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Java > Open Source Codes > org > jruby > lexer > yacc > StackState


1 /***** BEGIN LICENSE BLOCK *****
2  * Version: CPL 1.0/GPL 2.0/LGPL 2.1
3  *
4  * The contents of this file are subject to the Common Public
5  * License Version 1.0 (the "License"); you may not use this file
6  * except in compliance with the License. You may obtain a copy of
7  * the License at http://www.eclipse.org/legal/cpl-v10.html
8  *
9  * Software distributed under the License is distributed on an "AS
10  * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
11  * implied. See the License for the specific language governing
12  * rights and limitations under the License.
13  *
14  * Copyright (C) 2002 Jan Arne Petersen <jpetersen@uni-bonn.de>
15  * Copyright (C) 2004 Stefan Matthias Aust <sma@3plus4.de>
16  *
17  * Alternatively, the contents of this file may be used under the terms of
18  * either of the GNU General Public License Version 2 or later (the "GPL"),
19  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
20  * in which case the provisions of the GPL or the LGPL are applicable instead
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26  * the provisions above, a recipient may use your version of this file under
27  * the terms of any one of the CPL, the GPL or the LGPL.
28  ***** END LICENSE BLOCK *****/
29 package org.jruby.lexer.yacc;
30
31 /**
32  *
33  * @author jpetersen
34  */
35 public class StackState implements Cloneable JavaDoc {
36     private long stack = 0;
37
38     public void reset() {
39         reset(0);
40     }
41
42     public void reset(long backup) {
43         stack = backup;
44     }
45
46     public long begin() {
47         long old = stack;
48         stack <<= 1;
49         stack |= 1;
50         return old;
51     }
52
53     public void end() {
54         stack >>= 1;
55     }
56
57     public void stop() {
58         stack <<= 1;
59     }
60
61     public void restart() {
62         stack |= (stack & 1) << 1;
63         stack >>= 1;
64     }
65     
66     public boolean isInState() {
67         return (stack & 1) != 0;
68     }
69 }
70
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