Coding a DNS server

need it for an embedded system project.

would have used bind but it is too large. many others I find seemed a bit large too.

it would be just used as an authorative name server nothing else with limited function. anyone have a limited working one, I can take a look on?

Have you tried looking at tinydns from the djbdns suite? It might be exactly what you're looking for.
http://cr.yp.to/djbdns/tinydns.html
http://cr.yp.to/djbdns/blurb/server.html
http://cr.yp.to/djbdns.html
http://www.lifewithdjbdns.com/ <-- See section 5 for components of DJBDNS and how they fit together.

Briefly, the djbdns suite is built as a set of DNS programs that accomplish very specific functions, rather than one monolithic program that does a lot of things like BIND. DJB (the author) uses this "small is beautiful" philosophy on all his programs and tinydns does live up to its name. The tinydns program is written to act as an authoritative server on UDP port 53 alone. 99.99% of the time, DNS replies can fit into a UDP packet since they are usually under 512 bytes in size, so this might be the only program you need. For zone transfer purposes (and if you're one of the few people that have some zone information bigger than 512 bytes), there's a separate program called afxrdns in the djbdns suite that uses TCP socket 53.

In my case, I ran only tinydns on two authoritative servers and did all my zone transfers by simply transferring the config file to both servers using rsync over ssh. Hence, I didn't need afxrdns for anything at all.

Couple of negative points about djb is his personal standard for installation paths (which almost no one else in the world uses) and his licensing terms -- if you only want to use his code and don't intend to distribute it to others, you're free to make whatever changes you want to his code. However, if you do distribute his software for other people to use, he wants his code to be distributed unmodified.
http://cr.yp.to/distributors.html
People who make add-ons to his programs get around this by distributing his unmodified source and a separate script that makes the necessary changes. The end-user is then given the option to install DJB's software first and then run the add-on script separately as part of their installation procedure. Personally though, I've run djbdns with no third party add-ons at all, as it does everything that I ever needed (his qmail software is a different matter though). One more thing is that DJBDNS doesn't do everything that BIND does because DJB doesn't see the need for some of BIND's features and hasn't bothered to implement them at all.