src/string/strcspn.c

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