NAME

       CURLMOPT_TIMERFUNCTION - callback to receive timeout values

SYNOPSIS

       #include <curl/curl.h>

       int timer_callback(CURLM *multi,    /* multi handle */
                          long timeout_ms, /* timeout in number of ms */
                          void *clientp);    /* private callback pointer */

       CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_TIMERFUNCTION, timer_callback);

DESCRIPTION

       Pass a pointer to your callback function, which should match the prototype shown above.

       Certain  features,  such  as  timeouts  and retries, require you to call libcurl even when
       there is no activity on the file descriptors.

       Your callback function timer_callback should install a non-repeating timer with an  expire
       time    of    timeout_ms    milliseconds.    When    that   timer   fires,   call   either
       curl_multi_socket_action(3) or curl_multi_perform(3), depending  on  which  interface  you
       use.

       A  timeout_ms  value  of -1 passed to this callback means you should delete the timer. All
       other values are valid expire times in number of milliseconds.

       The timer_callback is called when the timeout expire time is changed.

       The clientp pointer is set with CURLMOPT_TIMERDATA(3).

       The timer callback should return 0 on success, and -1 on error. If this  callback  returns
       error,  all  transfers  currently in progress in this multi handle are aborted and made to
       fail.

       This callback can be used instead of, or in addition to, curl_multi_timeout(3).

       WARNING: do not call libcurl directly from within the callback itself when the  timeout_ms
       value is zero, since it risks triggering an unpleasant recursive behavior that immediately
       calls another call to the callback with a zero timeout...

DEFAULT

       NULL

PROTOCOLS

       This functionality affects all supported protocols

EXAMPLE

       struct priv {
         void *custom;
       };

       static int timerfunc(CURLM *multi, long timeout_ms, void *clientp)
       {
        struct priv *mydata = clientp;
        printf("our ptr: %p\n", mydata->custom);

        if(timeout_ms) {
          /* this is the new single timeout to wait for */
        }
        else {
          /* delete the timeout, nothing to wait for now */
        }
       }

       int main(void)
       {
         struct priv mydata;
         CURLM *multi = curl_multi_init();
         curl_multi_setopt(multi, CURLMOPT_TIMERFUNCTION, timerfunc);
         curl_multi_setopt(multi, CURLMOPT_TIMERDATA, &mydata);
       }

AVAILABILITY

       Added in curl 7.16.0

RETURN VALUE

       Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.

SEE ALSO

       CURLMOPT_SOCKETFUNCTION(3), CURLMOPT_TIMERDATA(3)