pysize/core/chdir_browsing.py

   1 import os
   2
   3 # We cannot use a generator because we rely on the finally block to
   4 # be sure finalize() will be called. Python 2.5 allows finally block
   5 # in generator, but it relies on the GC so it's not sure it will be
   6 # called at the right time.
   7 #
   8 # The expected use of these browsing functions is:
   9 #
  10 # cookie = chdir_browsing.init(path)
  11 # try:
  12 #     for child in chdir_browsing.listdir(cookie):
  13 #         .. Do something with child ..
  14 # finally:
  15 #     chdir_browsing.finalize(cookie)
  16
  17 def init(path):
  18     previous_cwd = os.open('.', os.O_RDONLY)
  19     try:
  20         os.chdir(path)
  21         return previous_cwd
  22     except OSError, e:
  23         os.close(previous_cwd)
  24         raise e
  25
  26 def listdir(unused_cookie):
  27     res = os.listdir('.')
  28     # We want the order to be always so same so that hard links
  29     # detection will be consistent across filesystems
  30     res.sort()
  31     return res
  32
  33 def finalize(previous_cwd):
  34     try:
  35         os.fchdir(previous_cwd)
  36     finally:
  37         os.close(previous_cwd)