How to convert hex value into decimal in painless language

Elastic Stack Elasticsearch
1

Can anyone inform the syntax to convert a value from hex to decimal for a bucket index ..
e.g. i want to convert this substring which is the IP in hex to a IP in decimal .. so, from string need to convert to hex and then int?

'IP': bucket.key[2].substring(0,2)+"."+bucket.key[2].substring(3,5)+"."+bucket.key[2].substring(6,8)+"."+bucket.key[2].substring(9,11)

2

'IP': bucket.key[2].substring(0,11)