1 #include <string.h>
2
3 #define BITOP(a,b,op) \
4 ((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a))))
5
strcspn(const char * s,const char * c)6 size_t strcspn(const char *s, const char *c)
7 {
8 const char *a = s;
9 size_t byteset[32/sizeof(size_t)];
10
11 if (!c[0] || !c[1]) return __strchrnul(s, *c)-a;
12
13 memset(byteset, 0, sizeof byteset);
14 for (; *c && BITOP(byteset, *(unsigned char *)c, |=); c++);
15 for (; *s && !BITOP(byteset, *(unsigned char *)s, &); s++);
16 return s-a;
17 }
18