nextTableIndex = -1;
      advance();
    }

    @Override
    public abstract T next();

    final void advance() {
      nextExternal = null;

      if (nextInChain()) {
        return;
      }

      if (nextInTable()) {
        return;
      }

      while (nextSegmentIndex >= 0) {
        currentSegment = segments[nextSegmentIndex--];