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;/*++
;
;Copyright (c) 2006, Intel Corporation. All rights reserved.<BR>
;This program and the accompanying materials
;are licensed and made available under the terms and conditions of the BSD License
;which accompanies this distribution. The full text of the license may be found at
;http://opensource.org/licenses/bsd-license.php
;
;THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
;WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
;
;Module Name:
;
; GetPowerOfTwo.c
;
;Abstract:
;
; Calculates the largest integer that is both
; a power of two and less than Input
;
;--*/
;---------------------------------------------------------------------------
.686
.model flat,C
.code
;---------------------------------------------------------------------------
;UINT64
;GetPowerOfTwo (
; IN UINT64 Input
; )
;/*++
;
;Routine Description:
;
; Calculates the largest integer that is both
; a power of two and less than Input
;
;Arguments:
;
; Input - value to calculate power of two
;
;Returns:
;
; the largest integer that is both a power of
; two and less than Input
;
;--*/
GetPowerOfTwo PROC
xor eax, eax
mov edx, eax
mov ecx, [esp + 8] ; dword ptr Input[4]
jecxz _F
bsr ecx, ecx
bts edx, ecx
jmp _Exit
_F:
mov ecx, [esp + 4] ; dword ptr Input[0]
jecxz _Exit
bsr ecx, ecx
bts eax, ecx
_Exit:
ret
GetPowerOfTwo ENDP
END
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