1/*
2 * Javassist, a Java-bytecode translator toolkit.
3 * Copyright (C) 1999-2007 Shigeru Chiba. All Rights Reserved.
4 *
5 * The contents of this file are subject to the Mozilla Public License Version
6 * 1.1 (the "License"); you may not use this file except in compliance with
7 * the License.  Alternatively, the contents of this file may be used under
8 * the terms of the GNU Lesser General Public License Version 2.1 or later.
9 *
10 * Software distributed under the License is distributed on an "AS IS" basis,
11 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
12 * for the specific language governing rights and limitations under the
13 * License.
14 */
15
16package javassist.runtime;
17
18/**
19 * A support class for implementing <code>$cflow</code>.
20 * This support class is required at runtime
21 * only if <code>$cflow</code> is used.
22 *
23 * @see javassist.CtBehavior#useCflow(String)
24 */
25public class Cflow extends ThreadLocal {
26    private static class Depth {
27        private int depth;
28        Depth() { depth = 0; }
29        int get() { return depth; }
30        void inc() { ++depth; }
31        void dec() { --depth; }
32    }
33
34    protected synchronized Object initialValue() {
35        return new Depth();
36    }
37
38    /**
39     * Increments the counter.
40     */
41    public void enter() { ((Depth)get()).inc(); }
42
43    /**
44     * Decrements the counter.
45     */
46    public void exit() { ((Depth)get()).dec(); }
47
48    /**
49     * Returns the value of the counter.
50     */
51    public int value() { return ((Depth)get()).get(); }
52}
53