blob: 9f0d962a63a574d0cfda86582daa34fb7d40757e (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
|
TITLE GetPowerOfTwo.asm: Calculates the power of two value just below input
;------------------------------------------------------------------------------
;
; Copyright (c) 2005 Intel Corporation
; All rights reserved. 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.asm
;
; Abstract:
;
; Calculates the largest integer that is both
; a power of two and less than Input
;
;------------------------------------------------------------------------------
.686P
.XMM
.MODEL SMALL
.CODE
_GetPowerOfTwo PROC
;------------------------------------------------------------------------------
; UINT32
; _GetPowerOfTwo (
; IN UINT32 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
;------------------------------------------------------------------------------
xor eax, eax
mov edx, eax
mov ecx, [esp + 8]
jecxz @F
bsr ecx, ecx
bts edx, ecx
jmp @Exit
@@:
mov ecx, [esp + 4]
jecxz @Exit
bsr ecx, ecx
bts eax, ecx
@Exit:
ret
_GetPowerOfTwo ENDP
END
|
