root/common/libc/string/memcpy.c

DEFINITIONS

1. memcpy

   1 /*
   2  * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
   3  *      The President and Fellows of Harvard College.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  30 /*
  31  * This file is shared between libc and the kernel, so don't put anything
  32  * in here that won't work in both contexts.
  33  */
  35 #ifdef _KERNEL
  36 #include <types.h>
  37 #include <lib.h>
  38 #else
  39 #include <stdint.h>
  40 #include <string.h>
  41 #endif
  43 /*
  44  * C standard function - copy a block of memory.
  45  */
  47 void *
memcpy(void *dst, const void *src, size_t len)
  49 {
size_t i;
  52         /*
  53          * memcpy does not support overlapping buffers, so always do it
  54          * forwards. (Don't change this without adjusting memmove.)
  55          *
  56          * For speedy copying, optimize the common case where both pointers
  57          * and the length are word-aligned, and copy word-at-a-time instead
  58          * of byte-at-a-time. Otherwise, copy by bytes.
  59          *
  60          * The alignment logic below should be portable. We rely on
  61          * the compiler to be reasonably intelligent about optimizing
  62          * the divides and modulos out. Fortunately, it is.
  63          */
  65         if ((uintptr_t)dst % sizeof(long) == 0 &&
  66             (uintptr_t)src % sizeof(long) == 0 &&
len % sizeof(long) == 0) {
  69                 long *d = dst;
  70                 const long *s = src;
  72                 for (i=0; i<len/sizeof(long); i++) {
d[i] = s[i];
  74                 }
  75         }
  76         else {
  77                 char *d = dst;
  78                 const char *s = src;
  80                 for (i=0; i<len; i++) {
d[i] = s[i];
  82                 }
  83         }
  85         return dst;
  86 }