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

   1 # Copyright (c) 2012 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 future import Gettable, Future
   6
   7
   8 class _BaseFileSystemException(Exception):
   9   def __init__(self, message):
  10     Exception.__init__(self, message)
  11
  12   @classmethod
  13   def RaiseInFuture(cls, message):
  14     def boom(): raise cls(message)
  15     return Future(delegate=Gettable(boom))
  16
  17
  18 class FileNotFoundError(_BaseFileSystemException):
  19   '''Raised when a file isn't found for read or stat.
  20   '''
  21   def __init__(self, filename):
  22     _BaseFileSystemException.__init__(self, filename)
  23
  24
  25 class FileSystemError(_BaseFileSystemException):
  26   '''Raised on when there are errors reading or statting files, such as a
  27   network timeout.
  28   '''
  29   def __init__(self, filename):
  30     _BaseFileSystemException.__init__(self, filename)
  31
  32
  33 class StatInfo(object):
  34   '''The result of calling Stat on a FileSystem.
  35   '''
  36   def __init__(self, version, child_versions=None):
  37     self.version = version
  38     self.child_versions = child_versions
  39
  40   def __eq__(self, other):
  41     return (isinstance(other, StatInfo) and
  42             self.version == other.version and
  43             self.child_versions == other.child_versions)
  44
  45   def __ne__(self, other):
  46     return not (self == other)
  47
  48   def __str__(self):
  49     return '{version: %s, child_versions: %s}' % (self.version,
  50                                                   self.child_versions)
  51
  52   def __repr__(self):
  53     return str(self)
  54
  55
  56 class FileSystem(object):
  57   '''A FileSystem interface that can read files and directories.
  58   '''
  59   def Read(self, paths):
  60     '''Reads each file in paths and returns a dictionary mapping the path to the
  61     contents. If a path in paths ends with a '/', it is assumed to be a
  62     directory, and a list of files in the directory is mapped to the path.
  63
  64     The contents will be a str.
  65
  66     If any path cannot be found, raises a FileNotFoundError. This is guaranteed
  67     to only happen once the Future has been resolved (Get() called).
  68
  69     For any other failure, raises a FileSystemError.
  70     '''
  71     raise NotImplementedError(self.__class__)
  72
  73   def ReadSingle(self, path):
  74     '''Reads a single file from the FileSystem. Returns a Future with the same
  75     rules as Read().
  76     '''
  77     read_single = self.Read([path])
  78     return Future(delegate=Gettable(lambda: read_single.Get()[path]))
  79
  80   def Refresh(self):
  81     '''Asynchronously refreshes the content of the FileSystem, returning a
  82     future to its completion.
  83     '''
  84     raise NotImplementedError(self.__class__)
  85
  86   # TODO(cduvall): Allow Stat to take a list of paths like Read.
  87   def Stat(self, path):
  88     '''Returns a |StatInfo| object containing the version of |path|. If |path|
  89     is a directory, |StatInfo| will have the versions of all the children of
  90     the directory in |StatInfo.child_versions|.
  91
  92     If the path cannot be found, raises a FileNotFoundError.
  93     For any other failure, raises a FileSystemError.
  94     '''
  95     raise NotImplementedError(self.__class__)
  96
  97   def GetIdentity(self):
  98     '''The identity of the file system, exposed for caching classes to
  99     namespace their caches. this will usually depend on the configuration of
 100     that file system - e.g. a LocalFileSystem with a base path of /var is
 101     different to that of a SubversionFileSystem with a base path of /bar, is
 102     different to a LocalFileSystem with a base path of /usr.
 103     '''
 104     raise NotImplementedError(self.__class__)
 105
 106   def Walk(self, root):
 107     '''Recursively walk the directories in a file system, starting with root.
 108     Emulates os.walk from the standard os module.
 109
 110     If the root cannot be found, raises a FileNotFoundError.
 111     For any other failure, raises a FileSystemError.
 112     '''
 113     basepath = root.rstrip('/') + '/'
 114
 115     def walk(root):
 116       if not root.endswith('/'):
 117         root += '/'
 118
 119       dirs, files = [], []
 120
 121       for f in self.ReadSingle(root).Get():
 122         if f.endswith('/'):
 123           dirs.append(f)
 124         else:
 125           files.append(f)
 126
 127       yield root[len(basepath):].rstrip('/'), dirs, files
 128
 129       for d in dirs:
 130         for walkinfo in walk(root + d):
 131           yield walkinfo
 132
 133     for walkinfo in walk(root):
 134       yield walkinfo
 135
 136   def __repr__(self):
 137     return '<%s>' % type(self).__name__
 138
 139   def __str__(self):
 140     return repr(self)