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
__stpncpy(char * restrict d,const char * restrict s,size_t n)10 char *__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++);
26 tail:
27 memset(d, 0, n);
28 return d;
29 }
30
31 weak_alias(__stpncpy, stpncpy);
32
33