Re: [9fans] Channel casting

[rog@vitanuova.com]

> For the case you describe, the client typically
> sends a (request, return-channel) pair and
> then recvs from the return channel, which is
> private to that client.

note that if clients adhere correctly to protocol, then it's not
strictly necessary to allocate a new channel each time.

to modify russ's examples:

an echo server:
	srvchan := chan of int;
	srvreplychan := chan of int;
	for(;;){
		n := <-srvchan;
		srvreplychan <-= n;
	}

	echothread(srvchan, replychan: chan of int)
	{
		for(i:=0;; i++){
			srvchan <-= i;
			j := <-replychan;
			sys->print("sent %d, got %d\n", i, j);
		}
	}

	spawn echothread(srvchan, srvreplychan);
	spawn echothread(srvchan, srvreplychan);
	spawn echothread(srvchan, srvreplychan);
	spawn echothread(srvchan, srvreplychan);

since we're using synchronous (unbuffered) channels, and clients
always write, then read, the server is guaranteed to be writing back
to the same client.

sometimes this makes things simpler; other times, sending a reply
channel makes more sense (particularly when the kind of reply might
depend on the particular request).

  cheers,
    rog.