public void set(long index) {
    int wordNum = (int) (index >> 6);
    int bit = (int) index & 0x3f;
    long bitmask = 1L << bit;
    bits[wordNum / PAGE_SIZE][wordNum % PAGE_SIZE] |= bitmask;
  }
Sets the bit at the specified index.
The index should be less than the OpenBitSet size.
ambry-utils/src/main/java/com/github/ambry/utils/OpenBitSet.java