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/**************************************************************************
*
* Copyright (c) 2012 Jakob Progsch, Václav Zeman
* Copyright (c) 2015 Emmanuel Gil Peyrot, Collabora Ltd.
*
* This software is provided 'as-is', without any express or implied
* warranty. In no event will the authors be held liable for any damages
* arising from the use of this software.
*
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
*
* 1. The origin of this software must not be misrepresented; you must not
* claim that you wrote the original software. If you use this software
* in a product, an acknowledgment in the product documentation would be
* appreciated but is not required.
*
* 2. Altered source versions must be plainly marked as such, and must not be
* misrepresented as being the original software.
*
* 3. This notice may not be removed or altered from any source
* distribution.
*
**************************************************************************/
#pragma once
#include <algorithm>
#include <cstddef>
#include <functional>
#include <queue>
#include <vector>
#include "os_thread.hpp"
class ThreadPool {
public:
ThreadPool(size_t);
template<class F, class... Args>
void enqueue(F&& f, Args&&... args);
~ThreadPool();
private:
// need to keep track of threads so we can join them
std::vector<std::thread> workers;
// the task queue
std::queue<std::function<void()>> tasks;
// synchronization
std::mutex queue_mutex;
std::condition_variable condition;
bool stop;
};
// the constructor just launches some amount of workers
inline ThreadPool::ThreadPool(size_t threads)
: stop(false)
{
for(size_t i = 0;i<threads;++i)
workers.emplace_back(
[this]
{
for(;;)
{
std::function<void()> task;
{
std::unique_lock<std::mutex> lock(this->queue_mutex);
this->condition.wait(lock,
[this]{ return this->stop || !this->tasks.empty(); });
if(this->stop && this->tasks.empty())
return;
task = std::move(this->tasks.front());
this->tasks.pop();
}
task();
}
}
);
}
// add new work item to the pool
template<class F, class... Args>
void ThreadPool::enqueue(F&& f, Args&&... args)
{
auto task = std::bind(std::forward<F>(f), std::forward<Args>(args)...);
{
std::unique_lock<std::mutex> lock(queue_mutex);
// don't allow enqueueing after stopping the pool
assert(!stop);
tasks.emplace(task);
}
condition.notify_one();
}
// the destructor joins all threads
inline ThreadPool::~ThreadPool()
{
{
std::unique_lock<std::mutex> lock(queue_mutex);
stop = true;
}
condition.notify_all();
for(std::thread &worker: workers)
worker.join();
}
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