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# 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.
class _CacheEntry(object):
def __init__(self, cache_data, version):
self._cache_data = cache_data
self.version = version
class CompiledFileSystem(object):
"""This class caches FileSystem data that has been processed.
"""
class Factory(object):
"""A class to build a CompiledFileSystem backed by |file_system|.
"""
def __init__(self, file_system, object_store_creator):
self._file_system = file_system
self._object_store_creator = object_store_creator
def Create(self, populate_function, cls, category=None):
"""Create a CompiledFileSystem that populates the cache by calling
|populate_function| with (path, data), where |data| is the data that was
fetched from |path|.
The namespace for the file system is derived like ObjectStoreCreator: from
|cls| along with an optional |category|.
"""
assert isinstance(cls, type)
assert not cls.__name__[0].islower() # guard against non-class types
full_name = cls.__name__
if category is not None:
full_name = '%s/%s' % (full_name, category)
def create_object_store(category):
return self._object_store_creator.Create(
CompiledFileSystem, category='%s/%s' % (full_name, category))
return CompiledFileSystem(self._file_system,
populate_function,
create_object_store('file'),
create_object_store('list'))
def CreateIdentity(self, cls):
'''Handy helper to get or create the identity compiled file system.
GetFromFile will return the file's contents.
GetFromFileListing will return the directory list.
'''
return self.Create(lambda _, x: x, cls)
def __init__(self,
file_system,
populate_function,
file_object_store,
list_object_store):
self._file_system = file_system
self._populate_function = populate_function
self._file_object_store = file_object_store
self._list_object_store = list_object_store
def _RecursiveList(self, path):
files = []
for filename in self._file_system.ReadSingle(path):
if filename.endswith('/'):
files.extend(['%s%s' % (filename, f)
for f in self._RecursiveList('%s%s' % (path, filename))])
else:
files.append(filename)
return files
def GetFromFile(self, path, binary=False):
"""Calls |populate_function| on the contents of the file at |path|. If
|binary| is True then the file will be read as binary - but this will only
apply for the first time the file is fetched; if already cached, |binary|
will be ignored.
"""
version = self._file_system.Stat(path).version
cache_entry = self._file_object_store.Get(path).Get()
if (cache_entry is not None) and (version == cache_entry.version):
return cache_entry._cache_data
cache_data = self._populate_function(
path,
self._file_system.ReadSingle(path, binary=binary))
self._file_object_store.Set(path, _CacheEntry(cache_data, version))
return cache_data
def GetFromFileListing(self, path):
"""Calls |populate_function| on the listing of the files at |path|.
Assumes that the path given is to a directory.
"""
if not path.endswith('/'):
path += '/'
version = self._file_system.Stat(path).version
cache_entry = self._list_object_store.Get(path).Get()
if (cache_entry is not None) and (version == cache_entry.version):
return cache_entry._cache_data
cache_data = self._populate_function(path, self._RecursiveList(path))
self._list_object_store.Set(path, _CacheEntry(cache_data, version))
return cache_data
def StatFile(self, path):
cache_entry = self._file_object_store.Get(path).Get()
if cache_entry is not None:
return cache_entry.version
return self._file_system.Stat(path).version
def StatFileListing(self, path):
if not path.endswith('/'):
path += '/'
cache_entry = self._list_object_store.Get(path).Get()
if cache_entry is not None:
return cache_entry.version
return self._file_system.Stat(path).version
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