1 #define _DEFAULT_SOURCE 2 #include <string.h> 3 4 #define BITOP(a,b,op) \ 5 ((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a)))) 6 7 size_t strcspn(const char *s, const char *c) 8 { 9 const char *a = s; 10 size_t byteset[32/sizeof(size_t)]; 11 12 if (!c[0] || !c[1]) return strchrnul(s, *c)-a; 13 14 memset(byteset, 0, sizeof byteset); 15 for (; *c && BITOP(byteset, *(unsigned char *)c, |=); c++); 16 for (; *s && !BITOP(byteset, *(unsigned char *)s, &); s++); 17 return s-a; 18 } 19