ceph/src/boost/libs/asio/example/cpp03/invocation/prioritised_handlers.cpp

   1 //
   2 // prioritised_handlers.cpp
   3 // ~~~~~~~~~~~~~~~~~~~~~~~~
   4 //
   5 // Copyright (c) 2003-2016 Christopher M. Kohlhoff (chris at kohlhoff dot com)
   6 //
   7 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   8 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   9 //
  10
  11 #include <boost/asio.hpp>
  12 #include <boost/function.hpp>
  13 #include <iostream>
  14 #include <queue>
  15
  16 using boost::asio::ip::tcp;
  17
  18 class handler_priority_queue
  19 {
  20 public:
  21   void add(int priority, boost::function<void()> function)
  22   {
  23     handlers_.push(queued_handler(priority, function));
  24   }
  25
  26   void execute_all()
  27   {
  28     while (!handlers_.empty())
  29     {
  30       queued_handler handler = handlers_.top();
  31       handler.execute();
  32       handlers_.pop();
  33     }
  34   }
  35
  36   // A generic wrapper class for handlers to allow the invocation to be hooked.
  37   template <typename Handler>
  38   class wrapped_handler
  39   {
  40   public:
  41     wrapped_handler(handler_priority_queue& q, int p, Handler h)
  42       : queue_(q), priority_(p), handler_(h)
  43     {
  44     }
  45
  46     void operator()()
  47     {
  48       handler_();
  49     }
  50
  51     template <typename Arg1>
  52     void operator()(Arg1 arg1)
  53     {
  54       handler_(arg1);
  55     }
  56
  57     template <typename Arg1, typename Arg2>
  58     void operator()(Arg1 arg1, Arg2 arg2)
  59     {
  60       handler_(arg1, arg2);
  61     }
  62
  63   //private:
  64     handler_priority_queue& queue_;
  65     int priority_;
  66     Handler handler_;
  67   };
  68
  69   template <typename Handler>
  70   wrapped_handler<Handler> wrap(int priority, Handler handler)
  71   {
  72     return wrapped_handler<Handler>(*this, priority, handler);
  73   }
  74
  75 private:
  76   class queued_handler
  77   {
  78   public:
  79     queued_handler(int p, boost::function<void()> f)
  80       : priority_(p), function_(f)
  81     {
  82     }
  83
  84     void execute()
  85     {
  86       function_();
  87     }
  88
  89     friend bool operator<(const queued_handler& a,
  90         const queued_handler& b)
  91     {
  92       return a.priority_ < b.priority_;
  93     }
  94
  95   private:
  96     int priority_;
  97     boost::function<void()> function_;
  98   };
  99
 100   std::priority_queue<queued_handler> handlers_;
 101 };
 102
 103 // Custom invocation hook for wrapped handlers.
 104 template <typename Function, typename Handler>
 105 void asio_handler_invoke(Function f,
 106     handler_priority_queue::wrapped_handler<Handler>* h)
 107 {
 108   h->queue_.add(h->priority_, f);
 109 }
 110
 111 //----------------------------------------------------------------------
 112
 113 void high_priority_handler(const boost::system::error_code& /*ec*/)
 114 {
 115   std::cout << "High priority handler\n";
 116 }
 117
 118 void middle_priority_handler(const boost::system::error_code& /*ec*/)
 119 {
 120   std::cout << "Middle priority handler\n";
 121 }
 122
 123 void low_priority_handler()
 124 {
 125   std::cout << "Low priority handler\n";
 126 }
 127
 128 int main()
 129 {
 130   boost::asio::io_service io_service;
 131
 132   handler_priority_queue pri_queue;
 133
 134   // Post a completion handler to be run immediately.
 135   io_service.post(pri_queue.wrap(0, low_priority_handler));
 136
 137   // Start an asynchronous accept that will complete immediately.
 138   tcp::endpoint endpoint(boost::asio::ip::address_v4::loopback(), 0);
 139   tcp::acceptor acceptor(io_service, endpoint);
 140   tcp::socket server_socket(io_service);
 141   acceptor.async_accept(server_socket,
 142       pri_queue.wrap(100, high_priority_handler));
 143   tcp::socket client_socket(io_service);
 144   client_socket.connect(acceptor.local_endpoint());
 145
 146   // Set a deadline timer to expire immediately.
 147   boost::asio::deadline_timer timer(io_service);
 148   timer.expires_at(boost::posix_time::neg_infin);
 149   timer.async_wait(pri_queue.wrap(42, middle_priority_handler));
 150
 151   while (io_service.run_one())
 152   {
 153     // The custom invocation hook adds the handlers to the priority queue
 154     // rather than executing them from within the poll_one() call.
 155     while (io_service.poll_one())
 156       ;
 157
 158     pri_queue.execute_all();
 159   }
 160
 161   return 0;
 162 }