FSMImpl.java

/*
 * Copyright (c) 2002, 2003, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package org.jboss.com.sun.corba.se.spi.orbutil.fsm;

import org.jboss.com.sun.corba.se.impl.orbutil.ORBUtility;
import org.jboss.com.sun.corba.se.impl.orbutil.fsm.StateEngineImpl;

/**
 * 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 FSMImpl implements FSM
{
    private boolean debug;

    private State state;

    private StateEngineImpl stateEngine;

    /**
     * Create an instance of an FSM using the StateEngine in a particular start state.
     */
    public FSMImpl(StateEngine se, State startState)
    {
        this(se, startState, false);
    }

    public FSMImpl(StateEngine se, State startState, boolean debug)
    {
        state = startState;
        stateEngine = (StateEngineImpl) se;
        this.debug = debug;
    }

    /**
     * Return the current state.
     */
    public State getState()
    {
        return state;
    }

    /**
     * Perform the transition for the given input in the current state. This proceeds as follows:
     * <p>
     * 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.
     * <ol>
     * <li>If a DEFERED result is returned, retry the input
     * <li>If a ENABLED result is returned, the action for the guarded action is the current action
     * <li>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).
     * </ol>
     * After the action is available, the transition proceeds as follows:
     * <ol>
     * <li>If the next state is not the current state, execute the current state postAction method.
     * <li>Execute the action.
     * <li>If the next state is not the current state, execute the next state preAction method.
     * <li>Set the current state to the next state.
     * </ol>
     */
    public void doIt(Input in)
    {
        stateEngine.doIt(this, in, debug);
    }

    // Methods for use only by StateEngineImpl

    public void internalSetState(State nextState)
    {
        if (debug)
        {
            ORBUtility.dprint(this, "Calling internalSetState with nextState = " + nextState);
        }

        state = nextState;

        if (debug)
        {
            ORBUtility.dprint(this, "Exiting internalSetState with state = " + state);
        }
    }
}

// end of FSMImpl.java