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62 lines (51 loc) · 1.94 KB
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# encoding: utf-8
# The MIT License
#
# Copyright (c) 2015 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
class FileLock(object):
"""Simple file locking
On platforms without fcntl, all operations in this class are no-ops.
"""
def __init__(self, fd, mode=None):
if has_fcntl and mode is None:
mode = fcntl.LOCK_EX
self.fd = fd
self.mode = mode
self.locked = False
def __enter__(self):
if has_fcntl:
try:
fcntl.flock(self.fd, self.mode)
self.locked = True
except IOError as e:
if e.errno != errno.ENOLCK:
raise e
return self
def __exit__(self, *args):
if has_fcntl and self.locked:
fcntl.flock(self.fd, fcntl.LOCK_UN)
# vim: sw=4 ts=4 sts=4 ai et