Used IP addresses

Anyone got some C code that loops over all used IP addresses?  Can you come up with any special optimizations?  (I need to handle them in the "%u.%u.%u.%u"-form; computations are independant and can be run in parallel)

Turned out my algorithm was wrong after all, oh well, I changed it and got OpenMP working.

The input:
/* http://dis.4chan.org/read/sci/1172747610
 * 1  Name: FrozenVoid : 2007-03-01 08:54  ID:fPuNCwa3 */

And the output:
80.230.22.238

Oh FrozenVoid, this explains everything.

Got 80.230.70.64 from the second day^[1], I'd say this pretty much confirms it.

_{[1] http://dis.4chan.org/read/sci/1172747610/20}