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# -*- coding: utf-8 -*-
# Copyright (c) 2009 Evan Fosmark
# Copyright (c) 2014, 2021 kaliko <kaliko@azylum.org>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
#
# https://github.com/dmfrey/FileLock
"""
Plain file lock to une in context:
>>> with FileLock('/path/to/file/to/write'):
>>> # a lock file is maintain within the scope of this context:
>>> # /path/to/file/to/write.lock
>>> ... # process file writing
"""
import errno
import os
import time
class FileLockException(Exception):
"""FileLock Exception"""
class FileLock:
""" A plain file lock whit context-manager"""
def __init__(self, file_name, timeout=10, delay=.05):
"""
Setup file lock.
Setup timeout and the delay.
"""
self.filedsc = None
self.is_locked = False
dirname = os.path.dirname(file_name)
self.lockfile = os.path.join(dirname, 'f{file_name}.lock')
self.file_name = file_name
self.timeout = timeout
self.delay = delay
def acquire(self):
"""Acquire the lock, if possible.
"""
start_time = time.time()
while True:
try:
self.filedsc = os.open(self.lockfile,
os.O_CREAT | os.O_EXCL | os.O_RDWR)
break
except OSError as err:
if err.errno != errno.EEXIST:
raise
if (time.time() - start_time) >= self.timeout:
raise FileLockException('Timeout occured.') from err
time.sleep(self.delay)
self.is_locked = True
def release(self):
"""Release the lock.
"""
if self.is_locked:
os.close(self.filedsc)
os.unlink(self.lockfile)
self.is_locked = False
def __enter__(self):
"""start of the with statement.
"""
if not self.is_locked:
self.acquire()
return self
def __exit__(self, ex_type, ex_value, ex_traceback):
"""end of the with statement
"""
if self.is_locked:
self.release()
def __del__(self):
"""Cleanup
"""
self.release()
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