**************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) 1998 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
*
* This software is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at https://curl.se/docs/copyright.html.
*
* You may opt to use, copy, modify, merge, publish, distribute and/or sell
* copies of the Software, and permit persons to whom the Software is
* furnished to do so, under the terms of the COPYING file.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
**************************************************************************

CURLOPT_HSTSWRITEDATA - pointer passed to the HSTS write callback #include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HSTSWRITEDATA, void *pointer); Data pointer to pass to the HSTS write function. If you use the CURLOPT_HSTSWRITEFUNCTION(3) option, this is the pointer you will get as input in the 4th argument to the callback. This option does not enable HSTS, you need to use CURLOPT_HSTS_CTRL(3) to do that. NULL This feature is only used for HTTP(S) transfer.

CURL *curl = curl_easy_init();
struct MyData this;
if(curl) {
 curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");

 /* pass pointer that gets passed in to the
 CURLOPT_HSTSWRITEFUNCTION callback */
 curl_easy_setopt(curl, CURLOPT_HSTSWRITEDATA, &this);

 curl_easy_perform(curl);
}

Added in 7.74.0 This will return CURLE_OK. CURLOPT_HSTSWRITEFUNCTION "(3), " CURLOPT_HSTSREADDATA "(3), " CURLOPT_HSTSREADFUNCTION "(3), "