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
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
|
#ifndef QPID_SYS_CONCURRENTQUEUE_H
#define QPID_SYS_CONCURRENTQUEUE_H
/*
*
* 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.
*
*/
#include "qpid/sys/Monitor.h"
#include "qpid/sys/ScopedIncrement.h"
#include <boost/bind.hpp>
#include <deque>
namespace qpid {
namespace sys {
/**
* Thread-safe queue that allows threads to push items onto
* the queue concurrently with threads popping items off the
* queue.
*
* Also allows consuming threads to wait until an item is available.
*/
template <class T> class ConcurrentQueue {
public:
ConcurrentQueue() : waiters(0), shutdown(false) {}
/** Threads in wait() are woken with ShutdownException before
* destroying the queue.
*/
~ConcurrentQueue() {
Mutex::ScopedLock l(lock);
shutdown = true;
lock.notifyAll();
while (waiters > 0)
lock.wait();
}
/** Push a data item onto the back of the queue */
void push(const T& data) {
Mutex::ScopedLock l(lock);
queue.push_back(data);
}
/** If the queue is non-empty, pop the front item into data and
* return true. If the queue is empty, return false
*/
bool pop(T& data) {
Mutex::ScopedLock l(lock);
return popInternal(data);
}
/** Wait up to deadline for a data item to be available.
*@return true if data was available, false if timed out.
*@throws ShutdownException if the queue is destroyed.
*/
bool waitPop(T& data, Duration timeout) {
Mutex::ScopedLock l(lock);
ScopedIncrement<size_t> w(
waiters, boost::bind(&ConcurrentQueue::noWaiters, this));
AbsTime deadline(now(), timeout);
while (queue.empty() && lock.wait(deadline))
;
return popInternal(data);
}
private:
bool popInternal(T& data) {
if (shutdown)
throw ShutdownException();
if (queue.empty())
return false;
else {
data = queue.front();
queue.pop_front();
return true;
}
}
void noWaiters() {
assert(waiters == 0);
if (shutdown)
lock.notify(); // Notify dtor thread.
}
Monitor lock;
std::deque<T> queue;
size_t waiters;
bool shutdown;
};
}} // namespace qpid::sys
#endif /*!QPID_SYS_CONCURRENTQUEUE_H*/
|
