Newbie Developer Question

Hey folks, I have a newbie developer question. I'm currently taking a
course called Database Systems & Implementation at Rochester Institute of
Technology and we've split up into groups and are working on extending
Postgres to get some experience with a real-world DBMS (as well as the
open-source initiative). My group is working on implementing the UNIQUE
functionality in indexes other than the b-tree (which is a TODO item on the
postgres website). We've been digging through the src/backend/access/hash/
and we're having a hard time figuring out the correct way to walk through
items in a page. Is this what the hashbeginscan() method is for? If so,
what should we provide for the keysz and scankey parameters?
backend/access/index/genam.c says these parameters are "key count" and "scan
key" respectively, but I'm still sort of lost on what these should be and
how we get them (I couldn't find any code that actually called the
hashbeginscan() function to use as reference).

Bear with me...I know it's the last thing you all want to hear but I'm more
a java developer than a C one, but I'm workin' on it :-D. Is there some
sort of reference equivalent of Javadocs that would show all the files, the
functions, the descriptions of the parameters, etc? As of now, we're just
grepping the code to find where else specific functions are used and trying
to figure it all out that way.

Thanks so much for the help (now and for the stuff in the future I'm sure
I'll be bugging you all about).

-Matt