ref: d89d90240080d1638ade3d650c3f83599a73613d
dir: /lib/c/memchr.c/
#include <string.h>
#undef memchr
void *
memchr(const void *s, int c, size_t n)
{
unsigned char *bp = (char *) s;
while (n > 0 && *bp++ != c)
--n;
return (n == 0) ? NULL : bp-1;
}