/* * 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; /** * A StateEngine defines the state transition function for a finite state machine (FSM). A FSM always has a current * state. In response to an Input, the FSM performs an Action and makes a transition to a new state. Note that any * object can be used as an input if it supports the Input interface. For example, a protocol message may be an input. * The FSM uses only the result of calling getLabel on the Input to drive the transition. * <p> * The function can be non-deterministic in that the same input may cause transitions to different new states from the * current state. In this case, the action that is executed for the transition must set the correct new state. * * @author Ken Cavanaugh */ public interface StateEngine { /** * Add a new transition (old,in,guard,act,new) to the state engine. Multiple calls to add with the same old and in * are permitted, in which case only a transition in which the guard evaluates to true will be taken. If no such * transition is enabled, a default will be taken. If more than one transition is enabled, one will be chosen * arbitrarily. This method can only be called before done(). An attempt to call it after done() results in an * IllegalStateException. */ public StateEngine add(State oldState, Input input, Guard guard, Action action, State newState) throws IllegalStateException; /** * Add a transition with a guard that always evaluates to true. */ public StateEngine add(State oldState, Input input, Action action, State newState) throws IllegalStateException; /** * Set the default transition and action for a state. This transition will be used if no more specific transition * was defined for the actual input. Repeated calls to this method simply change the default. This method can only * be called before done(). An attempt to call it after done() results in an IllegalStateException. */ public StateEngine setDefault(State oldState, Action action, State newState) throws IllegalStateException; /** * Equivalent to setDefault( oldState, act, newState ) where act is an action that does nothing. */ public StateEngine setDefault(State oldState, State newState) throws IllegalStateException; /** * Euaivalent to setDefault( oldState, oldState ) */ public StateEngine setDefault(State oldState) throws IllegalStateException; /** * Set the default action used in this state engine. This is the action that is called whenever there is no * applicable transition. Normally this would simply flag an error. This method can only be called before done(). An * attempt to call it after done() results in an IllegalStateException. */ public void setDefaultAction(Action act) throws IllegalStateException; /** * Called after all transitions have been added to the state engine. This provides an opportunity for the * implementation to optimize its representation before the state engine is used. This method may only be called * once. An attempt to call it more than once results in an IllegalStateException. */ public void done() throws IllegalStateException; /** * Create an instance of a FSM that uses this state engine. The initial state of the FSM will be the stateState * specified here. This method can only be called after done(). An attempt to call it before done results in an * IllegalStateException. */ public FSM makeFSM(State startState) throws IllegalStateException; } // end of StateEngine.java