@deftypefun {int} {gnutls_x509_crt_get_extension_data} (gnutls_x509_crt_t @var{cert}, unsigned @var{indx}, void * @var{data}, size_t * @var{sizeof_data})
@var{cert}: should contain a @code{gnutls_x509_crt_t}  type

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

@var{data}: a pointer to a structure to hold the data (may be null)

@var{sizeof_data}: initially holds the size of  @code{data} 

This function will return the requested extension data in the
certificate.  The extension data will be stored in the
provided buffer.

Use @code{gnutls_x509_crt_get_extension_info()}  to extract the OID and
critical flag.  Use @code{gnutls_x509_crt_get_extension_by_oid()}  instead,
if you want to get data indexed by the extension OID rather than
sequence.

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