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*
* ChkTeX v1.5, hashes a NULL-terminated string.
* Copyright (C) 1995-96 Jens T. Berger Thielemann
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* Contact the author at:
* Jens Berger
* Spektrumvn. 4
* N-0666 Oslo
* Norway
* E-mail: <jensthi@ifi.uio.no>
*
*
******* HashWord() ****************************************************
*
* NAME
* HashWord() - hashes a NULL-terminated string
*
* SYNOPSIS
*
* HashVal = @HashWord(char *String)
* D0.W A0
*
* HashVal = _HashWord(char *String)
* D0.W 4(SP)
*
* FUNCTION
* Hashes a NULL-terminated string.
*
* Well optimized (I believe), should be near optimal for this
* approach to hashing. Optimized for caches, loops and pipelines.
* Inner loop size: 12 bytes.
*
*
* INPUTS
* String - a NULL-terminated 8-bit C string. May be passed on
* stack or in A0, depending on entry point.
*
* RETURNS
* HashVal - the hashed value of the string.
*
* NOTES
* Registers a0 and d1 are destroyed.
*
* This function works best when there's a slight difference in
* the length of the strings.
*
* On non-Amiga machines a similar routine is implemented in
* "Utility.c" in the ChkTeX distribution.
*
* It should be possible to adopt this to other 680x0 computers,
* too.
*
* BUGS
* None known.
*
***********************************************************************
*
*
*
*
*
SECTION text,code
XDEF _HashWord
XDEF @HashWord
HashShift EQU 5 * Experiments show this to be best;
* reasonable, as most TeX commands
* only use lowercase letters.
REG_HashVal EQUR d0
REG_TmpChar EQUR d1
REG_StrLen EQUR d2
REG_String EQUR a0
Len_Incr EQU 6
CLRD MACRO \1 * Clears data reg
moveq #0,\1
ENDM
_HashWord * Stack entry
move.l 4(sp),REG_String
@HashWord * Register entry
CLRD REG_HashVal
CLRD REG_TmpChar
move.b (REG_String)+,REG_TmpChar
beq.b return
move.l REG_StrLen,-(sp)
CLRD REG_StrLen
loop
eor.w REG_TmpChar,REG_HashVal
addq.w #Len_Incr,REG_StrLen
ror.w #HashShift,REG_HashVal
eor.w REG_StrLen,REG_HashVal
move.b (REG_String)+,REG_TmpChar
bne.b loop
move.l (sp)+,REG_StrLen
return
rts
END
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