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