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      1 /** @file
      2   CompareMem() implementation.
      3 
      4   The following BaseMemoryLib instances contain the same copy of this file:
      5     BaseMemoryLib
      6     BaseMemoryLibMmx
      7     BaseMemoryLibSse2
      8     BaseMemoryLibRepStr
      9     BaseMemoryLibOptDxe
     10     BaseMemoryLibOptPei
     11     PeiMemoryLib
     12     UefiMemoryLib
     13 
     14 Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
     15 This program and the accompanying materials
     16 are licensed and made available under the terms and conditions of the BSD License
     17 which accompanies this distribution.  The full text of the license may be found at
     18 http://opensource.org/licenses/bsd-license.php.
     19 
     20 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
     21 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
     22 
     23 **/
     24 
     25 #include "MemLibInternals.h"
     26 
     27 /**
     28   Compares the contents of two buffers.
     29 
     30   This function compares Length bytes of SourceBuffer to Length bytes of DestinationBuffer.
     31   If all Length bytes of the two buffers are identical, then 0 is returned.  Otherwise, the
     32   value returned is the first mismatched byte in SourceBuffer subtracted from the first
     33   mismatched byte in DestinationBuffer.
     34 
     35   If Length > 0 and DestinationBuffer is NULL, then ASSERT().
     36   If Length > 0 and SourceBuffer is NULL, then ASSERT().
     37   If Length is greater than (MAX_ADDRESS - DestinationBuffer + 1), then ASSERT().
     38   If Length is greater than (MAX_ADDRESS - SourceBuffer + 1), then ASSERT().
     39 
     40   @param  DestinationBuffer The pointer to the destination buffer to compare.
     41   @param  SourceBuffer      The pointer to the source buffer to compare.
     42   @param  Length            The number of bytes to compare.
     43 
     44   @return 0                 All Length bytes of the two buffers are identical.
     45   @retval Non-zero          The first mismatched byte in SourceBuffer subtracted from the first
     46                             mismatched byte in DestinationBuffer.
     47 
     48 **/
     49 INTN
     50 EFIAPI
     51 CompareMem (
     52   IN CONST VOID  *DestinationBuffer,
     53   IN CONST VOID  *SourceBuffer,
     54   IN UINTN       Length
     55   )
     56 {
     57   if (Length == 0 || DestinationBuffer == SourceBuffer) {
     58     return 0;
     59   }
     60   ASSERT (DestinationBuffer != NULL);
     61   ASSERT (SourceBuffer != NULL);
     62   ASSERT ((Length - 1) <= (MAX_ADDRESS - (UINTN)DestinationBuffer));
     63   ASSERT ((Length - 1) <= (MAX_ADDRESS - (UINTN)SourceBuffer));
     64 
     65   return InternalMemCompareMem (DestinationBuffer, SourceBuffer, Length);
     66 }
     67