memmove.c

上一个上传的有问题,这个是好的。visopsys包括系统内核和GUI的全部SOURCE code ,还包括一些基本的docs文档。里面src子目录对应所有SOURCE code.对于想研究操作系统的朋

// 
//  Visopsys
//  Copyright (C) 1998-2007 J. Andrew McLaughlin
//  
//  This library is free software; you can redistribute it and/or modify it
//  under the terms of the GNU Lesser General Public License as published by
//  the Free Software Foundation; either version 2.1 of the License, or (at
//  your option) any later version.
//
//  This library is distributed in the hope that it will be useful, but
//  WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser
//  General Public License for more details.
//
//  You should have received a copy of the GNU Lesser General Public License
//  along with this library; if not, write to the Free Software Foundation,
//  Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//
//  memmove.c
//

// This is the standard "memmove" function, as found in standard C libraries

#include <string.h>


void *memmove(void *dest, const void *src, size_t len)
{
  // The memmove() function copies n bytes from memory area src to memory
  // area dest.  The memory areas may overlap.

  size_t count = 0;

  if (dest == src)
    // ...Okay then...
    return (dest);

  // In case the memory areas overlap, we will copy the data differently
  // depending on the position of the src and dest pointers
  else if (dest < src)
    {
      for (count = 0; count < len; count ++)
	((char *) dest)[count] = ((char *) src)[count];
    }
  else
    {
      count = (len - 1);
      while(1)
	{
	  ((char *) dest)[count] = ((char *) src)[count];

	  if (count == 0)
	    break;

	  count--;
	}
    }

      
  return (dest);
}