text: /*=========================================================================
   *
   *  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 itkCompositeTransformIOHelper_h
  #define itkCompositeTransformIOHelper_h
  
  #include "itkTransformIOBase.h"
  #include "itkCompositeTransform.h"
  
  namespace itk
  {
  
  /** \class CompositeTransformIOHelperTemplate
   *  \brief An adapter that adapts CompositeTransform into the
   *  TransformReader/Writer
   *
   *  The stumbling block with fitting CompositeTransforms into
   *  the Transform hierarchy is that it encapsulates a list of
   *  itk::Transform, templated to match the dimension and scalar
   *  type of the CompositeTransform itself.  But the Transform
   *  Reader/Writer uses instances of the superclass itk::TransformBase
   *  which is not templated.
   *
   *  This class handles this by hiding the conversion between a list
   *  of TransformBase and the queue of Transform.  It handles the
   *  conversion in a cascade of template function invocations to
   *  match up the transform list with the particular instantiation
   *  of CompositeTransform.
   * \ingroup ITKIOTransformBase
   */
  template <typename TScalar>
  class CompositeTransformIOHelperTemplate
  {
  public:
    typedef typename TransformIOBaseTemplate<TScalar>::TransformType          TransformType;
    typedef typename TransformIOBaseTemplate<TScalar>::TransformPointer       TransformPointer;
    typedef typename TransformIOBaseTemplate<TScalar>::TransformListType      TransformListType;
    typedef typename TransformIOBaseTemplate<TScalar>::ConstTransformPointer  ConstTransformPointer;
    typedef typename TransformIOBaseTemplate<TScalar>::ConstTransformListType ConstTransformListType;
  
    /** from a composite transform, recover a
     * TransformIOBase::ConstTransformList.
     * This will re-build the list each time it is called, so it is best
     * to call it once per CompositeTransform and access it through the
     * ConstTransformListType reference, as any subsequent calls will
     * rebuild the list and possibly invalidate any iterators on the
     * list.
     */
    ConstTransformListType &GetTransformList(const TransformType *transform);
    /** set a compositeTransform's transform list from a
     ** TransformIOABase::TransformList.  If there is any mismatch
     ** between a transform being added to composite and the composite,
     ** this will throw an exception
     */
    void SetTransformList(TransformType *transform,TransformListType &transformList);
  
  private:
    ConstTransformListType m_TransformList;
  
    /** Builds a list of TransformBase from the CompositeTransform's
     ** queue. A cascade of calls with different template parameters
     ** selects the correct concrete type for CompositeTransform.
     */
    template <unsigned TDim>
    int BuildTransformList(const TransformType *transform);
  
    /** Sets a CompositeTransform's TransformQueue from the
     **  TransformIO's list of TransformBase. Will throw an exception
     **  if the scalar type or dimension of the transform being added
     **  doesn't match that of the concrete CompositeTransform's type.
     */
    template <unsigned TDim>
    int InternalSetTransformList(TransformType *transform,TransformListType &transformList);
  
  };
  
  /** This helps to meet backward compatibility */
  typedef CompositeTransformIOHelperTemplate<double> CompositeTransformIOHelper;
  
  } // namespace itk
  
  #ifndef ITK_MANUAL_INSTANTIATION
  #include "itkCompositeTransformIOHelper.hxx"
  #endif
  
  #endif //  itkCompositeTransformIOHelper_h
  