itkWeakPointer.h

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/*=========================================================================

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: itkWeakPointer.h,v $
  Language:  C++
  Date:      $Date: 2006-05-10 20:27:16 $
  Version:   $Revision: 1.10 $

  Copyright (c) Insight Software Consortium. All rights reserved.
  See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm 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 notices for more information.

=========================================================================*/
#ifndef __itkWeakPointer_h
#define __itkWeakPointer_h

#include "itkMacro.h"
#include <iostream>

namespace itk
{

template <class TObjectType>
class ITK_EXPORT WeakPointer
{
public:
  typedef TObjectType ObjectType;

  WeakPointer ()
    { m_Pointer = 0; }

  WeakPointer (const WeakPointer<ObjectType> &p): m_Pointer(p.m_Pointer) {}

  WeakPointer (ObjectType *p): m_Pointer(p) { }

  ~WeakPointer ()
    { m_Pointer = 0; }

  ObjectType *operator -> () const
    { return m_Pointer; }

  operator ObjectType * () const
    { return m_Pointer; }

  template <typename R>
  bool operator == (R r) const
    {
    return (m_Pointer == (ObjectType*)r);
    }
  template <typename R>
  bool operator != (R r) const
    {
    return (m_Pointer != (ObjectType*)r);
    }

  ObjectType *GetPointer () const
    { return m_Pointer; }

  bool operator < (const WeakPointer &r) const
    { return (void*)m_Pointer < (void*) r.m_Pointer; }

  bool operator > (const WeakPointer &r) const
    { return (void*)m_Pointer > (void*) r.m_Pointer; }

  bool operator <= (const WeakPointer &r) const
    { return (void*)m_Pointer <= (void*) r.m_Pointer; }

  bool operator >= (const WeakPointer &r) const
    { return (void*)m_Pointer >= (void*) r.m_Pointer; }

  WeakPointer &operator = (const WeakPointer &r)
    { return this->operator = (r.GetPointer()); }

  WeakPointer &operator = (ObjectType *r)
    {
    m_Pointer = r;
    return *this;
    }

  ObjectType *Print (std::ostream& os) const
    {
    // This prints the object pointed to by the pointer
    (*m_Pointer).Print(os);
    return m_Pointer;
    }

private:
  ObjectType* m_Pointer;
};


template <typename T>
std::ostream& operator<< (std::ostream& os, WeakPointer<T> p)
{
  p.Print(os);
  return os;
}

} // end namespace itk

#endif