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/*=========================================================================
*
* Copyright Insight Software Consortium
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0.txt
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*=========================================================================*/
#ifndef itkSmartPointerForwardReference_h
#define itkSmartPointerForwardReference_h
#include "itkWeakPointer.h"
#include <iostream>
namespace itk
{
/** \class SmartPointerForwardReference
* \brief Implements transparent reference counting in situations where forward
* references / cyclic include dependencies are a problem.
*
* SmartPointerForwardReference implements reference counting by overloading
* operator -> (and *) among others. This allows natural interface
* to the class referred to by the pointer without having to invoke
* special Register()/UnRegister() methods directly.
*
* This class is nearly identical to itkSmartPointer except that is used in
* situations where forward references or cyclic include dependencies become
* a problem. This class requires that the .h file is included in the .h file
* of the class using it, and the .hxx file is included in the .cxx/.hxx file
* of the class using it. (Make sure that SmartPointerForwardReference.hxx is
* included last in the .cxx/.hxx list of includes.)
*
* \ingroup ITKSystemObjects
* \ingroup DataAccess
* \ingroup ITKCommon
*/
template< typename T >
class ITK_TEMPLATE_EXPORT SmartPointerForwardReference
{
public:
/** Constructor */
SmartPointerForwardReference ()
{ m_Pointer = ITK_NULLPTR; }
/** Const constructor */
SmartPointerForwardReference (const SmartPointerForwardReference< T > & p);
/** Construct from a WeakPointer */
SmartPointerForwardReference (const WeakPointer< T > & p);
/** Constructor to pointer p */
SmartPointerForwardReference (T *p);
/** Destructor */
~SmartPointerForwardReference ();
/** Overload operator -> */
T * operator->() const;
/** Return pointer to object. */
operator T *() const;
/** Access function to pointer. */
T * GetPointer() const;
/** Comparison of pointers. Less than comparison. */
bool operator<(const SmartPointerForwardReference & r);
/** Comparison of pointers. Greater than comparison. */
bool operator>(const SmartPointerForwardReference & r);
/** Comparison of pointers. Less than or equal to comparison. */
bool operator<=(const SmartPointerForwardReference & r);
/** Comparison of pointers. Greater than or equal to comparison. */
bool operator>=(const SmartPointerForwardReference & r);
/** Overload operator assignment. */
SmartPointerForwardReference & operator=(const SmartPointerForwardReference & r);
/** Overload operator assignment. */
SmartPointerForwardReference & operator=(const WeakPointer< T > & r);
/** Overload operator assignment. */
SmartPointerForwardReference & operator=(T *r);
/** Function to print object pointed to */
T * Print(std::ostream & os) const;
private:
/** The pointer to the object referred to by this smart pointer. */
T *m_Pointer;
void Register();
void UnRegister() ITK_NOEXCEPT;
};
template< typename T >
std::ostream & operator<<(std::ostream & os, SmartPointerForwardReference< T > p)
{
p.Print(os);
return os;
}
} // end namespace itk
#endif
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