Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!decwrl!ucbvax!ucsd!nosc!cod!murphys
From: murphys@cod.NOSC.MIL (Steven P. Murphy)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Passing pointers in C to 8086 assembler
Message-ID: <1076@cod.NOSC.MIL>
Date: 27 Apr 88 16:31:07 GMT
References: <7759@ihlpa.ATT.COM>
Organization: Naval Ocean Systems Center, San Diego
Lines: 62





The following example should help

if any errors are found let me know (I'm trying to do the same thing)


Assume MSC 5.0 & MASM 5.0   small model

main()
{
    char msg[12] = "Hello World";     /* 11 char + \0 */
    sub(msg);			      /* C always passes arrays by address */
}


DOSSEG
.CODE
    PUBLIC _sub
_sub	PROC	NEAR
    push    bp
    mov     bp,sp
    push    si
    push    di

    mov     ax,DGROUP	    ; DGROUP is the compiler's name for data seg
    mov     ds,ax	    ; ds now holds data seg ( just a guarantee)
    mov     si,[bp+4]	    ; load offset to msg[0] into si
			    ; now ds:si is the full address of msg
    lodsb		    ; LOaD String Byte, pointed to by ds:si into al
			    ; lodsb also automaticly increments si to point
			    ; to next byte in msg

; first char is now in al do what you what then lodsb to get next char
;
; suggestion:
;		also pass char count and load it into cx then you can
;		use the loop instruction's and lodsb's auto increment feature
;		to go through the whole string


    pop     di
    pop     si
    pop     bp
    ret
_sub	endp
    end


------------------------------------------- 
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------------------------

S. P. Murphy
Internet: murphys@cod.nosc.mil      UUCP: {ucbvax,hplabs}!sdcsvax!nosc!murphys