ceph/src/boost/libs/asio/example/cpp14/deferred/deferred_6.cpp

   1 //
   2 // deferred_6.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     )(
  31       deferred(
  32         [](boost::system::error_code ec, boost::asio::steady_timer* timer)
  33         {
  34           std::cout << "first timer wait finished: " << ec.message() << "\n";
  35           timer->expires_after(std::chrono::seconds(1));
  36           return deferred.when(!ec)
  37             .then(timer->async_wait(deferred))
  38             .otherwise(deferred.values(ec));
  39         }
  40       )
  41     )(
  42       deferred(
  43         [](boost::system::error_code ec)
  44         {
  45           std::cout << "second timer wait finished: " << ec.message() << "\n";
  46           return deferred.when(!ec)
  47             .then(deferred.values(42))
  48             .otherwise(deferred.values(0));
  49         }
  50       )
  51     )(
  52       std::forward<CompletionToken>(token)
  53     );
  54 }
  55
  56 int main()
  57 {
  58   boost::asio::io_context ctx;
  59
  60   boost::asio::steady_timer timer(ctx);
  61   timer.expires_after(std::chrono::seconds(1));
  62
  63   async_wait_twice(
  64       timer,
  65       [](int result)
  66       {
  67         std::cout << "result is " << result << "\n";
  68       }
  69     );
  70
  71   // Uncomment the following line to trigger an error in async_wait_twice.
  72   //timer.cancel();
  73
  74   ctx.run();
  75
  76   return 0;
  77 }