#

# Module implementing synchronization primitives

#

# multiprocessing/synchronize.py

#

# Copyright (c) 2006-2008, R Oudkerk --- see COPYING.txt

#

__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

        self.__enter__ = self._semlock.__enter__

        self.__exit__ = self._semlock.__exit__

    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)>' % value

#

# Bounded semaphore

#

class BoundedSemaphore(Semaphore):

    def __init__(self, value=1):

        SemLock.__init__(self, SEMAPHORE, value, value)

    def __repr__(self):

        try:

            value = self._semlock._get_value()

        except Exception:

            value = 'unknown'

        return '<BoundedSemaphore(value=%s, maxvalue=%s)>' % \

               (value, self._semlock.maxvalue)

#

# Non-recursive lock

#

class Lock(SemLock):

    def __init__(self):

        SemLock.__init__(self, SEMAPHORE, 1, 1)

    def __repr__(self):

        try:

            if self._semlock._is_mine():

                name = current_process().name

                if threading.current_thread().name != 'MainThread':

                    name += '|' + threading.current_thread().name

            elif self._semlock._get_value() == 1:

                name = 'None'

            elif self._semlock._count() > 0:

                name = 'SomeOtherThread'

            else:

                name = 'SomeOtherProcess'

        except Exception:

            name = 'unknown'

        return '<Lock(owner=%s)>' % name

#

# Recursive lock

#

class RLock(SemLock):

    def __init__(self):

        SemLock.__init__(self, RECURSIVE_MUTEX, 1, 1)

    def __repr__(self):

        try:

            if self._semlock._is_mine():

                name = current_process().name

                if threading.current_thread().name != 'MainThread':

                    name += '|' + threading.current_thread().name

                count = self._semlock._count()

            elif self._semlock._get_value() == 1:

                name, count = 'None', 0

            elif self._semlock._count() > 0:

                name, count = 'SomeOtherThread', 'nonzero'

            else:

                name, count = 'SomeOtherProcess', 'nonzero'

        except Exception:

            name, count = 'unknown', 'unknown'

        return '<RLock(%s, %s)>' % (name, count)

#

# Condition variable

#

class Condition(object):

    def __init__(self, lock=None):

        self._lock = lock or RLock()

        self._sleeping_count = Semaphore(0)

        self._woken_count = Semaphore(0)

        self._wait_semaphore = Semaphore(0)

        self._make_methods()

    def __getstate__(self):

        assert_spawning(self)

        return (self._lock, self._sleeping_count,

                self._woken_count, self._wait_semaphore)

    def __setstate__(self, state):

        (self._lock, self._sleeping_count,

         self._woken_count, self._wait_semaphore) = state

        self._make_methods()

    def _make_methods(self):

        self.acquire = self._lock.acquire

        self.release = self._lock.release

        self.__enter__ = self._lock.__enter__

        self.__exit__ = self._lock.__exit__

    def __repr__(self):

        try:

            num_waiters = (self._sleeping_count._semlock._get_value() -

                           self._woken_count._semlock._get_value())

        except Exception:

            num_waiters = 'unkown'

        return '<Condition(%s, %s)>' % (self._lock, num_waiters)

    def wait(self, timeout=None):

        assert self._lock._semlock._is_mine(), \

               'must acquire() condition before using wait()'

        # indicate that this thread is going to sleep

        self._sleeping_count.release()

        # release lock

        count = self._lock._semlock._count()

        for i in xrange(count):

            self._lock.release()

        try:

            # wait for notification or timeout

            self._wait_semaphore.acquire(True, timeout)

        finally:

            # indicate that this thread has woken

            self._woken_count.release()

            # reacquire lock

            for i in xrange(count):

                self._lock.acquire()

    def notify(self):

        assert self._lock._semlock._is_mine(), 'lock is not owned'

        assert not self._wait_semaphore.acquire(False)

        # to take account of timeouts since last notify() we subtract

        # woken_count from sleeping_count and rezero woken_count

        while self._woken_count.acquire(False):

            res = self._sleeping_count.acquire(False)

            assert res

        if self._sleeping_count.acquire(False): # try grabbing a sleeper

            self._wait_semaphore.release()      # wake up one sleeper

            self._woken_count.acquire()         # wait for the sleeper to wake

            # rezero _wait_semaphore in case a timeout just happened

            self._wait_semaphore.acquire(False)

    def notify_all(self):

        assert self._lock._semlock._is_mine(), 'lock is not owned'

        assert not self._wait_semaphore.acquire(False)

        # to take account of timeouts since last notify*() we subtract

        # woken_count from sleeping_count and rezero woken_count

        while self._woken_count.acquire(False):

            res = self._sleeping_count.acquire(False)

            assert res

        sleepers = 0

        while self._sleeping_count.acquire(False):

            self._wait_semaphore.release()        # wake up one sleeper

            sleepers += 1

        if sleepers:

            for i in xrange(sleepers):

                self._woken_count.acquire()       # wait for a sleeper to wake

            # rezero wait_semaphore in case some timeouts just happened

            while self._wait_semaphore.acquire(False):

                pass

#

# Event

#

class Event(object):

    def __init__(self):

        self._cond = Condition(Lock())

        self._flag = Semaphore(0)

    def is_set(self):

        self._cond.acquire()

        try:

            if self._flag.acquire(False):

                self._flag.release()

                return True

            return False

        finally:

            self._cond.release()

    def set(self):

        self._cond.acquire()

        try:

            self._flag.acquire(False)

            self._flag.release()

            self._cond.notify_all()

        finally:

            self._cond.release()

    def clear(self):

        self._cond.acquire()

        try:

            self._flag.acquire(False)

        finally:

            self._cond.release()

    def wait(self, timeout=None):

        self._cond.acquire()

        try:

            if self._flag.acquire(False):

                self._flag.release()

            else:

                self._cond.wait(timeout)

        finally:

            self._cond.release()