future.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 <QFuture>
#include <QFutureWatcher>
#include "taskfwd.h"
 
namespace LC::Util::detail
{
    template<typename R>
    struct FutureAwaiter
    {
        QFutureWatcher<R> Watcher_;
 
        FutureAwaiter (const QFuture<R>& future)
        {
            Watcher_.setFuture (future);
        }
 
        bool await_ready () const noexcept
        {
            return Watcher_.future ().isFinished ();
        }
 
        void await_suspend (std::coroutine_handle<> handle) noexcept
        {
            QObject::connect (&Watcher_,
                    &QFutureWatcher<R>::finished,
                    handle);
        }
 
        R await_resume () const noexcept
        {
            if constexpr (!std::is_same_v<R, void>)
                return Watcher_.future ().result ();
        }
    };
}
 
namespace LC::Util
{
    template<typename R>
    detail::FutureAwaiter<R> GetAwaiter (QFuture<R> future, AwaiterCPO)
    {
        return { future };
    }
}
 
namespace LC
{
    template<typename R>
    auto operator co_await (QFuture<R> future)
    {
        return Util::GetAwaiter (std::move (future), {});
    }
}