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import collections
import errno
import logging
import os
import struct
import sys
import time
import library.python.windows
logger = logging.getLogger(__name__)
# python2 compat
os_O_CLOEXEC = getattr(os, 'O_CLOEXEC', 1 << 19)
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)
# nonbuffered random access rw mode
self._lock = os.fdopen(os.open(self.path, os.O_RDWR | os.O_CREAT | os_O_CLOEXEC), 'r+b', 0)
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)
# nonbuffered random access rw mode
self._lock = os.fdopen(os.open(self.path, os.O_RDWR | os.O_CREAT | os.O_BINARY | os.O_NOINHERIT), 'r+b', 0)
try:
self._lock.write(b' ' * 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):
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(0.5)
else:
return False
def release(self):
if self._lock:
library.python.windows.unlock_file(self._lock, 0, self._LOCKED_BYTES_NUM, raises=False)
def __del__(self):
if getattr(self, '_lock', False):
self._lock.close()
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 %s (blocking=%s): %s', type(self).__name__, blocking, self.path)
return self._lock.acquire(blocking)
def release(self):
logger.debug('Ensuring %s released: %s', type(self).__name__, self.path)
return self._lock.release()
_LockInfo = collections.namedtuple('LockInfo', ['pid', 'time'])
class _PidLockMixin(object):
_LockedBytes = 0
_InfoFormat = 'QQ'
_InfoFmtSize = struct.calcsize(_InfoFormat)
def _register_lock(self):
self._lock.seek(self._LockedBytes, os.SEEK_SET)
self._lock.write(struct.pack(self._InfoFormat, os.getpid(), int(time.time())))
@property
def info(self):
self._lock.seek(self._LockedBytes, os.SEEK_SET)
try:
data = struct.unpack(self._InfoFormat, self._lock.read(self._InfoFmtSize))
except struct.error:
data = 0, 0
return _LockInfo(*data)
class _NixPidFileLock(_NixFileLock, _PidLockMixin):
def acquire(self, blocking=True):
if super(_NixPidFileLock, self).acquire(blocking):
self._register_lock()
return True
return False
class _WinPidFileLock(_WinFileLock, _PidLockMixin):
_LockedBytes = _WinFileLock._LOCKED_BYTES_NUM
def acquire(self, blocking=True):
if super(_WinPidFileLock, self).acquire(blocking):
self._register_lock()
return True
return False
class PidFileLock(FileLock):
def __init__(self, path):
AbstractFileLock.__init__(self, path)
if sys.platform.startswith('win'):
self._lock = _WinPidFileLock(path)
else:
self._lock = _NixPidFileLock(path)
@property
def info(self):
return self._lock.info
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