AttributeUsageMarker.java revision b9cc48a43ed984587c939d02fba5316bf5c0df6e 
1/*
2 * ProGuard -- shrinking, optimization, obfuscation, and preverification
3 *             of Java bytecode.
4 *
5 * Copyright (c) 2002-2013 Eric Lafortune (eric@graphics.cornell.edu)
6 *
7 * This program is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License as published by the Free
9 * Software Foundation; either version 2 of the License, or (at your option)
10 * any later version.
11 *
12 * This program is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
15 * more details.
16 *
17 * You should have received a copy of the GNU General Public License along
18 * with this program; if not, write to the Free Software Foundation, Inc.,
19 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20 */
21package proguard.obfuscate;
22
23import proguard.classfile.*;
24import proguard.classfile.attribute.Attribute;
25import proguard.classfile.attribute.visitor.AttributeVisitor;
26import proguard.classfile.util.SimplifiedVisitor;
27
28/**
29 * This AttributeVisitor marks all attributes that it visits.
30 *
31 * @see AttributeShrinker
32 *
33 * @author Eric Lafortune
34 */
35public class AttributeUsageMarker
36extends      SimplifiedVisitor
37implements   AttributeVisitor
38{
39    // A visitor info flag to indicate the attribute is being used.
40    private static final Object USED = new Object();
41
42
43    // Implementations for AttributeVisitor.
44
45    public void visitAnyAttribute(Clazz clazz, Attribute attribute)
46    {
47        markAsUsed(attribute);
48    }
49
50
51    // Small utility methods.
52
53    /**
54     * Marks the given VisitorAccepter as being used (or useful).
55     * In this context, the VisitorAccepter will be an Attribute object.
56     */
57    private static void markAsUsed(VisitorAccepter visitorAccepter)
58    {
59        visitorAccepter.setVisitorInfo(USED);
60    }
61
62
63    /**
64     * Returns whether the given VisitorAccepter has been marked as being used.
65     * In this context, the VisitorAccepter will be an Attribute object.
66     */
67    static boolean isUsed(VisitorAccepter visitorAccepter)
68    {
69        return visitorAccepter.getVisitorInfo() == USED;
70    }
71}
72