ProducerConsumerQueue.hpp

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/***************************************************
 *       _   _            _                        *
 *      | | | |          (_)                       *
 *      | |_| | ___  _ __ _ _______  _ __          *
 *      |  _  |/ _ \| '__| |_  / _ \| '_  \        *
 *      | | | | (_) | |  | |/ / (_) | | | |        *
 *      \_| |_/\___/|_|  |_/___\___/|_| |_|        *
 ***************************************************
 * This file is part of Horizon (c).
 *
 * Copyright (c) 2019 Sagun K. (sagunxp@gmail.com).
 * Copyright (c) 2019 Horizon Dev Team.
 *
 * Base Author - Sagun K. (sagunxp@gmail.com)
 *
 * This library 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 library 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 library.  If not, see <http://www.gnu.org/licenses/>.
 **************************************************/
 
#ifndef HORIZON_PRODUCERCONSUMERQUEUE_H
#define HORIZON_PRODUCERCONSUMERQUEUE_H
 
#include <condition_variable>
#include <mutex>
#include <queue>
#include <atomic>
#include <type_traits>
 
template <typename T>
class ProducerConsumerQueue
{
private:
    std::mutex _queueLock;
    std::queue<T> _queue;
    std::condition_variable _condition;
    std::atomic<bool> _shutdown;
 
public:
 
    ProducerConsumerQueue<T>() : _shutdown(false) { }
 
    void Push(const T& value)
    {
        std::lock_guard<std::mutex> lock(_queueLock);
        _queue.push(std::move(value));
 
        _condition.notify_one();
    }
 
    bool Empty()
    {
        std::lock_guard<std::mutex> lock(_queueLock);
 
        return _queue.empty();
    }
 
    bool Pop(T& value)
    {
        std::lock_guard<std::mutex> lock(_queueLock);
 
        if (_queue.empty() || _shutdown)
            return false;
 
        value = _queue.front();
 
        _queue.pop();
 
        return true;
    }
 
    void WaitAndPop(T& value)
    {
        std::unique_lock<std::mutex> lock(_queueLock);
 
        // we could be using .wait(lock, predicate) overload here but it is broken
        // https://connect.microsoft.com/VisualStudio/feedback/details/1098841
        while (_queue.empty() && !_shutdown)
            _condition.wait(lock);
 
        if (_queue.empty() || _shutdown)
            return;
 
        value = _queue.front();
 
        _queue.pop();
    }
 
    void Cancel()
    {
        std::unique_lock<std::mutex> lock(_queueLock);
 
        while (!_queue.empty())
        {
            T& value = _queue.front();
 
            DeleteQueuedObject(value);
 
            _queue.pop();
        }
 
        _shutdown = true;
 
        _condition.notify_all();
    }
 
private:
    template<typename E = T>
    typename std::enable_if<std::is_pointer<E>::value>::type DeleteQueuedObject(E& obj) { delete obj; }
 
    template<typename E = T>
    typename std::enable_if<!std::is_pointer<E>::value>::type DeleteQueuedObject(E const& /*packet*/) { }
};
 
 
 
#endif //HORIZON_PRODUCERCONSUMERQUEUE_H