docs: public static void flipBitmapRange(long[] bitmap, int start, int end) {
      if (start == end) {
        return;
      }
      int firstword = start / 64;
      int endword = (end - 1) / 64;
      bitmap[firstword] ^= ~(~0L << start);
      for (int i = firstword; i < endword; i++) {
        bitmap[i] = ~bitmap[i];
      }
      bitmap[endword] ^= ~0L >>> -end;
    }