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import errno
import logging
import os
import sys
import library.python.windows
logger = logging.getLogger(__name__)
def set_close_on_exec(stream):
if library.python.windows.on_win():
library.python.windows.set_handle_information(stream, inherit=False)
else:
import fcntl
fcntl.fcntl(stream, fcntl.F_SETFD, fcntl.FD_CLOEXEC)
class AbstractFileLock(object):
def __init__(self, path):
self.path = path
def acquire(self, blocking=True):
raise NotImplementedError
def release(self):
raise NotImplementedError
def __enter__(self):
self.acquire()
return self
def __exit__(self, type, value, traceback):
self.release()
class _NixFileLock(AbstractFileLock):
def __init__(self, path):
super(_NixFileLock, self).__init__(path)
from fcntl import flock, LOCK_EX, LOCK_UN, LOCK_NB
self._locker = lambda lock, blocking: flock(lock, LOCK_EX if blocking else LOCK_EX | LOCK_NB)
self._unlocker = lambda lock: flock(lock, LOCK_UN)
self._lock = open(self.path, 'a')
set_close_on_exec(self._lock)
def acquire(self, blocking=True):
import errno
try:
self._locker(self._lock, blocking)
except IOError as e:
if e.errno in (errno.EAGAIN, errno.EACCES) and not blocking:
return False
raise
return True
def release(self):
self._unlocker(self._lock)
def __del__(self):
if hasattr(self, "_lock"):
self._lock.close()
class _WinFileLock(AbstractFileLock):
"""
Based on LockFile / UnlockFile from win32 API
https://msdn.microsoft.com/en-us/library/windows/desktop/aa365202(v=vs.85).aspx
"""
_LOCKED_BYTES_NUM = 1
def __init__(self, path):
super(_WinFileLock, self).__init__(path)
self._lock = None
try:
with open(path, 'w') as lock_file:
lock_file.write(" " * self._LOCKED_BYTES_NUM)
except IOError as e:
if e.errno != errno.EACCES or not os.path.isfile(path):
raise
def acquire(self, blocking=True):
self._lock = open(self.path)
set_close_on_exec(self._lock)
import time
locked = False
while not locked:
locked = library.python.windows.lock_file(self._lock, 0, self._LOCKED_BYTES_NUM, raises=False)
if locked:
return True
if blocking:
time.sleep(.5)
else:
return False
def release(self):
if self._lock:
library.python.windows.unlock_file(self._lock, 0, self._LOCKED_BYTES_NUM, raises=False)
self._lock.close()
self._lock = None
class FileLock(AbstractFileLock):
def __init__(self, path):
super(FileLock, self).__init__(path)
if sys.platform.startswith('win'):
self._lock = _WinFileLock(path)
else:
self._lock = _NixFileLock(path)
def acquire(self, blocking=True):
logger.debug('Acquiring filelock (blocking=%s): %s', blocking, self.path)
return self._lock.acquire(blocking)
def release(self):
logger.debug('Ensuring filelock released: %s', self.path)
return self._lock.release()
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