/* -*- C++ -*-

  *

  * This file is a part of LEMON, a generic C++ optimization library

  *

  * Copyright (C) 2003-2008

  * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

  * (Egervary Research Group on Combinatorial Optimization, EGRES).

  *

  * Permission to use, modify and distribute this software is granted

  * provided that this copyright notice appears in all copies. For

  * precise terms see the accompanying LICENSE file.

  *

  * This software is provided "AS IS" with no warranty of any kind,

  * express or implied, and with no claim as to its suitability for any

  * purpose.

  *

  */

 #ifndef LEMON_REFPTR_H

 #define LEMON_REFPTR_H

 ///\ingroup misc

 ///\file

 ///\brief A reference counted pointer implementation.

 ///

 ///\todo Undocumented

 namespace lemon {

   ///Reference counted pointer

   ///This is a simple implementation of a reference counted pointer.

   ///

   ///\warning Current implementation is far from being thread-safe.

   template<class T>

   class RefPtr 

   {

     mutable RefPtr *prev, *next;

     T *ref;

     void lock() {}

     void unlock() {}

     void attach(RefPtr &r) 

     {

       if(r.ref) {

 	prev=&r; next=r.next; ref=r.ref;

 	r.next=this;

       }

     }

     void attach(const T *p) 

     {

       prev=0; next=0; ref=p;

     }

     void release() 

     {

       if(ref) {

 	bool fr=true;

 	if(prev) { fr=false; prev->next=next; }

 	if(next) { fr=false; next->prev=prev; }

 	if(fr) delete ref;

 	ref=0;

       }

     }

   public:

     ///\e

     RefPtr() : ref(0) {}

     ///\e

     RefPtr(const RefPtr &r) {

       lock();

       attach(const_cast<RefPtr&>(r));

       unlock();

     }

     ///\e

     RefPtr(T *p) : prev(0), next(0), ref(p) {}

     ///\e

     ~RefPtr() {

       lock();

       release();

       unlock();

     }

     ///\e

     const RefPtr &operator=(const RefPtr &r) { 

       if(ref!=r.ref) {

 	lock();

 	release(); attach(const_cast<RefPtr&>(r));

 	unlock();

       }

       return *this;

     }

     ///\e

     const RefPtr &operator=(const T* &p) { 

       if(ref!=p) { lock(); release(); attach(p); unlock(); }

       return *this;

     }

     ///\e

     void swap(RefPtr &r) {

       RefPtr *p;

       T *tp;

       lock();

       p=prev; prev=r.prev; r.prev=p;

       p=next; next=r.next; r.next=p;

       tp=ref; ref=r.ref; r.ref=tp;

       unlock();

     }

     ///\e

     void clear() { lock(); release(); unlock(); }

     ///\e

     T * operator->() { return ref; }

     ///\e

     const T * operator->() const { return ref; }

     ///\e

     operator T *() { return ref; }

     ///\e

     operator const T *() const { return ref; }

     ///\e

     bool operator<(const RefPtr &r) const { return this->ref < r.ref; }

     ///\e

     bool operator<=(const RefPtr &r) const { return this->ref <= r.ref; }

     ///\e

     bool operator==(const RefPtr &r) const { return this->ref == r.ref; }

     ///\e

     bool operator>=(const RefPtr &r) const { return this->ref >= r.ref; }

     ///\e

     bool operator>(const RefPtr &r) const { return this->ref > r.ref; }

     ///\e

     bool operator!=(const RefPtr &r) const { return this->ref != r.ref; }

     ///\e

     operator bool() const { return ref; }

     ///\e

     const RefPtr &borrow(const T* &p) { 

       lock();

       if(ref==p) {

 	if(prev) prev->next=next;

 	if(next) next->prev=prev;

       }

       else release();

       ref=p;

       next=prev=this;

       unlock();

       return *this;

     }

     ///\e

     const RefPtr &borrow() { 

       lock();

       if(prev) prev->next=next;

       if(next) next->prev=prev;

       next=prev=this;

       unlock();

       return *this;

     }

   };  //END OF CLASS REFPTR

 } //END OF NAMESPACE LEMON

 #endif