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Class syd.mpx.Mpx

java.lang.Object
   |
   +----syd.mpx.Mpx

public class Mpx

extends Object

Intended use:

• Each emitter is given a different identifier, and sets itself as alive calling the "connect" method of the Mpx. The collector does not execute any "select" statement before calling the "accept" Mpx method.
• The collector loops around a "select" statement serving the requests, until the "select" finally returns a negative value. On the other side, the emitter loops around a "submit" statement. Once the emitter wants to terminate the session, it calls the "quit" method, to cancel itself from the set of "alive" emitters.
• When the emitter submita a request to the collector, it blocks until the request is delivered: therefore it could block forever if the collector does not execute any more "select" methods.

The Mpx is primarily intended as multiplexer among several warm spare activities (the emitters): each of them periodically reports about its activity to one centralized entity (the collector), which coordinates their activity using such reports.

The responsability for its correct use is primarily of the program: the Mpx does not enforce the above policy.

Mpx(int)

CONSTRUCTOR: creates a new multiplexer.

first_alive()

ACCESSOR: returns the identifier if the first, with respect to the ordering of the identifiers, emitter that is alive.

is_alive(int)

ACCESSOR: tests whether the given emitter is alive or not.

mpx_accept(int)

ACCESSOR: blocks until the given emitter becomes alive.

mpx_connect(int)

MUTATOR: sets the emitter as alive.

mpx_quit(int)

MUTATOR: declares itself as not alive; emitter side.

mpx_select()

ACCESSOR: blocks until a request is submitted, or there are no more alive emitters.

mpx_submit(int)

MUTATOR: submits a request and wait for the request to be delivered; Emitter side.

next_not_alive()

ACCESSOR: returns the identifier if the next, with respect to the ordering of the identifiers, emitter that is not alive.

 public Mpx(int n)

CONSTRUCTOR: creates a new multiplexer. No request pending in this state, and all emitters are considered not alive.

 public synchronized int first_alive()

ACCESSOR: returns the identifier if the first, with respect to the ordering of the identifiers, emitter that is alive.

Returns:

an int indicating the emitter, or -1 if there are no alive emitters

 public synchronized int next_not_alive()

ACCESSOR: returns the identifier if the next, with respect to the ordering of the identifiers, emitter that is not alive.

The Mpx is remindful of the last answer to this method, that therefore implements a fair, although predictable, choice among non not alive emitters.

Returns:

an int indicating the emitter, or -1 if there are no alive emitters

 public synchronized boolean is_alive(int key)

ACCESSOR: tests whether the given emitter is alive or not. Collector side.

Parameters:

key - the identifier of an emitter

Returns:

s a boolean, true if the emitter is alive

 public synchronized void mpx_accept(int key) throws InterruptedException

ACCESSOR: blocks until the given emitter becomes alive. Collector side

Parameters:

key - the identifier of an emitter

 public synchronized int mpx_select() throws InterruptedException

ACCESSOR: blocks until a request is submitted, or there are no more alive emitters. Collector side.

In the first case the key of the requesting emitter is returned, in the latter the return value is negative.

Returns:

an int indicating the emitter that submitted a request, or that there are no alive emitters

 public synchronized void mpx_connect(int key) throws EmitterAliveException

MUTATOR: sets the emitter as alive. Emitter side.

Parameters:

key - an int that indicates an emitter

 public synchronized void mpx_submit(int key) throws InterruptedException

MUTATOR: submits a request and wait for the request to be delivered; Emitter side.

Parameters:

key - an int that indicates an emitter

 public synchronized void mpx_quit(int key) throws InterruptedException

MUTATOR: declares itself as not alive; emitter side.

Parameters:

key - an int that indicates an emitter

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