e3fe020089
Remove the PROTOCOLS section from the source files completely and instead generate them based on the header data in the curldown files. It also generates TLS backend information for options marked for TLS as protocol. Closes #13175
87 lines
1.9 KiB
Markdown
87 lines
1.9 KiB
Markdown
---
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c: Copyright (C) Daniel Stenberg, <daniel@haxx.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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Protocol:
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- All
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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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# 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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