89 lines
1.9 KiB
Markdown
89 lines
1.9 KiB
Markdown
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---
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c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
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SPDX-License-Identifier: curl
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Title: CURLOPT_RESOLVER_START_FUNCTION
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Section: 3
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Source: libcurl
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See-also:
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- CURLOPT_PREREQFUNCTION (3)
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- CURLOPT_RESOLVER_START_DATA (3)
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---
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# NAME
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CURLOPT_RESOLVER_START_FUNCTION - callback called before a new name resolve is started
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# SYNOPSIS
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~~~c
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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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~~~
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# 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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*resolver_state* points to a backend-specific resolver state. Currently only
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the ares resolver backend has a resolver state. It can be used to set up any
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desired option on the ares channel before it is used, for example setting up
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socket callback options.
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*reserved* is reserved.
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*userdata* is the user pointer set with the
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CURLOPT_RESOLVER_START_DATA(3) 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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# DEFAULT
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NULL (No callback)
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# PROTOCOLS
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All
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# EXAMPLE
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~~~c
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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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~~~
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# AVAILABILITY
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Added in 7.59.0
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# RETURN VALUE
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Returns CURLE_OK
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