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CURLMOPT_TIMERFUNCTION(3) curl_multi_setopt options CURLMOPT_TIMERFUNCTION(3)
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 *userp); /* 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 interval of timeout_ms. 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 will only be called when the timeout expire time is
changed.
The userp pointer is set with CURLMOPT_TIMERDATA(3).
The timer callback should return 0 on success, and -1 on error. This
callback can be used instead of, or in addition to,
curl_multi_timeout(3).
WARNING: even if it feels tempting, avoid calling 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
All
EXAMPLE
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);
AVAILABILITY
Added in 7.16.0
RETURN VALUE
Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION
if not.
SEE ALSO
CURLMOPT_TIMERDATA(3), CURLMOPT_SOCKETFUNCTION(3),
libcurl 7.79.1 September 8, 2021 CURLMOPT_TIMERFUNCTION(3)