MdePkg/Library/BaseMemoryLib/CompareMemWrapper.c

/** @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 - 2018, Intel Corporation. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#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);
}