@deftypefun {int} {gnutls_x509_crt_get_issuer_alt_name} (gnutls_x509_crt_t @var{cert}, unsigned int @var{seq}, void * @var{ian}, size_t * @var{ian_size}, unsigned int * @var{critical})
@var{cert}: should contain a @code{gnutls_x509_crt_t}  type

@var{seq}: specifies the sequence number of the alt name (0 for the first one, 1 for the second etc.)

@var{ian}: is the place where the alternative name will be copied to

@var{ian_size}: holds the size of ian.

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

This function retrieves the Issuer Alternative Name (2.5.29.18),
contained in the given certificate in the X509v3 Certificate
Extensions.

When the SAN type is otherName, it will extract the data in the
otherName's value field, and @code{GNUTLS_SAN_OTHERNAME}  is returned.
You may use @code{gnutls_x509_crt_get_subject_alt_othername_oid()}  to get
the corresponding OID and the "virtual" SAN types (e.g.,
@code{GNUTLS_SAN_OTHERNAME_XMPP} ).

If an otherName OID is known, the data will be decoded.  Otherwise
the returned data will be DER encoded, and you will have to decode
it yourself.  Currently, only the RFC 3920 id-on-xmppAddr Issuer
AltName is recognized.

@strong{Returns:} the alternative issuer name type on success, one of the
enumerated @code{gnutls_x509_subject_alt_name_t} .  It will return
@code{GNUTLS_E_SHORT_MEMORY_BUFFER}  if  @code{ian_size} is not large enough
to hold the value.  In that case  @code{ian_size} will be updated with
the required size.  If the certificate does not have an
Alternative name with the specified sequence number then
@code{GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE}  is returned.

@strong{Since:} 2.10.0
@end deftypefun