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ProGuard is a free Java class file shrinker, optimizer, and obfuscator. It removes unused classes, fields, methods, and attributes. It then optimizes the bytecode. It then renames the remaining classes, fields, and methods using short meaningless names. Finally, it preverifies the processed code for Java 6 or for Java Micro Edition.
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/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification
 *             of Java bytecode.
 *
 * Copyright (c) 2002-2009 Eric Lafortune ([email protected])
 *
 * 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.optimize.info;

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

/**
 * This ClassVisitor marks all class members that can not be made private in the
 * classes that it visits, and in the classes to which they refer.
 *
 * @author Eric Lafortune
 */
public class NonPrivateMemberMarker
extends      SimplifiedVisitor
implements   ClassVisitor,
             ConstantVisitor,
             MemberVisitor
{
    private final MethodImplementationFilter filteredMethodMarker = new MethodImplementationFilter(this);


    // Implementations for ClassVisitor.

    public void visitProgramClass(ProgramClass programClass)
    {
        // Mark all referenced class members in different classes.
        programClass.constantPoolEntriesAccept(this);

        // Explicitly mark the  method.
        programClass.methodAccept(ClassConstants.INTERNAL_METHOD_NAME_CLINIT,
                                  ClassConstants.INTERNAL_METHOD_TYPE_CLINIT,
                                  this);

        // Explicitly mark the parameterless  method.
        programClass.methodAccept(ClassConstants.INTERNAL_METHOD_NAME_INIT,
                                  ClassConstants.INTERNAL_METHOD_TYPE_INIT,
                                  this);

        // Mark all methods that may have implementations.
        programClass.methodsAccept(filteredMethodMarker);
    }


    public void visitLibraryClass(LibraryClass libraryClass)
    {
        // Go over all methods.
        libraryClass.methodsAccept(this);
    }


    // Implementations for ConstantVisitor.

    public void visitAnyConstant(Clazz clazz, Constant constant) {}


    public void visitStringConstant(Clazz clazz, StringConstant stringConstant)
    {
        Clazz referencedClass = stringConstant.referencedClass;

        // Is it refering to another class or class member?
        if (referencedClass != null &&
            !referencedClass.equals(clazz))
        {
            // The referenced class member, if any, can never be made private.
            stringConstant.referencedMemberAccept(this);
        }
    }


    public void visitAnyRefConstant(Clazz clazz, RefConstant refConstant)
    {
        Clazz referencedClass = refConstant.referencedClass;

        // Is it refering to a class member in another class?
        // The class member might be in another class, or
        // it may be referenced through another class.
        if (referencedClass != null &&
            !referencedClass.equals(clazz) ||
            !refConstant.getClassName(clazz).equals(clazz.getName()))
        {
            // The referenced class member can never be made private.
            refConstant.referencedMemberAccept(this);
        }
    }


    // Implementations for MemberVisitor.

    public void visitProgramField(ProgramClass programClass, ProgramField programField)
    {
        markCanNotBeMadePrivate(programField);
    }


    public void visitLibraryField(LibraryClass libraryClass, LibraryField libraryField)
    {
        markCanNotBeMadePrivate(libraryField);
    }


    public void visitProgramMethod(ProgramClass programClass, ProgramMethod programMethod)
    {
        markCanNotBeMadePrivate(programMethod);
    }


    public void visitLibraryMethod(LibraryClass libraryClass, LibraryMethod libraryMethod)
    {
        markCanNotBeMadePrivate(libraryMethod);
    }


    // Small utility methods.

    private static void markCanNotBeMadePrivate(Field field)
    {
        FieldOptimizationInfo info = FieldOptimizationInfo.getFieldOptimizationInfo(field);
        if (info != null)
        {
            info.setCanNotBeMadePrivate();
        }
    }


    /**
     * Returns whether the given field can be made private.
     */
    public static boolean canBeMadePrivate(Field field)
    {
        FieldOptimizationInfo info = FieldOptimizationInfo.getFieldOptimizationInfo(field);
        return info != null &&
               info.canBeMadePrivate();
    }


    private static void markCanNotBeMadePrivate(Method method)
    {
        MethodOptimizationInfo info = MethodOptimizationInfo.getMethodOptimizationInfo(method);
        if (info != null)
        {
            info.setCanNotBeMadePrivate();
        }
    }


    /**
     * Returns whether the given method can be made private.
     */
    public static boolean canBeMadePrivate(Method method)
    {
        MethodOptimizationInfo info = MethodOptimizationInfo.getMethodOptimizationInfo(method);
        return info != null &&
               info.canBeMadePrivate();
    }
}