写一个c++ 线程池

好的，以下是一个简单的 C++ 线程池的实现：

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

class ThreadPool {
public:
    ThreadPool(size_t numThreads) {
        for (size_t i = 0; i < numThreads; ++i) {
            threads.emplace_back([this] {
                while (true) {
                    std::function<void()> task;
                    {
                        std::unique_lock<std::mutex> lock(this->queueMutex);
                        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();
                }
            });
        }
    }

    ~ThreadPool() {
        {
            std::unique_lock<std::mutex> lock(queueMutex);
            stop = true;
        }

        condition.notify_all();

        for (std::thread& thread : threads) {
            thread.join();
        }
    }

    template<class F, class... Args>
    void enqueue(F&& f, Args&&... args) {
        auto task = std::make_shared<std::function<void()>>(std::bind(std::forward<F>(f), std::forward<Args>(args)...));

        {
            std::unique_lock<std::mutex> lock(queueMutex);
            tasks.emplace([task] { (*task)(); });
        }

        condition.notify_one();
    }

private:
    std::vector<std::thread> threads;
    std::queue<std::function<void()>> tasks;

    std::mutex queueMutex;
    std::condition_variable condition;

    bool stop = false;
};

实现了一个简单的线程池，使用方法如下：

void foo(int i) {
    std::cout << "Hello from thread " << i << std::endl;
}

int main() {
    ThreadPool pool(4);

    for (int i = 0; i < 8; ++i) {
        pool.enqueue(foo, i);
    }

    return 0;
}

这里创建了一个线程池，包含 4 个线程。然后循环了 8 次，将 foo 函数和循环变量 i 作为参数传递给线程池的 enqueue 函数，让线程池在空闲时执行这个函数。