C++11的future和promise、parkged_task使用

#include <iostream>
#include <future>
#include <unistd.h>

int main(int argc, char **argv) {

  std::future_status f_status;

  auto func = [](int b) -> int{
      std::cout << "async thread running...." << std::endl;
      for (int i = 0; i< b; i++) {
        ;
      }
      return b;
    };
  std::future<int> fut = std::async(std::launch::async, func, 888888888);
  std::cout << "main thread running ...." << std::endl;
  std::chrono::milliseconds span(100);
  //方法一,用于等待异步操作的数据
  while(1) {
    f_status = fut.wait_for(span);
    if (f_status == std::future_status::ready) {
      std::cout << "future_status::ready   ";
      break;
    } else if(f_status == std::future_status::deferred) {
      std::cout << "future_status::deferred ";
    } else if(f_status == std::future_status::timeout) {
      std::cout << "future_status::timeout  ";
    }
    std::cout << std::endl;
    std::cout << "................";
    std::cout << std::endl;
    //fut.wait(); //方法二，等待异步线程的数据
  }
  std::cout << "future result " << fut.get() << std::endl;
  return 0;

cmake_minimum_required(VERSION 2.6)
set(src ./async.cpp)
set(exe "async")
set(CMAKE_CXX_FLAGS -std=c++11)
add_executable(${exe} ${src})
target_link_libraries(${exe} -lpthread)

 std::promise<int> pr;
  std::thread t([](std::promise<int>& p){ p.set_value_at_thread_exit(9); },std::ref(pr));
  std::future<int> f = pr.get_future();
  auto r = f.get();

 std::packaged_task<int()> task([](){ return 7; });
  std::thread t1(std::ref(task)); 
  std::future<int> f1 = task.get_future(); 
  auto r1 = f1.get();