;--------------------------------------
; crc.asm - Performs a CRC on files specified in the command line.
comment */
The output can be redirected to a file in another directory. Subsequent
runs can be checked with DOS's FC.COM to check for differences in the
target directory. This is a crude program, a prototype for an eventual
disk log for anti-virus and general user information purposes.
Use at your own risk.
By James Vahn, based on Edwin T. Floyd 's CRC-32 routine.
May 15, 1994
Copyright 1994 by James Vahn, All Rights Reserved
I make this code available for educational purposes and if substantial code
from this is used in your software, I'd appreciate credit given to me and
Mr. Floyd in your documention.
/*
cseg segment
assume cs:cseg,ds:cseg
org 100h ;COM format
Begin proc far
cld ;Get the filename and wildcards
mov si,82h ;from the command tail.
lo1:
lodsb ;Find filename in PSP
cmp al,0Dh
jne lo1
mov byte ptr [si-1],0h ;Filename delimiter.
findfirst:
mov cx,16h ;incl. directories
mov dx,82h ;command tail location
mov ah,4Eh
int 21h
jnc findnext
jmp error
findnext:
mov si,9Eh
cmp byte ptr[si],'.' ;Don't print '.. <dir>'
jne pname
mov bx,95h
test byte ptr[bx],00010000b
jz pname
jmp close
pname: ;Print the filename onscreen.
lodsb
or al,al ;Is it a zero? ASCIIZ
je open
mov dl,al
mov ah,2h
int 21h
jmp pname
open:
mov bx,95h
mov al,byte ptr[bx]
test al,00010000b ;Is it a directory?
jz dofile ;nope!
mov dx,offset dirmsg ;Print <dir> and skip CRC
mov ah,09h
int 21h
jmp close
dofile:
mov dl,09h ;Tab seperator. 20h for space.
mov ah,2h
int 21h
mov ax,03D00h ;Open for read.
mov dx,9Eh ;Filename in default DTA (PSP)
int 21h
jc error2
mov word ptr [hndl],ax
read:
mov ah,03Fh
mov bx,word ptr [hndl]
mov dx,offset buf
mov cx,0FEFFh ;Leave room in buffer for stack.
sub cx,dx ;Maximum buffer size.
int 21h
jc error3
or ax,ax ;End of file?
je exit
call UpdateCRC32 ;calculate CRC.
jmp read
exit:
xor word ptr [initcrc],0FFFFh ;Finish CRC calculation.
xor word ptr [initcrc+2],0FFFFh
mov ax,word ptr [initcrc+2]
call bin2hex ;Print CRC to screen.
mov ax,word ptr [initcrc]
call bin2he
mov ax,0FFFFh
mov word ptr[initcrc],ax
mov word ptr[initcrc+2],ax
mov dx,offset CRLF ;linefeed
mov ah,09h
int 21h
close:
mov bx,word ptr [hndl]
mov ah,3Eh ;close file.
int 21h
mov ah,4Fh ;Do more files.
int 21h
jc toDOS
jmp findnext
toDOS:
mov ax,04C00h ;Normal exit to DOS.
int 21h
Begin endp
;*****************************************************
error proc near
mov ah,09h
mov dx,offset errmsg
int 21h
mov ax,04C01h ;Exit errorlevel 1.
int 21h
error endp
;*****************************************************
error2 proc near
mov ah,09h
mov dx,offset errmsg2
int 21h
mov ax,04C02h ;Exit errorlevel 2.
int 21h
error2 endp
;*****************************************************
error3 proc near
mov ah,09h
mov dx,offset errmsg3
int 21h
mov ax,04C03h ;Exit errorlevel 3.
int 21h
error3 endp
;*****************************************************
bin2hex proc near
;Convert AX to HEX ASCII output
bin2he: mov cx,4 ;4 hex digits
mov bx,10h ;divisor
bin2h1: xor dx,dx ;zero DX for 16 bit divide
div bx ;leaves quotient in AX
add dl,'0' ;convert remainder to ASCII
cmp dl,'9'
jna bin2h2
add dl,'A'-'9'-1
bin2h2: push dx ;put on stack
loop bin2h1 ;repeat
mov cx,4
bin2h3: pop ax ;pop most significant digit first
mov dl,al
mov ah,02h
int 21h
loop bin2h3
ret
bin2hex endp
;*****************************************************
UpdateCRC32 proc near
; UpdateCRC32 takes an initial CRC value and updates it from
; data in 'buf'. The updated CRC is then stored in InitCRC.
mov si,offset buf
mov cx,ax
jcxz bye
les ax,[initcrc]
mov dx,ES
lo2:
xor bh,bh
mov bl,al
lodsb
xor bl,al
mov al,ah
mov ah,dl
mov dl,dh
xor dh,dh
shl bx,1
shl bx,1
les bx,[crc32tab+bx]
xor ax,bx
mov bx,ES
xor dx,bx
loop lo2
mov word ptr [initcrc],ax ; Store result in InitCRC
mov word ptr [initcrc+2],dx
bye:
ret
UpdateCRC32 endp
;*****************************************************
; 32 bit reverse crc table for polynomial EDB88320h (Zmodem,PKZip)
; X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0
crc32tab dd 000000000h, 077073096h, 0ee0e612ch, 0990951bah, 0076dc419h
dd 0706af48fh, 0e963a535h, 09e6495a3h, 00edb8832h, 079dcb8a4h
dd 0e0d5e91eh, 097d2d988h, 009b64c2bh, 07eb17cbdh, 0e7b82d07h
dd 090bf1d91h, 01db71064h, 06ab020f2h, 0f3b97148h, 084be41deh
dd 01adad47dh, 06ddde4ebh, 0f4d4b551h, 083d385c7h, 0136c9856h
dd 0646ba8c0h, 0fd62f97ah, 08a65c9ech, 014015c4fh, 063066cd9h
dd 0fa0f3d63h, 08d080df5h, 03b6e20c8h, 04c69105eh, 0d56041e4h
dd 0a2677172h, 03c03e4d1h, 04b04d447h, 0d20d85fdh, 0a50ab56bh
dd 035b5a8fah, 042b2986ch, 0dbbbc9d6h, 0acbcf940h, 032d86ce3h
dd 045df5c75h, 0dcd60dcfh, 0abd13d59h, 026d930ach, 051de003ah
dd 0c8d75180h, 0bfd06116h, 021b4f4b5h, 056b3c423h, 0cfba9599h
dd 0b8bda50fh, 02802b89eh, 05f058808h, 0c60cd9b2h, 0b10be924h
dd 02f6f7c87h, 058684c11h, 0c1611dabh, 0b6662d3dh, 076dc4190h
dd 001db7106h, 098d220bch, 0efd5102ah, 071b18589h, 006b6b51fh
dd 09fbfe4a5h, 0e8b8d433h, 07807c9a2h, 00f00f934h, 09609a88eh
dd 0e10e9818h, 07f6a0dbbh, 0086d3d2dh, 091646c97h, 0e6635c01h
dd 06b6b51f4h, 01c6c6162h, 0856530d8h, 0f262004eh, 06c0695edh
dd 01b01a57bh, 08208f4c1h, 0f50fc457h, 065b0d9c6h, 012b7e950h
dd 08bbeb8eah, 0fcb9887ch, 062dd1ddfh, 015da2d49h, 08cd37cf3h
dd 0fbd44c65h, 04db26158h, 03ab551ceh, 0a3bc0074h, 0d4bb30e2h
dd 04adfa541h, 03dd895d7h, 0a4d1c46dh, 0d3d6f4fbh, 04369e96ah
dd 0346ed9fch, 0ad678846h, 0da60b8d0h, 044042d73h, 033031de5h
dd 0aa0a4c5fh, 0dd0d7cc9h, 05005713ch, 0270241aah, 0be0b1010h
dd 0c90c2086h, 05768b525h, 0206f85b3h, 0b966d409h, 0ce61e49fh
dd 05edef90eh, 029d9c998h, 0b0d09822h, 0c7d7a8b4h, 059b33d17h
dd 02eb40d81h, 0b7bd5c3bh, 0c0ba6cadh, 0edb88320h, 09abfb3b6h
dd 003b6e20ch, 074b1d29ah, 0ead54739h, 09dd277afh, 004db2615h
dd 073dc1683h, 0e3630b12h, 094643b84h, 00d6d6a3eh, 07a6a5aa8h
dd 0e40ecf0bh, 09309ff9dh, 00a00ae27h, 07d079eb1h, 0f00f9344h
dd 08708a3d2h, 01e01f268h, 06906c2feh, 0f762575dh, 0806567cbh
dd 0196c3671h, 06e6b06e7h, 0fed41b76h, 089d32be0h, 010da7a5ah
dd 067dd4acch, 0f9b9df6fh, 08ebeeff9h, 017b7be43h, 060b08ed5h
dd 0d6d6a3e8h, 0a1d1937eh, 038d8c2c4h, 04fdff252h, 0d1bb67f1h
dd 0a6bc5767h, 03fb506ddh, 048b2364bh, 0d80d2bdah, 0af0a1b4ch
dd 036034af6h, 041047a60h, 0df60efc3h, 0a867df55h, 0316e8eefh
dd 04669be79h, 0cb61b38ch, 0bc66831ah, 0256fd2a0h, 05268e236h
dd 0cc0c7795h, 0bb0b4703h, 0220216b9h, 05505262fh, 0c5ba3bbeh
dd 0b2bd0b28h, 02bb45a92h, 05cb36a04h, 0c2d7ffa7h, 0b5d0cf31h
dd 02cd99e8bh, 05bdeae1dh, 09b64c2b0h, 0ec63f226h, 0756aa39ch
dd 0026d930ah, 09c0906a9h, 0eb0e363fh, 072076785h, 005005713h
dd 095bf4a82h, 0e2b87a14h, 07bb12baeh, 00cb61b38h, 092d28e9bh
dd 0e5d5be0dh, 07cdcefb7h, 00bdbdf21h, 086d3d2d4h, 0f1d4e242h
dd 068ddb3f8h, 01fda836eh, 081be16cdh, 0f6b9265bh, 06fb077e1h
dd 018b74777h, 088085ae6h, 0ff0f6a70h, 066063bcah, 011010b5ch
dd 08f659effh, 0f862ae69h, 0616bffd3h, 0166ccf45h, 0a00ae278h
dd 0d70dd2eeh, 04e048354h, 03903b3c2h, 0a7672661h, 0d06016f7h
dd 04969474dh, 03e6e77dbh, 0aed16a4ah, 0d9d65adch, 040df0b66h
dd 037d83bf0h, 0a9bcae53h, 0debb9ec5h, 047b2cf7fh, 030b5ffe9h
dd 0bdbdf21ch, 0cabac28ah, 053b39330h, 024b4a3a6h, 0bad03605h
dd 0cdd70693h, 054de5729h, 023d967bfh, 0b3667a2eh, 0c4614ab8h
dd 05d681b02h, 02a6f2b94h, 0b40bbe37h, 0c30c8ea1h, 05a05df1bh
dd 02d02ef8dh
initcrc dd 0FFFFFFFFh ;Initial CRC value
errmsg db 'File not found- Useage: CRC FILENAME.*',0Dh,0Ah,24h
errmsg2 db 'error 2, cannot open file.',0Dh,0Ah,24h
errmsg3 db 'error 3, cannot read file.',0Dh,0Ah,24h
crlf db 0Dh,0Ah,24h
dirmsg db 9,'<dir>',0Dh,0Ah,24h
hndl dw 0 ;File handle storage.
buf db 0 ;Dynamic storage. Do not move!
cseg ends
end Begin
