@deftypefun {int} {gnutls_x509_crt_get_extension_by_oid2} (gnutls_x509_crt_t @var{cert}, const char * @var{oid}, unsigned @var{indx}, gnutls_datum_t * @var{output}, unsigned int * @var{critical})
@var{cert}: should contain a @code{gnutls_x509_crt_t}  type

@var{oid}: holds an Object Identified in null terminated string

@var{indx}: In case multiple same OIDs exist in the extensions, this specifies which to send. Use (0) to get the first one.

@var{output}: will hold the allocated extension data

@var{critical}: will be non-zero if the extension is marked as critical

This function will return the extension specified by the OID in the
certificate.  The extensions will be returned as binary data DER
encoded, in the provided buffer.

@strong{Returns:} On success, @code{GNUTLS_E_SUCCESS}  (0) is returned,
otherwise a negative error code is returned. If the certificate does not
contain the specified extension
GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE will be returned.

@strong{Since:} 3.3.8
@end deftypefun