util.h

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/**********************************************************************
 * LeechCraft - modular cross-platform feature rich internet client.
 * Copyright (C) 2006-2014  Georg Rudoy
 *
 * Boost Software License - Version 1.0 - August 17th, 2003
 *
 * Permission is hereby granted, free of charge, to any person or organization
 * obtaining a copy of the software and accompanying documentation covered by
 * this license (the "Software") to use, reproduce, display, distribute,
 * execute, and transmit the Software, and to prepare derivative works of the
 * Software, and to permit third-parties to whom the Software is furnished to
 * do so, all subject to the following:
 *
 * The copyright notices in the Software and this entire statement, including
 * the above license grant, this restriction and the following disclaimer,
 * must be included in all copies of the Software, in whole or in part, and
 * all derivative works of the Software, unless such copies or derivative
 * works are solely in the form of machine-executable object code generated by
 * a source language processor.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
 * SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
 * FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 **********************************************************************/

#pragma once

#include <memory>
#include <functional>
#include <stdexcept>

namespace LeechCraft
{
namespace Util
{
    namespace detail
    {
        using DefaultScopeGuardDeleter = std::function<void ()>;

        class 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;
        };

        template<typename F>
        class ScopeGuard
        {
            F F_;
            bool Perform_ = true;
        public:
            ScopeGuard () noexcept
            : F_ {}
            , Perform_ { false }
            {
            }

            ScopeGuard (const F& f) noexcept
            : F_ { f }
            {
            }

            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>
    detail::ScopeGuard<F> MakeScopeGuard (const F& f)
    {
        return { f };
    }
}
}