You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
143 lines
3.1 KiB
143 lines
3.1 KiB
"""
|
|
Platform-independent file locking. Inspired by and modeled after zc.lockfile.
|
|
"""
|
|
|
|
import os
|
|
|
|
try:
|
|
import msvcrt
|
|
except ImportError:
|
|
pass
|
|
|
|
try:
|
|
import fcntl
|
|
except ImportError:
|
|
pass
|
|
|
|
|
|
class LockError(Exception):
|
|
|
|
'Could not obtain a lock'
|
|
|
|
msg = 'Unable to lock %r'
|
|
|
|
def __init__(self, path):
|
|
super(LockError, self).__init__(self.msg % path)
|
|
|
|
|
|
class UnlockError(LockError):
|
|
|
|
'Could not release a lock'
|
|
|
|
msg = 'Unable to unlock %r'
|
|
|
|
|
|
# first, a default, naive locking implementation
|
|
class LockFile(object):
|
|
|
|
"""
|
|
A default, naive locking implementation. Always fails if the file
|
|
already exists.
|
|
"""
|
|
|
|
def __init__(self, path):
|
|
self.path = path
|
|
try:
|
|
fd = os.open(path, os.O_CREAT | os.O_WRONLY | os.O_EXCL)
|
|
except OSError:
|
|
raise LockError(self.path)
|
|
os.close(fd)
|
|
|
|
def release(self):
|
|
os.remove(self.path)
|
|
|
|
def remove(self):
|
|
pass
|
|
|
|
|
|
class SystemLockFile(object):
|
|
|
|
"""
|
|
An abstract base class for platform-specific locking.
|
|
"""
|
|
|
|
def __init__(self, path):
|
|
self.path = path
|
|
|
|
try:
|
|
# Open lockfile for writing without truncation:
|
|
self.fp = open(path, 'r+')
|
|
except IOError:
|
|
# If the file doesn't exist, IOError is raised; Use a+ instead.
|
|
# Note that there may be a race here. Multiple processes
|
|
# could fail on the r+ open and open the file a+, but only
|
|
# one will get the the lock and write a pid.
|
|
self.fp = open(path, 'a+')
|
|
|
|
try:
|
|
self._lock_file()
|
|
except:
|
|
self.fp.seek(1)
|
|
self.fp.close()
|
|
del self.fp
|
|
raise
|
|
|
|
self.fp.write(' %s\n' % os.getpid())
|
|
self.fp.truncate()
|
|
self.fp.flush()
|
|
|
|
def release(self):
|
|
if not hasattr(self, 'fp'):
|
|
return
|
|
self._unlock_file()
|
|
self.fp.close()
|
|
del self.fp
|
|
|
|
def remove(self):
|
|
"""
|
|
Attempt to remove the file
|
|
"""
|
|
try:
|
|
os.remove(self.path)
|
|
except:
|
|
pass
|
|
|
|
def _unlock_file(self):
|
|
"""Attempt to obtain the lock on self.fp. Raise UnlockError if not
|
|
released."""
|
|
|
|
|
|
class WindowsLockFile(SystemLockFile):
|
|
|
|
def _lock_file(self):
|
|
# Lock just the first byte
|
|
try:
|
|
msvcrt.locking(self.fp.fileno(), msvcrt.LK_NBLCK, 1)
|
|
except IOError:
|
|
raise LockError(self.fp.name)
|
|
|
|
def _unlock_file(self):
|
|
try:
|
|
self.fp.seek(0)
|
|
msvcrt.locking(self.fp.fileno(), msvcrt.LK_UNLCK, 1)
|
|
except IOError:
|
|
raise UnlockError(self.fp.name)
|
|
|
|
if 'msvcrt' in globals():
|
|
LockFile = WindowsLockFile
|
|
|
|
|
|
class UnixLockFile(SystemLockFile):
|
|
|
|
def _lock_file(self):
|
|
flags = fcntl.LOCK_EX | fcntl.LOCK_NB
|
|
try:
|
|
fcntl.flock(self.fp.fileno(), flags)
|
|
except IOError:
|
|
raise LockError(self.fp.name)
|
|
|
|
# no need to implement _unlock_file, it will be unlocked on close()
|
|
|
|
if 'fcntl' in globals():
|
|
LockFile = UnixLockFile
|