innerusagemarker.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 program 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 program 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 General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.shrink;

import proguard.classfile.*;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.visitor.*;
import proguard.classfile.constant.*;
import proguard.classfile.constant.visitor.ConstantVisitor;
import proguard.classfile.util.SimplifiedVisitor;
import proguard.classfile.visitor.ClassVisitor;

/**
 * This AttributeVisitor recursively marks all necessary inner class information
 * in the attributes that it visits.
 *
 * @see UsageMarker
 *
 * @author Eric Lafortune
 */
public class InnerUsageMarker
extends      SimplifiedVisitor
implements   AttributeVisitor,
             InnerClassesInfoVisitor,
             ConstantVisitor,
             ClassVisitor
{
    private UsageMarker usageMarker;

    // Fields acting as a return parameters for several methods.
    private boolean attributeUsed;
    private boolean classUsed;


    /**
     * Creates a new InnerUsageMarker.
     * @param usageMarker the usage marker that is used to mark the classes
     *                    and class members.
     */
    public InnerUsageMarker(UsageMarker usageMarker)
    {
        this.usageMarker = usageMarker;
    }


    // Implementations for AttributeVisitor.

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


    public void visitInnerClassesAttribute(Clazz clazz, InnerClassesAttribute innerClassesAttribute)
    {
        // Mark the necessary inner classes information.
        attributeUsed = false;
        innerClassesAttribute.innerClassEntriesAccept(clazz, this);

        if (attributeUsed)
        {
            // We got a positive used flag, so some inner class is being used.
            // Mark this attribute as being used as well.
            usageMarker.markAsUsed(innerClassesAttribute);

            markConstant(clazz, innerClassesAttribute.u2attributeNameIndex);
        }
    }


    // Implementations for InnerClassesInfoVisitor.

    public void visitInnerClassesInfo(Clazz clazz, InnerClassesInfo innerClassesInfo)
    {
        boolean innerClassesInfoUsed = usageMarker.isUsed(innerClassesInfo);

        if (!innerClassesInfoUsed)
        {
            int u2innerClassIndex = innerClassesInfo.u2innerClassIndex;
            int u2outerClassIndex = innerClassesInfo.u2outerClassIndex;
            int u2innerNameIndex  = innerClassesInfo.u2innerNameIndex;

            innerClassesInfoUsed = true;

            if (u2innerClassIndex != 0)
            {
                // Check if the inner class is marked as being used.
                markConstant(clazz, u2innerClassIndex);
                innerClassesInfoUsed &= classUsed;
            }

            if (u2outerClassIndex != 0)
            {
                // Check if the outer class is marked as being used.
                markConstant(clazz, u2outerClassIndex);
                innerClassesInfoUsed &= classUsed;
            }

            // If both the inner class and the outer class are marked as being
            // used, then mark this InnerClassesInfo as well.
            if (innerClassesInfoUsed)
            {
                usageMarker.markAsUsed(innerClassesInfo);

                if (u2innerNameIndex != 0)
                {
                    markConstant(clazz, u2innerNameIndex);
                }
            }
        }

        // The return value.
        attributeUsed |= innerClassesInfoUsed;
    }


    // Implementations for ConstantVisitor.

    public void visitClassConstant(Clazz clazz, ClassConstant classConstant)
    {
        classUsed = usageMarker.isUsed(classConstant);

        // Is the class constant marked as being used?
        if (!classUsed)
        {
            // Check the referenced class.
            classUsed = true;
            classConstant.referencedClassAccept(this);

            // Is the referenced class marked as being used?
            if (classUsed)
            {
                // Mark the class constant and its Utf8 constant.
                usageMarker.markAsUsed(classConstant);

                markConstant(clazz, classConstant.u2nameIndex);
            }
        }
    }


    public void visitUtf8Constant(Clazz clazz, Utf8Constant utf8Constant)
    {
        usageMarker.markAsUsed(utf8Constant);
    }


    // Implementations for ClassVisitor.

    public void visitProgramClass(ProgramClass programClass)
    {
        classUsed = usageMarker.isUsed(programClass);
    }


    public void visitLibraryClass(LibraryClass libraryClass)
    {
        classUsed = true;
    }


    // Small utility methods.

    /**
     * Marks the given constant pool entry of the given class. This includes
     * visiting any other referenced constant pool entries.
     */
    private void markConstant(Clazz clazz, int index)
    {
         clazz.constantPoolEntryAccept(index, this);
    }
}