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, 2007 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, account_deletion=True):
  48     res = os.listdir('.')
  49     if not cross_device:
  50         def same_dev(dev, path):
  51             try:
  52                 return os.lstat(path)[stat.ST_DEV] == dev
  53             except OSError:
  54                 return True
  55         dev = os.lstat('.')[stat.ST_DEV]
  56         res = [p for p in res if same_dev(dev, p)]
  57     if account_deletion:
  58         res = filter_deleted(res)
  59     # We want the order to be always so same so that hard links
  60     # detection will be consistent across filesystems
  61     res.sort()
  62     return res
  63
  64 def finalize(previous_cwd):
  65     if previous_cwd:
  66         try:
  67             os.fchdir(previous_cwd)
  68         finally:
  69             os.close(previous_cwd)
  70
  71 def listdir(path, cross_device):
  72     cookie = init(path)
  73     try:
  74         return browsedir(cookie, cross_device)
  75     finally:
  76         finalize(cookie)