig_attr)
+
+    self.stubs.append((orig_obj, attr_name, orig_attr))
+    setattr(orig_obj, attr_name, new_attr)
+
+  def SmartUnsetAll(self):
+    """Reverses all the SmartSet() calls, restoring things to their original
+    definition.  Its okay to call SmartUnsetAll() repeatedly, as later calls
+    have no effect if no SmartSet() calls have been made.
+
+    """
+    self.stubs.reverse()
+
+    for args in self.stubs:
+      setattr(*args)
+
+    self.stubs = []
+
+  def Set(self, parent, child_name, new_child):
+    """Replace child_name's old definition with new_child, in the context
+    of the given parent.  The parent could be a module when the child is a
+    function at module scope.  Or the parent could be a class when a class'
+    method is being replaced.  The named child is set to new_child, while
+    the prior definition is saved away for later, when UnsetAll() is called.
+
+    This method supports the case where child_name is a staticmethod or a
+    classmethod of parent.
+    """
+    old_child = getattr(parent, child_name)
+
+    old_attribute = parent.__dict__.get(child_name)
+    if old_attribute is not None and isinstance(old_attribute, staticmethod):
+      old_child = staticmethod(old_child)
+
+    self.cache.append((parent, old_child, child_name))
+    setattr(parent, child_name, new_child)
+
+  def UnsetAll(self):
+    """Reverses all the Set() calls, restoring things to their original
+    definition.  Its okay to call UnsetAll() repeatedly, as later calls have
+    no effect if no Set() calls have been made.
+
+    """
+    # Undo calls to Set() in reverse order, in case Set() was called on the
+    # same arguments repeatedly (want the original call to be last one undone)
+    self.cache.reverse()
+
+    for (parent, old_child, child_name) in self.cache:
+      setattr(parent, child_name, old_child)
+    self.cache = []