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