@loaders.gl/3d-tiles/src/lib/encoders/helpers/encode-3d-tile-header.ts

3D Tiles, an open standard for streaming massive heterogeneous 3D geospatial datasets.

// loaders.gl
// SPDX-License-Identifier: MIT
// Copyright vis.gl contributors

// HELPER ENCODERS
import {assert} from '@loaders.gl/loader-utils';

export function encode3DTileHeader(tile, dataView, byteOffset) {
  const HEADER_SIZE = 12;

  if (!dataView) {
    return byteOffset + HEADER_SIZE;
  }

  const {magic, version = 1, byteLength = 12} = tile;

  assert(Array.isArray(magic) && Number.isFinite(version) && Number.isFinite(byteLength));

  dataView.setUint8(byteOffset + 0, magic[0]);
  dataView.setUint8(byteOffset + 1, magic[1]);
  dataView.setUint8(byteOffset + 2, magic[2]);
  dataView.setUint8(byteOffset + 3, magic[3]);
  dataView.setUint32(byteOffset + 4, version, true); // version
  dataView.setUint32(byteOffset + 8, byteLength, true); // byteLength

  byteOffset += HEADER_SIZE;

  return byteOffset;
}

// Bytelength is sometimes only known at the end of writing a tile
export function encode3DTileByteLength(dataView, byteOffsetTileStart, byteLength) {
  if (!dataView) {
    return;
  }

  dataView.setUint32(byteOffsetTileStart + 8, byteLength, true); // byteLength
}