How can I convert a byte[] to a POSITIVE BigInteger in Java?

Question

I am working with another team who is working in C. The protocol which we communicate with sends an IP address in byte[] format, as well as 2 "mask" values which are byte[8]. I would like to use the IP address as a BigInteger so that I can do comparisons to see if an IP address is between 2 other IP addresses. To ensure that signedness doesn't screw me up, I need a way to convert the IP from a byte[] (either 4 byte for IPv4 or 16 byte for IPv6) into a positive value in a BigInteger. Could someone point me to a reference or suggest a method of accomplishing this?

Answer 1

Java has a BigInteger constructor that takes a sign integer and a byte array. So you could do:

BigInteger ip = new BigInteger(1, ipBytes);

See the docs here: BigInteger(int, byte[])