1#include <string.h>
 2#include <stdint.h>
 3#include <limits.h>
 4
 5#define ALIGN (sizeof(size_t)-1)
 6#define ONES ((size_t)-1/UCHAR_MAX)
 7#define HIGHS (ONES * (UCHAR_MAX/2+1))
 8#define HASZERO(x) ((x)-ONES & ~(x) & HIGHS)
 9
10char *__stpncpy(char *restrict d, const char *restrict s, size_t n)
11{
12#ifdef __GNUC__
13	typedef size_t __attribute__((__may_alias__)) word;
14	word *wd;
15	const word *ws;
16	if (((uintptr_t)s & ALIGN) == ((uintptr_t)d & ALIGN)) {
17		for (; ((uintptr_t)s & ALIGN) && n && (*d=*s); n--, s++, d++);
18		if (!n || !*s) goto tail;
19		wd=(void *)d; ws=(const void *)s;
20		for (; n>=sizeof(size_t) && !HASZERO(*ws);
21		       n-=sizeof(size_t), ws++, wd++) *wd = *ws;
22		d=(void *)wd; s=(const void *)ws;
23	}
24#endif
25	for (; n && (*d=*s); n--, s++, d++);
26tail:
27	memset(d, 0, n);
28	return d;
29}
30
31weak_alias(__stpncpy, stpncpy);
32