slixmpp/sleekxmpp/xmlstream/handler/waiter.py

"""
    SleekXMPP: The Sleek XMPP Library
    Copyright (C) 2010  Nathanael C. Fritz
    This file is part of SleekXMPP.

    See the file LICENSE for copying permission.
"""

import logging
try:
    import queue
except ImportError:
    import Queue as queue

from sleekxmpp.xmlstream import StanzaBase
from sleekxmpp.xmlstream.handler.base import BaseHandler


log = logging.getLogger(__name__)


class Waiter(BaseHandler):

    """
    The Waiter handler allows an event handler to block
    until a particular stanza has been received. The handler
    will either be given the matched stanza, or False if the
    waiter has timed out.

    Methods:
        check_delete -- Overrides BaseHandler.check_delete
        prerun       -- Overrides BaseHandler.prerun
        run          -- Overrides BaseHandler.run
        wait         -- Wait for a stanza to arrive and return it to
                        an event handler.
    """

    def __init__(self, name, matcher, stream=None):
        """
        Create a new Waiter.

        Arguments:
            name    -- The name of the waiter.
            matcher -- A matcher object to detect the desired stanza.
            stream  -- Optional XMLStream instance to monitor.
        """
        BaseHandler.__init__(self, name, matcher, stream=stream)
        self._payload = queue.Queue()

    def prerun(self, payload):
        """
        Store the matched stanza.

        Overrides BaseHandler.prerun

        Arguments:
            payload -- The matched stanza object.
        """
        self._payload.put(payload)

    def run(self, payload):
        """
        Do not process this handler during the main event loop.

        Overrides BaseHandler.run

        Arguments:
            payload -- The matched stanza object.
        """
        pass

    def wait(self, timeout=None):
        """
        Block an event handler while waiting for a stanza to arrive.

        Be aware that this will impact performance if called from a
        non-threaded event handler.

        Will return either the received stanza, or False if the waiter
        timed out.

        Arguments:
            timeout -- The number of seconds to wait for the stanza to
                       arrive. Defaults to the global default timeout
                       value sleekxmpp.xmlstream.RESPONSE_TIMEOUT.
        """
        if timeout is None:
            timeout = self.stream().response_timeout

        elapsed_time = 0
        stanza = False
        while elapsed_time < timeout and not self.stream().stop.is_set():
            try:
                stanza = self._payload.get(True, 1)
                break
            except queue.Empty:
                elapsed_time += 1
                if elapsed_time >= timeout:
                    log.warning("Timed out waiting for %s", self.name)
        self.stream().remove_handler(self.name)
        return stanza

    def check_delete(self):
        """
        Always remove waiters after use.

        Overrides BaseHandler.check_delete
        """
        return True