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CURLMOPT_TIMERFUNCTION.m: emphasize that only a single timer should run

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Closes #14886
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Daniel Stenberg 2024-09-12 17:35:58 +02:00
parent 61e48b4df1
commit 381de75ce8
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1 changed files with 22 additions and 18 deletions
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40
docs/libcurl/opts/CURLMOPT_TIMERFUNCTION.md
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@ -23,7 +23,7 @@ CURLMOPT_TIMERFUNCTION - callback to receive timeout values
int timer_callback(CURLM *multi, /* multi handle */
long timeout_ms, /* timeout in number of ms */
void *clientp); /* private callback pointer */
void *clientp); /* private callback pointer */
CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_TIMERFUNCTION, timer_callback);
~~~
@ -36,11 +36,15 @@ 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
Your callback function **timer_callback** should install a single
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.
If this callback is called when a timer is already running, this new expire
time *replaces* the former timeout. The application should then effectively
cancel the old timeout and set a new timeout using this new expire time.
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.
@ -49,16 +53,16 @@ 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.
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...
**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
@ -75,15 +79,15 @@ struct priv {
static int timerfunc(CURLM *multi, long timeout_ms, void *clientp)
{
struct priv *mydata = clientp;
printf("our ptr: %p\n", mydata->custom);
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 */
}
if(timeout_ms) {
/* this is the new single timeout to wait for */
}
else {
/* delete the timeout, nothing to wait for now */
}
}
int main(void)