function sign_url($file, $host = '')
{
$obj = new ALIOSS();
if ($host != '') {
$obj->set_vhost($host);
} else {
$obj->set_host_name("oss.aliyuncs.com");
}
$obj->set_enable_domain_style();
$obj->set_debug_mode(FALSE);
$bucket = $this->bucket;
$file = jishigou_oss::clear($file);
$timeout = $this->stimeout;
$response = $obj->get_sign_url($bucket, $file, $timeout);
return $response;
}