  const_iterator end() const {
    if (isASCII()) {
      return const_iterator(castToCharPtr() + length_);
    }
    return const_iterator(castToChar16Ptr() + length_);
  }
  const_iterator end() const {
    if (isASCII()) {
      return const_iterator(castToCharPtr() + length_);
    }
    return const_iterator(castToChar16Ptr() + length_);
  }