code: private static void vectorSwap(PagesIndex pagesIndex, int from, int l, int s)
      {
          for (int i = 0; i < s; i++, from++, l++) {
              pagesIndex.swap(from, l);
          }
      }
docs: Swaps x[a .. (a+n-1)] with x[b .. (b+n-1)].