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 22 package proguard.shrink; 23 24 import proguard.classfile.*; 25 import proguard.classfile.attribute.*; 26 import proguard.classfile.attribute.visitor.AttributeVisitor; 27 import proguard.classfile.constant.Constant; 28 import proguard.classfile.constant.visitor.ConstantVisitor; 29 import proguard.classfile.util.SimplifiedVisitor; 30 import proguard.classfile.visitor.ClassVisitor; 31 32 /** 33 * This AttributeVisitor recursively marks all Signature attributes that it 34 * visits and that point to used classes. 35 * 36 * @see UsageMarker 37 * 38 * @author Eric Lafortune 39 */ 40 public class SignatureUsageMarker 41 extends SimplifiedVisitor 42 implements AttributeVisitor, 43 ClassVisitor, 44 ConstantVisitor 45 { 46 private final UsageMarker usageMarker; 47 48 // Fields acting as a return parameters for several methods. 49 private boolean attributeUsed; 50 51 52 /** 53 * Creates a new SignatureUsageMarker. 54 * @param usageMarker the usage marker that is used to mark the classes 55 * and class members. 56 */ SignatureUsageMarker(UsageMarker usageMarker)57 public SignatureUsageMarker(UsageMarker usageMarker) 58 { 59 this.usageMarker = usageMarker; 60 } 61 62 63 // Implementations for AttributeVisitor. 64 visitAnyAttribute(Clazz clazz, Attribute attribute)65 public void visitAnyAttribute(Clazz clazz, Attribute attribute) {} 66 67 visitSignatureAttribute(Clazz clazz, SignatureAttribute signatureAttribute)68 public void visitSignatureAttribute(Clazz clazz, SignatureAttribute signatureAttribute) 69 { 70 // Only keep the signature if any of its classes are used. 71 attributeUsed = false; 72 signatureAttribute.referencedClassesAccept(this); 73 74 if (attributeUsed) 75 { 76 // We got a positive used flag, so the signature is useful. 77 usageMarker.markAsUsed(signatureAttribute); 78 79 markConstant(clazz, signatureAttribute.u2attributeNameIndex); 80 markConstant(clazz, signatureAttribute.u2signatureIndex); 81 } 82 } 83 84 85 // Implementations for ClassVisitor. 86 visitLibraryClass(LibraryClass libraryClass)87 public void visitLibraryClass(LibraryClass libraryClass) 88 { 89 attributeUsed = true; 90 } 91 92 visitProgramClass(ProgramClass programClass)93 public void visitProgramClass(ProgramClass programClass) 94 { 95 // Don't keep the signature if one of its classes is not used. 96 if (usageMarker.isUsed(programClass)) 97 { 98 attributeUsed = true; 99 } 100 } 101 102 103 // Implementations for ConstantVisitor. 104 visitAnyConstant(Clazz clazz, Constant constant)105 public void visitAnyConstant(Clazz clazz, Constant constant) 106 { 107 usageMarker.markAsUsed(constant); 108 } 109 110 111 // Small utility methods. 112 113 /** 114 * Marks the given constant pool entry of the given class. 115 */ markConstant(Clazz clazz, int index)116 private void markConstant(Clazz clazz, int index) 117 { 118 clazz.constantPoolEntryAccept(index, this); 119 } 120 } 121