CURLOPT_HSTSREADDATA(3)    Library Functions Manual    CURLOPT_HSTSREADDATA(3)

NAME
       CURLOPT_HSTSREADDATA - pointer passed to the HSTS read callback

SYNOPSIS
       #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
       This functionality affects http only

EXAMPLE
       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
       Added in curl 7.74.0

RETURN VALUE
       This returns CURLE_OK.

SEE ALSO
       CURLOPT_HSTS(3), CURLOPT_HSTSREADFUNCTION(3), CURLOPT_HSTSWRITEDATA(3),
       CURLOPT_HSTSWRITEFUNCTION(3)

libcurl                           2026-09-02           CURLOPT_HSTSREADDATA(3)