Tweaks to PPB_VarArrayBuffer in preperation for taking out of Dev.

* Add Unmap.
* Make ByteLength more consistent with the rest of PPAPI.
* Make C++ wrapper not cache the buffer.

BUG=
TEST=


Review URL: http://codereview.chromium.org/9169052

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@119286 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 76 insertions, 37 deletions

diff --git a/ppapi/cpp/dev/var_array_buffer_dev.cc b/ppapi/cpp/dev/var_array_buffer_dev.cc
index 61f697e..47ad9b3 100644
--- a/ppapi/cpp/dev/var_array_buffer_dev.cc
+++ b/ppapi/cpp/dev/var_array_buffer_dev.cc
@@ -1,9 +1,11 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ppapi/cpp/dev/var_array_buffer_dev.h"
 
+#include <limits>
+
 #include "ppapi/c/dev/ppb_var_array_buffer_dev.h"
 #include "ppapi/cpp/logging.h"
 #include "ppapi/cpp/module_impl.h"
@@ -18,50 +20,59 @@ template <> const char* interface_name<PPB_VarArrayBuffer_Dev>() {
 
 }  // namespace
 
-VarArrayBuffer_Dev::VarArrayBuffer_Dev(const Var& var)
-    : Var(var), buffer_(NULL) {
-  if (var.is_array_buffer()) {
-    buffer_ = Map();
-  } else {
+VarArrayBuffer_Dev::VarArrayBuffer_Dev(const Var& var) : Var(var) {
+  if (!var.is_array_buffer()) {
     PP_NOTREACHED();
     var_ = PP_MakeNull();
   }
 }
 
-VarArrayBuffer_Dev::VarArrayBuffer_Dev(uint32_t size_in_bytes)
-    : buffer_(NULL) {
+VarArrayBuffer_Dev::VarArrayBuffer_Dev(uint32_t size_in_bytes) {
   if (has_interface<PPB_VarArrayBuffer_Dev>()) {
     var_ = get_interface<PPB_VarArrayBuffer_Dev>()->Create(size_in_bytes);
     needs_release_ = true;
-    buffer_ = Map();
   } else {
     PP_NOTREACHED();
     var_ = PP_MakeNull();
   }
 }
 
-uint32_t VarArrayBuffer_Dev::ByteLength() const {
-  if (has_interface<PPB_VarArrayBuffer_Dev>()) {
-    return get_interface<PPB_VarArrayBuffer_Dev>()->ByteLength(var_);
+pp::VarArrayBuffer_Dev& VarArrayBuffer_Dev::operator=(
+    const VarArrayBuffer_Dev& other) {
+  Var::operator=(other);
+  return *this;
+}
+
+pp::Var& VarArrayBuffer_Dev::operator=(const Var& other) {
+  if (other.is_array_buffer()) {
+    return Var::operator=(other);
+  } else {
+    PP_NOTREACHED();
+    return *this;
   }
-  PP_NOTREACHED();
-  return 0;
 }
 
-const void* VarArrayBuffer_Dev::Map() const {
-  return const_cast<VarArrayBuffer_Dev*>(this)->Map();
+uint32_t VarArrayBuffer_Dev::ByteLength() const {
+  uint32_t byte_length = std::numeric_limits<uint32_t>::max();
+  if (is_array_buffer() && has_interface<PPB_VarArrayBuffer_Dev>())
+    get_interface<PPB_VarArrayBuffer_Dev>()->ByteLength(var_, &byte_length);
+  else
+    PP_NOTREACHED();
+  return byte_length;
 }
 
 void* VarArrayBuffer_Dev::Map() {
-  // TODO(dmichael): This is not thread-safe.
-  if (buffer_)
-    return buffer_;
-  if (has_interface<PPB_VarArrayBuffer_Dev>()) {
-    buffer_ = get_interface<PPB_VarArrayBuffer_Dev>()->Map(var_);
-    return buffer_;
-  }
+  if (is_array_buffer() && has_interface<PPB_VarArrayBuffer_Dev>())
+    return get_interface<PPB_VarArrayBuffer_Dev>()->Map(var_);
   PP_NOTREACHED();
-  return 0;
+  return NULL;
+}
+
+void VarArrayBuffer_Dev::Unmap() {
+  if (is_array_buffer() && has_interface<PPB_VarArrayBuffer_Dev>())
+    get_interface<PPB_VarArrayBuffer_Dev>()->Unmap(var_);
+  else
+    PP_NOTREACHED();
 }
 
 }  // namespace pp
diff --git a/ppapi/cpp/dev/var_array_buffer_dev.h b/ppapi/cpp/dev/var_array_buffer_dev.h
index 6f8c959..6f7c18a 100644
--- a/ppapi/cpp/dev/var_array_buffer_dev.h
+++ b/ppapi/cpp/dev/var_array_buffer_dev.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
@@ -20,18 +20,37 @@ namespace pp {
 class VarArrayBuffer_Dev : public Var {
  public:
   /// Contruct a VarArrayBuffer_Dev given a var for which is_array_buffer() is
-  /// true. This will refer to the same buffer as var, but allows you to access
-  /// methods specific to VarArrayBuffer_Dev.
+  /// true. This will refer to the same ArrayBuffer as var, but allows you to
+  /// access methods specific to VarArrayBuffer_Dev.
   ///
-  /// @param[in] var An array buffer Var.
+  /// @param[in] var An ArrayBuffer Var.
   explicit VarArrayBuffer_Dev(const Var& var);
 
+  /// Copy constructor.
   VarArrayBuffer_Dev(const VarArrayBuffer_Dev& buffer) : Var(buffer) {}
 
+  virtual ~VarArrayBuffer_Dev() {}
+
+  /// This function assigns one VarArrayBuffer to another VarArrayBuffer.
+  ///
+  /// @param[in] other The VarArrayBuffer to be assigned.
+  ///
+  /// @return The resulting VarArrayBuffer.
+  VarArrayBuffer_Dev& operator=(const VarArrayBuffer_Dev& other);
+
+  /// This function assigns one VarArrayBuffer to another VarArrayBuffer. Var's
+  /// assignment operator is overloaded here so that we can check for assigning
+  /// a non-ArrayBuffer var to a VarArrayBuffer_Dev.
+  ///
+  /// @param[in] other The VarArrayBuffer to be assigned.
+  ///
+  /// @return The resulting VarArrayBuffer (as a Var&).
+  virtual Var& operator=(const Var& other);
+
   /// Construct a new VarArrayBuffer_Dev which is size_in_bytes bytes long and
   /// initialized to zero.
   ///
-  /// @param[in] size_in_bytes The size of the constructed array in bytes.
+  /// @param[in] size_in_bytes The size of the constructed ArrayBuffer in bytes.
   VarArrayBuffer_Dev(uint32_t size_in_bytes);
 
   /// Return the length of the VarArrayBuffer_Dev in bytes.
@@ -39,17 +58,26 @@ class VarArrayBuffer_Dev : public Var {
   /// @return The length of the VarArrayBuffer_Dev in bytes.
   uint32_t ByteLength() const;
 
-  /// Return a pointer to the buffer associated with this VarArrayBuffer_Dev.
+  /// Maps the ArrayBuffer in to the module's address space and returns a
+  /// pointer to the internal buffer for this ArrayBuffer.
+  ///
+  /// Note that calling Map() can be a relatively expensive operation. Use care
+  /// when calling it in performance-critical code. For example, you should call
+  /// it only once when looping over an ArrayBuffer:
   ///
-  /// @return A pointer to the buffer associated with this VarArrayBuffer_Dev.
+  /// <code>
+  ///   char* data = static_cast<char*>(array_buffer_var.Map());
+  ///   uint32_t byte_length = array_buffer_var.ByteLength();
+  ///   for (uint32_t i = 0; i < byte_length; ++i)
+  ///     data[i] = 'A';
+  /// </code>
+  ///
+  /// @return A pointer to the internal buffer for this ArrayBuffer.
   void* Map();
-  const void* Map() const;
-
-  virtual ~VarArrayBuffer_Dev() {}
 
- private:
-  // We cache the buffer so that repeated calls to Map() are quick.
-  void* buffer_;
+  /// Unmaps this ArrayBuffer var from the module address space. Use this if
+  /// you want to save memory but might want to Map the buffer again later.
+  void Unmap();
 };
 
 }  // namespace pp