TrinityCore/src/server/shared/Dynamic/CountedReference/Reference.h

/*
 * Copyright (C) 2005-2009 MaNGOS <http://getmangos.com/>
 *
 * Copyright (C) 2008-2010 Trinity <http://www.trinitycore.org/>
 *
 * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#ifndef  TRINITY_REFERENCE_H
#define  TRINITY_REFERENCE_H

/**
 * Referencer<T>
 * Referencer is an object that holds a reference holder that  hold a reference
 * counted object.  When an object's reference count drop to zero, it removes
 * the object.  This is a non intrusive mechanism and any object at any point
 * in time can be referenced.  When and object is reference counted, do not
 * pass the object directly to other methods but rather, pass its
 * reference around.  Objects can be reference counted in both single threaded
 * model and multi-threaded model
 */

#include <stdexcept>
#include "Platform/Define.h"
#include "Policies/ThreadingModel.h"
#include "ReferenceHolder.h"

template
<
typename T,
class THREADING_MODEL = Trinity::SingleThreaded<T>
>
class Referencer
{
    typedef typename THREADING_MODEL::Lock Lock;
    typedef ReferenceHolder<T, THREADING_MODEL> ReferenceeHolder;
    public:

        /// Constructs a referencer.
        Referencer(T *ref = NULL);

        /// Copy constructor
        Referencer(const Referencer &obj) : i_holder(NULL) { *this = obj; }

        /// Destructor
        ~Referencer();

        /// Referencee accessor
        T* referencee(void) { return (i_holder == NULL ? NULL : i_holder->i_referencee); }
        const T* referencee(void) const { return (i_holder == NULL ? NULL : i_holder->i_referencee); }

        //T& referencee(void){ return _referencee(); }
        //const T& referencee(void) const { return const_cast<Referencer *>(this)->_referencee(); }
        operator T&(void) { return _referencee(); }
        operator const T&(void) const { return *const_cast<Referencer *>(this)->_referencee(); }

        /// cast operators
        T* operator*() { return (i_holder == NULL ? NULL : i_holder->i_referencee); }
        T const * operator*() const { return (i_holder == NULL ? NULL : i_holder->i_referencee); }

        /// overload operators
        T* operator->() { return (i_holder == NULL ? NULL : i_holder->i_referencee); }
        const T * operator->() const { return (i_holder == NULL ? NULL : i_holder->i_referencee); }

        /// operator =
        Referencer& operator=(const Referencer &obj);
        Referencer& operator=(T *);

        /// returns true if i_referencee is null
        bool isNull(void) const { return i_holder == NULL; }

    private:

        T& _referencee(void)
        {
            if( i_holder == NULL )
                throw std::runtime_error("Invalid access to null pointer");
            return *i_holder->i_referencee;
        }

        void deReference(ReferenceeHolder *);
        void addReference(ReferenceeHolder *);

        // private data
        ReferenceeHolder *i_holder;
};
#endif