Annotation of embedaddon/curl/docs/libcurl/opts/CURLMOPT_TIMERFUNCTION.3, revision 1.1.1.1
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23: .TH CURLMOPT_TIMERFUNCTION 3 "May 03, 2019" "libcurl 7.70.0" "curl_multi_setopt options"
24:
25: .SH NAME
26: CURLMOPT_TIMERFUNCTION \- set callback to receive timeout values
27: .SH SYNOPSIS
28: .nf
29: #include <curl/curl.h>
30:
31: int timer_callback(CURLM *multi, /* multi handle */
32: long timeout_ms, /* timeout in number of ms */
33: void *userp); /* private callback pointer */
34:
35: CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_TIMERFUNCTION, timer_callback);
36: .SH DESCRIPTION
37: Pass a pointer to your callback function, which should match the prototype
38: shown above.
39:
40: Certain features, such as timeouts and retries, require you to call libcurl
41: even when there is no activity on the file descriptors.
42:
43: Your callback function \fBtimer_callback\fP should install a non-repeating
44: timer with an interval of \fBtimeout_ms\fP. When time that timer fires, call
45: either \fIcurl_multi_socket_action(3)\fP or \fIcurl_multi_perform(3)\fP,
46: depending on which interface you use.
47:
48: A \fBtimeout_ms\fP value of -1 passed to this callback means you should delete
49: the timer. All other values are valid expire times in number of milliseconds.
50:
51: The \fBtimer_callback\fP will only be called when the timeout expire time is
52: changed.
53:
54: The \fBuserp\fP pointer is set with \fICURLMOPT_TIMERDATA(3)\fP.
55:
56: The timer callback should return 0 on success, and -1 on error. This callback
57: can be used instead of, or in addition to, \fIcurl_multi_timeout(3)\fP.
58:
59: \fBWARNING:\fP even if it feels tempting, avoid calling libcurl directly from
60: within the callback itself when the \fBtimeout_ms\fP value is zero, since it
61: risks triggering an unpleasant recursive behavior that immediately calls
62: another call to the callback with a zero timeout...
63: .SH DEFAULT
64: NULL
65: .SH PROTOCOLS
66: All
67: .SH EXAMPLE
68: .nf
69: static gboolean timeout_cb(gpointer user_data)
70: {
71: int running;
72: if(user_data) {
73: g_free(user_data);
74: curl_multi_setopt(curl_handle, CURLMOPT_TIMERDATA, NULL);
75: }
76: curl_multi_socket_action(multi, CURL_SOCKET_TIMEOUT, 0, &running);
77: return G_SOURCE_REMOVE;
78: }
79:
80: static int timerfunc(CURLM *multi, long timeout_ms, void *userp)
81: {
82: guint *id = userp;
83:
84: if(id)
85: g_source_remove(*id);
86:
87: /* -1 means we should just delete our timer. */
88: if(timeout_ms == -1) {
89: g_free(id);
90: id = NULL;
91: }
92: else {
93: if(!id)
94: id = g_new(guint, 1);
95: *id = g_timeout_add(timeout_ms, timeout_cb, id);
96: }
97: curl_multi_setopt(multi, CURLMOPT_TIMERDATA, id);
98: return 0;
99: }
100:
101: curl_multi_setopt(multi, CURLMOPT_TIMERFUNCTION, timerfunc);
102: .fi
103: .SH AVAILABILITY
104: Added in 7.16.0
105: .SH RETURN VALUE
106: Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
107: .SH "SEE ALSO"
108: .BR CURLMOPT_TIMERDATA "(3), " CURLMOPT_SOCKETFUNCTION "(3), "
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