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#
# 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
class Closed(Exception): pass
class Queue(BaseQueue):
END = object()
def __init__(self, *args, **kwargs):
BaseQueue.__init__(self, *args, **kwargs)
self._real_put = self.put
self.listener = self._real_put
def close(self):
self.put(Queue.END)
def get(self, block = True, timeout = None):
self.put = self._real_put
try:
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()
else:
return result
finally:
self.put = self.listener
pass
def listen(self, listener):
self.listener = listener
self.put = self.listener
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