1 /*
2  * ProGuard -- shrinking, optimization, obfuscation, and preverification
3  *             of Java bytecode.
4  *
5  * Copyright (c) 2002-2014 Eric Lafortune (eric@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 
visitProgramClass(ProgramClass programClass)47     public void visitProgramClass(ProgramClass programClass)
48     {
49         markAsKept(programClass);
50     }
51 
52 
visitLibraryClass(LibraryClass libraryClass)53     public void visitLibraryClass(LibraryClass libraryClass)
54     {
55         markAsKept(libraryClass);
56     }
57 
58 
59     // Implementations for MemberVisitor.
60 
visitProgramField(ProgramClass programClass, ProgramField programField)61     public void visitProgramField(ProgramClass programClass, ProgramField programField)
62     {
63         markAsKept(programField);
64     }
65 
66 
visitProgramMethod(ProgramClass programClass, ProgramMethod programMethod)67     public void visitProgramMethod(ProgramClass programClass, ProgramMethod programMethod)
68     {
69         markAsKept(MethodLinker.lastMember(programMethod));
70     }
71 
72 
visitLibraryField(LibraryClass libraryClass, LibraryField libraryField)73     public void visitLibraryField(LibraryClass libraryClass, LibraryField libraryField)
74     {
75         markAsKept(libraryField);
76     }
77 
78 
visitLibraryMethod(LibraryClass libraryClass, LibraryMethod libraryMethod)79     public void visitLibraryMethod(LibraryClass libraryClass, LibraryMethod libraryMethod)
80     {
81         markAsKept(MethodLinker.lastMember(libraryMethod));
82     }
83 
84 
85     // Small utility methods.
86 
markAsKept(VisitorAccepter visitorAccepter)87     private static void markAsKept(VisitorAccepter visitorAccepter)
88     {
89         visitorAccepter.setVisitorInfo(KEPT);
90     }
91 
92 
isKept(VisitorAccepter visitorAccepter)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