itkAutoPointer.h

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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 itkAutoPointer_h
#define itkAutoPointer_h

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

namespace itk
{
template< typename TObjectType >
class AutoPointer
{
public:
  using ObjectType = TObjectType;
  using Self = AutoPointer;

  AutoPointer ():m_Pointer(nullptr)
  {}

  explicit AutoPointer (AutoPointer & p)
  {
    m_IsOwner = p.IsOwner();          // Ownership can only be taken from
                                      // another owner
    m_Pointer = p.ReleaseOwnership(); // release ownership if appropriate
  }

  explicit AutoPointer (ObjectType *p, bool takeOwnership):
    m_Pointer(p), m_IsOwner(takeOwnership)
  {}

  ~AutoPointer ()
  {
    this->Reset();
  }

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

  void Reset()
  {
    if ( m_IsOwner )
      {
      delete m_Pointer;
      }
    m_Pointer = nullptr;
    m_IsOwner = false;
  }

  void TakeOwnership()
  { m_IsOwner = true; }

  void TakeOwnership(ObjectType *objectptr)
  {
    if ( m_IsOwner )
      {
      delete m_Pointer; // remove the current one
      }
    m_Pointer = objectptr;
    m_IsOwner = true;
  }

  void TakeNoOwnership(ObjectType *objectptr)
  {
    if ( m_IsOwner )
      {
      delete m_Pointer; // remove the current one
      }
    m_Pointer = objectptr;
    m_IsOwner = false;
  }

  bool IsOwner() const
  { return m_IsOwner; }

  ObjectType * ReleaseOwnership()
  {
    m_IsOwner = false;
    return m_Pointer;
  }

  ObjectType * GetPointer() const
  { return m_Pointer; }

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

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

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

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

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

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

  AutoPointer & operator=(AutoPointer & r)
  {
    AutoPointer(r).Swap(*this);
    return *this;
  }

  operator bool() const
                { return ( m_Pointer != nullptr ); }

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

private:

  void Swap(AutoPointer & r)
  noexcept
  {
    ObjectType *temp = m_Pointer;

    m_Pointer         = r.m_Pointer;
    r.m_Pointer       = temp;
  }

  ObjectType *m_Pointer;
  bool        m_IsOwner{false};
};

template< typename T >
std::ostream & operator<<(std::ostream & os, AutoPointer< T > p)
{
  p.Print(os);
  os << "Owner: " << p.IsOwner() << std::endl;
  return os;
}

template< typename TAutoPointerBase, typename TAutoPointerDerived >
void
 TransferAutoPointer(TAutoPointerBase & pa, TAutoPointerDerived & pb)
{
  // give a chance to natural polymorphism
  pa.TakeNoOwnership( pb.GetPointer() );
  if ( pb.IsOwner() )
    {
    pa.TakeOwnership();      // pa Take Ownership
    pb.ReleaseOwnership();   // pb Release Ownership and clears
    }
}
} // end namespace itk

#endif