strchrnul.c raw

   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);
  29