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 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
