執行緒池的實現

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

class ThreadPool {
public:
    ThreadPool(size_t threads) : stop(false) {
        for (size_t i = 0; i < threads; ++i) {
            workerThreads.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();
                }
            }
            );
        }
    }

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

        {
            std::unique_lock<std::mutex> lock(queueMutex);
            if (stop)
                throw std::runtime_error("enqueue on stopped ThreadPool");

            tasks.emplace(task);
        }
        condition.notify_one();
    }

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

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

    std::mutex queueMutex;
    std::condition_variable condition;
    bool stop;
};

// 使用例子
void taskFunction(int num) {
    std::cout << "Task " << num << " is running on thread "
        << std::this_thread::get_id() << std::endl;
}

int main() {
    ThreadPool pool(4); // 建立一個有4個執行緒的執行緒池
    for (int i = 0; i < 8; ++i) {
        pool.enqueue(taskFunction, i); // 向執行緒池新增任務
    }
    return 0;
}