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;

;  ABSDISK.ASM

;

;  Originally published as part of The MicroFirm Function Library

;  This version released to the public domain by the author, Bob Stout

;

;  Requires MASM 5.1 or later or equivalent

;

;  Assemble with:       MASM /Mx /z ...

;                       TASM /jMASM /mx /z ...

;


%       .MODEL  memodel,C               ;Add model support via

                                        ;command line macro,

                                        ;e.g. MASM /Dmemodel=LARGE ...

        extrn   _osmajor:BYTE
        public  absdisk

        .DATA
start   dw      ?
fill    dw      0
number  dw      ?
buf     dw      ?,?

        .CODE
absdisk PROC USES SI DI BP, func:BYTE, drive:WORD, num_sec:WORD, start_sec:WORD, buffer:PTR
        mov     AX,drive        ;Get drive number in AL

        mov     AH,_osmajor     ;Load OS version in AH

        mov     CX,num_sec      ;Set up regs for DOS 3 call

        mov     DX,start_sec
    IF  @DataSize
        push    DS              ;Save DS in L & C models

        lds     BX,buffer
    ELSE
        mov     BX,buffer
    ENDIF
        cmp     AH,4            ;DOS 4+?

        jb      doint           ;No, skip it

        mov     start,DX        ;Yes, fill in DCB structure

        mov     number,CX
        mov     buf,BX
        mov     buf+2,DS
        mov     cx,-1
    IF  @DataSize               ;Point to DCB

        mov     BX,@Data
        mov     DS,BX
    ENDIF
        mov     bx,OFFSET start
doint:  mov     AH,func         ;Read or Write?

        cmp     AH,25h
        jne     skip_1
        int     25h             ;Read sector

        jmp     skip_3
skip_1: cmp     AH,26h
        jne     skip_2
        int     26h             ;Write sector

        jmp     skip_3
skip_2: stc                     ;Invalid command

        mov     AX,-1
skip_3: jc      bye             ;Error?

        mov     AX,0            ;No, return SUCCESS

bye:    add     SP,2            ;Int 25h leave the flags on the stack

    IF  @DataSize
        pop     DS              ;Restore DS in L & C models

    ENDIF
        ret

absdisk ENDP  

        end


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