variablesizeupdater.java

ProGuard 是一个免费的 Java类文件的压缩

/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification
 *             of Java bytecode.
 *
 * Copyright (c) 2002-2007 Eric Lafortune ([e-mail])
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.classfile.editor;

import proguard.classfile.util.*;
import proguard.classfile.attribute.visitor.*;
import proguard.classfile.attribute.*;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.instruction.*;
import proguard.classfile.*;

/**
 * This AttributeVisitor computes and updates the maximum local variable frame
 * size of the code attributes that it visits.
 *
 * @author Eric Lafortune
 */
public class VariableSizeUpdater
extends      SimplifiedVisitor
implements   AttributeVisitor,
             InstructionVisitor
{
    //*
    private static final boolean DEBUG = false;
    /*/
    private static       boolean DEBUG = true;
    //*/


    // Implementations for AttributeVisitor.

    public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}


    public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute)
    {
//        DEBUG =
//            clazz.getName().equals("abc/Def") &&
//            method.getName(clazz).equals("abc");

        // The minimum variable size is determined by the arguments.
        codeAttribute.u2maxLocals = ClassUtil.internalMethodParameterSize(method.getDescriptor(clazz));

        // Non-static methods also have the 'this' variable.
        if ((method.getAccessFlags() & ClassConstants.INTERNAL_ACC_STATIC) == 0)
        {
            codeAttribute.u2maxLocals++;
        }

        if (DEBUG)
        {
            System.out.println("VariableSizeUpdater: "+clazz.getName()+"."+method.getName(clazz)+method.getDescriptor(clazz));
            System.out.println("Max locals: "+codeAttribute.u2maxLocals+" <- parameters");
        }

        // Go over all instructions.
        codeAttribute.instructionsAccept(clazz, method, this);
    }


    // Implementations for InstructionVisitor.

    public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction) {}


    public void visitVariableInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, VariableInstruction variableInstruction)
    {
        int variableSize = variableInstruction.variableIndex + 1;
        if (variableInstruction.isCategory2())
        {
            variableSize++;
        }

        if (codeAttribute.u2maxLocals < variableSize)
        {
            codeAttribute.u2maxLocals = variableSize;

            if (DEBUG)
            {
                System.out.println("Max locals: "+codeAttribute.u2maxLocals+" <- "+variableInstruction.toString(offset));
            }
        }
    }
}