quickjs-tart

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

CURLOPT_RESOLVER_START_FUNCTION.md (2113B)

      1 ---
      2 c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
      3 SPDX-License-Identifier: curl
      4 Title: CURLOPT_RESOLVER_START_FUNCTION
      5 Section: 3
      6 Source: libcurl
      7 See-also:
      8   - CURLOPT_PREREQFUNCTION (3)
      9   - CURLOPT_RESOLVER_START_DATA (3)
     10 Protocol:
     11   - All
     12 Added-in: 7.59.0
     13 ---
     14 
     15 # NAME
     16 
     17 CURLOPT_RESOLVER_START_FUNCTION - callback called before a new name resolve is started
     18 
     19 # SYNOPSIS
     20 
     21 ~~~c
     22 #include <curl/curl.h>
     23 
     24 int resolver_start_cb(void *resolver_state, void *reserved, void *userdata);
     25 
     26 CURLcode curl_easy_setopt(CURL *handle,
     27                           CURLOPT_RESOLVER_START_FUNCTION,
     28                           resolver_start_cb);
     29 ~~~
     30 
     31 # DESCRIPTION
     32 
     33 Pass a pointer to your callback function, which should match the prototype
     34 shown above.
     35 
     36 This callback function gets called by libcurl every time before a new resolve
     37 request is started.
     38 
     39 *resolver_state* points to a backend-specific resolver state. Currently only
     40 the ares resolver backend has a resolver state. It can be used to set up any
     41 desired option on the ares channel before it is used, for example setting up
     42 socket callback options.
     43 
     44 *reserved* is reserved.
     45 
     46 *userdata* is the user pointer set with the
     47 CURLOPT_RESOLVER_START_DATA(3) option.
     48 
     49 The callback must return 0 on success. Returning a non-zero value causes the
     50 resolve to fail.
     51 
     52 # DEFAULT
     53 
     54 NULL (No callback)
     55 
     56 # %PROTOCOLS%
     57 
     58 # EXAMPLE
     59 
     60 ~~~c
     61 static int start_cb(void *resolver_state, void *reserved,
     62                     void *userdata)
     63 {
     64   (void)reserved;
     65   printf("Received resolver_state=%p userdata=%p\n",
     66          resolver_state, userdata);
     67   return 0;
     68 }
     69 
     70 int main(void)
     71 {
     72   CURL *curl = curl_easy_init();
     73   if(curl) {
     74     curl_easy_setopt(curl, CURLOPT_RESOLVER_START_FUNCTION, start_cb);
     75     curl_easy_setopt(curl, CURLOPT_RESOLVER_START_DATA, curl);
     76     curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
     77     curl_easy_perform(curl);
     78     curl_easy_cleanup(curl);
     79   }
     80 }
     81 ~~~
     82 
     83 # %AVAILABILITY%
     84 
     85 # RETURN VALUE
     86 
     87 curl_easy_setopt(3) returns a CURLcode indicating success or error.
     88 
     89 CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
     90 libcurl-errors(3).