Source code of Windows XP (NT5)
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title ullshr - long shift right
;***
;ullshr.asm - long shift right
;
; Copyright (c) 1985-2001, Microsoft Corporation. All rights reserved.
;
;Purpose:
; define unsigned long shift right routine
; __aullshr
;
;Revision History:
; 11-??-83 HS initial version
; 11-30-83 DFW added medium model support
; 03-12-84 DFW broke apart; added long model support
; 06-01-84 RN modified to use cmacros
; 11-28-89 GJF Fixed copyright
; 11-19-93 SMK Modified to work on 64 bit integers
; 01-17-94 GJF Minor changes to build with NT's masm386.
; 07-08-94 GJF Faster, fatter version for NT.
; 07-13-94 GJF Further improvements from JonM.
;
;*******************************************************************************
.xlist
include cruntime.inc
include mm.inc
.list
;***
;ullshr - long shift right
;
;Purpose:
; Does a unsigned Long Shift Right
; Shifts a long right any number of bits.
;
;Entry:
; EDX:EAX - long value to be shifted
; CL - number of bits to shift by
;
;Exit:
; EDX:EAX - shifted value
;
;Uses:
; CL is destroyed.
;
;Exceptions:
;
;*******************************************************************************
CODESEG
_aullshr PROC NEAR
;
; Handle shifts of 64 bits or more (if shifting 64 bits or more, the result
; depends only on the high order bit of edx).
;
cmp cl,64
jae short RETZERO
;
; Handle shifts of between 0 and 31 bits
;
cmp cl, 32
jae short MORE32
shrd eax,edx,cl
shr edx,cl
ret
;
; Handle shifts of between 32 and 63 bits
;
MORE32:
mov eax,edx
xor edx,edx
and cl,31
shr eax,cl
ret
;
; return 0 in edx:eax
;
RETZERO:
xor eax,eax
xor edx,edx
ret
_aullshr ENDP
end