Guard.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
28/**
29 *
30 * @author Ken Cavanaugh
31 */
32public interface Guard
33{
34    public static final class Complement extends GuardBase {
35        private Guard guard ;
36
37        public Complement( GuardBase guard )
38        {
39            super( "not(" + guard.getName() + ")" ) ;
40            this.guard = guard ;
41        }
42
43        public Result evaluate( FSM fsm, Input in )
44        {
45            return guard.evaluate( fsm, in ).complement() ;
46        }
47    }
48
49    public static final class Result {
50        private String name ;
51
52        private Result( String name )
53        {
54            this.name = name ;
55        }
56
57        public static Result convert( boolean res )
58        {
59            return res ? ENABLED : DISABLED ;
60        }
61
62        public Result complement()
63        {
64            if (this == ENABLED)
65                return DISABLED ;
66            else if (this == DISABLED)
67                return ENABLED ;
68            else
69                return DEFERED ;
70        }
71
72        public String toString()
73        {
74            return "Guard.Result[" + name + "]" ;
75        }
76
77        public static final Result ENABLED = new Result( "ENABLED" ) ;
78        public static final Result DISABLED = new Result( "DISABLED" ) ;
79        public static final Result DEFERED = new Result( "DEFERED" ) ;
80    }
81
82    /** Called by the state engine to determine whether a
83    * transition is enabled, defered, or disabled.
84    * The result is interpreted as follows:
85    * <ul>
86    * <li>ENABLED if the transition is ready to proceed
87    * <li>DISABLED if the transition is not ready to proceed
88    * <li>DEFERED if the action associated with the transition
89    * is to be deferred.  This means that the input will not be
90    * acted upon, but rather it will be saved for later execution.
91    * Typically this is implemented using a CondVar wait, and the
92    * blocked thread represents the defered input.  The defered
93    * input is retried when the thread runs again.
94    * </ul>
95    *
96    * @param FSM fsm is the state machine causing this action.
97    * @param Input in is the input that caused the transition.
98    */
99    public Result evaluate( FSM fsm, Input in ) ;
100}
101
102// end of Action.java
103