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