boost::asio

1、同步：

  #include <iostream>
  #include <boost/asio.hpp>
  #include <boost/date_time/posix_time/posix_time.hpp>
  using std::cout;
  using std::endl;
  int main()
  {
      boost::asio::io_service io;
      boost::asio::deadline_timer t(io,boost::posix_time::seconds(5));
      t.wait();
      cout<<"Hello,world!"<<endl;
      return 0;
  }
//过5秒输出 "Hello,world!"

2、异步：相当于现在银行取票排队，时间到了会通知你。

  #include <iostream>
  #include <boost/asio.hpp>
  #include <boost/date_time/posix_time/posix_time.hpp>
  using std::cout;
  using std::endl;
  void print(const boost::system::error_code& error)
  {
      cout<<"Hello,world!"<<endl;
  }
  int main()
  {
      boost::asio::io_service io;
      boost::asio::deadline_timer t(io,boost::posix_time::seconds(5));
      t.async_wait(print);   //开始取票排队
      cout<<"Main fun..."<<endl;   //主线程该干嘛干嘛

      io.run();
      return 0;
  }
//先输出 "Main fun..."   过5秒输出 "Hello,world!"

 3、回调函数的参数：

  #include <iostream>
  #include <boost/asio.hpp>
  #include <boost/bind.hpp>
  #include <boost/date_time/posix_time/posix_time.hpp>

  void print(const boost::system::error_code& error,boost::asio::deadline_timer* t,int* count)
  {
      if(*count < 5)
      {
          std::cout<< *count << "\n";
          ++(*count);
          t->expires_at(t->expires_at() + boost::posix_time::seconds(1));
          t->async_wait(boost::bind(print, boost::asio::placeholders::error, t, count));
      }
  }

  int main()
  {
      boost::asio::io_service io;
      int count = 0;
      boost::asio::deadline_timer t(io, boost::posix_time::seconds(1));
      t.async_wait(boost::bind(print,boost::asio::placeholders::error,&t,&count));
      io.run();
      std::cout<<"Final count is "<<count<<"\n";
      return 0;
  }
//每隔一秒分别输出 0，1，2，3，4 最后输出 "Final count is 5"