dataqueue.h

/*
 * Copyright (c) 2015 Meltytech, LLC
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#ifndef DATAQUEUE_H
#define DATAQUEUE_H
 
#include <QMutex>
#include <QMutexLocker>
#include <QWaitCondition>
 
#include <deque>

 
template<class T>
class DataQueue
{
public:
    typedef enum {
        OverflowModeDiscardOldest = 0, 
        OverflowModeDiscardNewest,     
        OverflowModeWait               
    } OverflowMode;

    explicit DataQueue(int maxSize, OverflowMode mode);

    virtual ~DataQueue();

    void push(const T &item);

    T pop();

    int count() const;
 
private:
    std::deque<T> m_queue;
    int m_maxSize;
    OverflowMode m_mode;
    mutable QMutex m_mutex;
    QWaitCondition m_notEmptyCondition;
    QWaitCondition m_notFullCondition;
};
 
template<class T>
DataQueue<T>::DataQueue(int maxSize, OverflowMode mode)
    : m_queue()
    , m_maxSize(maxSize)
    , m_mode(mode)
    , m_mutex()
    , m_notEmptyCondition()
    , m_notFullCondition()
{}
 
template<class T>
DataQueue<T>::~DataQueue()
{}
 
template<class T>
void DataQueue<T>::push(const T &item)
{
    m_mutex.lock();
    if (m_queue.size() == m_maxSize) {
        switch (m_mode) {
        case OverflowModeDiscardOldest:
            m_queue.pop_front();
            m_queue.push_back(item);
            break;
        case OverflowModeDiscardNewest:
            // This item is the newest so discard it and exit
            break;
        case OverflowModeWait:
            m_notFullCondition.wait(&m_mutex);
            m_queue.push_back(item);
            break;
        }
    } else {
        m_queue.push_back(item);
        if (m_queue.size() == 1) {
            m_notEmptyCondition.wakeOne();
        }
    }
    m_mutex.unlock();
}
 
template<class T>
T DataQueue<T>::pop()
{
    T retVal;
    m_mutex.lock();
    if (m_queue.size() == 0) {
        m_notEmptyCondition.wait(&m_mutex);
    }
    retVal = m_queue.front();
    m_queue.pop_front();
    if (m_mode == OverflowModeWait && m_queue.size() == m_maxSize - 1) {
        m_notFullCondition.wakeOne();
    }
    m_mutex.unlock();
    return retVal;
}
 
template<class T>
int DataQueue<T>::count() const
{
    QMutexLocker locker(&m_mutex);
    return m_queue.size();
}
 
#endif // DATAQUEUE_H