ThreadPool.h

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/*******************************************************************************
* Copyright 2015-2016 Juan Francisco Crespo Galán
*
* Licensed 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.
******************************************************************************/
 
#pragma once

 
#include "Audaspace.h"
 
#include <mutex>
#include <condition_variable>
#include <vector>
#include <thread>
#include <queue>
#include <future>
#include <functional>
 
AUD_NAMESPACE_BEGIN
class AUD_API ThreadPool
{
private:
    std::queue<std::function<void()>> m_queue;

    std::vector<std::thread> m_threads;

    std::mutex m_mutex;

    std::condition_variable m_condition;

    bool m_stopFlag;

    unsigned int m_numThreads;
 
    // delete copy constructor and operator=
    ThreadPool(const ThreadPool&) = delete;
    ThreadPool& operator=(const ThreadPool&) = delete;
public:
    ThreadPool(unsigned int count);
 
    virtual ~ThreadPool();

    template<class T, class... Args>
    auto enqueue(T&& t, Args&&... args)
    {
        using pkgdTask = std::packaged_task<typename std::invoke_result<T, Args...>::type()>;
 
        std::shared_ptr<pkgdTask> task = std::make_shared<pkgdTask>(std::bind(std::forward<T>(t), std::forward<Args>(args)...));
        auto result = task->get_future();
 
        m_mutex.lock();
        m_queue.emplace([task]() { (*task)(); });
        m_mutex.unlock();
 
        m_condition.notify_one();
        return result;
    }

    unsigned int getNumOfThreads();
 
private:

    void threadFunction();
};
AUD_NAMESPACE_END