Method constructor

js/bundle/src/decoder.ts:32–96

(buffer: Uint8Array)

  private compatAdapter: CompatAdapter;

  constructor(buffer: Uint8Array) {
    const wbn = asArray(cborg.decode(buffer, { useMaps: true }));

    let peekVersion = bytestringToString(wbn[1]).replace(/\0+$/, '');
    if (!isApprovedVersion(peekVersion)) {
      throw new Error('Unsupported web bundle version.');
    }
    this.compatAdapter = this.createCompatAdapter(peekVersion);

    if (wbn.length !== this.compatAdapter.wbnLength) {
      throw new Error(
        `Wrong toplevel structure ${peekVersion} ${wbn.length} ${this.compatAdapter.wbnLength}`
      );
    }
    const [
      magic,
      version,
      primaryURL, // null in format version b2
      sectionLengthsCBOR,
      sections,
      length,
    ] = this.compatAdapter.destructureBundle(wbn);
    if (bytestringToString(magic) !== '🌐📦') {
      throw new Error('Wrong magic');
    }
    const tempVersion = bytestringToString(version).replace(/\0+$/, ''); // Strip off the '\0' paddings.
    if (!isApprovedVersion(tempVersion)) {
      throw new Error('Unsupported web bundle version.');
    }
    this.version = tempVersion;

    if (primaryURL) {
      this.b1PrimaryURL = asString(primaryURL);
    }
    const sectionLengths = asArray(
      cborg.decode(asBytestring(sectionLengthsCBOR), { useMaps: true })
    );
    const sectionsArray = asArray(sections);
    if (sectionLengths.length !== sectionsArray.length * 2) {
      throw new Error(
        "Number of elements in section-lengths and in sections don't match"
      );
    }
    for (let i = 0; i < sectionsArray.length; i++) {
      this.sections[asString(sectionLengths[i * 2])] = sectionsArray[i];
    }

    if (this.sections['critical']) {
      for (const name of asArray(this.sections['critical'])) {
        if (!knownSections.includes(asString(name))) {
          throw new Error(`unknown section ${name} is marked as critical`);
        }
      }
    }

    // The index section records (offset, length) of each response, but our
    // CBOR decoder doesn't preserve location information. So, recalculate
    // offset and length of each response here. This is inefficient, but works.