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                     23: .TH CURLMOPT_TIMERFUNCTION 3 "May 03, 2019" "libcurl 7.70.0" "curl_multi_setopt options"
                     24: 
                     25: .SH NAME
                     26: CURLMOPT_TIMERFUNCTION \- set callback to receive timeout values
                     27: .SH SYNOPSIS
                     28: .nf
                     29: #include <curl/curl.h>
                     30: 
                     31: int timer_callback(CURLM *multi,    /* multi handle */
                     32:                    long timeout_ms, /* timeout in number of ms */
                     33:                    void *userp);    /* private callback pointer */
                     34: 
                     35: CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_TIMERFUNCTION, timer_callback);
                     36: .SH DESCRIPTION
                     37: Pass a pointer to your callback function, which should match the prototype
                     38: shown above.
                     39: 
                     40: Certain features, such as timeouts and retries, require you to call libcurl
                     41: even when there is no activity on the file descriptors.
                     42: 
                     43: Your callback function \fBtimer_callback\fP should install a non-repeating
                     44: timer with an interval of \fBtimeout_ms\fP. When time that timer fires, call
                     45: either \fIcurl_multi_socket_action(3)\fP or \fIcurl_multi_perform(3)\fP,
                     46: depending on which interface you use.
                     47: 
                     48: A \fBtimeout_ms\fP value of -1 passed to this callback means you should delete
                     49: the timer. All other values are valid expire times in number of milliseconds.
                     50: 
                     51: The \fBtimer_callback\fP will only be called when the timeout expire time is
                     52: changed.
                     53: 
                     54: The \fBuserp\fP pointer is set with \fICURLMOPT_TIMERDATA(3)\fP.
                     55: 
                     56: The timer callback should return 0 on success, and -1 on error. This callback
                     57: can be used instead of, or in addition to, \fIcurl_multi_timeout(3)\fP.
                     58: 
                     59: \fBWARNING:\fP even if it feels tempting, avoid calling libcurl directly from
                     60: within the callback itself when the \fBtimeout_ms\fP value is zero, since it
                     61: risks triggering an unpleasant recursive behavior that immediately calls
                     62: another call to the callback with a zero timeout...
                     63: .SH DEFAULT
                     64: NULL
                     65: .SH PROTOCOLS
                     66: All
                     67: .SH EXAMPLE
                     68: .nf
                     69: static gboolean timeout_cb(gpointer user_data)
                     70: {
                     71:   int running;
                     72:   if(user_data) {
                     73:     g_free(user_data);
                     74:     curl_multi_setopt(curl_handle, CURLMOPT_TIMERDATA, NULL);
                     75:   }
                     76:   curl_multi_socket_action(multi, CURL_SOCKET_TIMEOUT, 0, &running);
                     77:   return G_SOURCE_REMOVE;
                     78: }
                     79: 
                     80: static int timerfunc(CURLM *multi, long timeout_ms, void *userp)
                     81: {
                     82:   guint *id = userp;
                     83: 
                     84:   if(id)
                     85:     g_source_remove(*id);
                     86: 
                     87:   /* -1 means we should just delete our timer. */
                     88:   if(timeout_ms == -1) {
                     89:     g_free(id);
                     90:     id = NULL;
                     91:   }
                     92:   else {
                     93:     if(!id)
                     94:       id = g_new(guint, 1);
                     95:     *id = g_timeout_add(timeout_ms, timeout_cb, id);
                     96:   }
                     97:   curl_multi_setopt(multi, CURLMOPT_TIMERDATA, id);
                     98:   return 0;
                     99: }
                    100: 
                    101: curl_multi_setopt(multi, CURLMOPT_TIMERFUNCTION, timerfunc);
                    102: .fi
                    103: .SH AVAILABILITY
                    104: Added in 7.16.0
                    105: .SH RETURN VALUE
                    106: Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
                    107: .SH "SEE ALSO"
                    108: .BR CURLMOPT_TIMERDATA "(3), " CURLMOPT_SOCKETFUNCTION "(3), "