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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.info;
     22 
     23 import proguard.classfile.*;
     24 import proguard.classfile.util.*;
     25 import proguard.classfile.visitor.MemberVisitor;
     26 
     27 /**
     28  * This MemberVisitor marks all methods that it visits as not having any side
     29  * effects. It will make the SideEffectMethodMarker consider them as such
     30  * without further analysis.
     31  *
     32  * @see SideEffectMethodMarker
     33  * @author Eric Lafortune
     34  */
     35 public class NoSideEffectMethodMarker
     36 extends      SimplifiedVisitor
     37 implements   MemberVisitor
     38 {
     39     // A visitor info flag to indicate the visitor accepter is being kept,
     40     // but that it doesn't have any side effects.
     41     public static final Object KEPT_BUT_NO_SIDE_EFFECTS = new Object();
     42 
     43 
     44     // Implementations for MemberVisitor.
     45 
     46     public void visitAnyMember(Clazz Clazz, Member member)
     47     {
     48         // Ignore any attempts to mark fields.
     49     }
     50 
     51 
     52     public void visitProgramMethod(ProgramClass programClass, ProgramMethod programMethod)
     53     {
     54         markNoSideEffects(programMethod);
     55     }
     56 
     57 
     58     public void visitLibraryMethod(LibraryClass libraryClass, LibraryMethod libraryMethod)
     59     {
     60         markNoSideEffects(libraryMethod);
     61     }
     62 
     63 
     64     // Small utility methods.
     65 
     66     private static void markNoSideEffects(Method method)
     67     {
     68         MethodOptimizationInfo info = MethodOptimizationInfo.getMethodOptimizationInfo(method);
     69         if (info != null)
     70         {
     71             info.setNoSideEffects();
     72         }
     73         else
     74         {
     75             MethodLinker.lastMember(method).setVisitorInfo(KEPT_BUT_NO_SIDE_EFFECTS);
     76         }
     77     }
     78 
     79 
     80     public static boolean hasNoSideEffects(Method method)
     81     {
     82         if (MethodLinker.lastVisitorAccepter(method).getVisitorInfo() == KEPT_BUT_NO_SIDE_EFFECTS)
     83         {
     84             return true;
     85         }
     86 
     87         MethodOptimizationInfo info = MethodOptimizationInfo.getMethodOptimizationInfo(method);
     88         return info != null &&
     89                info.hasNoSideEffects();
     90     }
     91 }
     92