aos.jack.util.cursor
Class Change

java.lang.Object
  aos.jack.jak.util.Watchable
      aos.jack.jak.cursor.Cursor
          aos.jack.util.cursor.Change

All Implemented Interfaces:

ObservableInt

Direct Known Subclasses:

Action

public class Change

extends Cursor

The Change class is a class that implements the necessary logic for a Cursor tied to Observable objects. A Change cursor is intended to be used in @wait_for statements, to block the condition testing until the Observable notifies. More exactly, the Change cursor makes the condition be triggered on a notification from the Observable. Thus, a conjunction of several Change cursors will be woken up by a notification from any of the Observables.

Field Summary

Fields inherited from class aos.jack.jak.cursor.Cursor

FALSE, falseCursor, TRUE, trueCursor, UNKNOWN

Constructor Summary

Change(java.util.Observable o)
Constructs a Change Cursor to an Observable.

Change(java.util.Observable o, boolean initial)
Constructs a Change Cursor to an Observable.

Change(Watchable w)

Change(Watchable w, boolean first)

Method Summary

protected boolean	condition() Determines whether the particular change has occurred.
void	finished() This informs the cursor that it is not going to be used again.
boolean	isTriggered() Returns true.
boolean	next() Used to test if the Observable has changed and if the condition is true.
void	register(java.util.Observer o)
Cursor	reset(aos.jack.jak.core.Generator g, int index) Resets the Cursor to its original state.
void	undo() Undo tells the cursor to backtrack anything it has done.
boolean	unRegister(java.util.Observer o)

Methods inherited from class aos.jack.jak.cursor.Cursor

negate

Methods inherited from class aos.jack.jak.util.Watchable

addObserver, countObservers, deleteObserver, deleteObservers, hasChanged, notifyObservers, notifyObservers

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Change

public Change(java.util.Observable o,
              boolean initial)

Constructs a Change Cursor to an Observable. Allows the user to specify whether the cursor condition will be tested on first access.

Parameters:

o - The object to be observed

initial - Specifies whether to test the cursor condition on first access to the cursor.

Change

public Change(java.util.Observable o)

Constructs a Change Cursor to an Observable. The cursor condition will be tested on first access.

Parameters:

o - The object to be observed.

Change

public Change(Watchable w,
              boolean first)

Change

public Change(Watchable w)

Method Detail

isTriggered

public boolean isTriggered()

Returns true.

Overrides:

isTriggered in class Cursor

next

public boolean next()

Used to test if the Observable has changed and if the condition is true.

Specified by:

next in class Cursor

Returns:

True if a change has occurred and the condition is true, false otherwise.

condition

protected boolean condition()

Determines whether the particular change has occurred. User-code that extends Change may re-implement the condition() method to specialise for particular conditions. The default condition() method always returns true.

reset

public Cursor reset(aos.jack.jak.core.Generator g,
                    int index)

Resets the Cursor to its original state. This method is called by the JACK kernel prior to calling next().

Overrides:

reset in class Cursor

Parameters:

g - The generator that generates an equivalent cursor

index - The index of the equivalent cursor in the generator.

Returns:

The reset cursor, or an equivalent one.

undo

public void undo()

Description copied from class: Cursor

Undo tells the cursor to backtrack anything it has done. It is a subset of the reset() functionality since it does not reinitialize the cursor. The only requirement is that any bindings made by the cursor are undone. The state of the cursor after the call is undefined. Most implementations will fail if next() is called after undo() without an intervening call to reset().

Overrides:

undo in class Cursor

finished

public void finished()

Description copied from class: Cursor

This informs the cursor that it is not going to be used again. This is typically used to clean up data strutures and to remove itself from any notification paths.

Overrides:

finished in class Cursor

register

public void register(java.util.Observer o)

Overrides:

register in class Cursor

unRegister

public boolean unRegister(java.util.Observer o)

Overrides:

unRegister in class Cursor