| 1 | // |
|---|---|
| 2 | // deferred_7.cpp |
| 3 | // ~~~~~~~~~~~~~~ |
| 4 | // |
| 5 | // Copyright (c) 2003-2024 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 <iostream> |
| 13 | |
| 14 | using boost::asio::append; |
| 15 | using boost::asio::deferred; |
| 16 | |
| 17 | template <typename CompletionToken> |
| 18 | auto async_wait_twice(boost::asio::steady_timer& timer, CompletionToken&& token) |
| 19 | { |
| 20 | return deferred.values(args: &timer) |
| 21 | | deferred( |
| 22 | [](boost::asio::steady_timer* timer) |
| 23 | { |
| 24 | timer->expires_after(expiry_time: std::chrono::seconds(1)); |
| 25 | return timer->async_wait(token: append(completion_token: deferred, values&: timer)); |
| 26 | } |
| 27 | ) |
| 28 | | deferred( |
| 29 | [](boost::system::error_code ec, boost::asio::steady_timer* timer) |
| 30 | { |
| 31 | std::cout << "first timer wait finished: "<< ec.message() << "\n"; |
| 32 | timer->expires_after(expiry_time: std::chrono::seconds(1)); |
| 33 | return deferred.when(b: !ec) |
| 34 | .then(on_true: timer->async_wait(token: deferred)) |
| 35 | .otherwise(on_false: deferred.values(args&: ec)); |
| 36 | } |
| 37 | ) |
| 38 | | deferred( |
| 39 | [](boost::system::error_code ec) |
| 40 | { |
| 41 | std::cout << "second timer wait finished: "<< ec.message() << "\n"; |
| 42 | return deferred.when(b: !ec) |
| 43 | .then(on_true: deferred.values(args: 42)) |
| 44 | .otherwise(on_false: deferred.values(args: 0)); |
| 45 | } |
| 46 | ) |
| 47 | | std::forward<CompletionToken>(token); |
| 48 | } |
| 49 | |
| 50 | int main() |
| 51 | { |
| 52 | boost::asio::io_context ctx; |
| 53 | |
| 54 | boost::asio::steady_timer timer(ctx); |
| 55 | timer.expires_after(expiry_time: std::chrono::seconds(1)); |
| 56 | |
| 57 | async_wait_twice( |
| 58 | timer, |
| 59 | token: [](int result) |
| 60 | { |
| 61 | std::cout << "result is "<< result << "\n"; |
| 62 | } |
| 63 | ); |
| 64 | |
| 65 | // Uncomment the following line to trigger an error in async_wait_twice. |
| 66 | //timer.cancel(); |
| 67 | |
| 68 | ctx.run(); |
| 69 | |
| 70 | return 0; |
| 71 | } |
| 72 |