Convert to .exe and crc help

From: Andrew Kennedy (andrewkennedy2_at_LOGev1.net)
Date: 03/05/04 

Date: Fri, 05 Mar 2004 01:46:59 -0000

I need help with two things.

1. I would like to be able to store the crc value in the program and check
it but when I insert the value the crc changes because of the value.

2. I want to convert this to an .exe. I don't understand all that is going
on.
It looks like buf db 0 needs to be at the end of the file.
 
; chkfile.asm - Modifications to do a CRC on a specified file
;
; Performs a CRC chkfile.com
; Com file
;
; Original code by James Vahn, based on Edwin T. Floyd 's CRC-32 ; routine.
 May 15, 1994
;
; Furthur improvements:
;
; encrypt filename and crc values

cseg segment
assume cs:cseg,ds:cseg
org 100h ;COM format

Begin proc far

        mov ax,03D00h ;Open for read.
        mov dx,offset filename
        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.
        loop 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 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!
 filename db 'chkfile.com',0 ; filename to do a CRC check
on
        
cseg ends
end Begin

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