基于C++11的线程池

使用方法:

#include "threadpool.h"
#include <iostream>
#include <windows.h>

using namespace std;

void fun1(int slp)
{
    printf("  hello, fun1 !  %d
", this_thread::get_id());
    if (slp > 0) {
        printf(" ======= fun1 sleep %d  =========  %d
", slp, this_thread::get_id());
        this_thread::sleep_for(chrono::milliseconds(slp));
        //Sleep(slp );
    }
}

struct gfun {
    int operator()(int n) {
        printf("%d  hello, gfun !  %d
", n, this_thread::get_id());
        return 42;
    }
};

class A {    //函数必须是 static 的才能使用线程池
public:
    static int Afun(int n = 0) {
        cout << n << "  hello, Afun !  " << this_thread::get_id() << endl;
        return n;
    }

    static string Bfun(int n, string str, char c) {
        cout << n << "  hello, Bfun !  " << str.c_str() << "  " << (int)c << "  " << this_thread::get_id() << endl;
        return str;
    }
};

int main()
try {
    threadpool executor{ 50 };
    A a;
    future<void> ff = executor.commit(fun1, 0);
    future<int> fg = executor.commit(gfun{}, 0);
    future<int> gg = executor.commit(a.Afun, 9999); //IDE提示错误,但可以编译运行
    future<string> gh = executor.commit(A::Bfun, 9998, "mult args", 123);
    future<string> fh = executor.commit([]()->string { cout << "hello, fh !  " << this_thread::get_id() << endl; return "hello,fh ret !"; });

    cout << " =======  sleep ========= " << this_thread::get_id() << endl;
    this_thread::sleep_for(chrono::microseconds(900));

    for (int i = 0; i < 50; i++) {
        executor.commit(fun1, i * 100);
    }
    cout << " =======  commit all ========= " << this_thread::get_id() << " idlsize=" << executor.idlCount() << endl;

    cout << " =======  sleep ========= " << this_thread::get_id() << endl;
    this_thread::sleep_for(chrono::seconds(3));

    ff.get(); //调用.get()获取返回值会等待线程执行完,获取返回值
    cout << fg.get() << "  " << fh.get().c_str() << "  " << this_thread::get_id() << endl;

    cout << " =======  sleep ========= " << this_thread::get_id() << endl;
    this_thread::sleep_for(chrono::seconds(3));

    cout << " =======  fun1,55 ========= " << this_thread::get_id() << endl;
    executor.commit(fun1, 55).get();    //调用.get()获取返回值会等待线程执行完

    cout << "end... " << this_thread::get_id() << endl;


    threadpool pool(4);
    vector< future<int> > results;

    for (int i = 0; i < 8; ++i) {
        results.emplace_back(
            pool.commit([i] {
                cout << "hello " << i << endl;
                this_thread::sleep_for(chrono::seconds(1));
                cout << "world " << i << endl;
                return i * i;
                })
        );
    }
    cout << " =======  commit all2 ========= " << this_thread::get_id() << endl;

    for (auto&& result : results)
        cout << result.get() << ' ';
    cout << endl;
    return 0;
}
catch (exception& e) {
    cout << "some unhappy happened...  " << this_thread::get_id() << e.what() << endl;
}

#pragma once
#ifndef THREAD_POOL_H
#define THREAD_POOL_H

#include <vector>
#include <queue>
#include <atomic>
#include <future>
//#include <condition_variable>
//#include <thread>
//#include <functional>
#include <stdexcept>

namespace std
{
    //线程池最大容量,应尽量设小一点
#define  THREADPOOL_MAX_NUM 16
//#define  THREADPOOL_AUTO_GROW

//线程池,可以提交变参函数或拉姆达表达式的匿名函数执行,可以获取执行返回值
//不直接支持类成员函数, 支持类静态成员函数或全局函数,Opteron()函数等
    class threadpool
    {
        using Task = function<void()>;    //定义类型
        vector<thread> _pool;            //线程池
        queue<Task> _tasks;                //任务队列
        mutex _lock;                    //同步
        condition_variable _task_cv;    //条件阻塞
        atomic<bool> _run{ true };        //线程池是否执行
        atomic<int>  _idlThrNum{ 0 };    //空闲线程数量

    public:
        inline threadpool(unsigned short size = 4) { addThread(size); }
        inline ~threadpool()
        {
            _run = false;
            _task_cv.notify_all(); // 唤醒所有线程执行
            for (thread& thread : _pool) {
                //thread.detach(); // 让线程“自生自灭”
                if (thread.joinable())
                    thread.join(); // 等待任务结束， 前提：线程一定会执行完
            }
        }

    public:
        // 提交一个任务
        // 调用.get()获取返回值会等待任务执行完,获取返回值
        // 有两种方法可以实现调用类成员，
        // 一种是使用   bind： .commit(std::bind(&Dog::sayHello, &dog));
        // 一种是用   mem_fn： .commit(std::mem_fn(&Dog::sayHello), this)
        template<class F, class... Args>
        auto commit(F&& f, Args&&... args) ->future<decltype(f(args...))>
        {
            if (!_run)    // stoped ??
                throw runtime_error("commit on ThreadPool is stopped.");

            using RetType = decltype(f(args...)); // typename std::result_of<F(Args...)>::type, 函数 f 的返回值类型
            auto task = make_shared<packaged_task<RetType()>>(
                bind(forward<F>(f), forward<Args>(args)...)
                ); // 把函数入口及参数,打包(绑定)
            future<RetType> future = task->get_future();
            {    // 添加任务到队列
                lock_guard<mutex> lock{ _lock };//对当前块的语句加锁  lock_guard 是 mutex 的 stack 封装类，构造的时候 lock()，析构的时候 unlock()
                _tasks.emplace([task]() { // push(Task{...}) 放到队列后面
                    (*task)();
                    });
            }
#ifdef THREADPOOL_AUTO_GROW
            if (_idlThrNum < 1 && _pool.size() < THREADPOOL_MAX_NUM)
                addThread(1);
#endif // !THREADPOOL_AUTO_GROW
            _task_cv.notify_one(); // 唤醒一个线程执行

            return future;
        }

        //空闲线程数量
        int idlCount() { return _idlThrNum; }
        //线程数量
        int thrCount() { return _pool.size(); }
#ifndef THREADPOOL_AUTO_GROW
    private:
#endif // !THREADPOOL_AUTO_GROW
        //添加指定数量的线程
        void addThread(unsigned short size)
        {
            for (; _pool.size() < THREADPOOL_MAX_NUM && size > 0; --size)
            {   //增加线程数量,但不超过 预定义数量 THREADPOOL_MAX_NUM
                _pool.emplace_back([this] { //工作线程函数
                    while (_run)
                    {
                        Task task; // 获取一个待执行的 task
                        {
                            // unique_lock 相比 lock_guard 的好处是：可以随时 unlock() 和 lock()
                            unique_lock<mutex> lock{ _lock };
                            _task_cv.wait(lock, [this] {
                                return !_run || !_tasks.empty();
                                }); // wait 直到有 task
                            if (!_run && _tasks.empty())
                                return;
                            task = move(_tasks.front()); // 按先进先出从队列取一个 task
                            _tasks.pop();
                        }
                        _idlThrNum--;
                        task();//执行任务
                        _idlThrNum++;
                    }
                    });
                _idlThrNum++;
            }
        }
    };

}

#endif