MdePkg/Library/BaseLib/Ia32/InterlockedCompareExchange32.c

   1 /** @file
   2   InterlockedCompareExchange32 function
   3
   4   Copyright (c) 2006 - 2007, 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 // Include common header file for this module.
  17 //
  18
  19
  20 /**
  21   Performs an atomic compare exchange operation on a 32-bit unsigned integer.
  22
  23   Performs an atomic compare exchange operation on the 32-bit unsigned integer
  24   specified by Value.  If Value is equal to CompareValue, then Value is set to
  25   ExchangeValue and CompareValue is returned.  If Value is not equal to CompareValue,
  26   then Value is returned.  The compare exchange operation must be performed using
  27   MP safe mechanisms.
  28
  29   @param  Value         A pointer to the 32-bit value for the compare exchange
  30                         operation.
  31   @param  CompareValue  32-bit value used in compare operation.
  32   @param  ExchangeValue 32-bit value used in exchange operation.
  33
  34   @return The original *Value before exchange.
  35
  36 **/
  37 UINT32
  38 EFIAPI
  39 InternalSyncCompareExchange32 (
  40   IN      UINT32                    *Value,
  41   IN      UINT32                    CompareValue,
  42   IN      UINT32                    ExchangeValue
  43   )
  44 {
  45   _asm {
  46     mov     ecx, Value
  47     mov     eax, CompareValue
  48     mov     edx, ExchangeValue
  49     lock    cmpxchg [ecx], edx
  50   }
  51 }
  52