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| .TH CURLMOPT_TIMERFUNCTION 3 "November 04, 2020" "libcurl 7.78.0" "curl_multi_setopt options" |
| |
| .SH NAME |
| CURLMOPT_TIMERFUNCTION \- set callback to receive timeout values |
| .SH SYNOPSIS |
| .nf |
| #include <curl/curl.h> |
| |
| int timer_callback(CURLM *multi, /* multi handle */ |
| long timeout_ms, /* timeout in number of ms */ |
| void *userp); /* private callback pointer */ |
| |
| CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_TIMERFUNCTION, timer_callback); |
| .SH 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 \fBtimer_callback\fP should install a non-repeating |
| timer with an interval of \fBtimeout_ms\fP. When time that timer fires, call |
| either \fIcurl_multi_socket_action(3)\fP or \fIcurl_multi_perform(3)\fP, |
| depending on which interface you use. |
| |
| A \fBtimeout_ms\fP 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 \fBtimer_callback\fP will only be called when the timeout expire time is |
| changed. |
| |
| The \fBuserp\fP pointer is set with \fICURLMOPT_TIMERDATA(3)\fP. |
| |
| The timer callback should return 0 on success, and -1 on error. This callback |
| can be used instead of, or in addition to, \fIcurl_multi_timeout(3)\fP. |
| |
| \fBWARNING:\fP even if it feels tempting, avoid calling libcurl directly from |
| within the callback itself when the \fBtimeout_ms\fP value is zero, since it |
| risks triggering an unpleasant recursive behavior that immediately calls |
| another call to the callback with a zero timeout... |
| .SH DEFAULT |
| NULL |
| .SH PROTOCOLS |
| All |
| .SH EXAMPLE |
| .nf |
| static gboolean timeout_cb(gpointer user_data) |
| { |
| int running; |
| if(user_data) { |
| g_free(user_data); |
| curl_multi_setopt(curl_handle, CURLMOPT_TIMERDATA, NULL); |
| } |
| curl_multi_socket_action(multi, CURL_SOCKET_TIMEOUT, 0, &running); |
| return G_SOURCE_REMOVE; |
| } |
| |
| static int timerfunc(CURLM *multi, long timeout_ms, void *userp) |
| { |
| guint *id = userp; |
| |
| if(id) |
| g_source_remove(*id); |
| |
| /* -1 means we should just delete our timer. */ |
| if(timeout_ms == -1) { |
| g_free(id); |
| id = NULL; |
| } |
| else { |
| if(!id) |
| id = g_new(guint, 1); |
| *id = g_timeout_add(timeout_ms, timeout_cb, id); |
| } |
| curl_multi_setopt(multi, CURLMOPT_TIMERDATA, id); |
| return 0; |
| } |
| |
| curl_multi_setopt(multi, CURLMOPT_TIMERFUNCTION, timerfunc); |
| .fi |
| .SH AVAILABILITY |
| Added in 7.16.0 |
| .SH RETURN VALUE |
| Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not. |
| .SH "SEE ALSO" |
| .BR CURLMOPT_TIMERDATA "(3), " CURLMOPT_SOCKETFUNCTION "(3), " |
