onEmpty method

Future<void> onEmpty()

Implementation

Future<void> onEmpty() {
  Completer c = Completer();
  if (_queue.size == 0) {
    c.complete();
  } else {
    var existingResolve = _resolveEmpty;
    _resolveEmpty = () {
      existingResolve();
      c.complete();
    };
  }
  return c.future;
}