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// SPDX-FileCopyrightText: Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
// SPDX-License-Identifier: BSD-3-Clause
// Funded by CEA, DAM, DIF, F-91297 Arpajon, France
#ifndef vtkConstantImplicitBackend_h
#define vtkConstantImplicitBackend_h
#include "vtkCommonCoreModule.h"
#include "vtkCompiler.h" // For VTK_USE_EXTERN_TEMPLATE
#include "vtkSetGet.h" // for vtkNotUsed
#include "vtkType.h" // For vtkExternTemplateMacro
/**
* \struct vtkConstantImplicitBackend
* \brief A utility structure serving as a backend for constant implicit arrays
*
* This structure can be classified as a closure and can be called using syntax similar to a
* function.
*
* At construction it takes one parameter which is the constant value that it returns from its main
* function call regardless of index.
*
* An example of potential usage in a vtkImplicitArray
* ```
* double constant = some_number;
* vtkNew<vtkImplicitArray<vtkConstantImplicitBackend<double>>> constArray;
* constArray->SetBackend(std::make_shared<vtkConstantImplicitBackend<double>>(constant));
* constArray->SetNumberOfTuples(however_many_you_want);
* constArray->SetNumberOfComponents(whatever_youd_like);
* double value = constArray->GetTypedComponent(index_in_tuple_range, index_in_component_range);
* CHECK(constant == value); // always true
* ```
*/
VTK_ABI_NAMESPACE_BEGIN
template <typename ValueType>
struct VTKCOMMONCORE_EXPORT vtkConstantImplicitBackend final
{
/**
* A non-trivially contructible constructor
*
* \param val the constant value to return for all indices
*/
vtkConstantImplicitBackend(ValueType val)
: Value(val)
{
}
/**
* The main call method for the backend
*
* \return the constant value
*/
ValueType operator()(vtkIdType vtkNotUsed(index)) const { return this->Value; }
/**
* The constant value stored in the backend
*/
const ValueType Value;
};
VTK_ABI_NAMESPACE_END
#endif // vtkConstantImplicitBackend_h
#if defined(VTK_CONSTANT_BACKEND_INSTANTIATING)
#define VTK_INSTANTIATE_CONSTANT_BACKEND(ValueType) \
VTK_ABI_NAMESPACE_BEGIN \
template struct VTKCOMMONCORE_EXPORT vtkConstantImplicitBackend<ValueType>; \
VTK_ABI_NAMESPACE_END
#elif defined(VTK_USE_EXTERN_TEMPLATE)
#ifndef VTK_CONSTANT_BACKEND_TEMPLATE_EXTERN
#define VTK_CONSTANT_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 VTKCOMMONCORE_EXPORT vtkConstantImplicitBackend);
VTK_ABI_NAMESPACE_END
#ifdef _MSC_VER
#pragma warning(pop)
#endif
#endif // VTK_CONSTANT_IMPLICIT_BACKEND_TEMPLATE_EXTERN
#endif
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