On Sun, 03 May 2009 04:59:26 +0300, BCS <[email protected]> wrote:
IIRC something like this is common:
hash_t ret = 0;
foreach(c;str) { ret *= SomePrime; ret += c; }
I think that's the basis for the best general string hashing funcs around.
IIRC from the university, it doesn't matter, in practice, if the
multiplier is a prime number or not. So, the multiplication can be
replaced with bit shifting (that's as fast as the addition operation).
E.g.
foreach(c; str)
{
ret = (ret << 4) + c;
}
I quickly googled around and found the algorithm djb2 which uses the
multiplier 33:
http://www.cse.yorku.ca/~oz/hash.html
djb2 is obviously a little bit slower but it *may* give slightly better
distribution (I'm not gonna run tests now to see if there is a real world
difference... ;) ).
