;
;  $VER: crc16.asm 1.3 (29 Mar 1996)
;
;  magplip.device - Parallel Line Internet Protocol
;
;  Fast table-driven CRC routines.
;
;  Original code written by Oliver Wagner and Michael Balzer.
;
;  This version has been completely reworked by Marius Gröger, introducing
;  slight protocol changes. The new source is a lot better organized and
;  maintainable.
;
;  Additional changes and code cleanup by Jan Kratochvil and Martin Mares.
;  The new source is significantly faster and yet better maintainable.
;
;  (C) Copyright 1993-1994 Oliver Wagner & Michael Balzer
;  (C) Copyright 1995 Jan Kratochvil & Martin Mares
;  (C) Copyright 1995-1996 Marius Gröger
;      All Rights Reserved
;
;  $HISTORY:
;
;  29 Mar 1996 : 001.003 :  changed copyright note
;  20 Aug 1995 : 001.002 :  tab->space conversion, minor face-lifting
;  13 Aug 1995 : 001.001 :  cleanup (jk/mm)
;  12 Feb 1995 : 001.000 :  created
;

        section "text",code

; crc16 = CRC16(dataptr,datalen)
;  d0[0:16]       a0      d0

         xdef    _CRC16

_CRC16   movem.l d2/d3/d4,-(sp)           ; preserve registers
         moveq   #0,d1                    ; init crc
         lea     crctab(pc),a1
         bra.s   crcloop2

crcloop  move.l  d1,d2
         move.l  d1,d3
         asl.w   #8,d3                    ; crc <<8
         lsr.w   #8,d2                    ; crc >>8
         add.w   d2,d2                    ; for 020+
         move.w  0(a1,d2.w),d1            ; move.w (a1,d2.w*2),d1
         eor.w   d3,d1
         move.b  (a0)+,d4
         eor.b   d4,d1
crcloop2 dbf     d0,crcloop

         movem.l (sp)+,d2/d3/d4           ; restore registers
         move.l  d1,d0                    ; return value
         rts

crctab   dc.w $0000,$1021,$2042,$3063,$4084,$50a5,$60c6,$70e7
         dc.w $8108,$9129,$a14a,$b16b,$c18c,$d1ad,$e1ce,$f1ef
         dc.w $1231,$0210,$3273,$2252,$52b5,$4294,$72f7,$62d6
         dc.w $9339,$8318,$b37b,$a35a,$d3bd,$c39c,$f3ff,$e3de
         dc.w $2462,$3443,$0420,$1401,$64e6,$74c7,$44a4,$5485
         dc.w $a56a,$b54b,$8528,$9509,$e5ee,$f5cf,$c5ac,$d58d
         dc.w $3653,$2672,$1611,$0630,$76d7,$66f6,$5695,$46b4
         dc.w $b75b,$a77a,$9719,$8738,$f7df,$e7fe,$d79d,$c7bc
         dc.w $48c4,$58e5,$6886,$78a7,$0840,$1861,$2802,$3823
         dc.w $c9cc,$d9ed,$e98e,$f9af,$8948,$9969,$a90a,$b92b
         dc.w $5af5,$4ad4,$7ab7,$6a96,$1a71,$0a50,$3a33,$2a12
         dc.w $dbfd,$cbdc,$fbbf,$eb9e,$9b79,$8b58,$bb3b,$ab1a
         dc.w $6ca6,$7c87,$4ce4,$5cc5,$2c22,$3c03,$0c60,$1c41
         dc.w $edae,$fd8f,$cdec,$ddcd,$ad2a,$bd0b,$8d68,$9d49
         dc.w $7e97,$6eb6,$5ed5,$4ef4,$3e13,$2e32,$1e51,$0e70
         dc.w $ff9f,$efbe,$dfdd,$cffc,$bf1b,$af3a,$9f59,$8f78
         dc.w $9188,$81a9,$b1ca,$a1eb,$d10c,$c12d,$f14e,$e16f
         dc.w $1080,$00a1,$30c2,$20e3,$5004,$4025,$7046,$6067
         dc.w $83b9,$9398,$a3fb,$b3da,$c33d,$d31c,$e37f,$f35e
         dc.w $02b1,$1290,$22f3,$32d2,$4235,$5214,$6277,$7256
         dc.w $b5ea,$a5cb,$95a8,$8589,$f56e,$e54f,$d52c,$c50d
         dc.w $34e2,$24c3,$14a0,$0481,$7466,$6447,$5424,$4405
         dc.w $a7db,$b7fa,$8799,$97b8,$e75f,$f77e,$c71d,$d73c
         dc.w $26d3,$36f2,$0691,$16b0,$6657,$7676,$4615,$5634
         dc.w $d94c,$c96d,$f90e,$e92f,$99c8,$89e9,$b98a,$a9ab
         dc.w $5844,$4865,$7806,$6827,$18c0,$08e1,$3882,$28a3
         dc.w $cb7d,$db5c,$eb3f,$fb1e,$8bf9,$9bd8,$abbb,$bb9a
         dc.w $4a75,$5a54,$6a37,$7a16,$0af1,$1ad0,$2ab3,$3a92
         dc.w $fd2e,$ed0f,$dd6c,$cd4d,$bdaa,$ad8b,$9de8,$8dc9
         dc.w $7c26,$6c07,$5c64,$4c45,$3ca2,$2c83,$1ce0,$0cc1
         dc.w $ef1f,$ff3e,$cf5d,$df7c,$af9b,$bfba,$8fd9,$9ff8
         dc.w $6e17,$7e36,$4e55,$5e74,$2e93,$3eb2,$0ed1,$1ef0

        end