src/chrome/common/extensions/docs/server2/patched_file_system.py

   1 # Copyright 2013 The Chromium Authors. All rights reserved.
   2 # Use of this source code is governed by a BSD-style license that can be
   3 # found in the LICENSE file.
   4
   5 from copy import deepcopy
   6
   7 from file_system import FileSystem, StatInfo, FileNotFoundError
   8 from future import Future
   9
  10
  11 def _GetAsyncFetchCallback(unpatched_files_future,
  12                            patched_files_future,
  13                            dirs_value,
  14                            patched_file_system):
  15   def patch_directory_listing(path, original_listing):
  16     added, deleted, modified = (
  17         patched_file_system._GetDirectoryListingFromPatch(path))
  18     if original_listing is None:
  19       if len(added) == 0:
  20         raise FileNotFoundError('Directory %s not found in the patch.' % path)
  21       return added
  22     return list((set(original_listing) | set(added)) - set(deleted))
  23
  24   def resolve():
  25     files = unpatched_files_future.Get()
  26     files.update(patched_files_future.Get())
  27     files.update(
  28         dict((path, patch_directory_listing(path, dirs_value[path]))
  29              for path in dirs_value))
  30     return files
  31
  32   return resolve
  33
  34
  35 class PatchedFileSystem(FileSystem):
  36   ''' Class to fetch resources with a patch applied.
  37   '''
  38   def __init__(self, base_file_system, patcher):
  39     self._base_file_system = base_file_system
  40     self._patcher = patcher
  41
  42   def Read(self, paths, skip_not_found=False):
  43     patched_files = set()
  44     added, deleted, modified = self._patcher.GetPatchedFiles()
  45     if set(paths) & set(deleted):
  46       def raise_file_not_found():
  47         raise FileNotFoundError('Files are removed from the patch.')
  48       return Future(callback=raise_file_not_found)
  49     patched_files |= (set(added) | set(modified))
  50     dir_paths = set(path for path in paths if path.endswith('/'))
  51     file_paths = set(paths) - dir_paths
  52     patched_paths = file_paths & patched_files
  53     unpatched_paths = file_paths - patched_files
  54     return Future(callback=_GetAsyncFetchCallback(
  55         self._base_file_system.Read(unpatched_paths,
  56                                     skip_not_found=skip_not_found),
  57         self._patcher.Apply(patched_paths, self._base_file_system),
  58         self._TryReadDirectory(dir_paths),
  59         self))
  60
  61   def Refresh(self):
  62     return self._base_file_system.Refresh()
  63
  64   ''' Given the list of patched files, it's not possible to determine whether
  65   a directory to read exists in self._base_file_system. So try reading each one
  66   and handle FileNotFoundError.
  67   '''
  68   def _TryReadDirectory(self, paths):
  69     value = {}
  70     for path in paths:
  71       assert path.endswith('/')
  72       try:
  73         value[path] = self._base_file_system.ReadSingle(path).Get()
  74       except FileNotFoundError:
  75         value[path] = None
  76     return value
  77
  78   def _GetDirectoryListingFromPatch(self, path):
  79     assert path.endswith('/')
  80     def _FindChildrenInPath(files, path):
  81       result = []
  82       for f in files:
  83         if f.startswith(path):
  84           child_path = f[len(path):]
  85           if '/' in child_path:
  86             child_name = child_path[0:child_path.find('/') + 1]
  87           else:
  88             child_name = child_path
  89           result.append(child_name)
  90       return result
  91
  92     added, deleted, modified = (tuple(
  93         _FindChildrenInPath(files, path)
  94         for files in self._patcher.GetPatchedFiles()))
  95
  96     # A patch applies to files only. It cannot delete directories.
  97     deleted_files = [child for child in deleted if not child.endswith('/')]
  98     # However, these directories are actually modified because their children
  99     # are patched.
 100     modified += [child for child in deleted if child.endswith('/')]
 101
 102     return (added, deleted_files, modified)
 103
 104   def _PatchStat(self, stat_info, version, added, deleted, modified):
 105     assert len(added) + len(deleted) + len(modified) > 0
 106     assert stat_info.child_versions is not None
 107
 108     # Deep copy before patching to make sure it doesn't interfere with values
 109     # cached in memory.
 110     stat_info = deepcopy(stat_info)
 111
 112     stat_info.version = version
 113     for child in added + modified:
 114       stat_info.child_versions[child] = version
 115     for child in deleted:
 116       if stat_info.child_versions.get(child):
 117         del stat_info.child_versions[child]
 118
 119     return stat_info
 120
 121   def Stat(self, path):
 122     version = self._patcher.GetVersion()
 123     assert version is not None
 124     version = 'patched_%s' % version
 125
 126     directory, filename = path.rsplit('/', 1)
 127     added, deleted, modified = self._GetDirectoryListingFromPatch(
 128         directory + '/')
 129
 130     if len(added) > 0:
 131       # There are new files added. It's possible (if |directory| is new) that
 132       # self._base_file_system.Stat will throw an exception.
 133       try:
 134         stat_info = self._PatchStat(
 135             self._base_file_system.Stat(directory + '/'),
 136             version,
 137             added,
 138             deleted,
 139             modified)
 140       except FileNotFoundError:
 141         stat_info = StatInfo(
 142             version,
 143             dict((child, version) for child in added + modified))
 144     elif len(deleted) + len(modified) > 0:
 145       # No files were added.
 146       stat_info = self._PatchStat(self._base_file_system.Stat(directory + '/'),
 147                                   version,
 148                                   added,
 149                                   deleted,
 150                                   modified)
 151     else:
 152       # No changes are made in this directory.
 153       return self._base_file_system.Stat(path)
 154
 155     if stat_info.child_versions is not None:
 156       if filename:
 157         if filename in stat_info.child_versions:
 158           stat_info = StatInfo(stat_info.child_versions[filename])
 159         else:
 160           raise FileNotFoundError('%s was not in child versions' % filename)
 161     return stat_info
 162
 163   def GetIdentity(self):
 164     return '%s(%s,%s)' % (self.__class__.__name__,
 165                           self._base_file_system.GetIdentity(),
 166                           self._patcher.GetIdentity())