1 files changed, 88 insertions, 0 deletions
diff --git a/qpid/python/qpid/queue.py b/qpid/python/qpid/queue.py
new file mode 100644
index 0000000000..63a7684843
--- /dev/null
+++ b/qpid/python/qpid/queue.py
@@ -0,0 +1,88 @@
+#
+# 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