1 /*
   2  * Copyright (c) 2002, 2003, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package com.sun.corba.se.spi.orbutil.fsm;
  27 
  28 /**
  29  * A StateEngine defines the state transition function for a
  30  * finite state machine (FSM). A FSM always has a current state.
  31  * In response to an Input, the FSM performs an Action and
  32  * makes a transition to a new state.  Note that any object can
  33  * be used as an input if it supports the Input interface.
  34  * For example, a protocol message may be an input.  The FSM
  35  * uses only the result of calling getLabel on the Input to
  36  * drive the transition.
  37  * <p>
  38  * The function can be non-deterministic
  39  * in that the same input may cause transitions to different new
  40  * states from the current state.  In this case, the action that
  41  * is executed for the transition must set the correct new state.
  42  *
  43  * @author Ken Cavanaugh
  44  */
  45 public interface StateEngine
  46 {
  47         /** Add a new transition (old,in,guard,act,new) to the state engine.
  48         * Multiple calls to add with the same old and in are permitted,
  49         * in which case only a transition in which the guard evaluates to
  50         * true will be taken.  If no such transition is enabled, a default
  51         * will be taken.  If more than one transition is enabled, one will
  52         * be chosen arbitrarily.
  53         * This method can only be called before done().  An attempt to
  54         * call it after done() results in an IllegalStateException.
  55         */
  56         public StateEngine add( State oldState, Input input, Guard guard,
  57             Action action, State newState ) throws IllegalStateException ;
  58 
  59         /** Add a transition with a guard that always evaluates to true.
  60         */
  61         public StateEngine add( State oldState, Input input,
  62             Action action, State newState ) throws IllegalStateException ;
  63 
  64         /** Set the default transition and action for a state.
  65         * This transition will be used if no more specific transition was
  66         * defined for the actual input.  Repeated calls to this method
  67         * simply change the default.
  68         * This method can only be called before done().  An attempt to
  69         * call it after done() results in an IllegalStateException.
  70         */
  71         public StateEngine setDefault( State oldState, Action action, State newState )
  72                 throws IllegalStateException ;
  73 
  74         /** Equivalent to setDefault( oldState, act, newState ) where act is an
  75          * action that does nothing.
  76          */
  77         public StateEngine setDefault( State oldState, State newState )
  78                 throws IllegalStateException ;
  79 
  80         /** Euaivalent to setDefault( oldState, oldState )
  81          */
  82         public StateEngine setDefault( State oldState )
  83                 throws IllegalStateException ;
  84 
  85         /** Set the default action used in this state engine.  This is the
  86         * action that is called whenever there is no applicable transition.
  87         * Normally this would simply flag an error.  This method can only
  88         * be called before done().  An attempt to
  89         * call it after done() results in an IllegalStateException.
  90         */
  91         public void setDefaultAction( Action act ) throws IllegalStateException ;
  92 
  93         /** Called after all transitions have been added to the state engine.
  94         * This provides an opportunity for the implementation to optimize
  95         * its representation before the state engine is used.  This method
  96         * may only be called once.  An attempt to call it more than once
  97         * results in an IllegalStateException.
  98         */
  99         public void done() throws IllegalStateException ;
 100 
 101         /** Create an instance of a FSM that uses this state engine.
 102         * The initial state of the FSM will be the stateState specified
 103         * here.  This method can only be called after done().  An attempt
 104         * to call it before done results in an IllegalStateException.
 105         */
 106         public FSM makeFSM( State startState ) throws IllegalStateException ;
 107 }
 108 
 109 // end of StateEngine.java