mic/utils/lock.py

   1 # Copyright (c) 2011 Intel, Inc.
   2 #
   3 # This program is free software; you can redistribute it and/or modify it
   4 # under the terms of the GNU General Public License as published by the Free
   5 # Software Foundation; either version 2 of the License, or any later version.
   6
   7 import os
   8 import errno
   9
  10 class LockfileError(Exception):
  11     """ Lockfile Exception"""
  12     pass
  13
  14 class SimpleLockfile(object):
  15     """ Simple implementation of lockfile """
  16     def __init__(self, fpath):
  17         self.fpath = fpath
  18         self.lockf = None
  19
  20     def acquire(self):
  21         """ acquire the lock """
  22         try:
  23             self.lockf = os.open(self.fpath,
  24                                  os.O_CREAT | os.O_EXCL | os.O_WRONLY)
  25         except OSError as err:
  26             if err.errno == errno.EEXIST:
  27                 raise LockfileError("File %s is locked already" % self.fpath)
  28             raise
  29         finally:
  30             if self.lockf:
  31                 os.close(self.lockf)
  32
  33     def release(self):
  34         """ release the lock """
  35         try:
  36             os.remove(self.fpath)
  37         except OSError as err:
  38             if err.errno == errno.ENOENT:
  39                 pass
  40
  41     def __enter__(self):
  42         self.acquire()
  43         return self
  44
  45     def __exit__(self, *args):
  46         self.release()
  47
  48     def __del__(self):
  49         self.release()