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https://gitlab.kitware.com/vtk/vtk-m
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83d4d4e495
The draft C++11 spec that GCC-4.X implemented against had some defects that made implementing void_t<...> tricky.
146 lines
4.4 KiB
C++
146 lines
4.4 KiB
C++
//============================================================================
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// Copyright (c) Kitware, Inc.
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// All rights reserved.
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// See LICENSE.txt for details.
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//
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// This software is distributed WITHOUT ANY WARRANTY; without even
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// the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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// PURPOSE. See the above copyright notice for more information.
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//============================================================================
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#ifndef vtk_m_cont_ArrayPortalToIterators_h
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#define vtk_m_cont_ArrayPortalToIterators_h
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#include <vtkm/cont/ArrayPortal.h>
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#include <vtkm/cont/internal/IteratorFromArrayPortal.h>
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namespace vtkmstd
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{
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/// Implementation of std::void_t (C++17):
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/// Allows for specialization of class templates based on members of template
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/// parameters.
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#if defined(VTKM_GCC) && (__GNUC__ < 5)
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// Due to a defect in the wording (CWG 1558) unused parameters in alias templates
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// were not guaranteed to ensure SFINAE, and therefore would consider everything
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// to match the 'true' side. For VTK-m the only known compiler that implemented
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// this defect is GCC < 5.
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template <class... T>
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struct void_pack
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{
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using type = void;
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};
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template <class... T>
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using void_t = typename void_pack<T...>::type;
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#else
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template <typename...>
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using void_t = void;
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#endif
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} // end namespace vtkmstd
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namespace vtkm
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{
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namespace cont
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{
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/// \brief Convert an \c ArrayPortal to STL iterators.
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///
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/// \c ArrayPortalToIterators is a class that holds an \c ArrayPortal and
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/// builds iterators that access the data in the \c ArrayPortal. The point of
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/// this class is to use an \c ArrayPortal with generic functions that expect
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/// STL iterators such as STL algorithms or Thrust operations.
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///
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/// The default template implementation constructs iterators that provide
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/// values through the \c ArrayPortal itself. This class can be specialized to
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/// provide iterators that more directly access the data. For example, \c
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/// ArrayPortalFromIterator has a specialization to return the original
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/// iterators.
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///
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template <typename PortalType, typename CustomIterSFINAE = void>
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class ArrayPortalToIterators
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{
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public:
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/// \c ArrayPortaltoIterators should be constructed with an instance of
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/// the array portal.
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///
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VTKM_SUPPRESS_EXEC_WARNINGS
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VTKM_EXEC_CONT
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explicit ArrayPortalToIterators(const PortalType& portal)
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: Portal(portal)
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{
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}
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/// The type of the iterator.
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///
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using IteratorType = vtkm::cont::internal::IteratorFromArrayPortal<PortalType>;
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/// Returns an iterator pointing to the beginning of the ArrayPortal.
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///
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VTKM_SUPPRESS_EXEC_WARNINGS
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VTKM_EXEC_CONT
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IteratorType GetBegin() const { return vtkm::cont::internal::make_IteratorBegin(this->Portal); }
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/// Returns an iterator pointing to one past the end of the ArrayPortal.
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///
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VTKM_SUPPRESS_EXEC_WARNINGS
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VTKM_EXEC_CONT
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IteratorType GetEnd() const { return vtkm::cont::internal::make_IteratorEnd(this->Portal); }
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private:
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PortalType Portal;
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};
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// Specialize for custom iterator types:
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template <typename PortalType>
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class ArrayPortalToIterators<PortalType, vtkmstd::void_t<typename PortalType::IteratorType>>
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{
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public:
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using IteratorType = typename PortalType::IteratorType;
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VTKM_SUPPRESS_EXEC_WARNINGS
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VTKM_EXEC_CONT
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explicit ArrayPortalToIterators(const PortalType& portal)
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: Begin(portal.GetIteratorBegin())
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, End(portal.GetIteratorEnd())
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{
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}
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VTKM_SUPPRESS_EXEC_WARNINGS
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VTKM_EXEC_CONT
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IteratorType GetBegin() const { return this->Begin; }
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VTKM_SUPPRESS_EXEC_WARNINGS
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VTKM_EXEC_CONT
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IteratorType GetEnd() const { return this->End; }
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private:
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IteratorType Begin;
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IteratorType End;
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};
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/// Convenience function for converting an ArrayPortal to a begin iterator.
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///
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VTKM_SUPPRESS_EXEC_WARNINGS
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template <typename PortalType>
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VTKM_EXEC_CONT typename vtkm::cont::ArrayPortalToIterators<PortalType>::IteratorType
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ArrayPortalToIteratorBegin(const PortalType& portal)
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{
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vtkm::cont::ArrayPortalToIterators<PortalType> iterators(portal);
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return iterators.GetBegin();
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}
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/// Convenience function for converting an ArrayPortal to an end iterator.
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///
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VTKM_SUPPRESS_EXEC_WARNINGS
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template <typename PortalType>
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VTKM_EXEC_CONT typename vtkm::cont::ArrayPortalToIterators<PortalType>::IteratorType
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ArrayPortalToIteratorEnd(const PortalType& portal)
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{
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vtkm::cont::ArrayPortalToIterators<PortalType> iterators(portal);
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return iterators.GetEnd();
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}
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}
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} // namespace vtkm::cont
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#endif //vtk_m_cont_ArrayPortalToIterators_h
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