ConstantParameterFilter.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.optimize;
22
23import proguard.classfile.*;
24import proguard.classfile.util.*;
25import proguard.classfile.visitor.MemberVisitor;
26import proguard.evaluation.value.Value;
27import proguard.optimize.evaluation.StoringInvocationUnit;
28import proguard.optimize.info.ParameterUsageMarker;
29
30/**
31 * This <code>MemberVisitor</code> delegates its visits to program methods
32 * to another given <code>MemberVisitor</code>, for each method parameter
33 * that has been marked as constant.
34 *
35 * @see StoringInvocationUnit
36 * @author Eric Lafortune
37 */
38public class ConstantParameterFilter
39extends      SimplifiedVisitor
40implements   MemberVisitor
41{
42    private final MemberVisitor constantParameterVisitor;
43
44
45    /**
46     * Creates a new ConstantParameterFilter.
47     * @param constantParameterVisitor the <code>MemberVisitor</code> to which
48     *                                 visits will be delegated.
49     */
50    public ConstantParameterFilter(MemberVisitor constantParameterVisitor)
51    {
52        this.constantParameterVisitor = constantParameterVisitor;
53    }
54
55
56    // Implementations for MemberVisitor.
57
58    public void visitProgramMethod(ProgramClass programClass, ProgramMethod programMethod)
59    {
60        // All parameters of non-static methods are shifted by one in the local
61        // variable frame.
62        int firstParameterIndex =
63            (programMethod.getAccessFlags() & ClassConstants.INTERNAL_ACC_STATIC) != 0 ?
64                0 : 1;
65
66        int parameterCount =
67            ClassUtil.internalMethodParameterCount(programMethod.getDescriptor(programClass));
68
69        for (int index = firstParameterIndex; index < parameterCount; index++)
70        {
71            Value value = StoringInvocationUnit.getMethodParameterValue(programMethod, index);
72            if (value != null &&
73                value.isParticular())
74            {
75                constantParameterVisitor.visitProgramMethod(programClass, programMethod);
76            }
77        }
78    }
79}