1 /* 2 * ProGuard -- shrinking, optimization, obfuscation, and preverification 3 * of Java bytecode. 4 * 5 * Copyright (c) 2002-2009 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.obfuscate; 22 23 import proguard.classfile.*; 24 import proguard.classfile.attribute.*; 25 import proguard.classfile.attribute.visitor.AttributeVisitor; 26 import proguard.classfile.util.SimplifiedVisitor; 27 import proguard.classfile.visitor.*; 28 29 /** 30 * This ClassVisitor removes attributes that are not marked as being used or 31 * required. 32 * 33 * @see AttributeUsageMarker 34 * 35 * @author Eric Lafortune 36 */ 37 public class AttributeShrinker 38 extends SimplifiedVisitor 39 implements ClassVisitor, 40 MemberVisitor, 41 AttributeVisitor 42 { 43 // Implementations for ClassVisitor. 44 visitProgramClass(ProgramClass programClass)45 public void visitProgramClass(ProgramClass programClass) 46 { 47 // Compact the array for class attributes. 48 programClass.u2attributesCount = 49 shrinkArray(programClass.attributes, 50 programClass.u2attributesCount); 51 52 // Compact the attributes in fields, methods, and class attributes, 53 programClass.fieldsAccept(this); 54 programClass.methodsAccept(this); 55 programClass.attributesAccept(this); 56 } 57 58 visitLibraryClass(LibraryClass libraryClass)59 public void visitLibraryClass(LibraryClass libraryClass) 60 { 61 // Library classes are left unchanged. 62 } 63 64 65 // Implementations for MemberVisitor. 66 visitProgramMember(ProgramClass programClass, ProgramMember programMember)67 public void visitProgramMember(ProgramClass programClass, ProgramMember programMember) 68 { 69 // Compact the attributes array. 70 programMember.u2attributesCount = 71 shrinkArray(programMember.attributes, 72 programMember.u2attributesCount); 73 74 // Compact any attributes of the remaining attributes. 75 programMember.attributesAccept(programClass, this); 76 } 77 78 79 // Implementations for AttributeVisitor. 80 visitAnyAttribute(Clazz clazz, Attribute attribute)81 public void visitAnyAttribute(Clazz clazz, Attribute attribute) {} 82 83 visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute)84 public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute) 85 { 86 // Compact the attributes array. 87 codeAttribute.u2attributesCount = 88 shrinkArray(codeAttribute.attributes, 89 codeAttribute.u2attributesCount); 90 } 91 92 93 // Small utility methods. 94 95 /** 96 * Removes all VisitorAccepter objects that are not marked as being used 97 * from the given array. 98 * @return the new number of VisitorAccepter objects. 99 */ shrinkArray(VisitorAccepter[] array, int length)100 private static int shrinkArray(VisitorAccepter[] array, int length) 101 { 102 int counter = 0; 103 104 // Shift the used objects together. 105 for (int index = 0; index < length; index++) 106 { 107 if (AttributeUsageMarker.isUsed(array[index])) 108 { 109 array[counter++] = array[index]; 110 } 111 } 112 113 // Clear the remaining array elements. 114 for (int index = counter; index < length; index++) 115 { 116 array[index] = null; 117 } 118 119 return counter; 120 } 121 } 122