strcspn.c

#define SYSCLIB_DISABLE_BUILTINS
#include <sysclib.h>
 
char *__strchrnul(const char *s, int c);
 
#define BITOP(a,b,op) \
 ((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a))))
 
size_t strcspn(const char *s, const char *c)
{
    const char *a = s;
    size_t byteset[32/sizeof(size_t)];
 
    if (!c[0] || !c[1]) return __strchrnul(s, *c)-a;
 
    memset(byteset, 0, sizeof byteset);
    for (; *c && BITOP(byteset, *(unsigned char *)c, |=); c++);
    for (; *s && !BITOP(byteset, *(unsigned char *)s, &); s++);
    return s-a;
}