size_t strlen(const char *str) {
    size_t len = 0;
    while (str[len])
        len++;
    return len;
}

size_t strcmp(const char *s1, const char *s2) {
    while (*s1 && (*s1 == *s2)) {
	s1++;
	s2++;
    }
    return *(const unsigned char*)s1 - *(const unsigned char*)s2;
}