gdcmSmartPointer.h

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/*=========================================================================
 
  Program: GDCM (Grassroots DICOM). A DICOM library
 
  Copyright (c) 2006-2011 Mathieu Malaterre
  All rights reserved.
  See Copyright.txt or http://gdcm.sourceforge.net/Copyright.html for details.
 
     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.
 
=========================================================================*/
#ifndef GDCMSMARTPOINTER_H
#define GDCMSMARTPOINTER_H
 
#include "gdcmObject.h"
 
namespace gdcm
{
template<class ObjectType>
class SmartPointer
{
public:
  SmartPointer():Pointer(nullptr) {}
  SmartPointer(const SmartPointer<ObjectType>& p):Pointer(p.Pointer)
    { Register(); }
  SmartPointer(ObjectType* p):Pointer(p)
    { Register(); }
  SmartPointer(ObjectType const & p)
    {
    Pointer = const_cast<ObjectType*>(&p);
    Register();
    }
  ~SmartPointer() {
    UnRegister();
    Pointer = nullptr;
  }
 
  ObjectType *operator -> () const
    { return Pointer; }
 
  ObjectType& operator * () const
    {
    assert( Pointer );
    return *Pointer; 
    }
 
  operator ObjectType * () const
    { return Pointer; }
 
  SmartPointer &operator = (SmartPointer const &r)
    { return operator = (r.Pointer); }
 
  SmartPointer &operator = (ObjectType *r)
    {
    // http://www.parashift.com/c++-faq-lite/freestore-mgmt.html#faq-16.22
    // DO NOT CHANGE THE ORDER OF THESE STATEMENTS!
    // (This order properly handles self-assignment)
    // (This order also properly handles recursion, e.g., if a ObjectType contains SmartPointer<ObjectType>s)
    if( Pointer != r )
      {
      ObjectType* old = Pointer;
      Pointer = r;
      Register();
      if ( old ) { old->UnRegister(); }
      }
    return *this;
    }
 
  SmartPointer &operator = (ObjectType const &r)
    {
    ObjectType* tmp = const_cast<ObjectType*>(&r);
    return operator = (tmp);
    }
 
  ObjectType *GetPointer() const
    { return Pointer; }
 
private:
  void Register()
    {
    if(Pointer) Pointer->Register();
    }
 
  void UnRegister()
    {
    if(Pointer) Pointer->UnRegister();
    }
 
  ObjectType* Pointer;
};
 
} // end namespace gdcm
 
#endif //GDCMSMARTPOINTER_H