git.maemo.org Git - watersofshiloah/blob - src/util/concurrent.py

   1 #!/usr/bin/env python
   2
   3 from __future__ import with_statement
   4
   5 import os
   6 import errno
   7 import time
   8 import functools
   9 import contextlib
  10
  11
  12 def synchronized(lock):
  13         """
  14         Synchronization decorator.
  15
  16         >>> import misc
  17         >>> misc.validate_decorator(synchronized(object()))
  18         """
  19
  20         def wrap(f):
  21
  22                 @functools.wraps(f)
  23                 def newFunction(*args, **kw):
  24                         lock.acquire()
  25                         try:
  26                                 return f(*args, **kw)
  27                         finally:
  28                                 lock.release()
  29                 return newFunction
  30         return wrap
  31
  32
  33 @contextlib.contextmanager
  34 def qlock(queue, gblock = True, gtimeout = None, pblock = True, ptimeout = None):
  35         """
  36         Locking with a queue, good for when you want to lock an item passed around
  37
  38         >>> import Queue
  39         >>> item = 5
  40         >>> lock = Queue.Queue()
  41         >>> lock.put(item)
  42         >>> with qlock(lock) as i:
  43         ...     print i
  44         5
  45         """
  46         item = queue.get(gblock, gtimeout)
  47         try:
  48                 yield item
  49         finally:
  50                 queue.put(item, pblock, ptimeout)
  51
  52
  53 @contextlib.contextmanager
  54 def flock(path, timeout=-1):
  55         WAIT_FOREVER = -1
  56         DELAY = 0.1
  57         timeSpent = 0
  58
  59         acquired = False
  60
  61         while timeSpent <= timeout or timeout == WAIT_FOREVER:
  62                 try:
  63                         fd = os.open(path, os.O_CREAT | os.O_EXCL | os.O_RDWR)
  64                         acquired = True
  65                         break
  66                 except OSError, e:
  67                         if e.errno != errno.EEXIST:
  68                                 raise
  69                 time.sleep(DELAY)
  70                 timeSpent += DELAY
  71
  72         assert acquired, "Failed to grab file-lock %s within timeout %d" % (path, timeout)
  73
  74         try:
  75                 yield fd
  76         finally:
  77                 os.unlink(path)