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
6 char* __strchrnul(const char*, int);
7
strcspn(const char * s,const char * c)8 size_t strcspn(const char* s, const char* c) {
9 const char* a = s;
10 size_t byteset[32 / sizeof(size_t)];
11
12 if (!c[0] || !c[1])
13 return __strchrnul(s, *c) - a;
14
15 memset(byteset, 0, sizeof byteset);
16 for (; *c && BITOP(byteset, *(unsigned char*)c, |=); c++)
17 ;
18 for (; *s && !BITOP(byteset, *(unsigned char*)s, &); s++)
19 ;
20 return s - a;
21 }
22