Function newReadableWritablePairFromDuplex

lib/internal/webstreams/adapters.js:672–728

* @param {Duplex} duplex * @param {{ readableType?: 'bytes' }} [options] * @returns {ReadableWritablePair}

(duplex, options = kEmptyObject)

 * @returns {ReadableWritablePair}
 */
function newReadableWritablePairFromDuplex(duplex, options = kEmptyObject) {
  // Not using the internal/streams/utils isWritableNodeStream and
  // isReadableNodeStream utilities here because they will return false
  // if the duplex was created with writable or readable options set to
  // false. Instead, we'll check the readable and writable state after
  // and return closed WritableStream or closed ReadableStream as
  // necessary.
  if (typeof duplex?._writableState !== 'object' ||
      typeof duplex?._readableState !== 'object') {
    throw new ERR_INVALID_ARG_TYPE('duplex', 'stream.Duplex', duplex);
  }

  validateObject(options, 'options');

  const readableOptions = {
    __proto__: null,
    type: options.readableType,
  };

  if (options.readableType == null && options.type != null) {
    // 'options.type' is a deprecated alias for 'options.readableType'
    emitDEP0201();
    readableOptions.type = options.type;
  }

  if (isDestroyed(duplex)) {
    const writable = new WritableStream();
    const readable = new ReadableStream({ type: readableOptions.type });
    writable.close();
    readable.cancel();
    return { readable, writable };
  }

  const writableOptions = {
    __proto__: null,
    [kValidateChunk]: options[kValidateChunk],
    [kDestroyOnSyncError]: options[kDestroyOnSyncError],
  };

  const writable =
    isWritable(duplex) ?
      newWritableStreamFromStreamWritable(duplex, writableOptions) :
      new WritableStream();

  if (!isWritable(duplex))
    writable.close();

  const readable =
    isReadable(duplex) ?
      newReadableStreamFromStreamReadable(duplex, readableOptions) :
      new ReadableStream({ type: readableOptions.type });

  if (!isReadable(duplex))
    readable.cancel();

  return { writable, readable };
}