Netmask to CIDR in ruby

Question

I've been using the ip-address gem and it doesn't seem to have the ability to convert from a netmask of the form

255.255.255.0 

into the CIDR form

/24

Does anyone have an ideas how to quickly convert the former to the latter ?

Answer 1

Here is a way to do it without the IPAddr gem

(('1'*cidr)+('0'*(32-cidr))).scan(/.{8}/m).map{|e|e.to_i(2)}.join('.')