public int getByte(int byteOffset) {
        return addressInteger.shiftRight(addressLength - 8 * (byteOffset + 1)).and(BigInteger.valueOf(0xFF)).intValueExact();
    }
Return the byte at the given offset.  0 refers to the most significant byte of the address.
vespajlib/src/main/java/ai/vespa/net/CidrBlock.java