defaulthandlers.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 <atomic>
#include <coroutine>
#include <stdexcept>
 
namespace LC::Util::detail
{
    template<typename E>
    concept IsAwaiterHandler = E::IsAwaiterHandler;
 
    template<typename...>
    struct DefaultAwaiterHandler
    {
        std::atomic<std::coroutine_handle<>> Continuation_ {};
 
        struct DoubleAwaitError : std::logic_error
        {
            DoubleAwaitError ()
            : std::logic_error { "double await" }
            {
            }
        };
 
        void AddAwaiter (std::coroutine_handle<> handle)
        {
            if (this->Continuation_.exchange (handle))
                throw DoubleAwaitError {};
        }
 
        void RemoveAwaiter (std::coroutine_handle<>) noexcept
        {
            this->Continuation_.exchange ({});
        }
 
        auto GetAwaiters (this auto&& self) noexcept
        {
            return self.Continuation_.exchange ({});
        }
    };
 
    template<typename... Extensions>
        requires (IsAwaiterHandler<Extensions> || ...)
    struct DefaultAwaiterHandler<Extensions...> {};
 
 
    template<typename E>
    concept IsLockingHandler = E::IsLockingHandler;
 
    template<typename...>
    struct DefaultLockingHandler
    {
        static void lock () {}
        static void unlock () {}
    };
 
    template<typename... Extensions>
        requires (IsLockingHandler<Extensions> || ...)
    struct DefaultLockingHandler<Extensions...> {};
 
 
    template<typename E>
    concept IsResumeValueHandler = E::IsResumeValueHandler;
 
    template<typename...>
    struct DefaultResumeValueHandler
    {
        template<typename R>
        static R&& ResumeValue (R& ret) noexcept
        {
            return std::move (ret);
        }
    };
 
    template<typename... Extensions>
        requires (IsResumeValueHandler<Extensions> || ...)
    struct DefaultResumeValueHandler<Extensions...> {};
}