Would it make any sense to a done state to the typical SRR.

Currently the receiving end can get a header, figure out the size, allocate the memory and receive the rest of the data.
 But that is not possible for the reply.

MsgSendReply (block until reply received)
                            MsgReceive
                            MsgRead
                            MsgReply, blocking
MsgSendReply ( unblock )
MsgReadReply  (read rest of data )
MsgReadDone ( indicate we are done)
                            MsgReply unblock.


With QNX4 it was somewhat simple to implement something like this on top of the existing API.  Simply two SSRs in a row.
 A first to send the command and get the size of the reply data. Memory area is grown or allocated for the reply and 
then another SSR is done to get the data.  Receive() takes the pid argument which make implementation easy because one 
can make Receive only wait for message from one process leaving.

With QNX6 implementing something similar looks quite complicated.

Suggestions?