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pckfix.asm
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Assembly Source File
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1988-08-24
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5KB
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213 lines
; PCKFIX.ASM --
; Input file: KERMIT.EXE
; Output file: KERMIT.FIX
; The new file is a printable version of the executable file. Each byte
; in the EXE file is converted to two bytes in the FIX file: a constant
; of "0" (30H) is added to each nibble.
;
; Daphne Tzoar, December 1983
; Columbia University Center for Computing Activities
DOS EQU 21H
STACK SEGMENT PARA STACK 'STACK'
DW 100 DUP (0)
STK EQU THIS WORD
STACK ENDS
DATAS SEGMENT PARA PUBLIC 'DATAS'
buff db 80H DUP(0) ; Use our own DTA.
bufone db 80H DUP(0) ; Data read from EXE file.
buftwo db 80H DUP(0) ; Data to write out to FIX file.
fcbold db 25H DUP(0) ; For the EXE file.
fcbnew db 25H DUP(0) ; File the FIX file.
oldstk dw ?
kold db 'KERMIT EXE$'
knew db 'KERMIT FIX$'
chrcnt db 0 ; Number of chars left in BUFONE.
datcnt db 0 ; Number of chars in BUFTWO.
eoflag db 0 ; Remember when we hit the EOF.
crflg db 0 ; Flag when it's time to add a CRLF.
cnt db 0 ; Determine when to add a CRLF.
DATAS ENDS
MAIN SEGMENT PARA PUBLIC 'MAIN'
START PROC FAR
ASSUME CS:MAIN,DS:DATAS,SS:STACK,ES:NOTHING
push ds ; Initialization
sub ax,ax
push ax
mov ax,datas ; More of the same.......
mov ds,ax
sub ax,ax
mov oldstk,sp
mov ah,1AH ; Use my own DTA
mov dx,offset buff
int dos
call one ; Do the important stuff.
mov sp,oldstk
ret ; Done.
START ENDP
ONE PROC NEAR
mov bx,offset fcbold
mov ah,0
mov [bx],ah ; Use default drive.
inc bx
mov di,offset kold ; Get name of original file.
kerm3: mov ah,[di]
cmp ah,'$' ; Got all the data?
je kerm4
mov [bx],ah
inc di
inc bx
jmp kerm3
kerm4: mov bx,offset fcbnew ; Put name of new file here.
mov ah,0
mov [bx],ah
inc bx
mov di,offset knew
kerm5: mov ah,[di]
cmp ah,'$'
je kerm6
mov [bx],ah
inc di
inc bx
jmp kerm5
kerm6: mov ax,0
mov bx,offset fcbold+0CH
mov [bx],ax ; Zero current block number.
mov bx,offset fcbold+0EH
mov [bx],ax ; Lrecl.
mov bx,offset fcbold+20H
mov [bx],ah ; Current record (of block).
inc bx
mov [bx],ax ; Current record (of file).
mov bx,offset fcbold+23H
mov [bx],ax
mov ah,0FH ; Open file.
mov dx,offset fcbold
int dos
mov ax,0
mov bx,offset fcbnew+0CH
mov [bx],ax ; Zero current block number.
mov bx,offset fcbnew+0EH
mov [bx],ax ; Lrecl.
mov bx,offset fcbnew+20H
mov [bx],ah ; Current record (of block).
inc bx
mov [bx],ax ; Current record (of file).
mov bx,offset fcbnew+23H
mov [bx],ax
mov ah,16H ; Create file.
mov dx,offset fcbnew
int dos
mov eoflag,0 ; Not end-of-file yet.
mov datcnt,0 ; Chars in write-out buffer.
mov chrcnt,0 ; Chars in read-to buffer.
mov crflg,0
mov cnt,0
mov bx,offset bufone
mov di,offset buftwo
kerm1: cmp chrcnt,0H ; Any chars left in buffer?
jne kerm0 ; Yes, continue.
call inbuf ; Else get a buffer-full.
jmp kerm9 ; Hit the EOF.
mov ax,ds
mov es,ax ; Move for Dest uses ES register.
mov si,offset buff
push di
mov di,offset bufone ; Move read-in data to bufone.
mov cx,80H
rep movs es:bufone,buff
pop di
mov bx,offset bufone ; Where the chars are.
mov chrcnt,80H ; Number of chars.
kerm0: cmp datcnt,80H ; Time to write out the buffer?
je kerm2 ; Yup.
dec chrcnt
mov ah,[bx] ; Get a char.
mov ch,ah ; Save here.
and ah,0F0H ; Get high nibble.
and ch,0FH ; Lower nibble.
mov cl,4
shr ax,cl
add ah,'0' ; Make printable.
mov [di],ah
inc datcnt
inc di
add ch,'0'
mov [di],ch
inc datcnt
inc di
inc bx
add cnt,2
cmp cnt,3EH ; Time to add CRLF?
jne kerm1 ; Nope, keep going.
mov cnt,0 ; Reset counter.
cmp datcnt,80H ; Have room for it?
jne kerm8 ; Yup, we do.
mov crflg,0FFH ; No - remember add it later.
jmp kerm2
kerm8: mov crflg,0
mov ax,0A0DH ; Add the CRLF.
mov [di],ax
inc di
inc di
add datcnt,2
jmp kerm1
kerm2: mov ax,ds
mov es,ax ; Move for Dest uses ES register.
mov si,offset buftwo
mov di,offset buff
mov cx,80H
rep movs es:buff,buftwo ; Must use BUFF for r/w to file.
mov ah,15H ; Write out to file two.
mov dx,offset fcbnew
int dos
mov datcnt,0
mov di,offset buftwo ; Start at beginning of buffer.
cmp crflg,0FFH ; Had our buffer filled prior to CRLF?
je kerm8 ; Yup.
jmp kerm1 ; Get new buffer-full.
kerm9: mov ah,10H ; Close files.
mov dx,offset fcbold
int dos
mov dx,offset fcbnew
int dos
ret
inbuf: cmp eoflag,0 ; End of file?
je inbuf0 ; Nope.
ret
inbuf0: mov dx,offset fcbold
mov ah,14H ; Read from file.
int dos
cmp al,0
je inbuf2
mov eoflag,0FFH
inbuf2: jmp rskp
ONE ENDP
RSKP PROC NEAR
pop bp
add bp,3
push bp
ret
RSKP ENDP
MAIN ENDS
END START