'===========================================================================
' Subject: FAR STRING ADDRESS                Date: 09-24-92 (15:03)       
' Author:  Tony Elliott                      Code: ASM, QB, PDS           
' Keys:    FAR,STRING,ADDRESS              Packet: TEXT.ABC
'===========================================================================
'From Basic
DECLARE SUB FarStringInfo (A$, Segment%, Offset%, Length%)
A$ = "Xyz123"
CALL FarStringInfo(A$, Segment%, Offset%, Length%)
PRINT "String's address: "; HEX$(Segment%); ":"; HEX$(Offset%)
PRINT "          Length:"; Length%
END

; ------------- Asm code here....

.Model Medium               ;I'll avoid the simplified ",BASIC" since
                            ; it's doubtful that A86 supports it.

Extrn StringLength :Far     ;A PDS/VBDOS API function call
Extrn StringAddress:Far     ;Ditto

.Code                       ;Code segment begins here

Public FarStringInfo
FarStringInfo proc far

    AString equ [bp+0ch]    ;We'll use equates to reference our parameters.
    Segm    equ [bp+0ah]    ;This just makes the code easier to read and
    Ofs     equ [bp+8]      ; maintain (should we add or remove parameters
    Leng    equ [bp+6]      ; in the future, we just need to change the
    Params  = 8             ; assignments here).

    push BP
    mov     bp,sp           ;Set up a stack frame

    push    ds              ;Save critical registers (even though in this
    push    si              ; example we don't change them).
    push di

    mov     ax,AString      ;Pointer to near descriptor into ax
    push    ax              ;Push two copies; 1 for StringLength and
    push    ax              ; another to StringAddress
    call    StringLength    ;Returns length of A$ in AX
    mov     bx,Leng         ;Pointer to Length% into BX
    mov     [bx],ax         ;Plug string length into Length%
    call    StringAddress   ;Returns far address to string data in
dx: AX
    mov     bx,Segm         ;Pointer to Segment% into bx
    mov     [bx],dx         ;String segment into Segment%
    mov     bx,Ofs          ;Pointer to Offset% into bx
    mov     [bx],ax         ;String offset into Offset%

    pop     di              ;Restore the registers we saved above
    pop si
    pop ds
    pop     bp              ;Restoring BP removes the "frame"
    ret     Params          ;Return to BASIC, popping parameters off of
                            ; the stack.
FarStringInfo endp
END