Extensions Docs Server: Internal file system

chrome/common/extensions/docs/server2/file_system_cache.py

+# 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.
+
+import os
+
+class FileSystemCache(object):
+  """This class caches FileSystem data that has been processed.
+  """
+  class Builder(object):
+    """A class to build a FileSystemCache.
+    """
+    def __init__(self, file_system):
+      self._file_system = file_system
+
+    def build(self, populate_function):
+      return FileSystemCache(self._file_system, populate_function)
+
+  class _CacheEntry(object):
+    def __init__(self, cache_data, version):
+      self._cache_data = cache_data
+      self.version = version
+
+  def __init__(self, file_system, populate_function):
+    self._file_system = file_system
+    self._populate_function = populate_function
+    self._cache = {}
+
+  def _FetchFile(self, filename):
+    return self._file_system.Read([filename]).Get()[filename]
+
+  def _RecursiveList(self, files):
+    all_files = files[:]
+    dirs = {}
+    for filename in files:
+      if filename.endswith('/'):
+        all_files.remove(filename)
+        dirs.update(self._file_system.Read([filename]).Get())
+    for dir_, files in dirs.iteritems():
+      all_files.extend(self._RecursiveList([dir_ + f for f in files]))
+    return all_files
+
+  def GetFromFile(self, path):
+    """Calls |populate_function| on the contents of the file at |path|.
+    """
+    version = self._file_system.Stat(path).version
+    if path in self._cache:
+      if version > self._cache[path].version:
+        self._cache.pop(path)
+      else:
+        return self._cache[path]._cache_data
+    cache_data = self._FetchFile(path)
+    self._cache[path] = self._CacheEntry(self._populate_function(cache_data),
+                                         version)
+    return self._cache[path]._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
+    if path in self._cache:
+      if version > self._cache[path].version:
+        self._cache.pop(path)
+      else:
+        return self._cache[path]._cache_data
+    cache_data = self._RecursiveList([path + f for f in self._FetchFile(path)])
+    self._cache[path] = self._CacheEntry(self._populate_function(cache_data),
+                                         version)
+    return self._cache[path]._cache_data