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# encoding: utf-8

# The MIT License

#

# Copyright (c) 2015-2016 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.

from __future__ import absolute_import

try:

import fcntl

import errno

has_fcntl = True

except ImportError:

has_fcntl = False

try:

import msvcrt

has_msvcrt = True

except ImportError:

has_msvcrt = False

class BaseLock(object):

"""Base class for file locking

"""

def __init__(self, fd):

self.fd = fd

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, fd, mode=None):

super(UnixFileLock, self).__init__(fd)

if mode is None:

mode = fcntl.LOCK_EX

self.mode = mode

def acquire(self):

try:

fcntl.flock(self.fd, self.mode)

self.locked = True

except IOError as e:

if e.errno != errno.ENOLCK:

raise e

def release(self):

fcntl.flock(self.fd, fcntl.LOCK_UN)

self.locked = False

class WindowsFileLock(BaseLock):

"""Simple file locking for Windows using msvcrt

"""

def __init__(self, fd, mode=None):

super(WindowsFileLock, self).__init__(fd)

def acquire(self):

msvcrt.locking(self.fd, msvcrt.LK_NBLCK, 1)

self.locked = True

def release(self):

msvcrt.locking(self.fd, msvcrt.LK_UNLCK, 1)

self.locked = False

if has_fcntl:

FileLock = UnixFileLock

elif has_msvcrt:

FileLock = WindowsFileLock

else:

FileLock = BaseLock

# vim: sw=4 ts=4 sts=4 ai et