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// SPDX-FileCopyrightText: Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
// SPDX-License-Identifier: BSD-3-Clause
#ifndef vtkDataObjectImplicitBackendInterface_h
#define vtkDataObjectImplicitBackendInterface_h
#include "vtkCommonDataModelModule.h"
#include "vtkAOSDataArrayTemplate.h"
#include "vtkDataArrayMeta.h"
#include "vtkSmartPointer.h" // for internal member
#include "vtkWeakPointer.h" // for internal member
/**
* \struct vtkDataObjectImplicitBackendInterface
* \brief A utility structure that can be used as a base for implicit array backend that relies
* on a vtkDataObject.
*
* \details Some backend need to use the vtkDataObject itself to compute
* the array value. This leads to a circular dependency, as the array is itself contained
* inside the vtkDataObject. To break this dependency and to avoid issues with memory management,
* those backends may inherits from this vtkDataObjectImplicitBackendInterface.
*
* vtkDataObjectImplicitBackendInterface observes the DeleteEvent of the vtkDataObject.
* When raised, the backend instantiates the whole array in memory before the
* actual dataobject deletion.
*
* The constructor requires an ArrayName and its Association in order to retrieve
* the whole array to initialize the cache.
*
* # Inheritance
* When inheriting from vtkDataObjectImplicitBackendInterface, `operator()`
* should not be defined by the child class.
* Only `GetValueFromDataObject()` should be overridden to return the expected value.
*
* Once the vtkDataObject is deleted, the parent class handle the memory allocation
* and initialization. Then `operator()` uses the allocated memory instead
* of calling the custom GetValueFromDataObject().
*
* Example of usage from vtkCountFaces:
* \code{.cpp}
* class vtkNumberOfFacesBackend : public vtkDataObjectImplicitBackendInterface<vtkIdType>
* {
* vtkNumberOfFacesBackend(vtkDataObject* input, const std::string& name, int type)
* : vtkDataObjectImplicitBackendInterface(input, name, type)
* {}
*
* ~vtkNumberOfFacesBackend() override = default;
*
* vtkIdType GetValueFromDataObject(const vtkIdType index) const override
* {
* return this->DataObject->GetCell(index)->GetNumberOfFaces();
* }
* };
* \endcode
*
*/
VTK_ABI_NAMESPACE_BEGIN
class vtkDataObject;
class vtkObject;
template <typename ValueType>
struct VTKCOMMONDATAMODEL_EXPORT vtkDataObjectImplicitBackendInterface
{
vtkDataObjectImplicitBackendInterface(
vtkDataObject* dataobject, const std::string& arrayName, int attributeType);
virtual ~vtkDataObjectImplicitBackendInterface();
/**
* Get the value at given index. Entry point for vtkImplicitArray to uses the backend.
*
* This delegates to GetValueFromDataObject when DataObject is not nullptr,
* and uses a local Cache otherwise.
* Should not be reimplemented by subclasses.
*/
ValueType operator()(vtkIdType idx) const;
protected:
/**
* Callback to call when DataObject is destroyed.
* Internally call InitializeCache.
*/
void OnDataObjectDeleted(vtkObject* caller, unsigned long eventId, void* calldata);
/**
* Return the actual value for given index.
* Should be reimplemented by any subclass.
*/
virtual ValueType GetValueFromDataObject(vtkIdType idx) const = 0;
/**
* Get the internal dataobject.
*/
vtkDataObject* GetDataObject() { return this->DataObject; }
private:
/**
* Return the vtkImplicitArray made from this backend.
* Useful to create the internal cache.
*/
vtkDataArray* GetArray();
vtkWeakPointer<vtkDataObject> DataObject;
vtkSmartPointer<vtkAOSDataArrayTemplate<ValueType>> Cache;
std::string ArrayName;
int AttributeType;
};
VTK_ABI_NAMESPACE_END
#endif
#if defined(VTK_DATAOBJECT_BACKEND_INSTANTIATING)
#define VTK_INSTANTIATE_DATAOBJECT_BACKEND(ValueType) \
VTK_ABI_NAMESPACE_BEGIN \
template struct VTKCOMMONDATAMODEL_EXPORT vtkDataObjectImplicitBackendInterface<ValueType>; \
VTK_ABI_NAMESPACE_END
#elif defined(VTK_USE_EXTERN_TEMPLATE)
#ifndef VTK_DATAOBJECT_BACKEND_TEMPLATE_EXTERN
#define VTK_DATAOBJECT_BACKEND_TEMPLATE_EXTERN
#ifdef _MSC_VER
#pragma warning(push)
#pragma warning(disable : 4910) // extern and dllexport incompatible
#endif
VTK_ABI_NAMESPACE_BEGIN
vtkExternTemplateMacro(
extern template struct VTKCOMMONDATAMODEL_EXPORT vtkDataObjectImplicitBackendInterface);
VTK_ABI_NAMESPACE_END
#ifdef _MSC_VER
#pragma warning(pop)
#endif
#endif // VTK_DATAOBJECT_IMPLICIT_BACKEND_TEMPLATE_EXTERN
#endif
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