ThreadPool.h

//
// Created by 陶睿 on 4/7/24.
//

#ifndef EVENTLOOPMANAGER_THREADPOOL_H
#define EVENTLOOPMANAGER_THREADPOOL_H


#include <vector>
#include <queue>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <functional>
#include <future>
#include <stdexcept>

class ThreadPool {
public:
    ThreadPool(size_t);

    ~ThreadPool();

    // 任务提交
    template<class F, class... Args>
    auto enqueue(F&& f, Args&&... args)
    -> std::future<typename std::invoke_result<F, Args...>::type>;

private:
    // 线程工作组
    std::vector<std::thread> workers;
    // 任务队列
    std::queue<std::function<void()> > tasks;

    // 同步
    std::mutex queue_mutex;
    std::condition_variable condition;
    bool stop;
};

// 构造函数
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();
                    }
                }
        );
}

// 析构函数
ThreadPool::~ThreadPool() {
    {
        std::unique_lock<std::mutex> lock(queue_mutex);
        stop = true;
    }
    condition.notify_all();
    for (std::thread &worker: workers)
        worker.join();
}

// 任务提交
template<class F, class... Args>
auto ThreadPool::enqueue(F&& f, Args&&... args)
-> std::future<typename std::invoke_result<F, Args...>::type> {
    using return_type = typename std::invoke_result<F, Args...>::type;

    auto task = std::make_shared<std::packaged_task<return_type()>>(
            [f = std::forward<F>(f), args...]() -> return_type {
                return 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 stopped ThreadPool");
        }
        tasks.emplace([task]() { (*task)(); });
    }
    condition.notify_one();
    return res;
}



#endif //EVENTLOOPMANAGER_THREADPOOL_H