1#include <string.h> 2#include <stdint.h> 3#include <limits.h> 4 5#define ALIGN (sizeof(size_t)) 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 10size_t strlen(const char *s) 11{ 12 const char *a = s; 13#ifdef __GNUC__ 14 typedef size_t __attribute__((__may_alias__)) word; 15 const word *w; 16 for (; (uintptr_t)s % ALIGN; s++) if (!*s) return s-a; 17 for (w = (const void *)s; !HASZERO(*w); w++); 18 s = (const void *)w; 19#endif 20 for (; *s; s++); 21 return s-a; 22} 23