c++如何实现线程池 c++高并发编程实践【实例】

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

class ThreadPool {
public:
    explicit ThreadPool(size_t threads = std::thread::hardware_concurrency())
        : m_stop(false) {
        for (size_t i = 0; i < threads; ++i) {
            m_workers.emplace_back([this] {
                while (true) {
                    std::function task;
                    {
                        std::unique_lock lock(m_queue_mutex);
                        m_condition.wait(lock, [this] { return m_stop.load() || !m_tasks.empty(); });
                        if (m_stop.load() && m_tasks.empty()) return;
                        task = std::move(m_tasks.front());
                        m_tasks.pop();
                    }
                    task();
                }
            });
        }
    }

    template
    auto enqueue(F&& f, Args&&... args)
        -> std::future::type> {
        using return_type = typename std::result_of::type;

        auto task = std::make_shared>(
            std::bind(std::forward(f), std::forward(args)...)
        );

        std::future res = task->get_future();
        {
            std::unique_lock lock(m_queue_mutex);
            if (m_stop.load()) {
                throw std::runtime_error("enqueue on stopped ThreadPool");
            }
            m_tasks.emplace([task]() { (*task)(); });
        }
        m_condition.notify_one();
        return res;
    }

    ~ThreadPool() {
        stop();
    }

private:
    void stop() {
        {
            std::unique_lock lock(m_queue_mutex);
            m_stop = true;
        }
        m_condition.notify_all();
        for (std::thread &t : m_workers) {
            if (t.joinable()) t.join();
        }
    }

    std::vector m_workers;
    std::queue> m_tasks;
    std::mutex m_queue_mutex;
    std::condition_variable m_condition;
    std::atomic m_stop;
};

int main() {
    ThreadPool pool(4);

    // 提交无返回值任务
    pool.enqueue([]{ std::cout << "Hello from thread\n"; });

    // 提交带参数的 lambda
    pool.enqueue([](int x, const std::string& s) {
        std::cout << "x=" << x << ", s=" << s << "\n";
    }, 42, "world");

    // 提交有返回值任务，获取 future
    auto fut = pool.enqueue([] -> int {
        std::this_thread::sleep_for(std::chrono::milliseconds(100));
        return 123;
    });

    std::cout << "Result: " << fut.get() << "\n"; // 阻塞等待结果

    return 0;
}