program example 1 - prince of songkla universitystaff.cs.psu.ac.th/iew//cs344-321/example2.doc ·...

CS344-321 Assembly Language Programming example2 page

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Figure 2-4.

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ARGC.ASM, a routine that returns the number of command-tail arguments.---------------------------------------------------------------------------------------------------

title ARGC.ASM --- Return Number of Arguments

page55,132

; ARGC.ASM --- Return number of command line arguments. Treats blanks; and tabs as whitespace, carriage return as terminator,; text enclosed in quotation marks as a single argument.;; Copyright (C) 1989 Ray Duncan;; Call with: ES:BX = command line;; Returns: AX = argument count (always >=1);; Destroys: Nothing

cr equ 0dh ; ASCII carriage returnlf equ 0ah ; ASCII line feedtab equ 09h ; ASCII tabblank equ 20h ; ASCII space characterquote equ 22h ; ASCII quote character

_TEXT segment word public 'CODE'

assume cs:_TEXT

public argcargc proc near

pushbx ; save original BX and CXpushcx ; for later

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mov ax,1 ; force count >= 1

argc1: mov cx,-1 ; set flag = outside argument

argc2: inc bx ; point to next character

cmp byte ptr es:[bx],crje argc5 ; exit if carriage

returncmp byte ptr es:[bx],quoteje argc3 ; beginning of quoted

argumentcmp byte ptr es:[bx],blankje argc1 ; outside argument if

ASCII blankcmp byte ptr es:[bx],tabje argc1 ; outside argument if

ASCII tab

; not blank, tab, or quote,jcxz argc2 ; jump if already

inside argument

inc ax ; else found argument, count it

not cx ; set flag = inside argument

jmp argc2 ; and look at next character

argc3: inc ax ; quote found, count argument

argc4: inc bx ; point to next character

cmp byte ptr es:[bx],quote ; found end of quoted argument?

je argc1 ; yes, jump

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cmp byte ptr es:[bx],cr ; found end of command line?

jne argc4 ; no, keep looking

argc5: pop cx ; restore original BX and CX

pop bxret ; return AX = argument

count

argc endp

_TEXT endsend

Figure 2-5.ARGV.ASM, a routine that returns the address and length of a specified command-tail argument

title ARGV.ASM -- Return Address and Length of Argument

page55,132

; ARGV.ASM --- Return address and length of command line argument; or fully-qualified program name. Treats blanks and tabs; as whitespace, carriage return as terminator, quoted; text as a single argument.;; Copyright (C) 1989 Ray Duncan;; Call with: ES:BX = command line address; (implicit: ES=PSP segment); AX = argument number (0 based);; Returns: ES:BX = argument address; AX = argument length; (0=argument not found);; Destroys: Nothing

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;; Note: if ARGV is called with AX=0 (argv[0]), and the host; system is MS-DOS version 3.0 or later, ARGV returns ES:BX =; address and AX = length of the fully-qualified program filename; at the end of the program's environment block. When ARGV is; called with AX=0 under MS-DOS versions 1.x and 2.x, it returns; ES:BX unchanged and AX=0.

cr equ 0dh ; ASCII carriage returnlf equ 0ah ; ASCII line feedtab equ 09h ; ASCII tabblank equ 20h ; ASCII space characterquote equ 22h ; ASCII quote character


assume cs:_TEXT

public argvargv proc near

pushcx ; save original CX and DIpushdi

or ax,ax ; is it argument 0?jz argv12 ; yes, jump to get

program name

xor ah,ah ; initialize argument counter

argv1: mov cx,-1 ; set flag = outside argument

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argv2: inc bx ; point to next character

cmp byte ptr es:[bx],crje argv9 ; exit if carriage

returncmp byte ptr es:[bx],quoteje argv7 ; beginning of quoted

argumentcmp byte ptr es:[bx],blankje argv1 ; outside argument if

ASCII blankcmp byte ptr es:[bx],tabje argv1 ; outside argument if

ASCII tab

; if not blank, tab, or quote...

jcxz argv2 ; jump if already inside argument

inc ah ; else count arguments found

cmp ah,al ; is this the right one?je argv4 ; yes, go find its

lengthnot cx ; no, set flag = inside

argumentjmp argv2 ; and look at next

character

argv4: ; found argument, calc. length

mov ax,bx ; save param. starting address


cmp byte ptr es:[bx],cr

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je argv6 ; found end if carriage return

cmp byte ptr es:[bx],blankje argv6 ; found end if ASCII

blankcmp byte ptr es:[bx],tabjne argv5 ; found end if ASCII

tab

argv6: xchg bx,ax ; set ES:BX = argument address

sub ax,bx ; and AX = argument length

jmp argv14 ; return to caller

argv7: ; start of quoted argument

inc ah ; count this argumentcmp ah,al ; is this the one we need?je argv10 ; yes, go find its

length

argv8: inc bx ; no, scan over itcmp byte ptr es:[bx],quote ; reached

trailing quote?je argv1 ; yes, found end of

argumentcmp byte ptr es:[bx],cr ; end of command

line?jne argv8 ; no, keep looking

argv9: xor ax,ax ; set AX = 0, argument not found

jmp argv14 ; return to caller

argv10: inc bx ; point to actual argument

mov ax,bx ; save its starting address

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cmp byte ptr es:[bx],crje argv6 ; found end if

carriage returncmp byte ptr es:[bx],quoteje argv6 ; found end if quote

markjmp argv11 ; keep looking

argv12: ; special handling for parameter 0

mov ax,3000h ; check if DOS 3.0 or laterint 21h ; (force AL=0 in case DOS

1)cmp al,3jb argv9 ; DOS 1 or 2, return

nothing

mov es,es:[2ch] ; get environment segment from PSP

xor di,di ; find the program name by

xor al,al ; first skipping over all themov cx,-1 ; environment variables...cld

argv13: repne scasb ; scan for double null (can't use

scasb ; (SCASW since might be odd addr.)

jne argv13 ; loop if it was a single null

add di,2 ; skip count word in environment

mov bx,di ; save program name address

mov cx,-1 ; now find its length...repne scasb ; scan for another

null byte

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not cx ; convert CX to lengthdec cxmov ax,cx ; return length in AX

argv14: ; common exit pointpop di ; restore registerspop cxret ; return to caller

argv endp

_TEXT ends

end

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Program TRYARGS.ASM title TRYARGS -- Demo of ARGC.ASM and

ARGV.ASM page 55,132

; TRYARGS.ASM --- Demonstration of command line argument; parsing by ARGC.ASM and ARGV.ASM;; Copyright (C) 1989 Ray Duncan;; Build with: MAKE TRYARGS

stdinequ 0 ; standard input handlestdout equ 1 ; standard output handlestderr equ 2 ; standard error handle

cmdtail equ 80h ; PSP offset of command tail

cr equ 0dh ; ASCII carriage returnlf equ 0ah ; ASCII line feedblank equ 020h ; ASCII blanktab equ 09h ; ASCII tab

DGROUP group _DATA,STACK


assume cs:_TEXT,ds:DGROUP,ss:STACK

extrn argc:nearextrn argv:near

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mainproc far

mov ax,DGROUP ; make our data segment

mov ds,ax ; addressable

mov psp,es ; save segment of PSP

mov bx,cmdtail ; ES:BX = command tail

call argc ; get number of command; line arguments

mov pars,ax ; and save it

mov bx,offset msg1a ; convert count to ASCII

call b2dec ; for output

mov dx,offset msg1 ; display the number of

mov cx,msg1_len ; command line arguments

mov bx,stdoutmov ah,40hint 21h

main1: mov ax,count ; display next argument

cmp ax,pars ; are we all done?je main2 ; yes, exit

mov bx,offset msg2a ; no, convert argument number

call b2dec

mov dx,offset msg2 ; and display the number

mov cx,msg2_lenmov bx,stdout

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mov ah,40hint 21h

mov ax,count ; now get the actual argument

mov es,psp ; ES:BX = command tail

mov bx,cmdtailcall argv

pushds ; save our data segment and

pushes ; display argument stringpop dsmov dx,bx ; now DS:DX =

argument addrmov cx,ax ; and CX = argument

lengthmov bx,stdoutmov ah,40hint 21hpop ds ; restore our data

segment

inc word ptr count ; go to next argument

jmp main1

main2: mov ax,4c00h ; exit to MS-DOSint 21h

mainendp

;; B2DEC - Convert binary value 0-99 to two decimal ASCII characters;; Call with: AL = binary value; BX = address to store ASCII characters;

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; Returns: Nothing;; Destroys: AX;b2dec proc near

aam ; divide AL by 10, leaving; AH=quotient,

AL=remainderadd ax,'00' ; convert to ASCIImov [bx],ah ; store ten's digitmov [bx+1],al ; store one's digitret ; return to caller

b2dec endp

_TEXT ends

_DATA segment word public 'DATA'

count dw 0 ; current command line argumentpars dw 0 ; total command line argumentspsp dw 0 ; segment base address of PSP

msg1 db cr,lfdb 'The command line contains '

msg1a db 'xx arguments'msg1_len equ $-msg1

msg2 db cr,lfdb 'Argument '

msg2a db 'xx is: 'msg2_len equ $-msg2

_DATA ends

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STACK segment para stack 'STACK'

dw 64 dup (?)

STACK ends

end mainMake file of TRYARGS.ASMargv.obj : argv.asm masm /Zi /T argv;

argc.obj : argc.asm masm /Zi /T argc;

tryargs.obj : tryargs.asm masm /Zi /T tryargs;

tryargs.exe : tryargs.obj argv.obj argc.obj link /CODEVIEW tryargs+argv+argc;

Program TRYARGS.C--------------------------------------/* TRYARGS.C - Demo of C runtime library command line argument processing Copyright (C) 1989 Ray Duncan*/

#include <stdio.h>

main(int argc,char *argv[]){ int x;

printf("\nThe command line contains %d arguments", argc);

for (x=0; x<argc; x++) printf("\nArgument %d is: %s ", x, argv[x]);

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puts("");}

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program example 1 - prince of songkla universitystaff.cs.psu.ac.th/iew//cs344-321/example2.doc ·...

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