dynamic large objects <-> C procs; HOWTO?

Greetings -

I was wondering what the best manner of transferring large objects to
and from user-defined "C" functions through the JDBC or libpq interfaces
might be. These objects are mostly transient query results, and shouldn't
be stored on the file system; they are really transcoded imagery, audio,
etc formatted on the fly to the user's specifications.

I've looked a bit at the lo interfaces, and it seems that (appropriately)
everything is geared towards commit/rollback within the executor, such
that things are allocated in palloc(), or one gets and oid and sticks
stuff into the file system.

But is there a way for a user-defined process to somehow support a
read(2) and/or a write(2) type of interface via the fastpath mechanisms,
given the caveat that these things are outside of transactional control?

suggestions/comments/flames welcome.

Chris Nicholas