pysize/core/chdir_browsing.py

   1 # This program is free software; you can redistribute it and/or modify
   2 # it under the terms of the GNU General Public License as published by
   3 # the Free Software Foundation; either version 2 of the License, or
   4 # (at your option) any later version.
   5 #
   6 # This program is distributed in the hope that it will be useful,
   7 # but WITHOUT ANY WARRANTY; without even the implied warranty of
   8 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   9 # GNU Library General Public License for more details.
  10 #
  11 # You should have received a copy of the GNU General Public License
  12 # along with this program; if not, write to the Free Software
  13 # Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  14 #
  15 # See the COPYING file for license information.
  16 #
  17 # Copyright (c) 2006 Guillaume Chazarain <guichaz@yahoo.fr>
  18
  19 import os
  20 import stat
  21
  22 from pysize.core.deletion import filter_deleted
  23
  24 # We cannot use a generator because we rely on the finally block to
  25 # be sure finalize() will be called. Python 2.5 allows finally block
  26 # in generator, but it relies on the GC so it's not sure it will be
  27 # called at the right time.
  28 #
  29 # The expected use of these browsing functions is:
  30 #
  31 # cookie = chdir_browsing.init(path)
  32 # try:
  33 #     for child in chdir_browsing.browsedir(cookie, (True|False)):
  34 #         .. Do something with child ..
  35 # finally:
  36 #     chdir_browsing.finalize(cookie)
  37
  38 def init(path):
  39     previous_cwd = os.open('.', os.O_RDONLY)
  40     try:
  41         os.chdir(path)
  42         return previous_cwd
  43     except OSError, e:
  44         os.close(previous_cwd)
  45         raise e
  46
  47 def browsedir(previous_cwd, cross_device):
  48     res = os.listdir('.')
  49     if not cross_device:
  50         dev = os.stat('.')[stat.ST_DEV]
  51         res = [p for p in res if os.stat(p)[stat.ST_DEV] == dev]
  52     res = filter_deleted(res)
  53     # We want the order to be always so same so that hard links
  54     # detection will be consistent across filesystems
  55     res.sort()
  56     return res
  57
  58 def finalize(previous_cwd):
  59     if previous_cwd:
  60         try:
  61             os.fchdir(previous_cwd)
  62         finally:
  63             os.close(previous_cwd)
  64
  65 def listdir(path, cross_device):
  66     cookie = init(path)
  67     try:
  68         return browsedir(cookie, cross_device)
  69     finally:
  70         finalize(cookie)