/* -*-	Mode:C++; c-basic-offset:8; tab-width:8; indent-tabs-mode:t -*- */
/*
 * Copyright (c) 2006 INRIA
 * All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation;
 *
 * 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
 *
 * Author: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
 */
#ifndef REFERENCE_LIST_H
#define REFERENCE_LIST_H

/* This is a reference list implementation. The technique underlying
 * this code was first described in 1995 by Risto Lankinen on Usenet
 * but I have never been able to find his original posting. Instead,
 * this code is based on the description of the technique found in
 * "Modern C++ design" by Andrei Alexandrescu in chapter 7.
 */


namespace ns3 {

template <typename OBJ_PTR>
class ReferenceList;

template <typename OBJ_PTR>
class ReferenceList {
public:
	ReferenceList () 
		:  m_objPtr (),
		   m_prev (), 
		   m_next () 
	{
		m_prev = this;
		m_next = this;
	}
	ReferenceList (ReferenceList &o) 
		: m_objPtr (),
		  m_prev (), 
		  m_next ()
	{
		m_prev = this;
		m_next = this;
		insertSelfInOther (o);
	}
	ReferenceList (ReferenceList const&o) 
		: m_objPtr (),
		  m_prev (), 
		  m_next ()
	{
		m_prev = this;
		m_next = this;
		insertSelfInOther (o);
	}
	ReferenceList (OBJ_PTR const &objPtr)
		: m_objPtr (objPtr), 
		  m_prev (), 
		  m_next ()
	{
		m_prev = this;
		m_next = this;
	}
	~ReferenceList () {
		removeFrom_list ();
	}
	ReferenceList & operator= (ReferenceList const&o) {
		removeFrom_list ();
		insertSelfInOther (o);
		return *this;
	}
	OBJ_PTR operator-> () {
		return m_objPtr;
	}
	void set (OBJ_PTR objPtr) {
		removeFrom_list ();
		m_objPtr = objPtr;
	}
	OBJ_PTR get (void) {
		// explicit conversion to raw pointer type.
		return m_objPtr;
	}
private:
	void insertSelfInOther (ReferenceList const&o) {
		m_prev = &o;
		m_next = o.m_next;
		m_next->m_prev = this;
		o.m_next = this;
		m_objPtr = o.m_objPtr;
	}
	void removeFrom_list (void) {
		if (m_prev == this) {
			//assert (m_next == this);
			delete m_objPtr;
			m_objPtr = OBJ_PTR ();
		}
		m_prev->m_next = m_next;
		m_next->m_prev = m_prev;
	}
	OBJ_PTR m_objPtr;
	mutable ReferenceList const*m_prev;
	mutable ReferenceList const*m_next;
};

}; // namespace ns3

#endif /* REFERENCE_LIST_H */