EdkCompatibilityPkg/Foundation/Library/EdkIIGlueLib/Library/BaseLib/HighBitSet64.c

   1 /*++
   2
   3 Copyright (c) 2004 - 2006, Intel Corporation. All rights reserved.<BR>
   4 This program and the accompanying materials
   5 are licensed and made available under the terms and conditions of the BSD License
   6 which accompanies this distribution.  The full text of the license may be found at
   7 http://opensource.org/licenses/bsd-license.php
   8
   9 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  10 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  11
  12
  13 Module Name:
  14
  15   HighBitSet64.c
  16
  17 Abstract:
  18
  19   Math worker functions.
  20
  21 --*/
  22
  23 #include "BaseLibInternals.h"
  24
  25 /**
  26   Returns the bit position of the highest bit set in a 64-bit value. Equivalent
  27   to log2(x).
  28
  29   This function computes the bit position of the highest bit set in the 64-bit
  30   value specified by Operand. If Operand is zero, then -1 is returned.
  31   Otherwise, a value between 0 and 63 is returned.
  32
  33   @param  Operand The 64-bit operand to evaluate.
  34
  35   @return Position of the highest bit set in Operand if found.
  36   @retval -1  Operand is zero.
  37
  38 **/
  39 INTN
  40 EFIAPI
  41 HighBitSet64 (
  42   IN      UINT64                    Operand
  43   )
  44 {
  45   if (Operand == (UINT32)Operand) {
  46     //
  47     // Operand is just a 32-bit integer
  48     //
  49     return HighBitSet32 ((UINT32)Operand);
  50   }
  51
  52   //
  53   // Operand is really a 64-bit integer
  54   //
  55   if (sizeof (UINTN) == sizeof (UINT32)) {
  56     return HighBitSet32 (((UINT32*)&Operand)[1]) + 32;
  57   } else {
  58     return HighBitSet32 ((UINT32)RShiftU64 (Operand, 32)) + 32;
  59   }
  60 }