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
  10
  11
  12 #include "BaseLibInternals.h"
  13
  14 /**
  15   Returns the bit position of the lowest bit set in a 32-bit value.
  16
  17   This function computes the bit position of the lowest bit set in the 32-bit
  18   value specified by Operand. If Operand is zero, then -1 is returned.
  19   Otherwise, a value between 0 and 31 is returned.
  20
  21   @param  Operand The 32-bit operand to evaluate.
  22
  23   @retval 0..31  The lowest bit set in Operand was found.
  24   @retval -1     Operand is zero.
  25
  26 **/
  27 INTN
  28 EFIAPI
  29 LowBitSet32 (
  30   IN      UINT32                    Operand
  31   )
  32 {
  33   INTN                              BitIndex;
  34
  35   if (Operand == 0) {
  36     return -1;
  37   }
  38
  39   for (BitIndex = 0; 0 == (Operand & 1); BitIndex++, Operand >>= 1);
  40   return BitIndex;
  41 }