---
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
Title: CURLOPT_HSTSREADDATA
Section: 3
Source: libcurl
Protocol:
  - HTTP
See-also:
  - CURLOPT_HSTS (3)
  - CURLOPT_HSTSREADFUNCTION (3)
  - CURLOPT_HSTSWRITEDATA (3)
  - CURLOPT_HSTSWRITEFUNCTION (3)
Added-in: 7.74.0
---

# NAME

CURLOPT_HSTSREADDATA - pointer passed to the HSTS read callback

# SYNOPSIS

~~~c
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HSTSREADDATA, void *pointer);
~~~

# DESCRIPTION

Data *pointer* to pass to the HSTS read function. If you use the
CURLOPT_HSTSREADFUNCTION(3) option, this is the pointer you get as input
in the 3rd argument to the callback.

This option does not enable HSTS, you need to use CURLOPT_HSTS_CTRL(3) to
do that.

# DEFAULT

NULL

# %PROTOCOLS%

# EXAMPLE

~~~c
struct MyData {
  void *custom;
};

static CURLSTScode hsts_cb(CURL *easy, struct curl_hstsentry *sts,
                           void *clientp)
{
  /* populate the struct as documented */
  return CURLSTS_OK;
}

int main(void)
{
  CURL *curl = curl_easy_init();
  struct MyData my_data;
  if(curl) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");

    /* pass pointer that gets passed in to the
       CURLOPT_HSTSREADFUNCTION callback */
    curl_easy_setopt(curl, CURLOPT_HSTSREADDATA, &my_data);
    /* set HSTS read callback */
    curl_easy_setopt(curl, CURLOPT_HSTSREADFUNCTION, hsts_cb);

    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
~~~

# %AVAILABILITY%

# RETURN VALUE

This returns CURLE_OK.
