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# The MIT License
#
# Copyright (c) 2015-2019 Sebastian Ramacher
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
try:
import fcntl
import errno
has_fcntl = True
except ImportError:
has_fcntl = False
try:
import msvcrt
import os
has_msvcrt = True
except ImportError:
has_msvcrt = False
class BaseLock:
"""Base class for file locking"""
def __init__(self, fileobj, mode=None, filename=None):
self.fileobj = fileobj
self.locked = False
def acquire(self):
pass
def release(self):
pass
def __enter__(self):
self.acquire()
return self
def __exit__(self, *args):
if self.locked:
self.release()
def __del__(self):
if self.locked:
self.release()
class UnixFileLock(BaseLock):
"""Simple file locking for Unix using fcntl"""
def __init__(self, fileobj, mode=None, filename=None):
super().__init__(fileobj)
if mode is None:
mode = fcntl.LOCK_EX
self.mode = mode
def acquire(self):
try:
fcntl.flock(self.fileobj, self.mode)
self.locked = True
except OSError as e:
if e.errno != errno.ENOLCK:
raise e
def release(self):
self.locked = False
fcntl.flock(self.fileobj, fcntl.LOCK_UN)
class WindowsFileLock(BaseLock):
"""Simple file locking for Windows using msvcrt"""
def __init__(self, fileobj, mode=None, filename=None):
super().__init__(None)
self.filename = f"{filename}.lock"
def acquire(self):
# create a lock file and lock it
self.fileobj = os.open(
self.filename, os.O_RDWR | os.O_CREAT | os.O_TRUNC
)
msvcrt.locking(self.fileobj, msvcrt.LK_NBLCK, 1)
self.locked = True
def release(self):
self.locked = False
# unlock lock file and remove it
msvcrt.locking(self.fileobj, msvcrt.LK_UNLCK, 1)
os.close(self.fileobj)
self.fileobj = None
try:
os.remove(self.filename)
except OSError:
pass
if has_fcntl:
FileLock = UnixFileLock
elif has_msvcrt:
FileLock = WindowsFileLock
else:
FileLock = BaseLock
# vim: sw=4 ts=4 sts=4 ai et
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