libc-top-half/musl/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 #if defined(__wasm_bulk_memory__)
  12         return __builtin_memmove(dest, src, n);
  13 #else
  14         char *d = dest;
  15         const char *s = src;
  16
  17         if (d==s) return d;
  18         if ((uintptr_t)s-(uintptr_t)d-n <= -2*n) return memcpy(d, s, n);
  19
  20         if (d<s) {
  21 #ifdef __GNUC__
  22                 if ((uintptr_t)s % WS == (uintptr_t)d % WS) {
  23                         while ((uintptr_t)d % WS) {
  24                                 if (!n--) return dest;
  25                                 *d++ = *s++;
  26                         }
  27                         for (; n>=WS; n-=WS, d+=WS, s+=WS) *(WT *)d = *(WT *)s;
  28                 }
  29 #endif
  30                 for (; n; n--) *d++ = *s++;
  31         } else {
  32 #ifdef __GNUC__
  33                 if ((uintptr_t)s % WS == (uintptr_t)d % WS) {
  34                         while ((uintptr_t)(d+n) % WS) {
  35                                 if (!n--) return dest;
  36                                 d[n] = s[n];
  37                         }
  38                         while (n>=WS) n-=WS, *(WT *)(d+n) = *(WT *)(s+n);
  39                 }
  40 #endif
  41                 while (n) n--, d[n] = s[n];
  42         }
  43
  44         return dest;
  45 #endif // __wasm_bulk_memory__
  46 }