/******************************************************************************

 *

 * Project:  CPL

 * Purpose:  Implementation of a thread-safe queue

 * Author:   Even Rouault <even dot rouault at spatialys.com>

 *

 ******************************************************************************

 * Copyright (c) 2022, Even Rouault <even dot rouault at spatialys.com>

 *

 * SPDX-License-Identifier: MIT

 ****************************************************************************/

#ifndef CPL_THREADSAFE_QUEUE_INCLUDED

#define CPL_THREADSAFE_QUEUE_INCLUDED

#include <condition_variable>

#include <mutex>

#include <queue>

namespace cpl

{

template <class T> class ThreadSafeQueue

{

  private:

    mutable std::mutex m_mutex{};

    std::condition_variable m_cv{};

    std::queue<T> m_queue{};

  public:

    ThreadSafeQueue() = default;

    void clear()

    {

        std::lock_guard<std::mutex> lock(m_mutex);

        while (!m_queue.empty())

            m_queue.pop();

    }

    bool empty() const

    {

        std::lock_guard<std::mutex> lock(m_mutex);

        return m_queue.empty();

    }

    size_t size() const

    {

        std::lock_guard<std::mutex> lock(m_mutex);

        return m_queue.size();

    }

    void push(const T &value)

    {

        std::lock_guard<std::mutex> lock(m_mutex);

        m_queue.push(value);

        m_cv.notify_one();

    }

    void push(T &&value)

    {

        std::lock_guard<std::mutex> lock(m_mutex);

        m_queue.push(std::move(value));

        m_cv.notify_one();

    }

    T get_and_pop_front()

    {

        std::unique_lock<std::mutex> lock(m_mutex);

        while (m_queue.empty())

        {

            m_cv.wait(lock);

        }

        T val = m_queue.front();

        m_queue.pop();

        return val;

    }

};

}  // namespace cpl

#endif  // CPL_THREADSAFE_QUEUE_INCLUDED