return (vstr_spn_cstr_chrs_fwd(s1, pos, len, cstr) == s1->len);
return (vstr_spn_cstr_chrs_fwd(s1, pos, len, cstr) == len);
int httpd_valid_url_filename(Vstr_base *s1, size_t pos, size_t len){  const char *const cstr = HTTPD__VALID_CSTR_CHRS_URL_FILENAME;  return (vstr_spn_cstr_chrs_fwd(s1, pos, len, cstr) == s1->len);}