#
# Copyright (c) 2006 The Apache Software Foundation
#
# Licensed 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 close(self):
    self.put(Queue.END)

  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()
    else:
      return result
