ref: 1da7f45ae0e42aff174c695d948449bf22bf4b33
dir: /lib/c/strspn.c/
#include <string.h>
#undef strspn
size_t
strspn(const char *s1, const char *s2)
{
size_t n;
int c;
const char *p;
for (n = 0; c = *s1++; ++n) {
for (p = s2; *p && *p != c; ++p)
;
if (*p == '\0')
break;
}
return n;
}