getresult.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 <type_traits>
#include <QEventLoop>
#include "task.h"
 
namespace LC::Util
{
    template<typename T, template<typename> typename... Extensions>
    T GetTaskResult (Task<T, Extensions...> task)
    {
        constexpr bool isVoid = std::is_same_v<T, void>;
        std::conditional_t<isVoid, void*, std::optional<T>> result;
 
        std::exception_ptr exception;
 
        QEventLoop loop;
        bool done = false;
        [] (auto task, auto& result, auto& exception, auto& done, auto& loop) -> Task<void>
        {
            try
            {
                if constexpr (isVoid)
                    co_await task;
                else
                    result.emplace (co_await task);
            }
            catch (...)
            {
                exception = std::current_exception ();
            }
            done = true;
            loop.quit ();
        } (task, result, exception, done, loop);
        if (!done)
            loop.exec ();
 
        if (exception)
            std::rethrow_exception (exception);
 
        if constexpr (!isVoid)
            return std::move (*result);
    }
}