WeakPtr.h

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/*
 *   ORXONOX - the hottest 3D action shooter ever to exist
 *                    > www.orxonox.net <
 *
 *
 *   License notice:
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation; either version 2
 *   of the License, or (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 *   Author:
 *      Fabian 'x3n' Landau
 *   Co-authors:
 *      ...
 *
 */

// Inspired by boost::intrusive_ptr by Peter Dimov

#ifndef _WeakPtr_H__
#define _WeakPtr_H__

#include "core/CorePrereqs.h"

#include <cassert>

#include "core/object/Destroyable.h"
#include "core/command/Functor.h"

namespace orxonox
{
    template <class T>
    class WeakPtr : public DestructionListener
    {
        public:
            inline WeakPtr() : pointer_(nullptr), base_(nullptr), callback_(nullptr)
            {
            }

            inline WeakPtr(T* pointer) : pointer_(pointer), base_(pointer), callback_(nullptr)
            {
                this->registerAsDestructionListener(this->base_);
            }

            inline WeakPtr(const WeakPtr& other) : pointer_(other.pointer_), base_(other.base_), callback_(nullptr)
            {
                this->registerAsDestructionListener(this->base_);
            }

            template <class O>
            inline WeakPtr(const WeakPtr<O>& other) : pointer_(other.get()), base_(other.getBase()), callback_(nullptr)
            {
                this->registerAsDestructionListener(this->base_);
            }

            virtual inline ~WeakPtr()
            {
                this->unregisterAsDestructionListener(this->base_);
            }

            inline WeakPtr& operator=(T* pointer)
            {
                WeakPtr(pointer).swap(*this);
                return *this;
            }

            inline WeakPtr& operator=(WeakPtr other)
            {
                other.swap(*this);
                return *this;
            }

            template <class O>
            inline WeakPtr& operator=(const WeakPtr<O>& other)
            {
                WeakPtr(other).swap(*this);
                return *this;
            }

            inline T* get() const
            {
                return this->pointer_;
            }

            inline Destroyable* getBase() const
            {
                return this->base_;
            }

            inline operator T*() const
            {
                return this->pointer_;
            }

            inline T* operator->() const
            {
                assert(this->pointer_ != nullptr);
                return this->pointer_;
            }

            inline T& operator*() const
            {
                assert(this->pointer_ != nullptr);
                return *this->pointer_;
            }

            inline explicit operator bool() const
            {
                return (this->pointer_ != nullptr);
            }

            inline void swap(WeakPtr& other)
            {
                this->unregisterAsDestructionListener(this->base_);
                other.unregisterAsDestructionListener(other.base_);

                {
                    T* temp = this->pointer_;
                    this->pointer_ = other.pointer_;
                    other.pointer_ = temp;
                }
                {
                    Destroyable* temp = this->base_;
                    this->base_ = other.base_;
                    other.base_ = temp;
                }

                this->registerAsDestructionListener(this->base_);
                other.registerAsDestructionListener(other.base_);
            }

            inline void reset()
            {
                WeakPtr().swap(*this);
            }

            inline void setCallback(const FunctorPtr& callback)
            {
                this->callback_ = callback;
            }

            inline const FunctorPtr& getCallback() const
            {
                return this->callback_;
            }

        private:
            virtual inline void objectDeleted() override
            {
                this->base_ = nullptr;
                this->pointer_ = nullptr;
                if (this->callback_)
                    (*this->callback_)();
            }

            T* pointer_;            
            Destroyable* base_;    
            FunctorPtr callback_;   
    };

    template <class T>
    void swap(WeakPtr<T>& a, WeakPtr<T>& b)
    {
        a.swap(b);
    }

    template <class T, class U>
    WeakPtr<T> static_pointer_cast(const WeakPtr<U>& p)
    {
        return static_cast<T*>(p.get());
    }

    template <class T, class U>
    WeakPtr<T> const_pointer_cast(const WeakPtr<U>& p)
    {
        return const_cast<T*>(p.get());
    }

    template <class T, class U>
    WeakPtr<T> dynamic_pointer_cast(const WeakPtr<U>& p)
    {
        return orxonox_cast<T*>(p.get());
    }
}

#endif /* _WeakPtr_H__ */