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87 lines
2.8 KiB
Groff
87 lines
2.8 KiB
Groff
.\" generated by cd2nroff 0.1 from CURLMOPT_TIMERFUNCTION.md
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.TH CURLMOPT_TIMERFUNCTION 3 "2024-11-09" libcurl
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.SH NAME
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CURLMOPT_TIMERFUNCTION \- callback to receive timeout values
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.SH SYNOPSIS
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.nf
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#include <curl/curl.h>
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int timer_callback(CURLM *multi, /* multi handle */
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long timeout_ms, /* timeout in number of ms */
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void *clientp); /* private callback pointer */
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CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_TIMERFUNCTION, timer_callback);
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.fi
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.SH DESCRIPTION
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Pass a pointer to your callback function, which should match the prototype
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shown above.
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Certain features, such as timeouts and retries, require you to call libcurl
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even when there is no activity on the file descriptors.
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Your callback function \fBtimer_callback\fP should install a single
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non\-repeating timer with an expire time of \fBtimeout_ms\fP milliseconds. When
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that timer fires, call either \fIcurl_multi_socket_action(3)\fP or
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\fIcurl_multi_perform(3)\fP, depending on which interface you use.
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If this callback is called when a timer is already running, this new expire
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time \fIreplaces\fP the former timeout. The application should then effectively
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cancel the old timeout and set a new timeout using this new expire time.
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A \fBtimeout_ms\fP value of \-1 passed to this callback means you should delete
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the timer. All other values are valid expire times in number of milliseconds.
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The \fBtimer_callback\fP is called when the timeout expire time is changed.
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The \fBclientp\fP pointer is set with \fICURLMOPT_TIMERDATA(3)\fP.
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The timer callback should return 0 on success, and \-1 on error. If this
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callback returns error, \fBall\fP transfers currently in progress in this multi
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handle are aborted and made to fail.
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This callback can be used instead of, or in addition to,
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\fIcurl_multi_timeout(3)\fP.
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\fBWARNING:\fP do not call libcurl directly from within the callback itself when
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the \fBtimeout_ms\fP value is zero, since it risks triggering an unpleasant
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recursive behavior that immediately calls another call to the callback with a
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zero timeout...
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.SH DEFAULT
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NULL
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.SH PROTOCOLS
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This functionality affects all supported protocols
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.SH EXAMPLE
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.nf
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struct priv {
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void *custom;
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};
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static int timerfunc(CURLM *multi, long timeout_ms, void *clientp)
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{
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struct priv *mydata = clientp;
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printf("our ptr: %p\\n", mydata->custom);
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if(timeout_ms) {
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/* this is the new single timeout to wait for */
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}
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else {
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/* delete the timeout, nothing to wait for now */
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}
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}
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int main(void)
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{
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struct priv mydata;
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CURLM *multi = curl_multi_init();
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curl_multi_setopt(multi, CURLMOPT_TIMERFUNCTION, timerfunc);
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curl_multi_setopt(multi, CURLMOPT_TIMERDATA, &mydata);
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}
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.fi
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.SH AVAILABILITY
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Added in curl 7.16.0
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.SH RETURN VALUE
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Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
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.SH SEE ALSO
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.BR CURLMOPT_SOCKETFUNCTION (3),
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.BR CURLMOPT_TIMERDATA (3)
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