@deftypefun {int} {gnutls_x509_crt_get_issuer_dn_oid} (gnutls_x509_crt_t @var{cert}, unsigned @var{indx}, void * @var{oid}, size_t * @var{oid_size})
@var{cert}: should contain a @code{gnutls_x509_crt_t}  type

@var{indx}: This specifies which OID to return. Use (0) to get the first one.

@var{oid}: a pointer to a buffer to hold the OID (may be null)

@var{oid_size}: initially holds the size of  @code{oid} 

This function will extract the OIDs of the name of the Certificate
issuer specified by the given index.

If  @code{oid} is null then only the size will be filled. The  @code{oid} returned will be null terminated, although  @code{oid_size} will not
account for the trailing null.

@strong{Returns:} @code{GNUTLS_E_SHORT_MEMORY_BUFFER}  if the provided buffer is not
long enough, and in that case the  @code{buf_size} will be updated with
the required size. @code{GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE}  if there
are no data in the current index. On success 0 is returned.
@end deftypefun