Method LoadFileMetaData

IO/Geometry/vtkGLTFDocumentLoaderInternals.cxx:114–184

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//------------------------------------------------------------------------------
bool vtkGLTFDocumentLoaderInternals::LoadFileMetaData(nlohmann::json& gltfRoot)
{
  try
  {
    const auto& stream = this->Self->GetInternalModel()->Stream;
    stream->Seek(this->Self->GetGLBStart(), vtkResourceStream::SeekDirection::Begin);

    // Determine the format
    std::string magic;
    magic.resize(4);
    stream->Read(magic.data(), magic.size());

    if (magic == "glTF")
    {
      std::uint32_t version;
      std::uint32_t fileLength;
      std::vector<vtkGLTFUtils::ChunkInfoType> chunkInfo;
      if (vtkGLTFUtils::ExtractGLBFileInformation(
            stream, version, fileLength, this->Self->GetGLBStart(), chunkInfo))
      {
        if (!vtkGLTFUtils::ValidateGLBFile(magic, version, fileLength, chunkInfo))
        {
          vtkErrorWithObjectMacro(this->Self, "Invalid binary glTF file");
          return false;
        }

        // Get JSON chunk's information (we know it exists and it's the first chunk)
        vtkGLTFUtils::ChunkInfoType& JSONChunkInfo = chunkInfo[0];

        // Jump to chunk data start
        stream->Seek(this->Self->GetGLBStart() + vtkGLTFUtils::GLBHeaderSize +
            vtkGLTFUtils::GLBChunkHeaderSize,
          vtkResourceStream::SeekDirection::Begin);
        // Read chunk data
        std::vector<char> JSONDataBuffer;
        JSONDataBuffer.resize(JSONChunkInfo.second);
        if (stream->Read(JSONDataBuffer.data(), JSONChunkInfo.second) != JSONChunkInfo.second)
        {
          vtkErrorWithObjectMacro(this->Self, "Failed to read chunk 0.");
          return false;
        }

        gltfRoot = nlohmann::json::parse(JSONDataBuffer);
      }
    }
    else
    {
      // Text gltf
      stream->Seek(0, vtkResourceStream::SeekDirection::End);
      const auto fileSize = static_cast<std::size_t>(stream->Tell()) - this->Self->GetGLBStart();
      stream->Seek(this->Self->GetGLBStart(), vtkResourceStream::SeekDirection::Begin);

      std::vector<char> fileData;
      fileData.resize(fileSize);
      if (stream->Read(fileData.data(), fileData.size()) != fileData.size())
      {
        vtkErrorWithObjectMacro(this->Self, "Failed to read GLTF file");
        return false;