github.com/afumu/libc@v0.0.6/musl/src/string/strchrnul.c (about)

     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);