FSMImpl.java revision 608:7e06bf1dcb09 
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
26package com.sun.corba.se.spi.orbutil.fsm ;
27
28import java.util.Set ;
29import java.util.HashSet ;
30
31import com.sun.corba.se.spi.orbutil.fsm.Input ;
32import com.sun.corba.se.spi.orbutil.fsm.StateEngine ;
33import com.sun.corba.se.impl.orbutil.fsm.StateEngineImpl ;
34import com.sun.corba.se.impl.orbutil.ORBUtility ;
35import com.sun.corba.se.spi.orbutil.fsm.FSM ;
36
37/**
38 * This is the main class that represents an instance of a state machine
39 * using a state engine.  It may be used as a base class, in which case
40 * the guards and actions have access to the derived class.
41 *
42 * @author Ken Cavanaugh
43 */
44public class FSMImpl implements FSM
45{
46    private boolean debug ;
47    private State state ;
48    private StateEngineImpl stateEngine ;
49
50    /** Create an instance of an FSM using the StateEngine
51    * in a particular start state.
52    */
53    public FSMImpl( StateEngine se, State startState )
54    {
55        this( se, startState, false ) ;
56    }
57
58    public FSMImpl( StateEngine se, State startState, boolean debug )
59    {
60        state = startState ;
61        stateEngine = (StateEngineImpl)se ;
62        this.debug = debug ;
63    }
64
65    /** Return the current state.
66    */
67    public State getState()
68    {
69        return state ;
70    }
71
72    /** Perform the transition for the given input in the current state.  This proceeds as follows:
73    * <p>Let S be the current state of the FSM.
74    * If there are guarded actions for S with input in, evaluate their guards successively until
75    * all have been evaluted, or one returns a non-DISABLED Result.
76    * <ol>
77    * <li>If a DEFERED result is returned, retry the input
78    * <li>If a ENABLED result is returned, the action for the guarded action
79    * is the current action
80    * <li>Otherwise there is no enabled action.  If S has a default action and next state, use them; otherwise
81    * use the state engine default action (the next state is always the current state).
82    * </ol>
83    * After the action is available, the transition proceeds as follows:
84    * <ol>
85    * <li>If the next state is not the current state, execute the current state postAction method.
86    * <li>Execute the action.
87    * <li>If the next state is not the current state, execute the next state preAction method.
88    * <li>Set the current state to the next state.
89    * </ol>
90    */
91    public void doIt( Input in )
92    {
93        stateEngine.doIt( this, in, debug ) ;
94    }
95
96    // Methods for use only by StateEngineImpl
97
98    public void internalSetState( State nextState )
99    {
100        if (debug) {
101            ORBUtility.dprint( this, "Calling internalSetState with nextState = " +
102                nextState ) ;
103        }
104
105        state = nextState ;
106
107        if (debug) {
108            ORBUtility.dprint( this, "Exiting internalSetState with state = " +
109                state ) ;
110        }
111    }
112}
113
114// end of FSMImpl.java
115