src/string/strchrnul.c

   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
  10 char *__strchrnul(const char *s, int c)
  11 {
  12         c = (unsigned char)c;
  13         if (!c) return (char *)s + strlen(s);
  14
  15 #ifdef __GNUC__
  16         typedef size_t __attribute__((__may_alias__)) word;
  17         const word *w;
  18         for (; (uintptr_t)s % ALIGN; s++)
  19                 if (!*s || *(unsigned char *)s == c) return (char *)s;
  20         size_t k = ONES * c;
  21         for (w = (void *)s; !HASZERO(*w) && !HASZERO(*w^k); w++);
  22         s = (void *)w;
  23 #endif
  24         for (; *s && *(unsigned char *)s != c; s++);
  25         return (char *)s;
  26 }
  27
  28 weak_alias(__strchrnul, strchrnul);