libc/string/memmove.c

   1 /*
   2  *  ZeX/OS
   3  *  Copyright (C) 2009  Tomas 'ZeXx86' Jedrzejek (zexx86@zexos.org)
   4  *
   5  *  This program is free software: you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation, either version 3 of the License, or
   8  *  (at your option) any later version.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19
  20 #include <string.h> /* size_t */
  21
  22 typedef long word;
  23
  24 #define lmask (sizeof (long) - 1)
  25
  26 void *memmove (void *dest, void const *src, size_t count)
  27 {
  28         char *d = (char *) dest;
  29         const char *s = (const char *) src;
  30         int len;
  31
  32         if (!count || dest == src)
  33                 return dest;
  34
  35         if ((long) d < (long) s) {
  36                 if (((long) d | (long) s) & lmask) {
  37                         if ((((long) d ^ (long) s) & lmask) || (count < sizeof (long)))
  38                                 len = count;
  39                         else
  40                                 len = sizeof (long) - ((long) d & lmask);
  41
  42                         count -= len;
  43                         for(; len > 0; len --)
  44                                 *d ++ = *s ++;
  45                 }
  46
  47                 for (len = count / sizeof (long); len > 0; len --) {
  48                         *(word *) d = *(word *) s;
  49                         d += sizeof (long);
  50                         s += sizeof (long);
  51                 }
  52
  53                 for (len = count & lmask; len > 0; len --)
  54                         *d ++ = *s ++;
  55         } else {
  56                 d += count;
  57                 s += count;
  58
  59                 if (((long) d | (long) s) & lmask) {
  60                         if ((((long) d ^ (long) s) & lmask) || (count <= sizeof (long)))
  61                                 len = count;
  62                         else
  63                                 len = ((long) d & lmask);
  64
  65                         count -= len;
  66
  67                         for (; len > 0; len --)
  68                                 *-- d = *-- s;
  69                 }
  70
  71                 for (len = count / sizeof (long); len > 0; len --) {
  72                         d -= sizeof (long);
  73                         s -= sizeof (long);
  74                         *(word *) d = *(word *) s;
  75                 }
  76
  77                 for (len = count & lmask; len > 0; len --)
  78                         *-- d = *-- s;
  79         }
  80
  81         return dest;
  82 }