Method ReadSlice

IO/MPIImage/vtkMPIImageReader.cxx:240–288

//------------------------------------------------------------------------------
#ifdef VTK_USE_MPI_IO
void vtkMPIImageReader::ReadSlice(int slice, const int extent[6], void* buffer)
{
  this->ComputeInternalFileName(slice);

  vtkMPICommunicator* mpiComm =
    vtkMPICommunicator::SafeDownCast(this->GroupedController->GetCommunicator());

  // Open the file for this slice.
  vtkMPIOpaqueFileHandle file;
  int result;
  result = MPI_File_open(*mpiComm->GetMPIComm()->GetHandle(), this->InternalFileName,
    MPI_MODE_RDONLY, MPI_INFO_NULL, &file.Handle);
  if (!(result == MPI_SUCCESS))
  {
    vtkErrorMacro("Could not open file: " << this->InternalFileName);
    return;
  }

  // Set up the file view based on the extents.
  this->SetupFileView(file, extent);

  // Figure out how many bytes to read.
  vtkIdType length = this->GetDataScalarTypeSize();
  length *= this->NumberOfScalarComponents;
  length *= extent[1] - extent[0] + 1;
  length *= extent[3] - extent[2] + 1;
  if (this->GetFileDimensionality() == 3)
    length *= extent[5] - extent[4] + 1;

  vtkIdType pos = 0;
  while (length > pos)
  {
    MPI_Status stat;
    // we know this will fit in an int because it can't exceed VTK_INT_MAX.
    const int remaining =
      static_cast<int>(std::min(length - pos, static_cast<vtkIdType>(VTK_INT_MAX)));
    MPICall(
      MPI_File_read(file.Handle, (static_cast<char*>(buffer)) + pos, remaining, MPI_BYTE, &stat));
    int rd = 0;
    MPICall(MPI_Get_elements(&stat, MPI_BYTE, &rd));
    if (MPI_UNDEFINED == rd)
    {
      vtkErrorMacro("Error obtaining number of values read in " << remaining << "-byte read.");
    }
    pos += static_cast<vtkIdType>(rd);
  }

  MPICall(MPI_File_close(&file.Handle));
}
#else  // VTK_USE_MPI_IO
void vtkMPIImageReader::ReadSlice(int, const int[6], void*)
{