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# Module implementing synchronization primitives
#
# multiprocessing/synchronize.py
#
# Copyright (c) 2006-2008, R Oudkerk
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
# 3. Neither the name of author nor the names of any contributors may be
#    used to endorse or promote products derived from this software
#    without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
#

__all__ = [
    'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore', 'Condition', 'Event'
    ]

import threading
import os
import sys

from time import time as _time, sleep as _sleep

import _multiprocessing
from multiprocessing.process import current_process
from multiprocessing.util import Finalize, register_after_fork, debug
from multiprocessing.forking import assert_spawning, Popen

# Try to import the mp.synchronize module cleanly, if it fails
# raise ImportError for platforms lacking a working sem_open implementation.
# See issue 3770
try:
    from _multiprocessing import SemLock
except (ImportError):
    raise ImportError("This platform lacks a functioning sem_open" +
                      " implementation, therefore, the required" +
                      " synchronization primitives needed will not" +
                      " function, see issue 3770.")

#
# Constants
#

RECURSIVE_MUTEX, SEMAPHORE = range(2)
SEM_VALUE_MAX = _multiprocessing.SemLock.SEM_VALUE_MAX

#
# Base class for semaphores and mutexes; wraps `_multiprocessing.SemLock`
#

class SemLock(object):

    def __init__(self, kind, value, maxvalue):
        sl = self._semlock = _multiprocessing.SemLock(kind, value, maxvalue)
        debug('created semlock with handle %s' % sl.handle)
        self._make_methods()

        if sys.platform != 'win32':
            def _after_fork(obj):
                obj._semlock._after_fork()
            register_after_fork(self, _after_fork)

    def _make_methods(self):
        self.acquire = self._semlock.acquire
        self.release = self._semlock.release

    def __enter__(self):
        return self._semlock.__enter__()

    def __exit__(self, *args):
        return self._semlock.__exit__(*args)

    def __getstate__(self):
        assert_spawning(self)
        sl = self._semlock
        return (Popen.duplicate_for_child(sl.handle), sl.kind, sl.maxvalue)

    def __setstate__(self, state):
        self._semlock = _multiprocessing.SemLock._rebuild(*state)
        debug('recreated blocker with handle %r' % state[0])
        self._make_methods()

#
# Semaphore
#

class Semaphore(SemLock):

    def __init__(self, value=1):
        SemLock.__init__(self, SEMAPHORE, value, SEM_VALUE_MAX)

    def get_value(self):
        return self._semlock._get_value()

    def __repr__(self):
        try:
            value = self._semlock._get_value()
        except Exception:
            value = 'unknown'
        return '<Semaphore(value=%s)>' %