ref: 844cf5ff2aa2a862b58d2e503e02534e133ad395
dir: /src/libc/string/strspn.c/
#include <string.h>
#undef strspn
size_t
strspn(const char *s1, const char *s2)
{
const unsigned char *s = s1;
const unsigned char *accept = s2;
size_t n;
unsigned ch;
char map[__NUMCHARS] = {0};
while ((ch = *accept++) != '\0')
map[ch] = 1;
for (n = 0; (ch = *s++) != '\0' && map[ch]; ++n)
;
return n;
}