docs: private static <T> void mergeTwoSizeKBuffers(
        final T[] keySrc1, final int arrStart1,
        final T[] keySrc2, final int arrStart2,
        final T[] keyDst,  final int arrStart3,
        final int k, final Comparator<? super T> comparator) {
      final int arrStop1 = arrStart1 + k;
      final int arrStop2 = arrStart2 + k;
  
      int i1 = arrStart1;
      int i2 = arrStart2;
      int i3 = arrStart3;
      while (i1 < arrStop1 && i2 < arrStop2) {
        if (comparator.compare(keySrc2[i2], keySrc1[i1]) < 0) {
          keyDst[i3++] = keySrc2[i2++];
        } else {
          keyDst[i3++] = keySrc1[i1++];
        }
      }
  
      if (i1 < arrStop1) {
        System.arraycopy(keySrc1, i1, keyDst, i3, arrStop1 - i1);
      } else {
        assert i2 < arrStop2;
        System.arraycopy(keySrc1, i2, keyDst, i3, arrStop2 - i2);
      }
    }