MdePkg/Library/BaseMemoryLib/CopyMem.c

   1 /** @file
   2   Implementation of the InternalMemCopyMem routine. This function is broken
   3   out into its own source file so that it can be excluded from a build for a
   4   particular platform easily if an optimized version is desired.
   5
   6   Copyright (c) 2006 - 2008, Intel Corporation<BR>
   7   All rights reserved. This program and the accompanying materials
   8   are licensed and made available under the terms and conditions of the BSD License
   9   which accompanies this distribution.  The full text of the license may be found at
  10   http://opensource.org/licenses/bsd-license.php
  11
  12   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  13   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  14
  15 **/
  16
  17
  18
  19
  20 #include "MemLibInternals.h"
  21
  22 /**
  23   Copy Length bytes from Source to Destination.
  24
  25   @param  Destination Target of copy
  26   @param  Source      Place to copy from
  27   @param  Length      Number of bytes to copy
  28
  29   @return Destination
  30
  31 **/
  32 VOID *
  33 EFIAPI
  34 InternalMemCopyMem (
  35   OUT     VOID                      *Destination,
  36   IN      CONST VOID                *Source,
  37   IN      UINTN                     Length
  38   )
  39 {
  40   //
  41   // Declare the local variables that actually move the data elements as
  42   // volatile to prevent the optimizer from replacing this function with
  43   // the intrinsic memcpy()
  44   //
  45   volatile UINT8                    *Destination8;
  46   CONST UINT8                       *Source8;
  47
  48   if (Source > Destination) {
  49     Destination8 = (UINT8*)Destination;
  50     Source8 = (CONST UINT8*)Source;
  51     while (Length-- != 0) {
  52       *(Destination8++) = *(Source8++);
  53     }
  54   } else if (Source < Destination) {
  55     Destination8 = (UINT8*)Destination + Length;
  56     Source8 = (CONST UINT8*)Source + Length;
  57     while (Length-- != 0) {
  58       *(--Destination8) = *(--Source8);
  59     }
  60   }
  61   return Destination;
  62 }