Category : C++ Source Code
Archive   : VCCRT2.ZIP
Filename : D_SEEK.ASM

page ,132
title d_seek - Position file pointer
;***
;d_seek.asm - Position file pointer
;
; Copyright (c) 1992, Microsoft Corporation. All rights reserved.
;
;Purpose:
; Direct interface to DOS "move file pointer" system call.
;
;*******************************************************************************


include version.inc
.xlist
include cmacros.inc
include msdos.inc
.list

sBegin code

assumes cs,code
assumes ds,data

extrn __dosretax:near

page
;***
;unsigned long _dos_seek(handle, offset, origin) - Seek file pointer
;
;Purpose:
; Seek file pointer: Direct interface to the DOS "move file pointer"
; system call (int 21h, 42h).
;
;Entry:
; int handle = open file handle
; unsigned long offset = offset of new position relative to the origin
; specified below
; int origin = 0 (seek relative to beginning of the file)
; 1 (seek relative to current file position)
; 2 (seek relative to end of file)
;
;Exit:
; If successful, the offset, in bytes, from the beginning of the file
; is returned.
; Otherwise, returns (unsigned long)(-1L) and sets __doserrno/errno.
;
;Uses:
; AX, BX, CX, DX
;
;Exceptions:
; None
;
;*******************************************************************************

cProc _dos_seek,,<>

parmW handle
parmD offst
parmW origin

cBegin

;Get the user's values

mov bx,handle
mov dx,word ptr [offst]
mov cx,word ptr [offst + 2]
mov ax,origin ;seek origin

;Issue the move file pointer system call

callos lseek

jmp __dosretax ;return 0 if successful

cEnd

sEnd
end