md5(large_object_id)

I have searched the mailing list archives as well as the
internet at large but haven't been able to find a _streaming_
version of md5 hashing for large objects. The closest thing I
found is this thread

http://www.postgresql.org/message-id/5d0f60990704081003p615530acx86257a70bff33fa4@mail.gmail.com

which eventually lead to this code

http://llg.cubic.org/pg-mdagg/

which, however, doesn't stream in the large object data
either. Essentially, for hashing _very_ large objects (to the
order of several GB per object, I am dealing with radiology
studies aka DICOM data) one would want an md5 function which
streams in parts of a large object piece by piece using
md5_update and m5_finalize or some such.

It didn't look like pgcrypto offers a streaming version either.

Anything I am overlooking ?

Thanks,
Karsten
--
GPG key ID E4071346 @ eu.pool.sks-keyservers.net
E167 67FD A291 2BEA 73BD 4537 78B9 A9F9 E407 1346