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argv.asm
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Assembly Source File
|
1991-10-24
|
3KB
|
165 lines
;
extrn PSP:word
;
StdGrp group stdlib,stddata
stddata segment para public 'sldata'
stddata ends
;
stdlib segment para public 'slcode'
assume cs:stdgrp
;
extrn sl_malloc:far
;
; Argv- Returns a string containing a specified command line
; parameter.
;
; inputs:
;
; AX- Contains the number of the parameter you wish to obtain.
; PSP- Global variable which must point at the PSP.
;
;
; Outputs:
;
; ES:DI- Points at the newly allocated string on the heap which contains
; the command line parameter.
;
;
cr equ 13
;
;
public sl_Argv
;
sl_Argv proc far
push ds
push si
push ax
push cx
;
mov si, seg PSP
mov ds, si
mov ds, ds:PSP
;
; Skip to the first parameter
;
mov si, 80h ;Pointer to start of cmd line-1
CntLoop: inc si ;Move on to next char.
cmp byte ptr [si], ' ' ;Skip all spaces here.
je CntLoop
;
mov cl, [si]
cmp cl, cr ;See if carriage return
je NoSuchParm
;
; We just encountered an argument, is it the one we want?
;
dec ax
jz GrabThisOne
;
; If this isn't the argument we want, skip it.
;
cmp cl, '"' ;See if it's a string.
je GotString
cmp cl, "'"
je GotString
;
; If not a string, skip to next space or CR.
;
SkipWord: inc si
cmp byte ptr [si], ' '
je CntLoop
cmp byte ptr [si], cr
je NoSuchParm
jmp skipWord
;
; If we've got a string, skip to the delimiter or to the end of the line.
;
GotString: inc si
cmp cl, [si] ;See if the delimiter
je CntLoop
cmp byte ptr [si], cr ;See if EOLN
jne GotString
jmp NoSuchParm
;
; If the argument counter just went to zero, return the specified string.
;
GrabThisOne: cmp cl, "'" ;Special case for strings
je GetAString
cmp cl, '"'
je GetAString
;
; This is not a parameter surrounded by quotes or apostrophes. Deal with that
; here.
;
; First, compute the length of this guy-
;
push ds
push si
mov cx, 0
CntChars: inc cx
inc si
cmp byte ptr [si], ' '
je EndOfParm
cmp byte ptr [si], cr
jne CntChars
;
EndOfParm: pop si
pop ds
;
; Okay, allocate storage for the new string
;
CopyString: inc cx ;Don't forget zero byte!
push cx
call sl_malloc
pop cx
jc ArgvDone ;Return if error.
push es
push di
rep movsb ;Copy the string
mov byte ptr es:[di-1], 0 ;Put in zero terminating byte.
pop di
pop es
clc ;Return w/no error.
jmp ArgvDone
;
;
; If the parameter is a string surrounded by " or ' then process that down
; here
;
GetAString: mov al, cl ;Save delimeter.
push ds
push si
mov cx, -1 ;Don't count quote char
CntChars2: inc cx
inc si
cmp al, [si]
je EndOfStr
cmp byte ptr [si], cr
jne CntChars2
;
EndOfStr: pop si
pop ds
inc si ;Skip delimeter
jmp CopyString
;
; If the user selected a phantom parameter, return a pointer to an
; empty string:
;
NoSuchParm: mov di, seg StdGrp:EmptyParm
mov es, di
mov di, offset StdGrp:EmptyParm
;
; Come down here when we're done:
;
ArgvDone: pop cx
pop ax
pop si
pop ds
ret
sl_Argv endp
;
EmptyParm db 0,0,0
;
stdlib ends
end