MdePkg/Library/BaseLib/GetPowerOfTwo64.c

   1 /** @file
   2   Math worker functions.
   3
   4   Copyright (c) 2006, Intel Corporation<BR>
   5   All rights reserved. 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 value of the highest bit set in a 64-bit value. Equivalent to
  22   1 << log2(x).
  23
  24   This function computes the value of the highest bit set in the 64-bit value
  25   specified by Operand. If Operand is zero, then zero is returned.
  26
  27   @param  Operand The 64-bit operand to evaluate.
  28
  29   @return 1 << HighBitSet64(Operand)
  30   @retval 0 Operand is zero.
  31
  32 **/
  33 UINT64
  34 EFIAPI
  35 GetPowerOfTwo64 (
  36   IN      UINT64                    Operand
  37   )
  38 {
  39   if (Operand == 0) {
  40     return 0;
  41   }
  42
  43   return LShiftU64 (1, HighBitSet64 (Operand));
  44 }