vtkCellArray.h

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/*=========================================================================
 
  Program:   Visualization Toolkit
  Module:    vtkCellArray.h
 
  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
 
     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.
 
=========================================================================*/
#ifndef vtkCellArray_h
#define vtkCellArray_h
 
#include "vtkCommonDataModelModule.h" // For export macro
#include "vtkObject.h"
 
#include "vtkAOSDataArrayTemplate.h" // Needed for inline methods
#include "vtkCell.h"                 // Needed for inline methods
#include "vtkDataArrayRange.h"       // Needed for inline methods
#include "vtkFeatures.h"             // for VTK_USE_MEMKIND
#include "vtkSmartPointer.h"         // For vtkSmartPointer
#include "vtkTypeInt32Array.h"       // Needed for inline methods
#include "vtkTypeInt64Array.h"       // Needed for inline methods
#include "vtkTypeList.h"             // Needed for ArrayList definition
 
#include <cassert>          // for assert
#include <initializer_list> // for API
#include <type_traits>      // for std::is_same
#include <utility>          // for std::forward
 
#define VTK_CELL_ARRAY_V2
 
class vtkCellArrayIterator;
class vtkIdTypeArray;
 
class VTKCOMMONDATAMODEL_EXPORT vtkCellArray : public vtkObject
{
public:
  using ArrayType32 = vtkTypeInt32Array;
  using ArrayType64 = vtkTypeInt64Array;
 
 
  static vtkCellArray* New();
  vtkTypeMacro(vtkCellArray, vtkObject);
  void PrintSelf(ostream& os, vtkIndent indent) override;
  void PrintDebug(ostream& os);
 
  using StorageArrayList = vtkTypeList::Create<ArrayType32, ArrayType64>;
 
  using InputArrayList =
    typename vtkTypeList::Unique<vtkTypeList::Create<vtkAOSDataArrayTemplate<int>,
      vtkAOSDataArrayTemplate<long>, vtkAOSDataArrayTemplate<long long>>>::Result;
 
  vtkTypeBool Allocate(vtkIdType sz, vtkIdType vtkNotUsed(ext) = 1000)
  {
    return this->AllocateExact(sz, sz) ? 1 : 0;
  }
 
  bool AllocateEstimate(vtkIdType numCells, vtkIdType maxCellSize)
  {
    return this->AllocateExact(numCells, numCells * maxCellSize);
  }
 
  bool AllocateExact(vtkIdType numCells, vtkIdType connectivitySize);
 
  bool AllocateCopy(vtkCellArray* other)
  {
    return this->AllocateExact(other->GetNumberOfCells(), other->GetNumberOfConnectivityIds());
  }
 
  bool ResizeExact(vtkIdType numCells, vtkIdType connectivitySize);
 
  void Initialize();
 
  void Reset();
 
  void Squeeze();
 
  bool IsValid();
 
  vtkIdType GetNumberOfCells() const
  {
    if (this->Storage.Is64Bit())
    {
      return this->Storage.GetArrays64().Offsets->GetNumberOfValues() - 1;
    }
    else
    {
      return this->Storage.GetArrays32().Offsets->GetNumberOfValues() - 1;
    }
  }
 
  vtkIdType GetNumberOfOffsets() const
  {
    if (this->Storage.Is64Bit())
    {
      return this->Storage.GetArrays64().Offsets->GetNumberOfValues();
    }
    else
    {
      return this->Storage.GetArrays32().Offsets->GetNumberOfValues();
    }
  }
 
  vtkIdType GetOffset(vtkIdType cellId)
  {
    if (this->Storage.Is64Bit())
    {
      return this->Storage.GetArrays64().Offsets->GetValue(cellId);
    }
    else
    {
      return this->Storage.GetArrays32().Offsets->GetValue(cellId);
    }
  }
 
  vtkIdType GetNumberOfConnectivityIds() const
  {
    if (this->Storage.Is64Bit())
    {
      return this->Storage.GetArrays64().Connectivity->GetNumberOfValues();
    }
    else
    {
      return this->Storage.GetArrays32().Connectivity->GetNumberOfValues();
    }
  }
 
  VTK_NEWINSTANCE vtkCellArrayIterator* NewIterator();
 
#ifndef __VTK_WRAP__ // The wrappers have issues with some of these templates
  void SetData(vtkTypeInt32Array* offsets, vtkTypeInt32Array* connectivity);
  void SetData(vtkTypeInt64Array* offsets, vtkTypeInt64Array* connectivity);
  void SetData(vtkIdTypeArray* offsets, vtkIdTypeArray* connectivity);
  void SetData(vtkAOSDataArrayTemplate<int>* offsets, vtkAOSDataArrayTemplate<int>* connectivity);
  void SetData(vtkAOSDataArrayTemplate<long>* offsets, vtkAOSDataArrayTemplate<long>* connectivity);
  void SetData(
    vtkAOSDataArrayTemplate<long long>* offsets, vtkAOSDataArrayTemplate<long long>* connectivity);
#endif // __VTK_WRAP__
 
  bool SetData(vtkDataArray* offsets, vtkDataArray* connectivity);
 
  bool SetData(vtkIdType cellSize, vtkDataArray* connectivity);
 
  bool IsStorage64Bit() const { return this->Storage.Is64Bit(); }
 
  bool IsStorageShareable() const
  {
    if (this->Storage.Is64Bit())
    {
      return this->Storage.GetArrays64().ValueTypeIsSameAsIdType;
    }
    else
    {
      return this->Storage.GetArrays32().ValueTypeIsSameAsIdType;
    }
  }
 
  void Use32BitStorage();
  void Use64BitStorage();
  void UseDefaultStorage();
  bool CanConvertTo32BitStorage() const;
  bool CanConvertTo64BitStorage() const;
  bool CanConvertToDefaultStorage() const;
  bool ConvertTo32BitStorage();
  bool ConvertTo64BitStorage();
  bool ConvertToDefaultStorage();
  bool ConvertToSmallestStorage();
  vtkDataArray* GetOffsetsArray()
  {
    if (this->Storage.Is64Bit())
    {
      return this->GetOffsetsArray64();
    }
    else
    {
      return this->GetOffsetsArray32();
    }
  }
  ArrayType32* GetOffsetsArray32() { return this->Storage.GetArrays32().Offsets; }
  ArrayType64* GetOffsetsArray64() { return this->Storage.GetArrays64().Offsets; }
  vtkDataArray* GetConnectivityArray()
  {
    if (this->Storage.Is64Bit())
    {
      return this->GetConnectivityArray64();
    }
    else
    {
      return this->GetConnectivityArray32();
    }
  }
  ArrayType32* GetConnectivityArray32() { return this->Storage.GetArrays32().Connectivity; }
  ArrayType64* GetConnectivityArray64() { return this->Storage.GetArrays64().Connectivity; }
  vtkIdType IsHomogeneous();
 
  void InitTraversal();
 
  int GetNextCell(vtkIdType& npts, vtkIdType const*& pts) VTK_SIZEHINT(pts, npts);
 
  int GetNextCell(vtkIdList* pts);
 
  void GetCellAtId(vtkIdType cellId, vtkIdType& cellSize, vtkIdType const*& cellPoints)
    VTK_SIZEHINT(cellPoints, cellSize) VTK_EXPECTS(0 <= cellId && cellId < GetNumberOfCells());
 
  void GetCellAtId(
    vtkIdType cellId, vtkIdType& cellSize, vtkIdType const*& cellPoints, vtkIdList* ptIds)
    VTK_SIZEHINT(cellPoints, cellSize) VTK_EXPECTS(0 <= cellId && cellId < GetNumberOfCells());
 
  void GetCellAtId(vtkIdType cellId, vtkIdList* pts)
    VTK_EXPECTS(0 <= cellId && cellId < GetNumberOfCells());
 
  vtkIdType GetCellSize(const vtkIdType cellId) const;
 
  vtkIdType InsertNextCell(vtkCell* cell);
 
  vtkIdType InsertNextCell(vtkIdType npts, const vtkIdType* pts) VTK_SIZEHINT(pts, npts);
 
  vtkIdType InsertNextCell(vtkIdList* pts);
 
  vtkIdType InsertNextCell(const std::initializer_list<vtkIdType>& cell)
  {
    return this->InsertNextCell(static_cast<vtkIdType>(cell.size()), cell.begin());
  }
 
  vtkIdType InsertNextCell(int npts);
 
  void InsertCellPoint(vtkIdType id);
 
  void UpdateCellCount(int npts);
 
  vtkIdType GetTraversalCellId();
  void SetTraversalCellId(vtkIdType cellId);
  void ReverseCellAtId(vtkIdType cellId) VTK_EXPECTS(0 <= cellId && cellId < GetNumberOfCells());
 
  void ReplaceCellAtId(vtkIdType cellId, vtkIdList* list);
  void ReplaceCellAtId(vtkIdType cellId, vtkIdType cellSize, const vtkIdType* cellPoints)
    VTK_EXPECTS(0 <= cellId && cellId < GetNumberOfCells()) VTK_SIZEHINT(cellPoints, cellSize);
  void ReplaceCellAtId(vtkIdType cellId, const std::initializer_list<vtkIdType>& cell)
  {
    return this->ReplaceCellAtId(cellId, static_cast<vtkIdType>(cell.size()), cell.begin());
  }
 
  int GetMaxCellSize();
 
  void DeepCopy(vtkCellArray* ca);
 
  void ShallowCopy(vtkCellArray* ca);
 
  void Append(vtkCellArray* src, vtkIdType pointOffset = 0);
 
  void ExportLegacyFormat(vtkIdTypeArray* data);
 
  void ImportLegacyFormat(vtkIdTypeArray* data);
  void ImportLegacyFormat(const vtkIdType* data, vtkIdType len) VTK_SIZEHINT(data, len);
  void AppendLegacyFormat(vtkIdTypeArray* data, vtkIdType ptOffset = 0);
  void AppendLegacyFormat(const vtkIdType* data, vtkIdType len, vtkIdType ptOffset = 0)
    VTK_SIZEHINT(data, len);
  unsigned long GetActualMemorySize() const;
 
  // The following code is used to support
 
  // The wrappers get understandably confused by some of the template code below
#ifndef __VTK_WRAP__
 
  // Holds connectivity and offset arrays of the given ArrayType.
  template <typename ArrayT>
  struct VisitState
  {
    using ArrayType = ArrayT;
    using ValueType = typename ArrayType::ValueType;
    using CellRangeType = decltype(vtk::DataArrayValueRange<1>(std::declval<ArrayType>()));
 
    // We can't just use is_same here, since binary compatible representations
    // (e.g. int and long) are distinct types. Instead, ensure that ValueType
    // is a signed integer the same size as vtkIdType.
    // If this value is true, ValueType pointers may be safely converted to
    // vtkIdType pointers via reinterpret cast.
    static constexpr bool ValueTypeIsSameAsIdType = std::is_integral<ValueType>::value &&
      std::is_signed<ValueType>::value && (sizeof(ValueType) == sizeof(vtkIdType));
 
    ArrayType* GetOffsets() { return this->Offsets; }
    const ArrayType* GetOffsets() const { return this->Offsets; }
 
    ArrayType* GetConnectivity() { return this->Connectivity; }
    const ArrayType* GetConnectivity() const { return this->Connectivity; }
 
    vtkIdType GetNumberOfCells() const;
 
    vtkIdType GetBeginOffset(vtkIdType cellId) const;
 
    vtkIdType GetEndOffset(vtkIdType cellId) const;
 
    vtkIdType GetCellSize(vtkIdType cellId) const;
 
    CellRangeType GetCellRange(vtkIdType cellId);
 
    friend class vtkCellArray;
 
  protected:
    VisitState()
    {
      this->Connectivity = vtkSmartPointer<ArrayType>::New();
      this->Offsets = vtkSmartPointer<ArrayType>::New();
      this->Offsets->InsertNextValue(0);
      if (vtkObjectBase::GetUsingMemkind())
      {
        this->IsInMemkind = true;
      }
    }
    ~VisitState() = default;
    void* operator new(size_t nSize)
    {
      void* r;
#ifdef VTK_USE_MEMKIND
      r = vtkObjectBase::GetCurrentMallocFunction()(nSize);
#else
      r = malloc(nSize);
#endif
      return r;
    }
    void operator delete(void* p)
    {
#ifdef VTK_USE_MEMKIND
      VisitState* a = static_cast<VisitState*>(p);
      if (a->IsInMemkind)
      {
        vtkObjectBase::GetAlternateFreeFunction()(p);
      }
      else
      {
        free(p);
      }
#else
      free(p);
#endif
    }
 
    vtkSmartPointer<ArrayType> Connectivity;
    vtkSmartPointer<ArrayType> Offsets;
 
  private:
    VisitState(const VisitState&) = delete;
    VisitState& operator=(const VisitState&) = delete;
    bool IsInMemkind = false;
  };
 
private: // Helpers that allow Visit to return a value:
  template <typename Functor, typename... Args>
  using GetReturnType = decltype(
    std::declval<Functor>()(std::declval<VisitState<ArrayType32>&>(), std::declval<Args>()...));
 
  template <typename Functor, typename... Args>
  struct ReturnsVoid : std::is_same<GetReturnType<Functor, Args...>, void>
  {
  };
 
public:
  template <typename Functor, typename... Args,
    typename = typename std::enable_if<ReturnsVoid<Functor, Args...>::value>::type>
  void Visit(Functor&& functor, Args&&... args)
  {
    if (this->Storage.Is64Bit())
    {
      // If you get an error on the next line, a call to Visit(functor, Args...)
      // is being called with arguments that do not match the functor's call
      // signature. See the Visit documentation for details.
      functor(this->Storage.GetArrays64(), std::forward<Args>(args)...);
    }
    else
    {
      // If you get an error on the next line, a call to Visit(functor, Args...)
      // is being called with arguments that do not match the functor's call
      // signature. See the Visit documentation for details.
      functor(this->Storage.GetArrays32(), std::forward<Args>(args)...);
    }
  }
 
  template <typename Functor, typename... Args,
    typename = typename std::enable_if<ReturnsVoid<Functor, Args...>::value>::type>
  void Visit(Functor&& functor, Args&&... args) const
  {
    if (this->Storage.Is64Bit())
    {
      // If you get an error on the next line, a call to Visit(functor, Args...)
      // is being called with arguments that do not match the functor's call
      // signature. See the Visit documentation for details.
      functor(this->Storage.GetArrays64(), std::forward<Args>(args)...);
    }
    else
    {
      // If you get an error on the next line, a call to Visit(functor, Args...)
      // is being called with arguments that do not match the functor's call
      // signature. See the Visit documentation for details.
      functor(this->Storage.GetArrays32(), std::forward<Args>(args)...);
    }
  }
 
  template <typename Functor, typename... Args,
    typename = typename std::enable_if<!ReturnsVoid<Functor, Args...>::value>::type>
  GetReturnType<Functor, Args...> Visit(Functor&& functor, Args&&... args)
  {
    if (this->Storage.Is64Bit())
    {
      // If you get an error on the next line, a call to Visit(functor, Args...)
      // is being called with arguments that do not match the functor's call
      // signature. See the Visit documentation for details.
      return functor(this->Storage.GetArrays64(), std::forward<Args>(args)...);
    }
    else
    {
      // If you get an error on the next line, a call to Visit(functor, Args...)
      // is being called with arguments that do not match the functor's call
      // signature. See the Visit documentation for details.
      return functor(this->Storage.GetArrays32(), std::forward<Args>(args)...);
    }
  }
  template <typename Functor, typename... Args,
    typename = typename std::enable_if<!ReturnsVoid<Functor, Args...>::value>::type>
  GetReturnType<Functor, Args...> Visit(Functor&& functor, Args&&... args) const
  {
    if (this->Storage.Is64Bit())
    {
      // If you get an error on the next line, a call to Visit(functor, Args...)
      // is being called with arguments that do not match the functor's call
      // signature. See the Visit documentation for details.
      return functor(this->Storage.GetArrays64(), std::forward<Args>(args)...);
    }
    else
    {
      // If you get an error on the next line, a call to Visit(functor, Args...)
      // is being called with arguments that do not match the functor's call
      // signature. See the Visit documentation for details.
      return functor(this->Storage.GetArrays32(), std::forward<Args>(args)...);
    }
  }
 
#endif // __VTK_WRAP__
 
  //=================== Begin Legacy Methods ===================================
  // These should be deprecated at some point as they are confusing or very slow
 
  virtual void SetNumberOfCells(vtkIdType);
 
  vtkIdType EstimateSize(vtkIdType numCells, int maxPtsPerCell);
 
  vtkIdType GetSize();
 
  vtkIdType GetNumberOfConnectivityEntries();
 
  void GetCell(vtkIdType loc, vtkIdType& npts, const vtkIdType*& pts)
    VTK_EXPECTS(0 <= loc && loc < GetNumberOfConnectivityEntries()) VTK_SIZEHINT(pts, npts);
 
  void GetCell(vtkIdType loc, vtkIdList* pts)
    VTK_EXPECTS(0 <= loc && loc < GetNumberOfConnectivityEntries());
 
  vtkIdType GetInsertLocation(int npts);
 
  vtkIdType GetTraversalLocation();
  vtkIdType GetTraversalLocation(vtkIdType npts);
  void SetTraversalLocation(vtkIdType loc);
  void ReverseCell(vtkIdType loc) VTK_EXPECTS(0 <= loc && loc < GetNumberOfConnectivityEntries());
 
  void ReplaceCell(vtkIdType loc, int npts, const vtkIdType pts[])
    VTK_EXPECTS(0 <= loc && loc < GetNumberOfConnectivityEntries()) VTK_SIZEHINT(pts, npts);
 
  void SetCells(vtkIdType ncells, vtkIdTypeArray* cells);
 
  vtkIdTypeArray* GetData();
 
  //=================== End Legacy Methods =====================================
 
  friend class vtkCellArrayIterator;
 
protected:
  vtkCellArray();
  ~vtkCellArray() override;
 
  // Encapsulates storage of the internal arrays as a discriminated union
  // between 32-bit and 64-bit storage.
  struct Storage
  {
    // Union type that switches 32 and 64 bit array storage
    union ArraySwitch {
      ArraySwitch() = default;  // handled by Storage
      ~ArraySwitch() = default; // handle by Storage
      VisitState<ArrayType32>* Int32;
      VisitState<ArrayType64>* Int64;
    };
 
    Storage()
    {
#ifdef VTK_USE_MEMKIND
      this->Arrays =
        static_cast<ArraySwitch*>(vtkObjectBase::GetCurrentMallocFunction()(sizeof(ArraySwitch)));
#else
      this->Arrays = new ArraySwitch;
#endif
 
      // Default to the compile-time setting:
#ifdef VTK_USE_64BIT_IDS
 
      this->Arrays->Int64 = new VisitState<ArrayType64>;
      this->StorageIs64Bit = true;
 
#else // VTK_USE_64BIT_IDS
 
      this->Arrays->Int32 = new VisitState<ArrayType32>;
      this->StorageIs64Bit = false;
 
#endif // VTK_USE_64BIT_IDS
#ifdef VTK_USE_MEMKIND
      if (vtkObjectBase::GetUsingMemkind())
      {
        this->IsInMemkind = true;
      }
#else
      (void)this->IsInMemkind; // comp warning workaround
#endif
    }
 
    ~Storage()
    {
      if (this->StorageIs64Bit)
      {
        this->Arrays->Int64->~VisitState();
        delete this->Arrays->Int64;
      }
      else
      {
        this->Arrays->Int32->~VisitState();
        delete this->Arrays->Int32;
      }
#ifdef VTK_USE_MEMKIND
      if (this->IsInMemkind)
      {
        vtkObjectBase::GetAlternateFreeFunction()(this->Arrays);
      }
      else
      {
        free(this->Arrays);
      }
#else
      delete this->Arrays;
#endif
    }
 
    // Switch the internal arrays to be 32-bit. Any old data is lost. Returns
    // true if the storage changes.
    bool Use32BitStorage()
    {
      if (!this->StorageIs64Bit)
      {
        return false;
      }
 
      this->Arrays->Int64->~VisitState();
      delete this->Arrays->Int64;
      this->Arrays->Int32 = new VisitState<ArrayType32>;
      this->StorageIs64Bit = false;
 
      return true;
    }
 
    // Switch the internal arrays to be 64-bit. Any old data is lost. Returns
    // true if the storage changes.
    bool Use64BitStorage()
    {
      if (this->StorageIs64Bit)
      {
        return false;
      }
 
      this->Arrays->Int32->~VisitState();
      delete this->Arrays->Int32;
      this->Arrays->Int64 = new VisitState<ArrayType64>;
      this->StorageIs64Bit = true;
 
      return true;
    }
 
    // Returns true if the storage is currently configured to be 64 bit.
    bool Is64Bit() const { return this->StorageIs64Bit; }
 
    // Get the VisitState for 32-bit arrays
    VisitState<ArrayType32>& GetArrays32()
    {
      assert(!this->StorageIs64Bit);
      return *this->Arrays->Int32;
    }
 
    const VisitState<ArrayType32>& GetArrays32() const
    {
      assert(!this->StorageIs64Bit);
      return *this->Arrays->Int32;
    }
 
    // Get the VisitState for 64-bit arrays
    VisitState<ArrayType64>& GetArrays64()
    {
      assert(this->StorageIs64Bit);
      return *this->Arrays->Int64;
    }
 
    const VisitState<ArrayType64>& GetArrays64() const
    {
      assert(this->StorageIs64Bit);
      return *this->Arrays->Int64;
    }
 
  private:
    // Access restricted to ensure proper union construction/destruction thru
    // API.
    ArraySwitch* Arrays;
    bool StorageIs64Bit;
    bool IsInMemkind = false;
  };
 
  Storage Storage;
  vtkNew<vtkIdList> TempCell;
  vtkIdType TraversalCellId{ 0 };
 
  vtkNew<vtkIdTypeArray> LegacyData; // For GetData().
 
private:
  vtkCellArray(const vtkCellArray&) = delete;
  void operator=(const vtkCellArray&) = delete;
};
 
template <typename ArrayT>
vtkIdType vtkCellArray::VisitState<ArrayT>::GetNumberOfCells() const
{
  return this->Offsets->GetNumberOfValues() - 1;
}
 
template <typename ArrayT>
vtkIdType vtkCellArray::VisitState<ArrayT>::GetBeginOffset(vtkIdType cellId) const
{
  return static_cast<vtkIdType>(this->Offsets->GetValue(cellId));
}
 
template <typename ArrayT>
vtkIdType vtkCellArray::VisitState<ArrayT>::GetEndOffset(vtkIdType cellId) const
{
  return static_cast<vtkIdType>(this->Offsets->GetValue(cellId + 1));
}
 
template <typename ArrayT>
vtkIdType vtkCellArray::VisitState<ArrayT>::GetCellSize(vtkIdType cellId) const
{
  return this->GetEndOffset(cellId) - this->GetBeginOffset(cellId);
}
 
template <typename ArrayT>
typename vtkCellArray::VisitState<ArrayT>::CellRangeType
vtkCellArray::VisitState<ArrayT>::GetCellRange(vtkIdType cellId)
{
  return vtk::DataArrayValueRange<1>(
    this->GetConnectivity(), this->GetBeginOffset(cellId), this->GetEndOffset(cellId));
}
 
namespace vtkCellArray_detail
{
 
struct InsertNextCellImpl
{
  // Insert full cell
  template <typename CellStateT>
  vtkIdType operator()(CellStateT& state, const vtkIdType npts, const vtkIdType pts[])
  {
    using ValueType = typename CellStateT::ValueType;
    auto* conn = state.GetConnectivity();
    auto* offsets = state.GetOffsets();
 
    const vtkIdType cellId = offsets->GetNumberOfValues() - 1;
 
    offsets->InsertNextValue(static_cast<ValueType>(conn->GetNumberOfValues() + npts));
 
    for (vtkIdType i = 0; i < npts; ++i)
    {
      conn->InsertNextValue(static_cast<ValueType>(pts[i]));
    }
 
    return cellId;
  }
 
  // Just update offset table (for incremental API)
  template <typename CellStateT>
  vtkIdType operator()(CellStateT& state, const vtkIdType npts)
  {
    using ValueType = typename CellStateT::ValueType;
    auto* conn = state.GetConnectivity();
    auto* offsets = state.GetOffsets();
 
    const vtkIdType cellId = offsets->GetNumberOfValues() - 1;
 
    offsets->InsertNextValue(static_cast<ValueType>(conn->GetNumberOfValues() + npts));
 
    return cellId;
  }
};
 
// for incremental API:
struct UpdateCellCountImpl
{
  template <typename CellStateT>
  void operator()(CellStateT& state, const vtkIdType npts)
  {
    using ValueType = typename CellStateT::ValueType;
 
    auto* offsets = state.GetOffsets();
    const ValueType cellBegin = offsets->GetValue(offsets->GetMaxId() - 1);
    offsets->SetValue(offsets->GetMaxId(), static_cast<ValueType>(cellBegin + npts));
  }
};
 
struct GetCellSizeImpl
{
  template <typename CellStateT>
  vtkIdType operator()(CellStateT& state, const vtkIdType cellId)
  {
    return state.GetCellSize(cellId);
  }
};
 
struct GetCellAtIdImpl
{
  template <typename CellStateT>
  void operator()(CellStateT& state, const vtkIdType cellId, vtkIdList* ids)
  {
    using ValueType = typename CellStateT::ValueType;
 
    const auto cellPts = state.GetCellRange(cellId);
 
    ids->SetNumberOfIds(cellPts.size());
    vtkIdType* idPtr = ids->GetPointer(0);
 
    for (ValueType ptId : cellPts)
    {
      *idPtr++ = static_cast<vtkIdType>(ptId);
    }
  }
 
  // SFINAE helper to check if a VisitState's connectivity array's memory
  // can be used as a vtkIdType*.
  template <typename CellStateT>
  struct CanShareConnPtr
  {
  private:
    using ValueType = typename CellStateT::ValueType;
    using ArrayType = typename CellStateT::ArrayType;
    using AOSArrayType = vtkAOSDataArrayTemplate<ValueType>;
    static constexpr bool ValueTypeCompat = CellStateT::ValueTypeIsSameAsIdType;
    static constexpr bool ArrayTypeCompat = std::is_base_of<AOSArrayType, ArrayType>::value;
 
  public:
    static constexpr bool value = ValueTypeCompat && ArrayTypeCompat;
  };
 
  template <typename CellStateT>
  typename std::enable_if<CanShareConnPtr<CellStateT>::value, void>::type operator()(
    CellStateT& state, const vtkIdType cellId, vtkIdType& cellSize, vtkIdType const*& cellPoints,
    vtkIdList* vtkNotUsed(temp))
  {
    const vtkIdType beginOffset = state.GetBeginOffset(cellId);
    const vtkIdType endOffset = state.GetEndOffset(cellId);
    cellSize = endOffset - beginOffset;
    // This is safe, see CanShareConnPtr helper above.
    cellPoints = reinterpret_cast<vtkIdType*>(state.GetConnectivity()->GetPointer(beginOffset));
  }
 
  template <typename CellStateT>
  typename std::enable_if<!CanShareConnPtr<CellStateT>::value, void>::type operator()(
    CellStateT& state, const vtkIdType cellId, vtkIdType& cellSize, vtkIdType const*& cellPoints,
    vtkIdList* temp)
  {
    using ValueType = typename CellStateT::ValueType;
 
    const auto cellPts = state.GetCellRange(cellId);
    cellSize = cellPts.size();
 
    // ValueType differs from vtkIdType, so we have to copy into a temporary
    // buffer:
    temp->SetNumberOfIds(cellSize);
    vtkIdType* tempPtr = temp->GetPointer(0);
    for (ValueType ptId : cellPts)
    {
      *tempPtr++ = static_cast<vtkIdType>(ptId);
    }
 
    cellPoints = temp->GetPointer(0);
  }
};
 
struct ResetImpl
{
  template <typename CellStateT>
  void operator()(CellStateT& state)
  {
    state.GetOffsets()->Reset();
    state.GetConnectivity()->Reset();
    state.GetOffsets()->InsertNextValue(0);
  }
};
 
} // end namespace vtkCellArray_detail
 
//----------------------------------------------------------------------------
inline void vtkCellArray::InitTraversal()
{
  this->TraversalCellId = 0;
}
 
//----------------------------------------------------------------------------
inline int vtkCellArray::GetNextCell(vtkIdType& npts, vtkIdType const*& pts) VTK_SIZEHINT(pts, npts)
{
  if (this->TraversalCellId < this->GetNumberOfCells())
  {
    this->GetCellAtId(this->TraversalCellId, npts, pts);
    ++this->TraversalCellId;
    return 1;
  }
 
  npts = 0;
  pts = nullptr;
  return 0;
}
 
//----------------------------------------------------------------------------
inline int vtkCellArray::GetNextCell(vtkIdList* pts)
{
  if (this->TraversalCellId < this->GetNumberOfCells())
  {
    this->GetCellAtId(this->TraversalCellId, pts);
    ++this->TraversalCellId;
    return 1;
  }
 
  pts->Reset();
  return 0;
}
//----------------------------------------------------------------------------
inline vtkIdType vtkCellArray::GetCellSize(const vtkIdType cellId) const
{
  return this->Visit(vtkCellArray_detail::GetCellSizeImpl{}, cellId);
}
 
//----------------------------------------------------------------------------
inline void vtkCellArray::GetCellAtId(vtkIdType cellId, vtkIdType& cellSize,
  vtkIdType const*& cellPoints) VTK_SIZEHINT(cellPoints, cellSize)
{
  this->Visit(vtkCellArray_detail::GetCellAtIdImpl{}, cellId, cellSize, cellPoints, this->TempCell);
}
 
//----------------------------------------------------------------------------
inline void vtkCellArray::GetCellAtId(vtkIdType cellId, vtkIdType& cellSize,
  vtkIdType const*& cellPoints, vtkIdList* ptIds) VTK_SIZEHINT(cellPoints, cellSize)
{
  this->Visit(vtkCellArray_detail::GetCellAtIdImpl{}, cellId, cellSize, cellPoints, ptIds);
}
 
//----------------------------------------------------------------------------
inline void vtkCellArray::GetCellAtId(vtkIdType cellId, vtkIdList* pts)
{
  this->Visit(vtkCellArray_detail::GetCellAtIdImpl{}, cellId, pts);
}
 
//----------------------------------------------------------------------------
inline vtkIdType vtkCellArray::InsertNextCell(vtkIdType npts, const vtkIdType* pts)
  VTK_SIZEHINT(pts, npts)
{
  return this->Visit(vtkCellArray_detail::InsertNextCellImpl{}, npts, pts);
}
 
//----------------------------------------------------------------------------
inline vtkIdType vtkCellArray::InsertNextCell(int npts)
{
  return this->Visit(vtkCellArray_detail::InsertNextCellImpl{}, npts);
}
 
//----------------------------------------------------------------------------
inline void vtkCellArray::InsertCellPoint(vtkIdType id)
{
  if (this->Storage.Is64Bit())
  {
    using ValueType = typename ArrayType64::ValueType;
    this->Storage.GetArrays64().Connectivity->InsertNextValue(static_cast<ValueType>(id));
  }
  else
  {
    using ValueType = typename ArrayType32::ValueType;
    this->Storage.GetArrays32().Connectivity->InsertNextValue(static_cast<ValueType>(id));
  }
}
 
//----------------------------------------------------------------------------
inline void vtkCellArray::UpdateCellCount(int npts)
{
  this->Visit(vtkCellArray_detail::UpdateCellCountImpl{}, npts);
}
 
//----------------------------------------------------------------------------
inline vtkIdType vtkCellArray::InsertNextCell(vtkIdList* pts)
{
  return this->Visit(
    vtkCellArray_detail::InsertNextCellImpl{}, pts->GetNumberOfIds(), pts->GetPointer(0));
}
 
//----------------------------------------------------------------------------
inline vtkIdType vtkCellArray::InsertNextCell(vtkCell* cell)
{
  vtkIdList* pts = cell->GetPointIds();
  return this->Visit(
    vtkCellArray_detail::InsertNextCellImpl{}, pts->GetNumberOfIds(), pts->GetPointer(0));
}
 
//----------------------------------------------------------------------------
inline void vtkCellArray::Reset()
{
  this->Visit(vtkCellArray_detail::ResetImpl{});
}
 
#endif // vtkCellArray.h