trackingpointer.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 <functional>
#include <stdexcept>
#include <QObject>
#include <QPointer>
#include "sllconfig.h"
 
namespace LC::Util
{
    struct UTIL_SLL_API BadTrackingPointerAccess : std::runtime_error
    {
        BadTrackingPointerAccess ();
    };
 
    [[noreturn, gnu::cold]]
    UTIL_SLL_API void ReportBadAccess ();
 
    template<typename T, auto QObjectGetter = &T::GetQObject>
    class TrackingPointer
    {
        T *Ptr_ = nullptr;
        QPointer<const QObject> Guard_;
    public:
        TrackingPointer () = default;
 
        explicit (false) TrackingPointer (T *ptr)
        : Ptr_ { ptr }
        , Guard_ { ptr ? std::invoke (QObjectGetter, ptr) : nullptr }
        {
        }
 
        TrackingPointer (const TrackingPointer&) = default;
        TrackingPointer (TrackingPointer&&) = default;
        TrackingPointer& operator= (const TrackingPointer&) = default;
        TrackingPointer& operator= (TrackingPointer&&) = default;
        ~TrackingPointer () = default;
 
        bool operator== (const TrackingPointer& other) const
        {
            return Ptr_ == other.Ptr_;
        }
 
        explicit operator bool () const
        {
            return Guard_;
        }
 
        T* UnsafeGet () const
        {
            return Ptr_;
        }
 
        T* operator-> () const
        {
            if (!Guard_)
                ReportBadAccess ();
            return Ptr_;
        }
 
        T& operator* () const
        {
            if (!Guard_)
                ReportBadAccess ();
            return *Ptr_;
        }
    };
}