1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
|
#
# 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
class Closed(Exception): pass
class Queue(BaseQueue):
END = object()
STOP = object()
def __init__(self, *args, **kwargs):
BaseQueue.__init__(self, *args, **kwargs)
self.error = None
self.listener = None
self.thread = None
def close(self, error = None):
self.error = error
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(self.error)
else:
return result
def listen(self, listener):
self.listener = listener
if listener == None:
if self.thread != None:
self.put(Queue.STOP)
self.thread.join()
self.thread = None
else:
if self.thread == 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:
break
|
