subnet mask calculation source code

[DrBudz]

Hello,

I have designed ethernet controller, and I am programming pc software to interface the controller via rs232.

In pc software I have fileds to set the IP address of the controller and subnet mask, and then write it to controller via rs 232.
I need source code for Subnet mask calculation.

When I enter IP adress in the fields, I need subnet mask to be generated automatically, just like in windows network properties settings.

When I enter IP address (for example

192.168.1.10

I need subnet mask to be generated automatically:

255.255.255.0

Can someone help with the IP subnet mask calculation?
Does anybody has a source code for this calculation?

Thanks!

 

[papunblg]

http://www.networkclue.com/routing/tcpip/calculating-masks.aspx