Method ReadUncompressedData

IO/XMLParser/vtkXMLDataParser.cxx:632–701

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//------------------------------------------------------------------------------
size_t vtkXMLDataParser::ReadUncompressedData(
  unsigned char* data, vtkTypeUInt64 startWord, size_t numWords, size_t wordSize)
{
  // First read the length of the data.
  std::unique_ptr<vtkXMLDataHeader> uh(vtkXMLDataHeader::New(this->HeaderType, 1));

  size_t const headerSize = uh->DataSize();
  size_t r = this->DataStream->Read(uh->Data(), headerSize);
  if (r < headerSize)
  {
    vtkErrorMacro("Error reading uncompressed binary data header.  "
                  "Read "
      << r << " of " << headerSize << " bytes.");
    return 0;
  }
  this->PerformByteSwap(uh->Data(), uh->WordCount(), uh->WordSize());
  vtkTypeUInt64 rsize = uh->Get(0);

  // Adjust the size to be a multiple of the wordSize by taking
  // advantage of integer division.  This will only change the value
  // when the input file is invalid.
  vtkTypeUInt64 size = (rsize / wordSize) * wordSize;

  // Convert the start/length into bytes.
  vtkTypeUInt64 offset = startWord * wordSize;
  size_t length = numWords * wordSize;

  // Make sure the begin/end offsets fall within total size.
  if (offset > size)
  {
    return 0;
  }
  vtkTypeUInt64 end = offset + length;
  end = std::min(end, size);
  length = end - offset;

  // Read the data.
  if (!this->DataStream->Seek(headerSize + offset))
  {
    return 0;
  }

  // Read data in 2MB blocks and report progress.
  constexpr size_t blockSize = 2097152;
  size_t left = length;
  unsigned char* p = data;
  this->UpdateProgress(0);
  while (left > 0 && !this->Abort)
  {
    // Read this block.
    size_t n = (blockSize < left) ? blockSize : left;
    if (!this->DataStream->Read(p, n))
    {
      return 0;
    }

    // Byte swap this block.  Note that n will always be an integer
    // multiple of the word size.