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.optimize.info; 22 23 import proguard.classfile.*; 24 import proguard.classfile.attribute.CodeAttribute; 25 import proguard.classfile.constant.*; 26 import proguard.classfile.constant.visitor.ConstantVisitor; 27 import proguard.classfile.instruction.*; 28 import proguard.classfile.instruction.visitor.InstructionVisitor; 29 import proguard.classfile.util.SimplifiedVisitor; 30 import proguard.classfile.visitor.MemberVisitor; 31 32 /** 33 * This InstructionVisitor marks all fields that are write-only. 34 * 35 * @author Eric Lafortune 36 */ 37 public class ReadWriteFieldMarker 38 extends SimplifiedVisitor 39 implements InstructionVisitor, 40 ConstantVisitor, 41 MemberVisitor 42 { 43 // Parameters for the visitor methods. 44 private boolean reading = true; 45 private boolean writing = true; 46 47 48 // Implementations for InstructionVisitor. 49 visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction)50 public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction) {} 51 52 visitConstantInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, ConstantInstruction constantInstruction)53 public void visitConstantInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, ConstantInstruction constantInstruction) 54 { 55 byte opcode = constantInstruction.opcode; 56 57 // Check for instructions that involve fields. 58 switch (opcode) 59 { 60 case InstructionConstants.OP_LDC: 61 case InstructionConstants.OP_LDC_W: 62 // Mark the field, if any, as being read from and written to. 63 reading = true; 64 writing = true; 65 clazz.constantPoolEntryAccept(constantInstruction.constantIndex, this); 66 break; 67 68 case InstructionConstants.OP_GETSTATIC: 69 case InstructionConstants.OP_GETFIELD: 70 // Mark the field as being read from. 71 reading = true; 72 writing = false; 73 clazz.constantPoolEntryAccept(constantInstruction.constantIndex, this); 74 break; 75 76 case InstructionConstants.OP_PUTSTATIC: 77 case InstructionConstants.OP_PUTFIELD: 78 // Mark the field as being written to. 79 reading = false; 80 writing = true; 81 clazz.constantPoolEntryAccept(constantInstruction.constantIndex, this); 82 break; 83 } 84 } 85 86 87 // Implementations for ConstantVisitor. 88 visitAnyConstant(Clazz clazz, Constant constant)89 public void visitAnyConstant(Clazz clazz, Constant constant) {} 90 91 visitStringConstant(Clazz clazz, StringConstant stringConstant)92 public void visitStringConstant(Clazz clazz, StringConstant stringConstant) 93 { 94 // Mark the referenced field, if any. 95 stringConstant.referencedMemberAccept(this); 96 } 97 98 visitFieldrefConstant(Clazz clazz, FieldrefConstant fieldrefConstant)99 public void visitFieldrefConstant(Clazz clazz, FieldrefConstant fieldrefConstant) 100 { 101 // Mark the referenced field. 102 fieldrefConstant.referencedMemberAccept(this); 103 } 104 105 106 // Implementations for MemberVisitor. 107 visitAnyMember(Clazz Clazz, Member member)108 public void visitAnyMember(Clazz Clazz, Member member) {} 109 110 visitProgramField(ProgramClass programClass, ProgramField programField)111 public void visitProgramField(ProgramClass programClass, ProgramField programField) 112 { 113 // Mark the field if it is being read from. 114 if (reading) 115 { 116 markAsRead(programField); 117 } 118 119 // Mark the field if it is being written to. 120 if (writing) 121 { 122 markAsWritten(programField); 123 } 124 } 125 126 127 // Small utility methods. 128 markAsRead(Field field)129 private static void markAsRead(Field field) 130 { 131 FieldOptimizationInfo info = FieldOptimizationInfo.getFieldOptimizationInfo(field); 132 if (info != null) 133 { 134 info.setRead(); 135 } 136 } 137 138 isRead(Field field)139 public static boolean isRead(Field field) 140 { 141 FieldOptimizationInfo info = FieldOptimizationInfo.getFieldOptimizationInfo(field); 142 return info == null || 143 info.isRead(); 144 } 145 146 markAsWritten(Field field)147 private static void markAsWritten(Field field) 148 { 149 FieldOptimizationInfo info = FieldOptimizationInfo.getFieldOptimizationInfo(field); 150 if (info != null) 151 { 152 info.setWritten(); 153 } 154 } 155 156 isWritten(Field field)157 public static boolean isWritten(Field field) 158 { 159 FieldOptimizationInfo info = FieldOptimizationInfo.getFieldOptimizationInfo(field); 160 return info == null || 161 info.isWritten(); 162 } 163 } 164