Function CloneGrid

Parallel/DIY/vtkDIYGhostUtilities.cxx:3399–3502

 */
template <class GridDataSetT>
void CloneGrid(GridDataSetT* grid, GridDataSetT* clone, const ExtentType& extent)
{
  ::CloneDataObject(grid, clone);

  vtkCellData* cloneCellData = clone->GetCellData();
  vtkCellData* gridCellData = grid->GetCellData();
  cloneCellData->CopyAllOn();
  cloneCellData->CopyAllocate(gridCellData, clone->GetNumberOfCells());
  cloneCellData->SetNumberOfTuples(clone->GetNumberOfCells());

  const int* cloneExtent = clone->GetExtent();
  const int* gridExtent = grid->GetExtent();

  // We use `std::max` here to work for grids of dimension 2 and 1.
  // This gives "thickness" to the degenerate dimension
  int imin = extent[0];
  int imax = std::max(extent[1], extent[0] + 1);
  int jmin = extent[2];
  int jmax = std::max(extent[3], extent[2] + 1);
  int kmin = extent[4];
  int kmax = std::max(extent[5], extent[4] + 1);

  int ijk[3];

  if (cloneCellData->GetNumberOfTuples())
  {
    for (ijk[2] = kmin; ijk[2] < kmax; ++ijk[2])
    {
      for (ijk[1] = jmin; ijk[1] < jmax; ++ijk[1])
      {
        for (ijk[0] = imin; ijk[0] < imax; ++ijk[0])
        {
          cloneCellData->SetTuple(vtkStructuredData::ComputeCellIdForExtent(cloneExtent, ijk),
            vtkStructuredData::ComputeCellIdForExtent(gridExtent, ijk), gridCellData);
        }
      }
    }
  }

  // We need to reset the newly allocated ghost cells to 0 if there was a ghost array in the input
  if (vtkUnsignedCharArray* ghostCells = cloneCellData->GetGhostArray())
  {
    auto ghostRange = vtk::DataArrayValueRange<1>(ghostCells);
    for (ijk[2] = cloneExtent[4]; ijk[2] < cloneExtent[5]; ++ijk[2])
    {
      for (ijk[1] = cloneExtent[2]; ijk[1] < cloneExtent[3]; ++ijk[1])
      {
        for (ijk[0] = cloneExtent[0]; ijk[0] < cloneExtent[1]; ++ijk[0])
        {
          if (ijk[0] < imin || ijk[0] >= imax || ijk[1] < jmin || ijk[1] >= jmax || ijk[2] < kmin ||
            ijk[2] >= kmax)
          {
            ghostRange[vtkStructuredData::ComputeCellIdForExtent(cloneExtent, ijk)] = 0;
          }
        }
      }
    }
  }