@deftypefun {int} {gnutls_ocsp_req_get_cert_id} (gnutls_ocsp_req_const_t @var{req}, unsigned @var{indx}, gnutls_digest_algorithm_t * @var{digest}, gnutls_datum_t * @var{issuer_name_hash}, gnutls_datum_t * @var{issuer_key_hash}, gnutls_datum_t * @var{serial_number})
@var{req}: should contain a @code{gnutls_ocsp_req_t}  type

@var{indx}: Specifies which extension OID to get. Use (0) to get the first one.

@var{digest}: output variable with @code{gnutls_digest_algorithm_t}  hash algorithm

@var{issuer_name_hash}: output buffer with hash of issuer's DN

@var{issuer_key_hash}: output buffer with hash of issuer's public key

@var{serial_number}: output buffer with serial number of certificate to check

This function will return the certificate information of the
 @code{indx} 'ed request in the OCSP request.  The information returned
corresponds to the CertID structure:

<informalexample><programlisting>
CertID	  ::=     SEQUENCE @{
hashAlgorithm       AlgorithmIdentifier,
issuerNameHash      OCTET STRING, -- Hash of Issuer's DN
issuerKeyHash       OCTET STRING, -- Hash of Issuers public key
serialNumber	CertificateSerialNumber @}
</programlisting></informalexample>

Each of the pointers to output variables may be NULL to indicate
that the caller is not interested in that value.

@strong{Returns:} On success, @code{GNUTLS_E_SUCCESS}  (0) is returned, otherwise a
negative error code is returned.  If you have reached the last
CertID available @code{GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE}  will be
returned.
@end deftypefun