mirror of https://github.com/curl/curl.git synced 2024-12-21 06:50:10 +08:00

Daniel Stenberg 5a488251f7

- make DEFAULT sections less repetitive

- make historic mentions use HISTORY

- generate the protocols section on `# %PROTOCOLS%` instead of guessing
  where to put it

- generate the availability section on `# %AVAILABILITY%` instead of
  guessing where to put it

- make the protocols section more verbose

Closes #14227

2024-07-19 17:03:25 +02:00

1.9 KiB

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SPDX-License-Identifier

Title

Section

Source

See-also

Protocol

Added-in

curl

CURLOPT_RESOLVER_START_FUNCTION

libcurl

CURLOPT_PREREQFUNCTION (3)

CURLOPT_RESOLVER_START_DATA (3)

All

7.59.0

NAME

CURLOPT_RESOLVER_START_FUNCTION - callback called before a new name resolve is started

SYNOPSIS

#include <curl/curl.h>

int resolver_start_cb(void *resolver_state, void *reserved, void *userdata);

CURLcode curl_easy_setopt(CURL *handle,
                          CURLOPT_RESOLVER_START_FUNCTION,
                          resolver_start_cb);

DESCRIPTION

Pass a pointer to your callback function, which should match the prototype shown above.

This callback function gets called by libcurl every time before a new resolve request is started.

resolver_state points to a backend-specific resolver state. Currently only the ares resolver backend has a resolver state. It can be used to set up any desired option on the ares channel before it is used, for example setting up socket callback options.

reserved is reserved.

userdata is the user pointer set with the CURLOPT_RESOLVER_START_DATA(3) option.

The callback must return 0 on success. Returning a non-zero value causes the resolve to fail.

DEFAULT

NULL (No callback)

%PROTOCOLS%

EXAMPLE

static int start_cb(void *resolver_state, void *reserved,
                    void *userdata)
{
  (void)reserved;
  printf("Received resolver_state=%p userdata=%p\n",
         resolver_state, userdata);
  return 0;
}

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_RESOLVER_START_FUNCTION, start_cb);
    curl_easy_setopt(curl, CURLOPT_RESOLVER_START_DATA, curl);
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
    curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}

%AVAILABILITY%

RETURN VALUE

Returns CURLE_OK

1.9 KiB Raw Blame History