Assembly

Assembly RSS

Assembly project problem

•

Join Date: Apr 2009

Posts: 2

Reputation: Matt23488 is an unknown quantity at this point

Solved Threads: 0

Matt23488

Offline

Newbie Poster

Assembly project problem

Apr 2nd, 2009

I am working on homework for my x86 assembly class. The purpose of the program is to open an existing file and display the first 20 lines of the file and then pause, display the next 20 lines, pause, etc. until the end of the file is reached. My professor is really terrible, he rarely ever takes us to the lab so we don't get much practice, and so it's hard to understand. The problem is that it doesn't pause after 20 lines, and once the end of the file is reached, it starts dumping register values and garbage data and then crashes. I am really stuck, can anyone help me? Here is my code:

 Help with Code Tags 
 Assembly Syntax (Toggle Plain Text) 
TITLE MASM Template						(main.asm)
 
; Description:
; 
; Revision date:
 
INCLUDE Irvine32.inc
 
 
.data
buffer BYTE 500 dup(?)
bufSize DWORD ($-buffer)-1
errMsg BYTE "Cannot open file.",0dh,0ah,0
fileprompt BYTE "Enter file to display",0dh,0ah,0
filename BYTE 100 dup(?)
fileHandle DWORD ?
byteCount DWORD ?
lines BYTE 0
asdf BYTE ?
 
.code
main PROC
	mov edx,OFFSET fileprompt
	call WriteString
	mov edx,OFFSET filename
	mov ecx,99
	call ReadString
	invoke CreateFile,ADDR filename,GENERIC_READ,DO_NOT_SHARE,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,0
	mov fileHandle,eax
	cmp eax,INVALID_HANDLE_VALUE
	jne disploop
	mov edx,OFFSET errMsg
	call WriteString
	jmp QuitNow
disploop:
	invoke ReadFile,fileHandle,ADDR buffer,bufSize,ADDR byteCount,NULL
	cmp byteCount,0
	je atEOF
	mov edi,0
s:
	mov esi,byteCount
	mov buffer[esi],0
	mov al,buffer[edi]
	mov asdf,al
	mov edx,OFFSET asdf
	call WriteString
	cmp buffer[edi],13
	jne cm
	inc lines
	cmp lines,20
	je p
	jmp cm
p:
	mov lines,0
	pause
cm:
	cmp byteCount,0
	je disploop
	inc edi
	jmp s
atEOF:
	invoke CloseHandle,fileHandle
QuitNow:
	exit
main ENDP
 
END main
TITLE MASM Template						(main.asm)

; Description:
; 
; Revision date:

INCLUDE Irvine32.inc


.data
buffer BYTE 500 dup(?)
bufSize DWORD ($-buffer)-1
errMsg BYTE "Cannot open file.",0dh,0ah,0
fileprompt BYTE "Enter file to display",0dh,0ah,0
filename BYTE 100 dup(?)
fileHandle DWORD ?
byteCount DWORD ?
lines BYTE 0
asdf BYTE ?

.code
main PROC
	mov edx,OFFSET fileprompt
	call WriteString
	mov edx,OFFSET filename
	mov ecx,99
	call ReadString
	invoke CreateFile,ADDR filename,GENERIC_READ,DO_NOT_SHARE,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,0
	mov fileHandle,eax
	cmp eax,INVALID_HANDLE_VALUE
	jne disploop
	mov edx,OFFSET errMsg
	call WriteString
	jmp QuitNow
disploop:
	invoke ReadFile,fileHandle,ADDR buffer,bufSize,ADDR byteCount,NULL
	cmp byteCount,0
	je atEOF
	mov edi,0
s:
	mov esi,byteCount
	mov buffer[esi],0
	mov al,buffer[edi]
	mov asdf,al
	mov edx,OFFSET asdf
	call WriteString
	cmp buffer[edi],13
	jne cm
	inc lines
	cmp lines,20
	je p
	jmp cm
p:
	mov lines,0
	pause
cm:
	cmp byteCount,0
	je disploop
	inc edi
	jmp s
atEOF:
	invoke CloseHandle,fileHandle
QuitNow:
	exit
main ENDP

END main

The irvine32.inc is from our textbook, so hopefully you guys can help me. If you need to know parameters or anything from any of the procedures, just say so and I'll post them, but I'm fairly certain that the problem lies elsewhere.

•

Join Date: May 2006

Posts: 1,826

Reputation: ithelp is a name known to all

Solved Threads: 117

ithelp

Offline

Posting Virtuoso

Re: Assembly project problem

Apr 3rd, 2009

Have a counter increment it when it reaches 20 jmp to pause.

•

Join Date: Apr 2009

Posts: 2

Reputation: Matt23488 is an unknown quantity at this point

Solved Threads: 0

Matt23488

Offline

Newbie Poster

Re: Assembly project problem

Apr 3rd, 2009

•

Originally Posted by ithelp

Have a counter increment it when it reaches 20 jmp to pause.

I have that:

 Help with Code Tags 
 Assembly Syntax (Toggle Plain Text) 
        inc lines
	cmp lines,20
	je p
	jmp cm
p:
	mov lines,0
	pause
        inc lines
	cmp lines,20
	je p
	jmp cm
p:
	mov lines,0
	pause

but it doesn't work.