text: /*
   * Copyright 2020-2021 CM4all GmbH
   * All rights reserved.
   *
   * author: Max Kellermann <mk@cm4all.com>
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * - Redistributions of source code must retain the above copyright
   * notice, this list of conditions and the following disclaimer.
   *
   * - Redistributions in binary form must reproduce the above copyright
   * notice, this list of conditions and the following disclaimer in the
   * documentation and/or other materials provided with the
   * distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
   * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
   * OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #pragma once
  
  #include "Compat.hxx"
  #include "event/FineTimerEvent.hxx"
  
  namespace Co {
  
  /**
   * Put a coroutine to sleep by suspending it on `co_await` and
   * resuming it as soon as the #FineTimerEvent fires.
   */
  class Sleep final {
  	FineTimerEvent event;
  
  	std::coroutine_handle<> continuation;
  
  public:
  	Sleep(EventLoop &event_loop, Event::Duration d) noexcept
  		:event(event_loop, BIND_THIS_METHOD(OnTimer))
  	{
  		event.Schedule(d);
  	}
  
  	auto operator co_await() noexcept {
  		struct Awaitable final {
  			Sleep &sleep;
  
  			bool await_ready() const noexcept {
  				return !sleep.event.IsPending();
  			}
  
  			std::coroutine_handle<> await_suspend(std::coroutine_handle<> _continuation) noexcept {
  				sleep.continuation = _continuation;
  				return std::noop_coroutine();
  			}
  
  			void await_resume() noexcept {
  			}
  		};
  
  		return Awaitable{*this};
  	}
  
  private:
  	void OnTimer() noexcept {
  		continuation.resume();
  	}
  };
  
  } // namespace Co
  
  