ceph/src/boost/libs/asio/example/cpp14/deferred/deferred_4.cpp

   1 //
   2 // deferred_4.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/deferred.hpp>
  13 #include <iostream>
  14
  15 using boost::asio::experimental::deferred;
  16
  17 template <typename CompletionToken>
  18 auto async_wait_twice(boost::asio::steady_timer& timer, CompletionToken&& token)
  19 {
  20   return timer.async_wait(
  21       deferred(
  22         [&](boost::system::error_code ec)
  23         {
  24           std::cout << "first timer wait finished: " << ec.message() << "\n";
  25           timer.expires_after(std::chrono::seconds(1));
  26           return timer.async_wait(deferred);
  27         }
  28       )
  29     )(
  30       deferred(
  31         [&](boost::system::error_code ec)
  32         {
  33           std::cout << "second timer wait finished: " << ec.message() << "\n";
  34           return deferred.values(42);
  35         }
  36       )
  37     )(
  38       std::forward<CompletionToken>(token)
  39     );
  40 }
  41
  42 int main()
  43 {
  44   boost::asio::io_context ctx;
  45
  46   boost::asio::steady_timer timer(ctx);
  47   timer.expires_after(std::chrono::seconds(1));
  48
  49   async_wait_twice(
  50       timer,
  51       [](int result)
  52       {
  53         std::cout << "result is " << result << "\n";
  54       }
  55     );
  56
  57   ctx.run();
  58
  59   return 0;
  60 }