static size_t progress_callback(void *clientp,
                                 curl_off_t dltotal,
                                 curl_off_t dlnow,
                                 curl_off_t ultotal,
                                 curl_off_t ulnow)
 {
   struct memory *progress = (struct progress *)userp;
 
   /* use the values */
 
   return 0; /* all is good */
 }