memmove.c raw

   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  }
  43