CSC231 readWriteTextFile.asm

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---

;;; readWriteTextFile.asm
;;; D. Thiebaut
;;; Combining readTextFile.asm and writeTextFile.asm
;;; This program reads the contents of a text file,
;;; transforms all of its characters to uppercase, then
;;; stores the result back in the file.
;;; 
%assign SYS_EXIT	1
%assign SYS_WRITE	4
%assign SYS_READ	3
%assign SYS_LSEEK	19
%assign SEEKSET	0
%assign STDOUT		1
%assign SYS_OPEN   5
%assign SYS_CLOSE	6
%assign SYS_CREATE	8


%assign O_RDONLY	000000q
%assign O_WRONLY        000001q	
%assign O_RDWR          000002q
%assign O_CREAT		000100q

%assign S_IRUSR		00400q
%assign S_IWUSR		00200q
%assign S_IXUSR		00100q

;;; --- MACRO -----------------------------------------------
;;;     print           msg,length
%macro  print           2               ; %1 = address %2 = # of chars
        pushad                          ; save all registers
        mov             edx,%2
        lea             ecx,[%1]
        mov             eax,SYS_WRITE
        mov             ebx,STDOUT
        int             0x80
        popad                           ; restore all registers
%endmacro

;;; --- MACRO -----------------------------------------------
;;;     print2        "quoted string"
%macro  print2        1               ; %1 = immediate string,
        section .data
%%str   db              %1
%%strL  equ             $-%%str
        section .text
        print           %%str, %%strL
%endmacro
	
;;; --- MACRO -----------------------------------------------
;;; 	createFile filename,  handle
%macro	createFile 2
	mov	eax,SYS_CREATE
	mov	ebx,%1
	mov	edx, S_IRUSR|S_IWUSR|S_IXUSR
	int	0x80

	test	eax,eax
	jns	%%createfile
	print2  "Could not open file"
	mov	eax,SYS_EXIT
	mov	ebx,0
	int	0x80		; final system call

%%createfile:
	mov	%2,eax		; save handle
%endmacro	

	
	
;;; --- MACRO -----------------------------------------------
;;; 	openFile filename, mode, handle
%macro	openFile 3
	mov	eax,SYS_OPEN
	mov	ebx,%1
	mov	ecx,%2
	mov	edx, S_IRUSR|S_IWUSR|S_IXUSR
	int	0x80

	test	eax,eax
	jns	%%readFile
	print2  "Could not open file"
	mov	eax,SYS_EXIT
	mov	ebx,0
	int	0x80		; final system call

%%readFile:
	mov	%3,eax		; save handle
%endmacro	

	
;;; --- MACRO -----------------------------------------------
;;; 	readFile handle, buffer, buffer-length, number-bytes-read
%macro  readFile 4
	mov	eax,SYS_READ
	mov	ebx,%1		; file descriptor in bx
	mov	ecx,%2		; buffer address
	mov	edx,%3		; max number of bytes to read
	int	0x80
	mov	%4,eax		; save number bytes read
%endmacro

	
;;; --- MACRO -----------------------------------------------
;;; 	writeBuf handle, buffer, noBytesToWrite
%macro  writeFile 3
	mov	eax,SYS_WRITE
	mov	ebx,%1
	mov	ecx,%2
	mov	edx,%3
	int	0x80	
%endmacro

	
;;; --- MACRO -----------------------------------------------
;;;	close   handle
%macro	close   1
	mov	eax,SYS_CLOSE
	mov	ebx,%1
	int	0x80
%endmacro
	

        
	;; -------------------------
	;; data segment
	;; -------------------------

	section	.data
fileName db     "test.dat",0
handle   dd     0
noRead   dd     0
        
        section .bss
MAXBUF  equ     100000
buffer  resb    MAXBUF          ; 100,000 bytes of storage

	;; -------------------------
	;; code area
	;; -------------------------

	section	.text
	global	_start

_start:
;;; open the file and put its contents in Buffer.
;;; keep track of # of bytes read in noRead
        
        openFile        fileName, O_RDWR,  [handle]
        readFile        [handle], buffer, MAXBUF, [noRead]
        close           [handle]

;;; transform buffer to uppercase
        
        call            toUpper

;;; write contents of buffer (noRead bytes) to same
;;; file
        
        createFile      fileName, [handle]
        writeFile       [handle], buffer, [noRead]
        close           [handle]
         
	;; exit()

	mov	eax,SYS_EXIT
	mov	ebx,0
	int	0x80		; final system call

;;; -----------------------------------------------------------
;;; toUpper: transforms all the chars in buffer to uppercase.
;;;          variable noRead contains # of valid chars.
;;; -----------------------------------------------------------
toUpper:
        mov     ecx,[noRead]    ; get # of chars
        mov     ebx,buffer      ; point to 1st char
.for:   cmp     byte[ebx],'a'   ; less than 'a'?
        jb      .next
        cmp     byte[ebx],'z'   ; greater than 'z'?
        ja      .next            
        add     byte[ebx],'A'-'a' ; no... change it
.next:  inc     ebx
        loop    .for
        ret