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      1 /*
      2  * ProGuard -- shrinking, optimization, obfuscation, and preverification
      3  *             of Java bytecode.
      4  *
      5  * Copyright (c) 2002-2009 Eric Lafortune (eric (at) 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  */
     21 package proguard.obfuscate;
     22 
     23 import proguard.classfile.*;
     24 import proguard.classfile.attribute.*;
     25 import proguard.classfile.attribute.visitor.AttributeVisitor;
     26 import proguard.classfile.constant.*;
     27 import proguard.classfile.constant.visitor.ConstantVisitor;
     28 import proguard.classfile.util.SimplifiedVisitor;
     29 import proguard.classfile.visitor.ClassVisitor;
     30 
     31 /**
     32  * This ClassVisitor marks all NameAndType constant pool entries that are
     33  * being used in the program classes it visits.
     34  *
     35  * @see NameAndTypeShrinker
     36  *
     37  * @author Eric Lafortune
     38  */
     39 public class NameAndTypeUsageMarker
     40 extends      SimplifiedVisitor
     41 implements   ClassVisitor,
     42              ConstantVisitor,
     43              AttributeVisitor
     44 {
     45     // A visitor info flag to indicate the NameAndType constant pool entry is being used.
     46     private static final Object USED = new Object();
     47 
     48 
     49     // Implementations for ClassVisitor.
     50 
     51     public void visitProgramClass(ProgramClass programClass)
     52     {
     53         // Mark the NameAndType entries referenced by all other constant pool
     54         // entries.
     55         programClass.constantPoolEntriesAccept(this);
     56 
     57         // Mark the NameAndType entries referenced by all EnclosingMethod
     58         // attributes.
     59         programClass.attributesAccept(this);
     60     }
     61 
     62 
     63     // Implementations for ConstantVisitor.
     64 
     65     public void visitAnyConstant(Clazz clazz, Constant constant) {}
     66 
     67 
     68     public void visitFieldrefConstant(Clazz clazz, FieldrefConstant fieldrefConstant)
     69     {
     70         visitRefConstant(clazz, fieldrefConstant);
     71     }
     72 
     73 
     74     public void visitInterfaceMethodrefConstant(Clazz clazz, InterfaceMethodrefConstant interfaceMethodrefConstant)
     75     {
     76         visitRefConstant(clazz, interfaceMethodrefConstant);
     77     }
     78 
     79 
     80     public void visitMethodrefConstant(Clazz clazz, MethodrefConstant methodrefConstant)
     81     {
     82         visitRefConstant(clazz, methodrefConstant);
     83     }
     84 
     85 
     86     private void visitRefConstant(Clazz clazz, RefConstant refConstant)
     87     {
     88         markNameAndTypeConstant(clazz, refConstant.u2nameAndTypeIndex);
     89     }
     90 
     91 
     92     // Implementations for AttributeVisitor.
     93 
     94     public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
     95 
     96 
     97     public void visitEnclosingMethodAttribute(Clazz clazz, EnclosingMethodAttribute enclosingMethodAttribute)
     98     {
     99         if (enclosingMethodAttribute.u2nameAndTypeIndex != 0)
    100         {
    101             markNameAndTypeConstant(clazz, enclosingMethodAttribute.u2nameAndTypeIndex);
    102         }
    103     }
    104 
    105 
    106     // Small utility methods.
    107 
    108     /**
    109      * Marks the given UTF-8 constant pool entry of the given class.
    110      */
    111     private void markNameAndTypeConstant(Clazz clazz, int index)
    112     {
    113          markAsUsed((NameAndTypeConstant)((ProgramClass)clazz).getConstant(index));
    114     }
    115 
    116 
    117     /**
    118      * Marks the given VisitorAccepter as being used.
    119      * In this context, the VisitorAccepter will be a NameAndTypeConstant object.
    120      */
    121     private static void markAsUsed(VisitorAccepter visitorAccepter)
    122     {
    123         visitorAccepter.setVisitorInfo(USED);
    124     }
    125 
    126 
    127     /**
    128      * Returns whether the given VisitorAccepter has been marked as being used.
    129      * In this context, the VisitorAccepter will be a NameAndTypeConstant object.
    130      */
    131     static boolean isUsed(VisitorAccepter visitorAccepter)
    132     {
    133         return visitorAccepter.getVisitorInfo() == USED;
    134     }
    135 }
    136