C++ 超完善的线程池实现

以下是一个C++实现的线程池，包含了线程池的创建、任务的添加、线程的工作和销毁等功能。

#include <thread>
#include <mutex>
#include <condition_variable>
#include <queue>
#include <functional>

class ThreadPool {
public:
    ThreadPool(size_t threads): stop(false) {
        // 创建指定数量的线程
        for (size_t i = 0; i < threads; ++i) {
            workers.emplace_back(
                [this] {
                    // 线程工作函数
                    for (;;) {
                        std::function<void()> task;
                        {
                            // 获取任务
                            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();
                        }
                        // 执行任务
                        task();
                    }
                }
            );
        }
    }

    template<class F, class... Args>
    auto 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);

            // 不允许向已停止的线程池中添加任务
            if (stop)
                throw std::runtime_error("enqueue on stopped ThreadPool");

            tasks.emplace([task]() { (*task)(); });
        }
        condition.notify_one();
        return res;
    }

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

private:
    std::vector<std::thread> workers;
    std::queue<std::function<void()>> tasks;
    std::mutex queue_mutex;
    std::condition_variable condition;
    bool stop;
};

使用方法如下：

#include <iostream>
#include <chrono>

void task(int num) {
    std::this_thread::sleep_for(std::chrono::seconds(1));
    std::cout << "Task " << num << " completed." << std::endl;
}

int main() {
    ThreadPool pool(4);

    std::vector<std::future<void>> results;
    for (int i = 1; i <= 8; ++i) {
        results.emplace_back(pool.enqueue(task, i));
    }

    for (auto && result: results) {
        result.get();
    }
    return 0;
}

输出结果为：

Task 1 completed.
Task 2 completed.
Task 3 completed.
Task 4 completed.
Task 5 completed.
Task 6 completed.
Task 7 completed.
Task 8 completed.

可以看到，线程池中的4个线程依次执行了8个任务，每个任务都等待1秒钟后输出完成信息。