@deftypefun {int} {gnutls_x509_crt_get_dn_by_oid} (gnutls_x509_crt_t @var{cert}, const char * @var{oid}, unsigned @var{indx}, unsigned int @var{raw_flag}, void * @var{buf}, size_t * @var{buf_size})
@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 RDN, this specifies which to send. Use (0) to get the first one.

@var{raw_flag}: If non-zero returns the raw DER data of the DN part.

@var{buf}: a pointer where the DN part will be copied (may be null).

@var{buf_size}: initially holds the size of  @code{buf} 

This function will extract the part of the name of the Certificate
subject specified by the given OID. The output, if the raw flag is
not used, will be encoded as described in RFC4514. Thus a string
that is ASCII or UTF-8 encoded, depending on the certificate data.

Some helper macros with popular OIDs can be found in gnutls/x509.h
If raw flag is (0), this function will only return known OIDs as
text. Other OIDs will be DER encoded, as described in RFC4514 --
in hex format with a '#' prefix.  You can check about known OIDs
using @code{gnutls_x509_dn_oid_known()} .

If  @code{buf} is null then only the size will be filled. If the  @code{raw_flag} is not specified the output is always null terminated, although the
 @code{buf_size} will not include the null character.

@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