src/string/memmove.c

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