CURLMOPT_TIMERFUNCTION(3)

1CURLMOPT_TIMERFUNCTION(3)  curl_multi_setopt options CURLMOPT_TIMERFUNCTION(3)
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NAME

6       CURLMOPT_TIMERFUNCTION - set callback to receive timeout values
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SYNOPSIS

9       #include <curl/curl.h>
10
11       int timer_callback(CURLM *multi,    /* multi handle */
12                          long timeout_ms, /* timeout in number of ms */
13                          void *userp);    /* private callback pointer */
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15       CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_TIMERFUNCTION, timer_callback);
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DESCRIPTION

18       Pass a pointer to your callback function, which should match the proto‐
19       type shown above.
20
21       Certain features, such as timeouts and retries,  require  you  to  call
22       libcurl even when there is no activity on the file descriptors.
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24       Your  callback  function  timer_callback should install a non-repeating
25       timer with an interval of timeout_ms. When time that timer fires,  call
26       either  curl_multi_socket_action(3) or curl_multi_perform(3), depending
27       on which interface you use.
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29       A timeout_ms value of -1 passed  to  this  callback  means  you  should
30       delete  the timer. All other values are valid expire times in number of
31       milliseconds.
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33       The timer_callback will only be called when the timeout expire time  is
34       changed.
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36       The userp pointer is set with CURLMOPT_TIMERDATA(3).
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38       The  timer  callback  should return 0 on success, and -1 on error. This
39       callback can be used instead of, or in  addition  to,  curl_multi_time‐
40       out(3).
41
42       WARNING: even if it feels tempting, avoid calling libcurl directly from
43       within the callback itself when the timeout_ms value is zero, since  it
44       risks  triggering  an  unpleasant  recursive  behavior that immediately
45       calls another call to the callback with a zero timeout...
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DEFAULT

48       NULL
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PROTOCOLS

51       All
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EXAMPLE

54       static gboolean timeout_cb(gpointer user_data)
55       {
56         int running;
57         if(user_data) {
58           g_free(user_data);
59           curl_multi_setopt(curl_handle, CURLMOPT_TIMERDATA, NULL);
60         }
61         curl_multi_socket_action(multi, CURL_SOCKET_TIMEOUT, 0, &running);
62         return G_SOURCE_REMOVE;
63       }
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65       static int timerfunc(CURLM *multi, long timeout_ms, void *userp)
66       {
67         guint *id = userp;
68
69         if(id)
70           g_source_remove(*id);
71
72         /* -1 means we should just delete our timer. */
73         if(timeout_ms == -1) {
74           g_free(id);
75           id = NULL;
76         }
77         else {
78           if(!id)
79             id = g_new(guint, 1);
80           *id = g_timeout_add(timeout_ms, timeout_cb, id);
81         }
82         curl_multi_setopt(multi, CURLMOPT_TIMERDATA, id);
83         return 0;
84       }
85
86       curl_multi_setopt(multi, CURLMOPT_TIMERFUNCTION, timerfunc);
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AVAILABILITY

89       Added in 7.16.0
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RETURN VALUE

92       Returns CURLM_OK if the option is supported,  and  CURLM_UNKNOWN_OPTION
93       if not.
94