scc

 1#include <string.h>
 2
 3#undef strspn
 4
 5size_t
 6strspn(const char *s1, const char *s2)
 7{
 8	const unsigned char *s = (const unsigned char *) s1;
 9	const unsigned char *accept = (const unsigned char *) s2;
10	size_t n;
11	unsigned ch;
12	char map[__NUMCHARS] = {0};
13
14	while ((ch = *accept++) != '\0')
15		map[ch] = 1;
16
17	for (n = 0; (ch = *s++) != '\0' && map[ch]; ++n)
18		;
19
20	return n;
21}