Q:

Very low cost hash function

I need a hash function for a Look Up table, so that if my values are from 0 to N, I need a hash function that give me a value from 0 to n, being n << N. Another piece of information is that I already know N in advance.
I have been investigatinv about different low cost hash functions and I have found only this:
h = z mod n  range(z) - 0 to N, range(h) - 0 to n

My hash function needs to be implemented in HW, so it needs to have a very low cost. Can anyone recommend any other formula or algorithm apart from that simple thing?. When I say HW I mean a truly implementation in HW, and not instructions in a microprocessor.
Thank you. 
Update with the solution
Thanks for all the answer, I am not going to select a favourite one, because all of them are equally valid depending on the characteristics of the target application.

A:

The canonical form of that is h(x) = (a*x + b) mod n, where a and b are constants and n is the size of your hash table.  You want to make n a prime number, to get optimal(ish) distribution.
Note that this is sensitive to certain kind of distributions -- for example, just doing x mod n is mostly relying on randomness of low-order bits; if they are not random in your set, you will get fairly significant skew.
Bob Jenkins has designed several very good hashing functions; here's one specifically designed to be simple to implement in hardware:
http://burtleburtle.net/bob/hash/nandhash.html
For a lot of different hash functions, design discussions, etc, see the rest of the site: http://burtleburtle.net/bob/hash/

