boost::asio学习 - multithreaded programs

今天在测试boost::asio Tutorial中的 Timer.5 - Synchronising handlers in multithreaded programs 程序时，发现数据处理始终是在主线程中执行的，为了验证“If you find yourself running into these limitations, an alternative approach is to have a pool of threads calling io_service::run()”遂对timer.cpp进行了一些修改：

1.取消使用boost::asio::strand::wrap()来封装回调函数；

2.在printer::print1()中强制线程sleep(1)来检测多线程的并发处理；

 

完整代码如下：

timer.cpp

   
     

    
      
    
       1 
    
      #include 
    
      <
    
      iostream
    
      >
    
      

    
       2 
    
      #include 
    
      <
    
      boost
    
      /
    
      asio.hpp
    
      >
    
      

    
       3 
    
      #include 
    
      <
    
      boost
    
      /
    
      thread.hpp
    
      >
    
      

    
       4 
    
      #include 
    
      <
    
      boost
    
      /
    
      bind.hpp
    
      >
    
      

    
       5 
    
      #include 
    
      <
    
      boost
    
      /
    
      date_time
    
      /
    
      posix_time
    
      /
    
      posix_time.hpp
    
      >
    
      

    
       6 
    
      

    
       7 
    
       
    
      class
    
       printer

    
       8 
    
      {

    
       9 
    
       
    
      public
    
      :

    
      10 
    
       printer(boost::asio::io_service
    
      &
    
       io)

    
      11 
    
       : strand_(io),

    
      12 
    
       timer1_(io, boost::posix_time::seconds(
    
      1
    
      )),

    
      13 
    
       timer2_(io, boost::posix_time::seconds(
    
      1
    
      )),

    
      14 
    
       count_(
    
      0
    
      )

    
      15 
    
       {

    
      16 
    
       timer1_.async_wait(boost::bind(
    
      &
    
      printer::print1, 
    
      this
    
      ));

    
      17 
    
       timer2_.async_wait(boost::bind(
    
      &
    
      printer::print2, 
    
      this
    
      ));

    
      18 
    
       }

    
      19 
    
      

    
      20 
    
       
    
      ~
    
      printer()

    
      21 
    
       {

    
      22 
    
       std::cout 
    
      <<
    
       
    
      "
    
      Final count is 
    
      "
    
       
    
      <<
    
       count_ 
    
      <<
    
       
    
      "
    
      \n
    
      "
    
      ;

    
      23 
    
       }

    
      24 
    
      

    
      25 
    
       
    
      void
    
       print1()

    
      26 
    
       {

    
      27 
    
       std::cout 
    
      <<
    
       boost::this_thread::get_id() 
    
      <<
    
       
    
      "
    
      \n
    
      "
    
      ;

    
      28 
    
      

    
      29 
    
       
    
      if
    
       (count_ 
    
      <
    
       
    
      10
    
      )

    
      30 
    
       {

    
      31 
    
       std::cout 
    
      <<
    
       
    
      "
    
      Timer 1: 
    
      "
    
       
    
      <<
    
       count_ 
    
      <<
    
       
    
      "
    
      \n
    
      "
    
      ;

    
      32 
    
       
    
      ++
    
      count_;

    
      33 
    
      

    
      34 
    
       timer1_.expires_at(timer1_.expires_at() 
    
      +
    
       boost::posix_time::seconds(
    
      1
    
      ));

    
      35 
    
       timer1_.async_wait(boost::bind(
    
      &
    
      printer::print1, 
    
      this
    
      ));

    
      36 
    
       }

    
      37 
    
       sleep(
    
      1
    
      );

    
      38 
    
       }

    
      39 
    
      

    
      40 
    
       
    
      void
    
       print2()

    
      41 
    
       {

    
      42 
    
       std::cout 
    
      <<
    
       boost::this_thread::get_id() 
    
      <<
    
       
    
      "
    
      \n
    
      "
    
      ;

    
      43 
    
      

    
      44 
    
       
    
      if
    
       (count_ 
    
      <
    
       
    
      10
    
      )

    
      45 
    
       {

    
      46 
    
       std::cout 
    
      <<
    
       
    
      "
    
      Timer 2: 
    
      "
    
       
    
      <<
    
       count_ 
    
      <<
    
       
    
      "
    
      \n
    
      "
    
      ;

    
      47 
    
       
    
      ++
    
      count_;

    
      48 
    
      

    
      49 
    
       timer2_.expires_at(timer2_.expires_at() 
    
      +
    
       boost::posix_time::seconds(
    
      1
    
      ));

    
      50 
    
       timer2_.async_wait(boost::bind(
    
      &
    
      printer::print2, 
    
      this
    
      ));

    
      51 
    
       }

    
      52 
    
       }

    
      53 
    
      

    
      54 
    
       
    
      private
    
      :

    
      55 
    
       boost::asio::strand strand_;

    
      56 
    
       boost::asio::deadline_timer timer1_;

    
      57 
    
       boost::asio::deadline_timer timer2_;

    
      58 
    
       
    
      int
    
       count_;

    
      59 
    
      };

    
      60 
    
      

    
      61 
    
       
    
      int
    
       main()

    
      62 
    
      {

    
      63 
    
       std::cout 
    
      <<
    
       boost::this_thread::get_id() 
    
      <<
    
       
    
      "
    
      \n
    
      "
    
      ;

    
      64 
    
      

    
      65 
    
       boost::asio::io_service io;

    
      66 
    
       printer p(io);

    
      67 
    
       boost::thread t(boost::bind(
    
      &
    
      boost::asio::io_service::run, 
    
      &
    
      io));

    
      68 
    
       io.run();

    
      69 
    
       t.join();

    
      70 
    
      

    
      71 
    
       
    
      return
    
       
    
      0
    
      ;

    
      72 
    
      }
   
     

 

程序运行输出：

0x850e050
0x850e050
Timer 1: 0
0x850e810
Timer 2: 1
0x850e810
Timer 1: 2
0x850e050
Timer 2: 3
0x850e050
Timer 1: 4
0x850e810
Timer 2: 5
0x850e810
Timer 1: 6
0x850e050
Timer 2: 7
0x850e050
Timer 1: 8
0x850e810
Timer 2: 9
0x850e810
0x850e050

 

从输出结果可以看出：当多个线程运行同一个io_service::run()时，它们将并发执行该io_service上的待处理的handlers！