线程 packaged_task future

http://www.cnblogs.com/haippy/p/3279565.html


#include <iostream>     // std::cout
#include <future>       // std::packaged_task, std::future
#include <chrono>       // std::chrono::seconds
#include <thread>       // std::thread, std::this_thread::sleep_for

// count down taking a second for each value:
int countdown (int from, int to) {
    for (int i=from; i!=to; --i) {
        std::cout << i << ‘\n‘;
        std::this_thread::sleep_for(std::chrono::seconds(1));
    }
    std::cout << "Finished!\n";
    return from - to;
}

int main ()
{
    std::packaged_task<int(int,int)> task(countdown); // 设置 packaged_task
    std::future<int> ret = task.get_future(); // 获得与 packaged_task 共享状态相关联的 future 对象.

    std::thread th(std::move(task), 10, 0);   //创建一个新线程完成计数任务.

    int value = ret.get();                    // 等待任务完成并获取结果.

    std::cout << "The countdown lasted for " << value << " seconds.\n";

    th.join();
    return 0;
}

#include <iostream>     // std::cout
#include <utility>      // std::move
#include <future>       // std::packaged_task, std::future
#include <thread>       // std::thread

int main ()
{
    std::packaged_task<int(int)> foo; // 默认构造函数.

    // 使用 lambda 表达式初始化一个 packaged_task 对象.
    std::packaged_task<int(int)> bar([](int x){return x*2;});

    foo = std::move(bar); // move-赋值操作，也是 C++11 中的新特性.

    // 获取与 packaged_task 共享状态相关联的 future 对象.
    std::future<int> ret = foo.get_future();

    std::thread(std::move(foo), 10).detach(); // 产生线程，调用被包装的任务.

    int value = ret.get(); // 等待任务完成并获取结果.
    std::cout << "The double of 10 is " << value << ".\n";

return 0;
}

#include <iostream>     // std::cout
#include <utility>      // std::move
#include <future>       // std::packaged_task, std::future
#include <thread>       // std::thread

// a simple task:
int triple(int x) { return x * 3; }

int main()
{
    std::packaged_task<int(int)> tsk(triple); // package task


    std::future<int> fut = tsk.get_future();
    std::thread(std::ref(tsk), 100).detach();
    std::cout << "The triple of 100 is " << fut.get() << ".\n";


    // re-use same task object:
    tsk.reset();
    fut = tsk.get_future();
    std::thread(std::move(tsk), 200).detach();
    std::cout << "Thre triple of 200 is " << fut.get() << ".\n";

    return 0;
}