// @(#)root/cont:$Id$
// Author: Rene Brun   28/09/2001

/*************************************************************************
 * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/

#ifndef ROOT_TRef
#define ROOT_TRef


//////////////////////////////////////////////////////////////////////////
//                                                                      //
// TRef                                                                 //
//                                                                      //
// Persistent Reference link to a TObject                               //
//                                                                      //
//////////////////////////////////////////////////////////////////////////


#ifndef ROOT_TObject
#include "TObject.h"
#endif

class TProcessID;
class TFile;
class TExec;
class TObjArray;

class TRef : public TObject {

protected:
   TProcessID       *fPID;     //!Pointer to ProcessID when TRef was written

   static TObjArray  *fgExecs;  //List of execs
   static TObject    *fgObject; //In: this, Out: pointer to object (used by Action on Demand)

public:
   //status bits
   enum { kNotComputed = BIT(12)};

   TRef(): fPID(0) { }
   TRef(TObject *obj);
   TRef(const TRef &ref);
   void  operator=(TObject *obj);
   TRef& operator=(const TRef &ref);
   virtual ~TRef() { }

   TObject           *GetObject() const;
   TProcessID        *GetPID() const {return fPID;}
   Bool_t             IsValid() const {return GetUniqueID()!=0 ? kTRUE : kFALSE;}
   virtual void       SetAction(const char *name);
   virtual void       SetAction(TObject *parent);

   static void        SetObject(TObject *obj);
   static void        SetStaticObject(TObject *obj);
   static Int_t       AddExec(const char *name);
   static TObjArray  *GetListOfExecs();
   static TObject    *GetStaticObject();

   friend Bool_t operator==(const TRef &r1, const TRef &r2);
   friend Bool_t operator!=(const TRef &r1, const TRef &r2);

   ClassDef(TRef,1)  //Persistent Reference link to a TObject
};

#endif