90 lines
2.9 KiB
Groff
90 lines
2.9 KiB
Groff
.\" **************************************************************************
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.\" * _ _ ____ _
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.\" * Project ___| | | | _ \| |
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.\" * / __| | | | |_) | |
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.\" * | (__| |_| | _ <| |___
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.\" * \___|\___/|_| \_\_____|
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.\" *
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.\" * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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.\" *
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.\" * This software is licensed as described in the file COPYING, which
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.\" * you should have received as part of this distribution. The terms
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.\" * are also available at https://curl.se/docs/copyright.html.
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.\" *
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.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
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.\" * copies of the Software, and permit persons to whom the Software is
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.\" * furnished to do so, under the terms of the COPYING file.
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.\" *
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.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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.\" * KIND, either express or implied.
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.\" *
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.\" * SPDX-License-Identifier: curl
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.\" *
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.\" **************************************************************************
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.\"
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.TH CURLOPT_RESOLVER_START_FUNCTION 3 "14 Feb 2018" libcurl libcurl
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.SH NAME
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CURLOPT_RESOLVER_START_FUNCTION \- callback called before a new name resolve is started
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.SH SYNOPSIS
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.nf
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#include <curl/curl.h>
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int resolver_start_cb(void *resolver_state, void *reserved, void *userdata);
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CURLcode curl_easy_setopt(CURL *handle,
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CURLOPT_RESOLVER_START_FUNCTION,
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resolver_start_cb);
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.SH DESCRIPTION
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Pass a pointer to your callback function, which should match the prototype
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shown above.
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This callback function gets called by libcurl every time before a new resolve
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request is started.
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\fIresolver_state\fP points to a backend-specific resolver state. Currently
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only the ares resolver backend has a resolver state. It can be used to set up
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any desired option on the ares channel before it's used, for example setting up
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socket callback options.
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\fIreserved\fP is reserved.
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\fIuserdata\fP is the user pointer set with the
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\fICURLOPT_RESOLVER_START_DATA(3)\fP option.
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The callback must return 0 on success. Returning a non-zero value causes the
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resolve to fail.
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.SH DEFAULT
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NULL (No callback)
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.SH PROTOCOLS
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All
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.SH EXAMPLE
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.nf
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static int start_cb(void *resolver_state, void *reserved,
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void *userdata)
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{
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(void)reserved;
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printf("Received resolver_state=%p userdata=%p\\n",
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resolver_state, userdata);
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return 0;
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}
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int main(void)
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{
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CURL *curl = curl_easy_init();
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if(curl) {
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curl_easy_setopt(curl, CURLOPT_RESOLVER_START_FUNCTION, start_cb);
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curl_easy_setopt(curl, CURLOPT_RESOLVER_START_DATA, curl);
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
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curl_easy_perform(curl);
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curl_easy_cleanup(curl);
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}
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}
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.fi
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.SH AVAILABILITY
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Added in 7.59.0
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.SH RETURN VALUE
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Returns CURLE_OK
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.SH "SEE ALSO"
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.BR CURLOPT_PREREQFUNCTION (3),
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.BR CURLOPT_RESOLVER_START_DATA (3)
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