Method values

lib/internal/webstreams/readablestream.js:489–618

* @param {{ * preventCancel? : boolean, * }} [options] * @returns {AsyncIterable}

(options = kEmptyObject)

   * @returns {AsyncIterable}
   */
  values(options = kEmptyObject) {
    if (!isReadableStream(this))
      throw new ERR_INVALID_THIS('ReadableStream');
    validateObject(options, 'options', kValidateObjectAllowObjectsAndNull);
    const preventCancel = !!(options?.preventCancel);

    // eslint-disable-next-line no-use-before-define
    const reader = new ReadableStreamDefaultReader(this);

    // No __proto__ here to avoid the performance hit.
    const state = {
      done: false,
      current: undefined,
    };
    let started = false;

    // The nextSteps function is not an async function in order
    // to make it more efficient. Because nextSteps explicitly
    // creates a Promise and returns it in the common case,
    // making it an async function just causes two additional
    // unnecessary Promise allocations to occur, which just add
    // cost.
    function nextSteps() {
      if (state.done)
        return PromiseResolve({ done: true, value: undefined });

      if (reader[kState].stream === undefined) {
        return PromiseReject(
          new ERR_INVALID_STATE.TypeError(
            'The reader is not bound to a ReadableStream'));
      }
      const promise = PromiseWithResolvers();

      // eslint-disable-next-line no-use-before-define
      readableStreamDefaultReaderRead(reader, new ReadableStreamAsyncIteratorReadRequest(reader, state, promise));
      return promise.promise;
    }

    async function returnSteps(value) {
      if (state.done)
        return { done: true, value }; // eslint-disable-line node-core/avoid-prototype-pollution
      state.done = true;

      if (reader[kState].stream === undefined) {
        throw new ERR_INVALID_STATE.TypeError(
          'The reader is not bound to a ReadableStream');
      }
      assert(!reader[kState].readRequests.length);
      if (!preventCancel) {
        const result = readableStreamReaderGenericCancel(reader, value);
        readableStreamReaderGenericRelease(reader);
        await result;
        return { done: true, value }; // eslint-disable-line node-core/avoid-prototype-pollution
      }

      readableStreamReaderGenericRelease(reader);
      return { done: true, value }; // eslint-disable-line node-core/avoid-prototype-pollution
    }