MdePkg/Library/BaseMemoryLib/CopyMem.c

   1 /** @file
   2   Implementation of the EfiCopyMem routine. This function is broken
   3   out into its own source file so that it can be excluded from a
   4   build for a particular platform easily if an optimized version
   5   is desired.
   6
   7   Copyright (c) 2006, Intel Corporation<BR>
   8   All rights reserved. This program and the accompanying materials
   9   are licensed and made available under the terms and conditions of the BSD License
  10   which accompanies this distribution.  The full text of the license may be found at
  11   http://opensource.org/licenses/bsd-license.php
  12
  13   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  14   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  15
  16 **/
  17
  18 //
  19 // Include common header file for this module.
  20 //
  21
  22
  23 #include "MemLibInternals.h"
  24
  25 /**
  26   Copy Length bytes from Source to Destination.
  27
  28   @param  Destination Target of copy
  29   @param  Source Place to copy from
  30   @param  Length Number of bytes to copy
  31
  32   @return Destination
  33
  34 **/
  35 VOID *
  36 EFIAPI
  37 InternalMemCopyMem (
  38   OUT     VOID                      *Destination,
  39   IN      CONST VOID                *Source,
  40   IN      UINTN                     Length
  41   )
  42 {
  43   //
  44   // Declare the local variables that actually move the data elements as
  45   // volatile to prevent the optimizer from replacing this function with
  46   // the intrinsic memcpy()
  47   //
  48   volatile UINT8                    *Destination8;
  49   CONST UINT8                       *Source8;
  50
  51   if (Source > Destination) {
  52     Destination8 = (UINT8*)Destination;
  53     Source8 = (CONST UINT8*)Source;
  54     while (Length-- != 0) {
  55       *(Destination8++) = *(Source8++);
  56     }
  57   } else if (Source < Destination) {
  58     Destination8 = (UINT8*)Destination + Length;
  59     Source8 = (CONST UINT8*)Source + Length;
  60     while (Length-- != 0) {
  61       *(--Destination8) = *(--Source8);
  62     }
  63   }
  64   return Destination;
  65 }