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      1 /*
      2  * ProGuard -- shrinking, optimization, obfuscation, and preverification
      3  *             of Java bytecode.
      4  *
      5  * Copyright (c) 2002-2014 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.optimize;
     22 
     23 import proguard.classfile.*;
     24 import proguard.classfile.util.MethodLinker;
     25 import proguard.classfile.visitor.*;
     26 import proguard.optimize.info.NoSideEffectMethodMarker;
     27 
     28 
     29 /**
     30  * This <code>ClassVisitor</code> and <code>MemberVisitor</code>
     31  * marks classes and class members it visits. The marked elements
     32  * will remain unchanged as necessary in the optimization step.
     33  *
     34  * @see NoSideEffectMethodMarker
     35  * @author Eric Lafortune
     36  */
     37 public class KeepMarker
     38 implements   ClassVisitor,
     39              MemberVisitor
     40 {
     41     // A visitor info flag to indicate the visitor accepter is being kept.
     42     private static final Object KEPT = new Object();
     43 
     44 
     45     // Implementations for ClassVisitor.
     46 
     47     public void visitProgramClass(ProgramClass programClass)
     48     {
     49         markAsKept(programClass);
     50     }
     51 
     52 
     53     public void visitLibraryClass(LibraryClass libraryClass)
     54     {
     55         markAsKept(libraryClass);
     56     }
     57 
     58 
     59     // Implementations for MemberVisitor.
     60 
     61     public void visitProgramField(ProgramClass programClass, ProgramField programField)
     62     {
     63         markAsKept(programField);
     64     }
     65 
     66 
     67     public void visitProgramMethod(ProgramClass programClass, ProgramMethod programMethod)
     68     {
     69         markAsKept(MethodLinker.lastMember(programMethod));
     70     }
     71 
     72 
     73     public void visitLibraryField(LibraryClass libraryClass, LibraryField libraryField)
     74     {
     75         markAsKept(libraryField);
     76     }
     77 
     78 
     79     public void visitLibraryMethod(LibraryClass libraryClass, LibraryMethod libraryMethod)
     80     {
     81         markAsKept(MethodLinker.lastMember(libraryMethod));
     82     }
     83 
     84 
     85     // Small utility methods.
     86 
     87     private static void markAsKept(VisitorAccepter visitorAccepter)
     88     {
     89         visitorAccepter.setVisitorInfo(KEPT);
     90     }
     91 
     92 
     93     public static boolean isKept(VisitorAccepter visitorAccepter)
     94     {
     95         // We're also checking for the constant in NoSideEffectMethodMarker,
     96         // to keep things simple.
     97         Object visitorInfo =
     98             MethodLinker.lastVisitorAccepter(visitorAccepter).getVisitorInfo();
     99 
    100         return visitorInfo == KEPT ||
    101                visitorInfo == NoSideEffectMethodMarker.KEPT_BUT_NO_SIDE_EFFECTS;
    102     }
    103 }
    104