VariableSizeUpdater.java revision 9f606f95f03a75961498803e24bee6799a7c0885 
1/*
2 * ProGuard -- shrinking, optimization, obfuscation, and preverification
3 *             of Java bytecode.
4 *
5 * Copyright (c) 2002-2009 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.classfile.editor;
22
23import proguard.classfile.*;
24import proguard.classfile.attribute.*;
25import proguard.classfile.attribute.visitor.AttributeVisitor;
26import proguard.classfile.instruction.*;
27import proguard.classfile.instruction.visitor.InstructionVisitor;
28import proguard.classfile.util.*;
29
30/**
31 * This AttributeVisitor computes and updates the maximum local variable frame
32 * size of the code attributes that it visits.
33 *
34 * @author Eric Lafortune
35 */
36public class VariableSizeUpdater
37extends      SimplifiedVisitor
38implements   AttributeVisitor,
39             InstructionVisitor
40{
41    //*
42    private static final boolean DEBUG = false;
43    /*/
44    private static       boolean DEBUG = true;
45    //*/
46
47
48    // Implementations for AttributeVisitor.
49
50    public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
51
52
53    public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute)
54    {
55//        DEBUG =
56//            clazz.getName().equals("abc/Def") &&
57//            method.getName(clazz).equals("abc");
58
59        // The minimum variable size is determined by the arguments.
60        codeAttribute.u2maxLocals =
61            ClassUtil.internalMethodParameterSize(method.getDescriptor(clazz),
62                                                  method.getAccessFlags());
63
64        if (DEBUG)
65        {
66            System.out.println("VariableSizeUpdater: "+clazz.getName()+"."+method.getName(clazz)+method.getDescriptor(clazz));
67            System.out.println("  Max locals: "+codeAttribute.u2maxLocals+" <- parameters");
68        }
69
70        // Go over all instructions.
71        codeAttribute.instructionsAccept(clazz, method, this);
72    }
73
74
75    // Implementations for InstructionVisitor.
76
77    public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction) {}
78
79
80    public void visitVariableInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, VariableInstruction variableInstruction)
81    {
82        int variableSize = variableInstruction.variableIndex + 1;
83        if (variableInstruction.isCategory2())
84        {
85            variableSize++;
86        }
87
88        if (codeAttribute.u2maxLocals < variableSize)
89        {
90            codeAttribute.u2maxLocals = variableSize;
91
92            if (DEBUG)
93            {
94                System.out.println("Max locals: "+codeAttribute.u2maxLocals+" <- "+variableInstruction.toString(offset));
95            }
96        }
97    }
98}
99