quickjs-tart

quickjs-based runtime for wallet-core logic
Log | Files | Refs | README | LICENSE

CURLMOPT_TIMERFUNCTION.md (3023B)

      1 ---
      2 c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
      3 SPDX-License-Identifier: curl
      4 Title: CURLMOPT_TIMERFUNCTION
      5 Section: 3
      6 Source: libcurl
      7 See-also:
      8   - CURLMOPT_SOCKETFUNCTION (3)
      9   - CURLMOPT_TIMERDATA (3)
     10 Protocol:
     11   - All
     12 Added-in: 7.16.0
     13 ---
     14 
     15 # NAME
     16 
     17 CURLMOPT_TIMERFUNCTION - callback to receive timeout values
     18 
     19 # SYNOPSIS
     20 
     21 ~~~c
     22 #include <curl/curl.h>
     23 
     24 int timer_callback(CURLM *multi,    /* multi handle */
     25                    long timeout_ms, /* timeout in number of ms */
     26                    void *clientp);  /* private callback pointer */
     27 
     28 CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_TIMERFUNCTION, timer_callback);
     29 ~~~
     30 
     31 # DESCRIPTION
     32 
     33 Pass a pointer to your callback function, which should match the prototype
     34 shown above.
     35 
     36 Certain features, such as timeouts and retries, require you to call libcurl
     37 even when there is no activity on the file descriptors.
     38 
     39 Your callback function **timer_callback** should install a single
     40 non-repeating timer with an expire time of **timeout_ms** milliseconds. When
     41 that timer fires, call either curl_multi_socket_action(3) or
     42 curl_multi_perform(3), depending on which interface you use.
     43 
     44 If this callback is called when a timer is already running, this new expire
     45 time *replaces* the former timeout. The application should then effectively
     46 cancel the old timeout and set a new timeout using this new expire time.
     47 
     48 A **timeout_ms** 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 including zero milliseconds.
     51 
     52 The **timer_callback** is called when the timeout expire time is changed.
     53 
     54 The **clientp** pointer is set with CURLMOPT_TIMERDATA(3).
     55 
     56 The timer callback should return 0 on success, and -1 on error. If this
     57 callback returns error, **all** transfers currently in progress in this multi
     58 handle are aborted and made to fail.
     59 
     60 This callback can be used instead of, or in addition to,
     61 curl_multi_timeout(3).
     62 
     63 **WARNING:** do not call libcurl directly from within the callback itself when
     64 the **timeout_ms** value is zero, since it risks triggering an unpleasant
     65 recursive behavior that immediately calls another call to the callback with a
     66 zero timeout...
     67 
     68 # DEFAULT
     69 
     70 NULL
     71 
     72 # %PROTOCOLS%
     73 
     74 # EXAMPLE
     75 
     76 ~~~c
     77 struct priv {
     78   void *custom;
     79 };
     80 
     81 static int timerfunc(CURLM *multi, long timeout_ms, void *clientp)
     82 {
     83   struct priv *mydata = clientp;
     84   printf("our ptr: %p\n", mydata->custom);
     85 
     86   if(timeout_ms >= 0) {
     87     /* this is the new single timeout to wait for, including zero */
     88   }
     89   else {
     90     /* delete the timeout, nothing to wait for now */
     91   }
     92   return 0;
     93 }
     94 
     95 int main(void)
     96 {
     97   struct priv mydata;
     98   CURLM *multi = curl_multi_init();
     99   curl_multi_setopt(multi, CURLMOPT_TIMERFUNCTION, timerfunc);
    100   curl_multi_setopt(multi, CURLMOPT_TIMERDATA, &mydata);
    101 }
    102 ~~~
    103 
    104 # %AVAILABILITY%
    105 
    106 # RETURN VALUE
    107 
    108 curl_multi_setopt(3) returns a CURLMcode indicating success or error.
    109 
    110 CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
    111 libcurl-errors(3).