Lib/multiprocessing/dummy/connection.py

#
# Analogue of `multiprocessing.connection` which uses queues instead of sockets
#
# multiprocessing/dummy/connection.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__ = [ 'Client', 'Listener', 'Pipe' ]

from queue import Queue


families = [None]


class Listener(object):

    def __init__(self, address=None, family=None, backlog=1):
        self._backlog_queue = Queue(backlog)

    def accept(self):
        return Connection(*self._backlog_queue.get())

    def close(self):
        self._backlog_queue = None

    address = property(lambda self: self._backlog_queue)

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_value, exc_tb):
        self.close()


def Client(address):
    _in, _out = Queue(), Queue()
    address.put((_out, _in))
    return Connection(_in, _out)


def Pipe(duplex=True):
    a, b = Queue(), Queue()
    return Connection(a, b), Connection(b, a)


class Connection(object):

    def __init__(self, _in, _out):
        self._out = _out
        self._in = _in
        self.send = self.send_bytes = _out.put
        self.recv = self.recv_bytes = _in.get

    def poll(self, timeout=0.0):
        if self._in.qsize() > 0:
            return True
        if timeout <= 0.0:
            return False
        self._in.not_empty.acquire()
        self._in.not_empty.wait(timeout)
        self._in.not_empty.release()
        return self._in.qsize() > 0

    def close(self):
        pass

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_value, exc_tb):
        self.close()