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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
/**
* @file ThreadPool.h
* @ingroup util
* The ThreadPool class.
*/
#include "Audaspace.h"
#include <mutex>
#include <condition_variable>
#include <vector>
#include <thread>
#include <queue>
#include <future>
#include <functional>
AUD_NAMESPACE_BEGIN
/**
* This represents pool of threads.
*/
class AUD_API ThreadPool
{
private:
/**
* A queue of tasks.
*/
std::queue<std::function<void()>> m_queue;
/**
* A vector of thread objects.
*/
std::vector<std::thread> m_threads;
/**
* A mutex for synchronization.
*/
std::mutex m_mutex;
/**
* A condition variable used to stop the threads when there are no tasks.
*/
std::condition_variable m_condition;
/**
* Stop flag.
*/
bool m_stopFlag;
/**
* The number fo threads.
*/
unsigned int m_numThreads;
// delete copy constructor and operator=
ThreadPool(const ThreadPool&) = delete;
ThreadPool& operator=(const ThreadPool&) = delete;
public:
/**
* Creates a new ThreadPool object.
* \param count The number of threads of the pool. It must not be 0.
*/
ThreadPool(unsigned int count);
virtual ~ThreadPool();
/**
* Enqueues a new task for the threads to realize.
* \param t A function that realices a task.
* \param args The arguments of the task.
* \return A future of the same type as the return type of the task.
*/
#if __cplusplus > 201703L
template<class T, class... Args>
std::future<typename std::invoke_result<T, Args...>::type> enqueue(T&& t, Args&&... args)
{
using pkgdTask = std::packaged_task<typename std::invoke_result<T, Args...>::type()>;
#else
template<class T, class... Args>
std::future<typename std::result_of<T(Args...)>::type> enqueue(T&& t, Args&&... args)
{
using pkgdTask = std::packaged_task<typename std::result_of<T(Args...)>::type()>;
#endif
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;
}
/**
* Retrieves the number of threads of the pool.
* \return The number of threads.
*/
unsigned int getNumOfThreads();
private:
/**
* Worker thread function.
*/
void threadFunction();
};
AUD_NAMESPACE_END
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