Category : Pascal Source Code
Archive   : CRCASM.ZIP
Filename : CRCARC.ASM

IDEAL
; This CRC-16 routine and tables were converted from pascal code discovered
; in DEARC.PAS (author unknown). The result matches the 16 bit CRC computed
; by SEA's "ARC" utility. This CRC routine is contributed to the public
; domain.
;
; The Pascal logic is:
;
; crc := ((crc shr 8) and $00FF) xor crctab[(crc xor c) and $00FF];
;
; This TASM conversion done by:
;
; Edwin T. Floyd [76067h747]
; #9 Adams Park Ct.
; Columbus, GA 31909
; 404-576-3305 (work)
; 404-322-0076 (home)
;
; Borland's Turbo Assembler - TASM is required to assemble this program.
;
SEGMENT code BYTE PUBLIC
ASSUME cs:code
; 0
crctab dw 00000h, 0C0C1h, 0C181h, 00140h, 0C301h, 003C0h, 00280h, 0C241h
dw 0C601h, 006C0h, 00780h, 0C741h, 00500h, 0C5C1h, 0C481h, 00440h
; 1
dw 0CC01h, 00CC0h, 00D80h, 0CD41h, 00F00h, 0CFC1h, 0CE81h, 00E40h
dw 00A00h, 0CAC1h, 0CB81h, 00B40h, 0C901h, 009C0h, 00880h, 0C841h
; 2
dw 0D801h, 018C0h, 01980h, 0D941h, 01B00h, 0DBC1h, 0DA81h, 01A40h
dw 01E00h, 0DEC1h, 0DF81h, 01F40h, 0DD01h, 01DC0h, 01C80h, 0DC41h
; 3
dw 01400h, 0D4C1h, 0D581h, 01540h, 0D701h, 017C0h, 01680h, 0D641h
dw 0D201h, 012C0h, 01380h, 0D341h, 01100h, 0D1C1h, 0D081h, 01040h
; 4
dw 0F001h, 030C0h, 03180h, 0F141h, 03300h, 0F3C1h, 0F281h, 03240h
dw 03600h, 0F6C1h, 0F781h, 03740h, 0F501h, 035C0h, 03480h, 0F441h
; 5
dw 03C00h, 0FCC1h, 0FD81h, 03D40h, 0FF01h, 03FC0h, 03E80h, 0FE41h
dw 0FA01h, 03AC0h, 03B80h, 0FB41h, 03900h, 0F9C1h, 0F881h, 03840h
; 6
dw 02800h, 0E8C1h, 0E981h, 02940h, 0EB01h, 02BC0h, 02A80h, 0EA41h
dw 0EE01h, 02EC0h, 02F80h, 0EF41h, 02D00h, 0EDC1h, 0EC81h, 02C40h
; 7
dw 0E401h, 024C0h, 02580h, 0E541h, 02700h, 0E7C1h, 0E681h, 02640h
dw 02200h, 0E2C1h, 0E381h, 02340h, 0E101h, 021C0h, 02080h, 0E041h
; 8
dw 0A001h, 060C0h, 06180h, 0A141h, 06300h, 0A3C1h, 0A281h, 06240h
dw 06600h, 0A6C1h, 0A781h, 06740h, 0A501h, 065C0h, 06480h, 0A441h
; 9
dw 06C00h, 0ACC1h, 0AD81h, 06D40h, 0AF01h, 06FC0h, 06E80h, 0AE41h
dw 0AA01h, 06AC0h, 06B80h, 0AB41h, 06900h, 0A9C1h, 0A881h, 06840h
; A
dw 07800h, 0B8C1h, 0B981h, 07940h, 0BB01h, 07BC0h, 07A80h, 0BA41h
dw 0BE01h, 07EC0h, 07F80h, 0BF41h, 07D00h, 0BDC1h, 0BC81h, 07C40h
; B
dw 0B401h, 074C0h, 07580h, 0B541h, 07700h, 0B7C1h, 0B681h, 07640h
dw 07200h, 0B2C1h, 0B381h, 07340h, 0B101h, 071C0h, 07080h, 0B041h
; C
dw 05000h, 090C1h, 09181h, 05140h, 09301h, 053C0h, 05280h, 09241h
dw 09601h, 056C0h, 05780h, 09741h, 05500h, 095C1h, 09481h, 05440h
; D
dw 09C01h, 05CC0h, 05D80h, 09D41h, 05F00h, 09FC1h, 09E81h, 05E40h
dw 05A00h, 09AC1h, 09B81h, 05B40h, 09901h, 059C0h, 05880h, 09841h
; E
dw 08801h, 048C0h, 04980h, 08941h, 04B00h, 08BC1h, 08A81h, 04A40h
dw 04E00h, 08EC1h, 08F81h, 04F40h, 08D01h, 04DC0h, 04C80h, 08C41h
; F
dw 04400h, 084C1h, 08581h, 04540h, 08701h, 047C0h, 04680h, 08641h
dw 08201h, 042C0h, 04380h, 08341h, 04100h, 081C1h, 08081h, 04040h

MODEL TPASCAL

PUBLIC UpdateCRCArc
PROC UpdateCRCArc FAR initcrc:WORD,inbuf:DWORD,inlen:WORD
; UpdateCRCArc takes an initial CRC value and updates it with inlen bytes from
; inbuf. The updated CRC is returned in AX. The Pascal declaration is:
; Function UpdateCRCArc(InitCRC : Word; Var InBuf; InLen : Word) : Word;
; Stomps registers: AX,BX,CX,SI
push ds
lds si,[inbuf] ; ds:si := ^inbuf
mov ax,[initcrc] ; ax := initcrc
mov cx,[inlen] ; cx := inlen
or cx,cx
jz @@done
@@loop:
xor bh,bh
mov bl,al
lodsb
xor bl,al
shl bx,1
mov bx,[crctab+bx]
xor bl,ah
mov ax,bx
loop @@loop
@@done:
pop ds
ret
ENDP

ENDS
END