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e3fe020089
Remove the PROTOCOLS section from the source files completely and instead generate them based on the header data in the curldown files. It also generates TLS backend information for options marked for TLS as protocol. Closes #13175
102 lines
2.6 KiB
Markdown
102 lines
2.6 KiB
Markdown
---
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c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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SPDX-License-Identifier: curl
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Title: CURLMOPT_TIMERFUNCTION
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Section: 3
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Source: libcurl
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See-also:
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- CURLMOPT_SOCKETFUNCTION (3)
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- CURLMOPT_TIMERDATA (3)
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Protocol:
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- All
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---
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# NAME
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CURLMOPT_TIMERFUNCTION - callback to receive timeout values
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# SYNOPSIS
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~~~c
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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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~~~
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# 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 **timer_callback** should install a non-repeating
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timer with an expire time of **timeout_ms** milliseconds. When that timer
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fires, call either curl_multi_socket_action(3) or
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curl_multi_perform(3), depending on which interface you use.
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A **timeout_ms** 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 **timer_callback** is called when the timeout expire time is changed.
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The **clientp** pointer is set with CURLMOPT_TIMERDATA(3).
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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, **all** transfers currently in progress in this
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multi 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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curl_multi_timeout(3).
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**WARNING:** do not call libcurl directly from within the callback itself
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when the **timeout_ms** value is zero, since it risks triggering an
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unpleasant recursive behavior that immediately calls another call to the
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callback with a zero timeout...
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# DEFAULT
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NULL
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# EXAMPLE
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~~~c
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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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~~~
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# AVAILABILITY
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Added in 7.16.0
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# RETURN VALUE
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Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
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