aclitem binary encoding

Hi all,

I was using a PostgreSQL driver that used binary input/output to query
some ACL data and was surprised to see the following error:

no binary output function available for type aclitem

In fact, aclitem has no binary input or output functions

postgres=# SELECT typinput, typoutput, typreceive, typsend FROM pg_type
WHERE typname = 'aclitem';
typinput | typoutput | typreceive | typsend
-----------+------------+------------+---------
aclitemin | aclitemout | - | -
(1 row)

Is this an intentional decision to not support a binary encoding for
aclitem types? Or is it just a lack of a feature?

Thanks,
Joe Koshakow