SynchronizedQueue.h

/*
╔══════════════════════════════════════════════════════════════════════════════╗
║                       SIMPLY POWERFUL TOOLKIT (SPTK)                         ║
╟──────────────────────────────────────────────────────────────────────────────╢
║  copyright            © 1999-2022 Alexey Parshin. All rights reserved.       ║
║  email                alexeyp@gmail.com                                      ║
╚══════════════════════════════════════════════════════════════════════════════╝
┌──────────────────────────────────────────────────────────────────────────────┐
│   This library is free software; you can redistribute it and/or modify it    │
│   under the terms of the GNU Library General Public License as published by  │
│   the Free Software Foundation; either version 2 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 Library   │
│   General Public License for more details.                                   │
│                                                                              │
│   You should have received a copy of the GNU Library General Public License  │
│   along with this library; if not, write to the Free Software Foundation,    │
│   Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.               │
│                                                                              │
│   Please report all bugs and problems to alexeyp@gmail.com.                  │
└──────────────────────────────────────────────────────────────────────────────┘
*/
 
#pragma once
 
#include <functional>
#include <mutex>
#include <queue>
#include <sptk5/sptk.h>
#include <sptk5/threads/Semaphore.h>
 
namespace sptk {
 
template<class T>
class SynchronizedQueue
{
public:
    virtual ~SynchronizedQueue() = default;
 
    using CallbackFunction = std::function<bool(T& item)>;
 
    void push(T&& data)
    {
        std::unique_lock lock(m_mutex);
        m_queue->push(std::move(data));
        lock.unlock();
        m_semaphore.post();
    }
 
    void push(const T& data)
    {
        std::unique_lock lock(m_mutex);
        m_queue->push(data);
        lock.unlock();
        m_semaphore.post();
    }
 
    bool pop(T& item, std::chrono::milliseconds timeout)
    {
        if (m_semaphore.sleep_for(timeout))
        {
            std::scoped_lock lock(m_mutex);
            if (!m_queue->empty())
            {
                item = std::move(m_queue->front());
                m_queue->pop();
                return true;
            }
        }
        return false;
    }
 
    virtual void wakeup()
    {
        m_semaphore.post();
    }
 
    bool empty() const
    {
        std::scoped_lock lock(m_mutex);
        return m_queue->empty();
    }
 
    size_t size() const
    {
        std::scoped_lock lock(m_mutex);
        return m_queue->size();
    }
 
    void clear()
    {
        std::scoped_lock lock(m_mutex);
        m_queue = std::make_shared<std::queue<T>>();
    }
 
    bool each(const CallbackFunction& callbackFunction)
    {
        std::scoped_lock lock(m_mutex);
 
        auto newQueue = std::make_shared<std::queue<T>>();
 
        // Iterating through queue until callback returns false
        bool rc = true;
        while (m_queue->size())
        {
            T& item = m_queue->front();
            m_queue->pop();
            newQueue->push(item);
            // When rc switches to false, don't execute callback
            // for the remaining queue items
            if (rc)
            {
                try
                {
                    rc = callbackFunction(item);
                }
                catch (const Exception&)
                {
                    rc = false;
                }
            }
        }
 
        m_queue = newQueue;
 
        return rc;
    }
 
private:
    mutable std::mutex m_mutex;
 
    Semaphore m_semaphore;
 
    std::shared_ptr<std::queue<T>> m_queue {std::make_shared<std::queue<T>>()};
};
} // namespace sptk