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.TH CURLOPT_HSTSREADFUNCTION 3 "14 Sep 2020" libcurl libcurl
.SH NAME
CURLOPT_HSTSREADFUNCTION \- read callback for HSTS hosts
.SH SYNOPSIS
.nf
#include <curl/curl.h>

struct curl_hstsentry {
  char *name;
  size_t namelen;
  unsigned int includeSubDomains:1;
  char expire[18]; /* YYYYMMDD HH:MM:SS [null-terminated] */
};

CURLSTScode hstsread(CURL *easy, struct curl_hstsentry *sts, void *clientp);

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HSTSREADFUNCTION, hstsread);
.fi
.SH DESCRIPTION
Pass a pointer to your callback function, as the prototype shows above.

This callback function gets called by libcurl repeatedly when it populates the
in-memory HSTS cache.

Set the \fIclientp\fP argument with the \fICURLOPT_HSTSREADDATA(3)\fP option
or it is NULL.

When this callback is invoked, the \fIsts\fP pointer points to a populated
struct: Copy the host name to \fIname\fP (no longer than \fInamelen\fP
bytes). Make it null-terminated. Set \fIincludeSubDomains\fP to TRUE or
FALSE. Set \fIexpire\fP to a date stamp or a zero length string for *forever*
(wrong date stamp format might cause the name to not get accepted)

The callback should return \fICURLSTS_OK\fP if it returns a name and is
prepared to be called again (for another host) or \fICURLSTS_DONE\fP if it has
no entry to return. It can also return \fICURLSTS_FAIL\fP to signal
error. Returning \fICURLSTS_FAIL\fP stops the transfer from being performed
and make \fICURLE_ABORTED_BY_CALLBACK\fP get returned.

This option does not enable HSTS, you need to use \fICURLOPT_HSTS_CTRL(3)\fP to
do that.
.SH DEFAULT
NULL - no callback.
.SH PROTOCOLS
This feature is only used for HTTP(S) transfer.
.SH EXAMPLE
.nf
{
  /* set HSTS read callback */
  curl_easy_setopt(curl, CURLOPT_HSTSREADFUNCTION, hstsread);

  /* pass in suitable argument to the callback */
  curl_easy_setopt(curl, CURLOPT_HSTSREADDATA, &hstspreload[0]);

  result = curl_easy_perform(curl);
}
.fi
.SH AVAILABILITY
Added in 7.74.0
.SH RETURN VALUE
This returns CURLE_OK.
.SH "SEE ALSO"
.BR CURLOPT_HSTSREADDATA "(3), " CURLOPT_HSTSWRITEFUNCTION "(3), "
.BR CURLOPT_HSTS "(3), " CURLOPT_HSTS_CTRL "(3), "