Category : C++ Source Code
Archive   : VCCRT1.ZIP
Filename : AULSHR.ASM

page ,132
title aulshr - assigning unsigned long shift right
;***
;aulshr.asm - Assigning Unsigned Long Shift Right routine
;
; Copyright (c) 1985-1992, Microsoft Corporation. All rights reserved.
;
;Purpose:
; defines assigning unsigned long shift right routines
; creates the following routines:
; __aFFaulshr (large model)
; __aFNaulshr (medium model)
; __aNFaulshr (compact model)
; __aNNaulshr (small model)
;
;*******************************************************************************

.xlist
include version.inc
include cmacros.inc
include mm.inc
include cmphlp.inc
.list

sBegin code
assumes cs,code
assumes ds,data

page
;***
;aulshr - assigning unsigned long shift right
;
;Purpose:
; does a unsigned long shift right, assigning the result to the dividend.
; calls ulshr to do all the real work
;
;Entry:
; parameters passed on stack as follows:
; 1st pushed: shift count (WORD)
; 2nd pushed: address of unsigned long to be shifted
; (DWORD in models C,L; WORD in models S,M)
;
;Exit:
; the unsigned long is updated
; NOTE: parameters are removed from stack by this routine
;
;Uses:
; AX, CX, DX
;
;Exceptions:
;
;*******************************************************************************

aASGN ulshr

; Move arguments into registers and invoke the regular shift routine, ulshr,
; to do the work. The local stack looks as follows after it has been set up:
;
; -------------------------
; | |
; |-----------------------|
; | shift count |
; |-----------------------|
; |pointer to long value**|
; |-----------------------|
; | return address* |
; |-----------------------|
;BP,SP-->| old BP |
; |-----------------------|
; | |
; -------------------------
;
; * - 2 bytes if small/compact model; 4 bytes if medium/large model
; ** - 2 bytes if small/medium model; 4 bytes if large/compact model

PNTR equ BPARGBAS[bp] ; stack addr. of data pointer
SHFTCNT equ DAT_ADDR_SZ+BPARGBAS[bp] ; stack addr. of shift count
VAL equ [bx] ; address of data value

if sizeD
push ds
endif
push bx

LOAD bx,PNTR ; get pointer to data into bx or ds:bx
mov ax,LOWORD(VAL) ; dx:ax <- long data value
mov dx,HIWORD(VAL)
mov cx,SHFTCNT ; cx <- shift count

callnahlpr ulshr ; use __a?ulshr to do the actual shifting

; store away shifted value and return

mov LOWORD(VAL),ax ; store shifted value
mov HIWORD(VAL),dx

pop bx
if sizeD
pop ds
endif

cEnd nolocals
return 2+DAT_ADDR_SZ

sEnd

end