finalsuspender.h

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/**********************************************************************
 * LeechCraft - modular cross-platform feature rich internet client.
 * Copyright (C) 2006-2014  Georg Rudoy
 *
 * Distributed under the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE or copy at https://www.boost.org/LICENSE_1_0.txt)
 **********************************************************************/
 
#pragma once
 
#include <coroutine>
#include <mutex>
 
namespace LC::Util::detail
{
    template<typename Promise>
    struct FinalSuspender
    {
        Promise& Promise_;
 
        bool await_ready () const noexcept { return false; }
 
        std::coroutine_handle<> await_suspend (std::coroutine_handle<>) noexcept
        {
            auto handles = [this]
            {
                std::lock_guard guard { Promise_ };
                return Promise_.GetAwaiters ();
            } ();
            Promise_.DecRef ();
 
            if constexpr (std::is_same_v<decltype (handles), std::coroutine_handle<>>)
                return handles ? handles : std::noop_coroutine ();
            else
            {
                if (handles.size () == 1)
                    return handles [0];
 
                for (const auto& h : handles)
                    h.resume ();
                return std::noop_coroutine ();
            }
        }
 
        void await_resume () const noexcept {}
    };
}