src/chrome/common/extensions/docs/server2/host_file_system_iterator.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
   6 class HostFileSystemIterator(object):
   7   '''Provides methods for iterating through host file systems, in both
   8   ascending (oldest to newest version) and descending order.
   9   '''
  10
  11   def __init__(self, file_system_provider, branch_utility):
  12     self._file_system_provider = file_system_provider
  13     self._branch_utility = branch_utility
  14
  15   def _ForEach(self, channel_info, callback, get_next):
  16     '''Iterates through a sequence of file systems defined by |get_next| until
  17     |callback| returns False, or until the end of the sequence of file systems
  18     is reached. Returns the BranchUtility.ChannelInfo of the last file system
  19     for which |callback| returned True.
  20     '''
  21     last_true = None
  22     while channel_info is not None:
  23       if channel_info.branch == 'master':
  24         file_system = self._file_system_provider.GetMaster()
  25       else:
  26         file_system = self._file_system_provider.GetBranch(channel_info.branch)
  27       if not callback(file_system, channel_info):
  28         return last_true
  29       last_true = channel_info
  30       channel_info = get_next(channel_info)
  31     return last_true
  32
  33   def Ascending(self, channel_info, callback):
  34     return self._ForEach(channel_info, callback, self._branch_utility.Newer)
  35
  36   def Descending(self, channel_info, callback):
  37     return self._ForEach(channel_info, callback, self._branch_utility.Older)