src/string/memmove.c

   1 #include <string.h>
   2 #include <stdint.h>
   3
   4 #ifdef __GNUC__
   5 typedef __attribute__((__may_alias__)) size_t WT;
   6 #define WS (sizeof(WT))
   7 #endif
   8
   9 void *memmove(void *dest, const void *src, size_t n)
  10 {
  11         char *d = dest;
  12         const char *s = src;
  13
  14         if (d==s) return d;
  15         if ((uintptr_t)s-(uintptr_t)d-n <= -2*n) return memcpy(d, s, n);
  16
  17         if (d<s) {
  18 #ifdef __GNUC__
  19                 if ((uintptr_t)s % WS == (uintptr_t)d % WS) {
  20                         while ((uintptr_t)d % WS) {
  21                                 if (!n--) return dest;
  22                                 *d++ = *s++;
  23                         }
  24                         for (; n>=WS; n-=WS, d+=WS, s+=WS) *(WT *)d = *(WT *)s;
  25                 }
  26 #endif
  27                 for (; n; n--) *d++ = *s++;
  28         } else {
  29 #ifdef __GNUC__
  30                 if ((uintptr_t)s % WS == (uintptr_t)d % WS) {
  31                         while ((uintptr_t)(d+n) % WS) {
  32                                 if (!n--) return dest;
  33                                 d[n] = s[n];
  34                         }
  35                         while (n>=WS) n-=WS, *(WT *)(d+n) = *(WT *)(s+n);
  36                 }
  37 #endif
  38                 while (n) n--, d[n] = s[n];
  39         }
  40
  41         return dest;
  42 }