Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!ukc!warwick!covpoly!csg019
From: csg019@cck.cov.ac.uk (-~=Zaphod=~-)
Newsgroups: comp.sys.amiga
Subject: Re: CATS? ANYONE?
Message-ID: <1991Jan9.163927.2808@cck.cov.ac.uk>
Date: 9 Jan 91 16:39:27 GMT
References: <2.27842025@weyr.FIDONET.ORG>
Organization: Coventry Polytechnic, Coventry, UK
Lines: 51

In article <2.27842025@weyr.FIDONET.ORG> David.Plummer@f70.n140.z1.FIDONET.ORG (David Plummer) writes:
>Below is the function I'm using to calculate the hash value for a
>filename:
> 
>int Hash(unsigned char *filename)                      
>{                                                      
>   int val;                                            
>                                                       
>   val=strlen(filename);                               
>   while(*filename)                                    
>      val=((val*13)+(int)toupper(*filename++)) & 0x7ff;
>   return (val % 72);                                  
>}
> 

The way i did it (for ZDIR, the worlds fastest dir program. - end of plug)
is:
	hash=length
	repeat
		hash=hash*13
		hash=hash+ascii code of char
		and hash with $7ff
		length=length - 1
	until length = 0
	final_hash=hash MOD 72

length equ 6          <-Just for example
lea filename,a0
move.w #length-1,d0
move.w #length,d1
hashloop:
mulu #13,d1
clr.w d2
move.b (a0)+,d2
add.w d2,d1
and.w #$7ff,d1
dbra d0,hashloop
divu #72,d1
;Could use a few ror.l's instead if divu #72....
swap d1
rts

filename dc.b "file.s"

d1.w contains hash.

-- 
*********///  O O **A member of S.H.I.T. (Super High Intelegence Team)**///***
*       ///    u    Fight, defeat and kill organized laming.           ///   *
*  \\\ ///    ---      Zaphod (TCC)  csg019@uk.ac.cov.cck ok?     \\\ ///    *
****\\X//**********************************************************\\X//******