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From - Fri Sep 24 12:35:31 1999
Message-ID: <md5:C1D667E4B36ABEE47FEBB82102E8C7AC>
Date: Wed, 30 Mar 94 19:05:02 +0200
From: Kees Schuerman <kees@scorpio>
To: eclipse
Subject: Message Passing System Users Only
Cc: kees
Content-Length: 1465
Status: RO
X-Lines: 60


The message passing system consists of two layers: the a-layer (used to
be structure layer) and the b-layer (used to be byte layer). The a-layer
sits on top of the b-layer. The main difference between the two layers
is that the a-layer provides several ports and the b-layer only a single
port.

Since the design draft presented in ECLiPSe Note 94-01, there have been
various modifications to the interface. You can get an up to date view 
of the a-layer and b-layer interfaces by looking in the files

			amsg.h
			bmsg.h

You can find them in ~kees/public/MPS.

Note 1. Relevant primitives for worker management are:

	bport_register()
	bport_deregister()

Note 2. Relevant primitives for stack copying are:

	bmem_put()
	bmem_get()
	bmem_ack()	/* upcall */

        On return of bmem_put() it is safe to start changing the data
	being put to the destination process.

	On the invocation of bmem_ack() the data transfer of a put/get
	operation is complete!

        Pitfall: bmemack() may be called before the return of bmem_put
		 or bmem_get !

Note 3. Relevant primitives for scheduler are:

	amsg_alloc()
	amsg_send()
	amsg_receive()
	amsg_free()

	Sending messages which contain just bytes does not involve
	any data format conversions !

Note 4. Initialization

	amsg_init() is currently being redefined. It will
	be able to get a specified number of ports with 
	specified notification procedures.


Hope this helps you to make some progress.

Kees