MdePkg/Library/BaseLib/LowBitSet32.c

   1 /** @file
   2   Math worker functions.
   3
   4   Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
   5   SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9 #include "BaseLibInternals.h"
  10
  11 /**
  12   Returns the bit position of the lowest bit set in a 32-bit value.
  13
  14   This function computes the bit position of the lowest bit set in the 32-bit
  15   value specified by Operand. If Operand is zero, then -1 is returned.
  16   Otherwise, a value between 0 and 31 is returned.
  17
  18   @param  Operand The 32-bit operand to evaluate.
  19
  20   @retval 0..31  The lowest bit set in Operand was found.
  21   @retval -1     Operand is zero.
  22
  23 **/
  24 INTN
  25 EFIAPI
  26 LowBitSet32 (
  27   IN      UINT32  Operand
  28   )
  29 {
  30   INTN  BitIndex;
  31
  32   if (Operand == 0) {
  33     return -1;
  34   }
  35
  36   for (BitIndex = 0; 0 == (Operand & 1); BitIndex++, Operand >>= 1) {
  37   }
  38
  39   return BitIndex;
  40 }