More networking issues

I'm trying to understand the changes to Socket.gethostbyname/addr

In 1.6, gethostbyname returned (for IPv4) the 4 byte address of the 
given host. In Ruby 1.9, it returns a 16 byte structure, which I'm 
assuming is a sockaddr_in.

First, is that correct--was there a change between 1.6 and 1.8/9 on the 
return type of gethostbyname?

If so, how do I then use gethostbyaddr? It seems wrong to say

         require 'socket'
         a = Socket.gethostbyname("161.58.146.238")
         res = Socket.gethostbyaddr(a[3][4..7], a[2])

Shouldn't the two be compatible?


Cheers

Dave