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#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/Waitable.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 Waitable {
public:
struct ShutdownException {};
ConcurrentQueue() : shutdownFlag(false) {}
/** Waiting threads are notified by ~Waitable */
~ConcurrentQueue() { shutdown(); }
bool shutdown(bool wait=true) {
ScopedLock l(lock);
if (!shutdownFlag) {
shutdownFlag=true;
lock.notifyAll();
if (wait) lock.waitAll();
shutdownFlag=true;
return true;
}
return false;
}
/** Push a data item onto the back of the queue */
void push(const T& data) {
Mutex::ScopedLock l(lock);
queue.push_back(data);
lock.notify();
}
/** If the queue is non-empty, pop the front item into data and
* return true. If the queue is empty, return false
*/
bool tryPop(T& data) {
Mutex::ScopedLock l(lock);
if (shutdownFlag || queue.empty())
return false;
data = queue.front();
queue.pop_front();
return true;
}
/** Wait for a data item to be available.
* Return false if shut down.
*/
bool waitPop(T& data) {
ScopedLock l(lock);
{
ScopedWait(*this);
while (!shutdownFlag && queue.empty())
lock.wait();
}
if (queue.empty())
return false;
data = queue.front();
queue.pop_front();
return true;
}
bool isShutdown() { ScopedLock l(lock); return shutdownFlag; }
protected:
Waitable lock;
private:
std::deque<T> queue;
bool shutdownFlag;
};
}} // namespace qpid::sys
#endif /*!QPID_SYS_CONCURRENTQUEUE_H*/
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