org.glassfish.pfl.basic.fsm.Runner Maven / Gradle / Ivy
/*
* Copyright (c) 1997, 2018 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0, which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.glassfish.pfl.basic.fsm ;
/**
* This is the main class that represents an instance of a state machine
* using a state engine. It may be used as a base class, in which case
* the guards and actions have access to the derived class.
*
* @author Ken Cavanaugh
*/
public class Runner {
private boolean debug ;
private FSM current ;
/** Create a new Runner with fsm on top of the stack.
*/
public Runner( FSM fsm ) {
this( fsm, false ) ;
}
public Runner( FSM fsm, boolean debug ) {
current = fsm ;
this.debug = debug ;
}
/** Return the top fsm on the stack.
*/
public FSM peek() {
return current ;
}
/** Push a new fsm onto the stack.
*/
public void push( FSM fsm ) {
fsm.setParent( current ) ;
current = fsm ;
}
public FSM pop() {
FSM result = current ;
current = current.getParent() ;
return result ;
}
/** Return true if the stack is empty, which means that the runner is
* finished.
*/
public boolean done() {
return current == null ;
}
/** Perform the transition for the given input in the current state.
* This proceeds as follows:
* Let S be the current state of the FSM.
* If there are guarded actions for S with input in, evaluate their guards
* successively until all have been evaluted, or one returns a
* non-DISABLED Result.
*
* - If a DEFERED result is returned, retry the input
*
- If a ENABLED result is returned, the action for the guarded action
* is the current action
*
- Otherwise there is no enabled action. If S has a default action
* and next state, use them; otherwise use the state engine default action
* (the next state is always the current state).
*
* After the action is available, the transition proceeds as follows:
*
* - If the next state is not the current state, execute the current state
* postAction method.
*
- Execute the action.
*
- If the next state is not the current state, execute the next state
* preAction method.
*
- Set the current state to the next state.
*
*/
public void doIt( Input in ) {
current.getStateEngine().doIt( this, in, debug ) ;
}
}