@kitware/vtk.js/IO/Geometry/GLTFImporter/Decoder.js

Visualization Toolkit for the Web

import BinaryHelper from '../../Core/BinaryHelper.js';
import { BINARY_HEADER_MAGIC, BINARY_CHUNK_TYPES, BINARY_CHUNK_HEADER_INTS, BINARY_HEADER_LENGTH, BINARY_HEADER_INTS } from './Constants.js';

function getChunkInfo(headerStart, data) {
  const header = new Uint32Array(data, headerStart, BINARY_CHUNK_HEADER_INTS);
  const chunkStart = headerStart + BINARY_CHUNK_HEADER_INTS * 4;
  const chunkLength = header[0];
  const chunkType = header[1];
  return {
    start: chunkStart,
    length: chunkLength,
    type: chunkType
  };
}
function getAllChunkInfos(data) {
  const infos = [];
  let chunkStart = BINARY_HEADER_INTS * 4;
  while (chunkStart < data.byteLength) {
    const chunkInfo = getChunkInfo(chunkStart, data);
    infos.push(chunkInfo);
    chunkStart += chunkInfo.length + BINARY_CHUNK_HEADER_INTS * 4;
  }
  return infos;
}
function getJsonFromChunk(chunkInfo, data) {
  const chunkLength = chunkInfo.length;
  const jsonStart = (BINARY_HEADER_INTS + BINARY_CHUNK_HEADER_INTS) * 4;
  const jsonSlice = new Uint8Array(data, jsonStart, chunkLength);
  const stringBuffer = BinaryHelper.arrayBufferToString(jsonSlice);
  return JSON.parse(stringBuffer);
}
function getBufferFromChunk(chunkInfo, data) {
  return data.slice(chunkInfo.start, chunkInfo.start + chunkInfo.length);
}
function parseGLB(data) {
  let json;
  const buffers = [];
  const headerView = new DataView(data, 0, BINARY_HEADER_LENGTH);
  const header = {
    magic: BinaryHelper.arrayBufferToString(new Uint8Array(data, 0, 4)),
    version: headerView.getUint32(4, true),
    length: headerView.getUint32(8, true)
  };
  if (header.magic !== BINARY_HEADER_MAGIC) {
    throw new Error('Unsupported glTF-Binary header.');
  } else if (header.version < 2.0) {
    throw new Error('Unsupported legacy binary file detected.');
  }
  const chunkInfos = getAllChunkInfos(data);
  chunkInfos.forEach(chunkInfo => {
    if (chunkInfo.type === BINARY_CHUNK_TYPES.JSON && !json) {
      json = getJsonFromChunk(chunkInfo, data);
    } else if (chunkInfo.type === BINARY_CHUNK_TYPES.BIN) {
      buffers.push(getBufferFromChunk(chunkInfo, data));
    }
  });
  if (!json) {
    throw new Error('glTF-Binary: JSON content not found.');
  }
  if (!buffers) {
    throw new Error('glTF-Binary: Binary chunk not found.');
  }
  return {
    json,
    buffers
  };
}

export { parseGLB as default };