memberdescriptorspecializer.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.optimize;

import proguard.optimize.evaluation.StoringInvocationUnit;
import proguard.classfile.util.*;
import proguard.classfile.visitor.MemberVisitor;
import proguard.classfile.attribute.visitor.AttributeVisitor;
import proguard.classfile.attribute.Attribute;
import proguard.classfile.attribute.annotation.*;
import proguard.classfile.editor.*;
import proguard.classfile.*;
import proguard.evaluation.value.Value;

/**
 * This MemberVisitor removes unused parameters descriptors of the methods that
 * it visits.
 *
 * @see StoringInvocationUnit
 * @see ClassReferenceFixer
 * @author Eric Lafortune
 */
public class MemberDescriptorSpecializer
extends      SimplifiedVisitor
implements   MemberVisitor
{
    private static final boolean DEBUG = true;


    private MemberVisitor extraParameterMemberVisitor;


    /**
     * Creates a new MethodDescriptorShrinker.
     */
    public MemberDescriptorSpecializer()
    {
        this(null);
    }


    /**
     * Creates a new MethodDescriptorShrinker with an extra visitor.
     * @param extraParameterMemberVisitor an optional extra visitor for all
     *                                    class members whose parameters have
     *                                    been specialized.
     */
    public MemberDescriptorSpecializer(MemberVisitor extraParameterMemberVisitor)
    {
        this.extraParameterMemberVisitor = extraParameterMemberVisitor;
    }


    // Implementations for MemberVisitor.

    public void visitProgramField(ProgramClass programClass, ProgramField programField)
    {
        Value parameterValue = StoringInvocationUnit.getFieldValue(programField);
        if (parameterValue.computationalType() == Value.TYPE_REFERENCE)
        {
            Clazz referencedClass = parameterValue.referenceValue().getReferencedClass();
            if (referencedClass != null)
            {
                programField.referencedClass = referencedClass;
            }
        }
    }


    public void visitProgramMethod(ProgramClass programClass, ProgramMethod programMethod)
    {
        // All parameters of non-static methods are shifted by one in the local
        // variable frame.
        int firstParameterIndex =
            (programMethod.getAccessFlags() & ClassConstants.INTERNAL_ACC_STATIC) != 0 ?
                0 : 1;

        int parameterCount =
            ClassUtil.internalMethodParameterCount(programMethod.getDescriptor(programClass));

        int classIndex = 0;

        // Go over the parameters.
        for (int parameterIndex = firstParameterIndex; parameterIndex < parameterCount; parameterIndex++)
        {
            Value parameterValue = StoringInvocationUnit.getMethodParameterValue(programMethod, parameterIndex);
             if (parameterValue.computationalType() == Value.TYPE_REFERENCE)
             {
                 Clazz referencedClass = parameterValue.referenceValue().getReferencedClass();
                 if (referencedClass != null)
                 {
                     if (DEBUG)
                     {
                         if (!referencedClass.equals(programMethod.referencedClasses[classIndex]))
                         {
                             System.out.println("MemberDescriptorSpecializer: "+programClass.getName()+"."+programMethod.getName(programClass)+programMethod.getDescriptor(programClass));
                             System.out.println("  "+programMethod.referencedClasses[classIndex].getName()+" -> "+referencedClass.getName());
                         }
                     }

                     programMethod.referencedClasses[classIndex] = referencedClass;
                 }

                 classIndex++;
             }
        }
    }
}