util.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 <memory>
#include <functional>
#include <stdexcept>
 
namespace LC
{
namespace Util
{
    class [[nodiscard]] SharedScopeGuard
    {
        std::shared_ptr<void> Guard_;
        public:
        template<typename F>
        SharedScopeGuard (const F& f)
        : Guard_ { nullptr, [f] (void*) { f (); } }
        {
        }
 
        SharedScopeGuard () = delete;
 
        SharedScopeGuard (const SharedScopeGuard&) = default;
        SharedScopeGuard (SharedScopeGuard&&) = default;
 
        SharedScopeGuard& operator= (const SharedScopeGuard&) = default;
        SharedScopeGuard& operator= (SharedScopeGuard&&) = default;
    };
 
    namespace detail
    {
        using DefaultScopeGuardDeleter = std::function<void ()>;
 
        template<typename F>
        class [[nodiscard]] ScopeGuard
        {
            F F_;
            bool Perform_ = true;
        public:
            ScopeGuard () noexcept
            : F_ {}
            , Perform_ { false }
            {
            }
 
            ScopeGuard (const F& f) noexcept
            : F_ { f }
            {
            }
 
            template<typename F1, typename F2>
                requires std::is_same_v<F, DefaultScopeGuardDeleter>
            explicit ScopeGuard (ScopeGuard<F1>&& g1, ScopeGuard<F2>&& g2)
            : F_
            {
                [f1 = std::move (g1.F_), p1 = g1.Perform_, f2 = std::move (g2.F_), p2 = g2.Perform_]
                {
                    if (p1)
                        f1 ();
                    if (p2)
                        f2 ();
                }
            }
            , Perform_ { g1.Perform_ || g2.Perform_ }
            {
                g1.Perform_ = false;
                g2.Perform_ = false;
            }
 
            ScopeGuard (const ScopeGuard&) = delete;
            ScopeGuard& operator= (const ScopeGuard&) = delete;
 
            ScopeGuard& operator= (ScopeGuard&& other)
            {
                if (Perform_)
                    F_ ();
 
                F_ = other.F_;
                Perform_ = other.Perform_;
                other.Perform_ = false;
                return *this;
            }
 
            ScopeGuard (ScopeGuard&& other) noexcept
            : F_ { other.F_ }
            , Perform_ { other.Perform_ }
            {
                other.Perform_ = false;
            }
 
            ~ScopeGuard ()
            {
                if (Perform_)
                    F_ ();
            }
 
            void Dismiss () noexcept
            {
                Perform_ = false;
            }
 
            ScopeGuard<DefaultScopeGuardDeleter> EraseType ()
            {
                Dismiss ();
                return ScopeGuard<DefaultScopeGuardDeleter> { F_ };
            }
 
            operator ScopeGuard<DefaultScopeGuardDeleter> ()
            {
                return EraseType ();
            }
 
            SharedScopeGuard Shared () &&
            {
                if (!Perform_)
                    throw std::logic_error { "this scope guard has already been converted to a shared one" };
 
                Perform_ = false;
                return { F_ };
            }
        };
    }
 
    using DefaultScopeGuard = detail::ScopeGuard<detail::DefaultScopeGuardDeleter>;

    template<typename F>
    [[nodiscard]] detail::ScopeGuard<F> MakeScopeGuard (const F& f)
    {
        return { f };
    }
}
}