/** @file
  CompareMem() implementation.

  The following BaseMemoryLib instances contain the same copy of this file:
    BaseMemoryLib
    BaseMemoryLibMmx
    BaseMemoryLibSse2
    BaseMemoryLibRepStr
    BaseMemoryLibOptDxe
    BaseMemoryLibOptPei
    PeiMemoryLib
    UefiMemoryLib

Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD License
which accompanies this distribution.  The full text of the license may be found at
http://opensource.org/licenses/bsd-license.php.

THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

**/

#include "MemLibInternals.h"

/**
  Compares the contents of two buffers.

  This function compares Length bytes of SourceBuffer to Length bytes of DestinationBuffer.
  If all Length bytes of the two buffers are identical, then 0 is returned.  Otherwise, the
  value returned is the first mismatched byte in SourceBuffer subtracted from the first
  mismatched byte in DestinationBuffer.
  
  If Length > 0 and DestinationBuffer is NULL, then ASSERT().
  If Length > 0 and SourceBuffer is NULL, then ASSERT().
  If Length is greater than (MAX_ADDRESS - DestinationBuffer + 1), then ASSERT().
  If Length is greater than (MAX_ADDRESS - SourceBuffer + 1), then ASSERT().

  @param  DestinationBuffer A pointer to the destination buffer to compare.
  @param  SourceBuffer      A pointer to the source buffer to compare.
  @param  Length            The number of bytes to compare.

  @return 0                 All Length bytes of the two buffers are identical.
  @retval Non-zero          The first mismatched byte in SourceBuffer subtracted from the first
                            mismatched byte in DestinationBuffer.
                            
**/
INTN
EFIAPI
CompareMem (
  IN CONST VOID  *DestinationBuffer,
  IN CONST VOID  *SourceBuffer,
  IN UINTN       Length
  )
{
  if (Length == 0 || DestinationBuffer == SourceBuffer) {
    return 0;
  }
  ASSERT (DestinationBuffer != NULL);
  ASSERT (SourceBuffer != NULL);
  ASSERT ((Length - 1) <= (MAX_ADDRESS - (UINTN)DestinationBuffer));
  ASSERT ((Length - 1) <= (MAX_ADDRESS - (UINTN)SourceBuffer));

  return InternalMemCompareMem (DestinationBuffer, SourceBuffer, Length);
}