| # |
| # Licensed to the Apache Software Foundation (ASF) under one |
| # or more contributor license agreements. See the NOTICE file |
| # distributed with this work for additional information |
| # regarding copyright ownership. The ASF licenses this file |
| # to you under the Apache License, Version 2.0 (the |
| # "License"); you may not use this file except in compliance |
| # with the License. You may obtain a copy of the License at |
| # |
| # http://www.apache.org/licenses/LICENSE-2.0 |
| # |
| # Unless required by applicable law or agreed to in writing, |
| # software distributed under the License is distributed on an |
| # "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| # KIND, either express or implied. See the License for the |
| # specific language governing permissions and limitations |
| # under the License. |
| # |
| |
| """ |
| This module augments the standard python multithreaded Queue |
| implementation to add a close() method so that threads blocking on the |
| content of a queue can be notified if the queue is no longer in use. |
| """ |
| |
| from Queue import Queue as BaseQueue, Empty, Full |
| from threading import Thread |
| from exceptions import Closed |
| |
| class Queue(BaseQueue): |
| |
| END = object() |
| STOP = object() |
| |
| def __init__(self, *args, **kwargs): |
| BaseQueue.__init__(self, *args, **kwargs) |
| self.error = None |
| self.listener = None |
| self.exc_listener = None |
| self.thread = None |
| |
| def close(self, error = None): |
| self.error = error |
| self.put(Queue.END) |
| if self.thread is not None: |
| self.thread.join() |
| self.thread = None |
| |
| def get(self, block = True, timeout = None): |
| result = BaseQueue.get(self, block, timeout) |
| if result == Queue.END: |
| # this guarantees that any other waiting threads or any future |
| # calls to get will also result in a Closed exception |
| self.put(Queue.END) |
| raise Closed(self.error) |
| else: |
| return result |
| |
| def listen(self, listener, exc_listener = None): |
| if listener is None and exc_listener is not None: |
| raise ValueError("cannot set exception listener without setting listener") |
| |
| if listener is None: |
| if self.thread is not None: |
| self.put(Queue.STOP) |
| # loop and timed join permit keyboard interrupts to work |
| while self.thread.isAlive(): |
| self.thread.join(3) |
| self.thread = None |
| |
| self.listener = listener |
| self.exc_listener = exc_listener |
| |
| if listener is not None and self.thread is None: |
| self.thread = Thread(target = self.run) |
| self.thread.setDaemon(True) |
| self.thread.start() |
| |
| def run(self): |
| while True: |
| try: |
| o = self.get() |
| if o == Queue.STOP: break |
| self.listener(o) |
| except Closed, e: |
| if self.exc_listener is not None: |
| self.exc_listener(e) |
| break |