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;===========================================================================
; Copyright (c) 1990-2000 Info-ZIP. All rights reserved.
;
; See the accompanying file LICENSE, version 2000-Apr-09 or later
; (the contents of which are also included in zip.h) for terms of use.
; If, for some reason, all these files are missing, the Info-ZIP license
; also may be found at: ftp://ftp.info-zip.org/pub/infozip/license.html
;===========================================================================
; crc_68 created by Paul Kienitz, last modified 04 Jan 96.
;
; Return an updated 32 bit CRC value, given the old value and a block of data.
; The CRC table used to compute the value is gotten by calling get_crc_table().
; This replaces the older updcrc() function used in Zip and fUnZip. The
; prototype of the function is:
;
; ulg crc32(ulg crcval, uch *text, extent textlen);
;
; On the Amiga, type extent is always unsigned long, not unsigned int, because
; int can be short or long at whim, but size_t is long.
;
; If using this source on a non-Amiga 680x0 system, note that we treat
; a0/a1/d0/d1 as scratch registers not preserved across function calls.
; We do not bother to support registerized arguments for crc32() -- the
; textlen parm is usually large enough so that savings outside the loop
; are pointless.
;
; Define NO_UNROLLED_LOOPS to use a simple short loop which might be more
; efficient on certain machines with dinky instruction caches ('020?), or for
; processing short strings. If loops are unrolled, the textlen parm must be
; less than 512K; if not unrolled, it must be less than 64K.
;
; 1999/09/23: for Human68k: Modified by Shimazaki Ryo.
xdef _crc32 ; (ulg val, uch *buf, extent bufsize)
DO_CRC0 MACRO
moveq #0,ltemp
move.b (textbuf)+,ltemp
eor.b crcval,ltemp
lsl.w #2,ltemp
move.l (crc_table,ltemp.w),ltemp
lsr.l #8,crcval
eor.l ltemp,crcval
ENDM
DO_CRC2 MACRO
move.b (textbuf)+,btemp
eor.b crcval,btemp
lsr.l #8,crcval
move.l (crc_table,btemp.w*4),ltemp
eor.l ltemp,crcval
ENDM
crc_table reg a0 array of unsigned long
crcval reg d0 unsigned long initial value
textbuf reg a1 array of unsigned char
textbufsize reg d1 unsigned long (count of bytes in textbuf)
btemp reg d2
ltemp reg d3
xref _get_crc_table ; ulg *get_crc_table(void)
quad
_crc32:
move.l 8(sp),d0
bne.s valid
;;;;; moveq #0,d0
rts
valid: movem.l btemp/ltemp,-(sp)
jsr _get_crc_table
movea.l d0,crc_table
move.l 12(sp),crcval
move.l 16(sp),textbuf
move.l 20(sp),textbufsize
not.l crcval
ifdef NO_UNROLLED_LOOPS
if CPU==68000
bra.s decr
loop: DO_CRC0
decr: dbra textbufsize,loop
bra.s done
else
twenty: moveq #0,btemp
bra.s decr2
loop2: DO_CRC2
decr2: dbra textbufsize,loop2
endif
ELSE ; !NO_UNROLLED_LOOPS
if CPU==68000
moveq #7,btemp
and textbufsize,btemp
lsr.l #3,textbufsize
bra decr8
loop8: DO_CRC0
DO_CRC0
DO_CRC0
DO_CRC0
DO_CRC0
DO_CRC0
DO_CRC0
DO_CRC0
decr8: dbra textbufsize,loop8
bra.s decr1
loop1: DO_CRC0
decr1: dbra btemp,loop1
bra done
else
twenty: moveq #0,btemp
move.l textbufsize,-(sp)
lsr.l #3,textbufsize
bra decr82
quad
loop82: DO_CRC2
DO_CRC2
DO_CRC2
DO_CRC2
DO_CRC2
DO_CRC2
DO_CRC2
DO_CRC2
decr82: dbra textbufsize,loop82
moveq #7,textbufsize
and.l (sp)+,textbufsize
bra.s decr12
loop12: DO_CRC2
decr12: dbra textbufsize,loop12
endif
ENDC ; ?NO_UNROLLED_LOOPS
done: movem.l (sp)+,btemp/ltemp
not.l crcval
;;;;; move.l crcval,d0 ; crcval already is d0
rts
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