1 /** @file
2 Math worker functions.
3
4 Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
5 This program and the accompanying materials
6 are licensed and made available under the terms and conditions of the BSD License
7 which accompanies this distribution. The full text of the license may be found at
8 http://opensource.org/licenses/bsd-license.php.
9
10 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
11 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
12
13 **/
14
15
16
17
18 #include "BaseLibInternals.h"
19
20 /**
21 Returns the bit position of the highest bit set in a 32-bit value. Equivalent
22 to log2(x).
23
24 This function computes the bit position of the highest bit set in the 32-bit
25 value specified by Operand. If Operand is zero, then -1 is returned.
26 Otherwise, a value between 0 and 31 is returned.
27
28 @param Operand The 32-bit operand to evaluate.
29
30 @retval 0..31 Position of the highest bit set in Operand if found.
31 @retval -1 Operand is zero.
32
33 **/
34 INTN
35 EFIAPI
HighBitSet32(IN UINT32 Operand)36 HighBitSet32 (
37 IN UINT32 Operand
38 )
39 {
40 INTN BitIndex;
41
42 if (Operand == 0) {
43 return - 1;
44 }
45 for (BitIndex = 31; (INT32)Operand > 0; BitIndex--, Operand <<= 1);
46 return BitIndex;
47 }
48