Function simpleRangeHeaderValue

deps/undici/src/lib/web/fetch/util.js:1079–1204

* @see https://fetch.spec.whatwg.org/#simple-range-header-value * @param {string} value * @param {boolean} allowWhitespace * @return {RangeHeaderValue|'failure'}

(value, allowWhitespace)

 * @return {RangeHeaderValue|'failure'}
 */
function simpleRangeHeaderValue (value, allowWhitespace) {
  // 1. Let data be the isomorphic decoding of value.
  // Note: isomorphic decoding takes a sequence of bytes (ie. a Uint8Array) and turns it into a string,
  // nothing more. We obviously don't need to do that if value is a string already.
  const data = value

  // 2. If data does not start with "bytes", then return failure.
  if (!data.startsWith('bytes')) {
    return 'failure'
  }

  // 3. Let position be a position variable for data, initially pointing at the 5th code point of data.
  const position = { position: 5 }

  // 4. If allowWhitespace is true, collect a sequence of code points that are HTTP tab or space,
  //    from data given position.
  if (allowWhitespace) {
    collectASequenceOfCodePoints(
      (char) => char === '\t' || char === ' ',
      data,
      position
    )
  }

  // 5. If the code point at position within data is not U+003D (=), then return failure.
  if (data.charCodeAt(position.position) !== 0x3D) {
    return 'failure'
  }

  // 6. Advance position by 1.
  position.position++

  // 7. If allowWhitespace is true, collect a sequence of code points that are HTTP tab or space, from
  //    data given position.
  if (allowWhitespace) {
    collectASequenceOfCodePoints(
      (char) => char === '\t' || char === ' ',
      data,
      position
    )
  }

  // 8. Let rangeStart be the result of collecting a sequence of code points that are ASCII digits,
  //    from data given position.
  const rangeStart = collectASequenceOfCodePoints(
    (char) => {
      const code = char.charCodeAt(0)

      return code >= 0x30 && code <= 0x39
    },
    data,
    position
  )

  // 9. Let rangeStartValue be rangeStart, interpreted as decimal number, if rangeStart is not the
  //    empty string; otherwise null.
  const rangeStartValue = rangeStart.length ? Number(rangeStart) : null