ceph/src/boost/libs/asio/example/cpp14/deferred/deferred_7.cpp

   1 //
   2 // deferred_7.cpp
   3 // ~~~~~~~~~~~~~~
   4 //
   5 // Copyright (c) 2003-2022 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/asio/experimental/append.hpp>
  13 #include <boost/asio/experimental/deferred.hpp>
  14 #include <iostream>
  15
  16 using boost::asio::experimental::append;
  17 using boost::asio::experimental::deferred;
  18
  19 template <typename CompletionToken>
  20 auto async_wait_twice(boost::asio::steady_timer& timer, CompletionToken&& token)
  21 {
  22   return deferred.values(&timer)
  23     | deferred(
  24         [](boost::asio::steady_timer* timer)
  25         {
  26           timer->expires_after(std::chrono::seconds(1));
  27           return timer->async_wait(append(deferred, timer));
  28         }
  29       )
  30     | deferred(
  31         [](boost::system::error_code ec, boost::asio::steady_timer* timer)
  32         {
  33           std::cout << "first timer wait finished: " << ec.message() << "\n";
  34           timer->expires_after(std::chrono::seconds(1));
  35           return deferred.when(!ec)
  36             .then(timer->async_wait(deferred))
  37             .otherwise(deferred.values(ec));
  38         }
  39       )
  40     | deferred(
  41         [](boost::system::error_code ec)
  42         {
  43           std::cout << "second timer wait finished: " << ec.message() << "\n";
  44           return deferred.when(!ec)
  45             .then(deferred.values(42))
  46             .otherwise(deferred.values(0));
  47         }
  48       )
  49     | std::forward<CompletionToken>(token);
  50 }
  51
  52 int main()
  53 {
  54   boost::asio::io_context ctx;
  55
  56   boost::asio::steady_timer timer(ctx);
  57   timer.expires_after(std::chrono::seconds(1));
  58
  59   async_wait_twice(
  60       timer,
  61       [](int result)
  62       {
  63         std::cout << "result is " << result << "\n";
  64       }
  65     );
  66
  67   // Uncomment the following line to trigger an error in async_wait_twice.
  68   //timer.cancel();
  69
  70   ctx.run();
  71
  72   return 0;
  73 }