ref: 7b8f9336dd0170c6dcaf12368b0c03c8019c5ab5
dir: /lib/c/strcspn.c/
#include <string.h>
#undef strcspn
size_t
strcspn(const char *s1, const char *s2)
{
const unsigned char *s = s1;
const unsigned char *accept = s2;
unsigned ch;
size_t n;
char buf[__NUMCHARS];
memset(buf, 0, sizeof(buf));
while (ch = *accept++)
buf[ch] = 1;
for (n = 0; (ch = *s++) && !buf[ch]; ++n)
;
return n;
}