Method ReadCompressionHeader

IO/XMLParser/vtkXMLDataParser.cxx:518–578

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//------------------------------------------------------------------------------
int vtkXMLDataParser::ReadCompressionHeader()
{
  std::unique_ptr<vtkXMLDataHeader> ch(vtkXMLDataHeader::New(this->HeaderType, 3));

  this->DataStream->StartReading();

  // Read the standard part of the header.
  size_t const headerSize = ch->DataSize();
  size_t r = this->DataStream->Read(ch->Data(), headerSize);
  if (r < headerSize)
  {
    vtkErrorMacro("Error reading beginning of compression header.  Read "
      << r << " of " << headerSize << " bytes.");
    return 0;
  }

  // Byte swap the header to make sure the values are correct.
  this->PerformByteSwap(ch->Data(), ch->WordCount(), ch->WordSize());

  // Get the standard values.
  this->NumberOfBlocks = size_t(ch->Get(0));
  this->BlockUncompressedSize = size_t(ch->Get(1));
  this->PartialLastBlockUncompressedSize = size_t(ch->Get(2));

  // Allocate the size and offset parts of the header.
  ch->Resize(this->NumberOfBlocks);
  delete[] this->BlockCompressedSizes;
  this->BlockCompressedSizes = nullptr;
  delete[] this->BlockStartOffsets;
  this->BlockStartOffsets = nullptr;
  if (this->NumberOfBlocks > 0)
  {
    this->BlockCompressedSizes = new size_t[this->NumberOfBlocks];
    this->BlockStartOffsets = new vtkTypeInt64[this->NumberOfBlocks];

    // Read the compressed block sizes.
    size_t len = ch->DataSize();
    if (this->DataStream->Read(ch->Data(), len) < len)
    {
      vtkErrorMacro("Error reading compression header.");
      return 0;
    }

    // Byte swap the sizes to make sure the values are correct.
    this->PerformByteSwap(ch->Data(), ch->WordCount(), ch->WordSize());
  }

  this->DataStream->EndReading();

  // Use the compressed block sizes to calculate the starting offset
  // of each block.
  vtkTypeInt64 offset = 0;
  for (size_t i = 0; i < this->NumberOfBlocks; ++i)
  {
    size_t const sz = size_t(ch->Get(i));
    this->BlockCompressedSizes[i] = sz;
    this->BlockStartOffsets[i] = offset;
    offset += sz;