TinyThreadPool.h

#ifndef THREAD_POOL_H
#define THREAD_POOL_H

#include<vector>
#include<queue>
#include<memory>
#include<future>
#include<mutex>
#include<future>
class TinyThreadPool {

public:
    TinyThreadPool(size_t);
    template<class F, class... Args>
    auto enqueue(F&& f, Args&& ... args)
        ->std::future<typename std::result_of<F(Args...)>::type>;
    ~TinyThreadPool();    
private:
    std::vector<std::thread> workers;
    std::queue<std::function<void()>> tasks;
    std::mutex queue_mutex;
    std::condition_variable condition;
    bool stop;
};

inline TinyThreadPool::TinyThreadPool(size_t threads) : stop(false) {
    
     for(size_t i = 0; i < threads; i++) {

         workers.emplace_back(
            [this]
            {
                for(;;) {
                    std::function<void()> tasks;
                    {
                        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;
                        }
                        tasks = std::move(this->tasks.front());
                        this->tasks.pop();
                    }
                    tasks();
                }
            }
         );
     }
}
template<class F, class ... Args> 
auto TinyThreadPool::enqueue(F&& f, Args&&... args)
        -> std::future<typename std::result_of<F(Args...)>::type>
{
    using return_type = typename std::result_of<F(Args...)>::type;

    auto task = std::make_shared<std::packaged_task<return_type()> >(
        std::bind(std::forward<F>(f), std::forward<Args>(args) ...)
    );

    std::future<return_type> res = task->get_future();
    {
        std::unique_lock<std::mutex> lock(queue_mutex);
        if(stop) {
            throw std::runtime_error("enqueue on stop ThreadPool");
        }
        tasks.emplace([task](){(*task)();});
    }
    condition.notify_one();
    return res;
}


inline TinyThreadPool::~TinyThreadPool() {
    {
        std::unique_lock<std::mutex> lock(queue_mutex);
        stop = true;
    }
    condition.notify_all();
    for(std::thread &worker : workers) {
        worker.join();
    }
}
#endif