c++ - 如何等待两个计时器中的任何一个完成（Boost Asio）

Question

当两者 都完成时timer1，下面的代码将打印到控制台。timer2如何将其更改为在其中一个或完成时打印， timer1然后timer2取消另一个计时器。

#include <iostream>
#include <boost/asio.hpp>
#include <boost/asio/spawn.hpp>

int main() {

  boost::asio::io_context io;

  boost::asio::deadline_timer timer1(io, boost::posix_time::seconds(5));
  boost::asio::deadline_timer timer2(io, boost::posix_time::seconds(1));

  boost::asio::spawn(io, [&](boost::asio::yield_context yield){
    timer1.async_wait(yield);
    timer2.async_wait(yield);
    std::cout << "Both timer1 and timer2 have finished" << std::endl;
  });

  io.run();

}

标签： c++c++11boostboost-asioboost-coroutine

Answer 1

怎么样：

#include <iostream>
#include <boost/asio.hpp>
#include <boost/asio/spawn.hpp>

void print_timer_expired( bool& flag)
{
 if( flag )
     return;
 flag = true;
 std::cout << "Timer1 or timer2 has finished" << std::endl;
}
int main() {

  boost::asio::io_context io;
  bool flag = false;  // true if message has been printed

  boost::asio::deadline_timer timer1(io, boost::posix_time::seconds(5));
  boost::asio::deadline_timer timer2(io, boost::posix_time::seconds(1));

  boost::asio::spawn(io, [&](boost::asio::yield_context yield){
    timer1.async_wait(yield);
    print_timer_expired( flag );
  });
  boost::asio::spawn(io, [&](boost::asio::yield_context yield){
    timer2.async_wait(yield);
    print_timer_expired( flag );
  });

  io.run();

}