Function toReadableSync

lib/internal/streams/iter/classic.js:354–402

* Create a byte-mode Readable from an Iterable . * Fully synchronous -- _read() pulls from the iterator directly. * @param {Iterable } source * @param {object} [options] * @param {number} [options.highWaterMark] * @returns {stream.Readable}

(source, options = kNullPrototype)

 * @returns {stream.Readable}
 */
function toReadableSync(source, options = kNullPrototype) {
  if (typeof source?.[SymbolIterator] !== 'function') {
    throw new ERR_INVALID_ARG_TYPE('source', 'Iterable', source);
  }

  validateObject(options, 'options');
  const {
    highWaterMark = 64 * 1024,
  } = options;
  validateInteger(highWaterMark, 'options.highWaterMark', 0);

  const ReadableCtor = lazyReadable();
  const iterator = source[SymbolIterator]();
  let hasBatch = false;
  let batch;
  let batchIndex = 0;

  return new ReadableCtor({
    __proto__: null,
    highWaterMark,
    read() {
      for (;;) {
        if (hasBatch) {
          while (batchIndex < batch.length) {
            if (!this.push(batch[batchIndex++])) return;
          }
          batch = undefined;
          hasBatch = false;
          batchIndex = 0;
        }

        const result = iterator.next();
        const { done } = result;
        if (done) {
          this.push(null);
          return;
        }
        batch = result.value;
        hasBatch = true;
      }
    },
    destroy(err, cb) {
      batch = undefined;
      hasBatch = false;
      if (typeof iterator.return === 'function') iterator.return();
      cb(err);
    },
  });
}


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