1 /* 2 * ProGuard -- shrinking, optimization, obfuscation, and preverification 3 * of Java bytecode. 4 * 5 * Copyright (c) 2002-2009 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.classfile.instruction; 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.visitor.InstructionVisitor; 28 import proguard.classfile.util.ClassUtil; 29 30 /** 31 * This Instruction represents an instruction that refers to an entry in the 32 * constant pool. 33 * 34 * @author Eric Lafortune 35 */ 36 public class ConstantInstruction extends Instruction 37 implements ConstantVisitor 38 { 39 public int constantIndex; 40 public int constant; 41 42 43 // Fields acting as return parameters for the ConstantVisitor methods. 44 private int parameterStackDelta; 45 private int typeStackDelta; 46 47 48 /** 49 * Creates an uninitialized ConstantInstruction. 50 */ 51 public ConstantInstruction() {} 52 53 54 /** 55 * Creates a new ConstantInstruction with the given opcode and constant pool 56 * index. 57 */ 58 public ConstantInstruction(byte opcode, int constantIndex) 59 { 60 this(opcode, constantIndex, 0); 61 } 62 63 64 /** 65 * Creates a new ConstantInstruction with the given opcode, constant pool 66 * index, and constant. 67 */ 68 public ConstantInstruction(byte opcode, int constantIndex, int constant) 69 { 70 this.opcode = opcode; 71 this.constantIndex = constantIndex; 72 this.constant = constant; 73 } 74 75 76 /** 77 * Copies the given instruction into this instruction. 78 * @param constantInstruction the instruction to be copied. 79 * @return this instruction. 80 */ 81 public ConstantInstruction copy(ConstantInstruction constantInstruction) 82 { 83 this.opcode = constantInstruction.opcode; 84 this.constantIndex = constantInstruction.constantIndex; 85 this.constant = constantInstruction.constant; 86 87 return this; 88 } 89 90 91 // Implementations for Instruction. 92 93 public byte canonicalOpcode() 94 { 95 // Remove the _w extension, if any. 96 switch (opcode) 97 { 98 case InstructionConstants.OP_LDC_W: 99 case InstructionConstants.OP_LDC2_W: return InstructionConstants.OP_LDC; 100 101 default: return opcode; 102 } 103 } 104 105 public Instruction shrink() 106 { 107 // Do we need a short index or a long index? 108 if (requiredConstantIndexSize() == 1) 109 { 110 // Can we replace the long instruction by a short instruction? 111 if (opcode == InstructionConstants.OP_LDC_W) 112 { 113 opcode = InstructionConstants.OP_LDC; 114 } 115 } 116 else 117 { 118 // Should we replace the short instruction by a long instruction? 119 if (opcode == InstructionConstants.OP_LDC) 120 { 121 opcode = InstructionConstants.OP_LDC_W; 122 } 123 } 124 125 return this; 126 } 127 128 protected void readInfo(byte[] code, int offset) 129 { 130 int constantIndexSize = constantIndexSize(); 131 int constantSize = constantSize(); 132 133 constantIndex = readValue(code, offset, constantIndexSize); offset += constantIndexSize; 134 constant = readValue(code, offset, constantSize); 135 } 136 137 138 protected void writeInfo(byte[] code, int offset) 139 { 140 int constantIndexSize = constantIndexSize(); 141 int constantSize = constantSize(); 142 143 if (requiredConstantIndexSize() > constantIndexSize) 144 { 145 throw new IllegalArgumentException("Instruction has invalid constant index size ("+this.toString(offset)+")"); 146 } 147 148 writeValue(code, offset, constantIndex, constantIndexSize); offset += constantIndexSize; 149 writeValue(code, offset, constant, constantSize); 150 } 151 152 153 public int length(int offset) 154 { 155 return 1 + constantIndexSize() + constantSize(); 156 } 157 158 159 public void accept(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, InstructionVisitor instructionVisitor) 160 { 161 instructionVisitor.visitConstantInstruction(clazz, method, codeAttribute, offset, this); 162 } 163 164 165 public int stackPopCount(Clazz clazz) 166 { 167 int stackPopCount = super.stackPopCount(clazz); 168 169 // Some special cases. 170 switch (opcode) 171 { 172 case InstructionConstants.OP_MULTIANEWARRAY: 173 // For each dimension, an integer size is popped from the stack. 174 stackPopCount += constant; 175 break; 176 177 case InstructionConstants.OP_PUTSTATIC: 178 case InstructionConstants.OP_PUTFIELD: 179 // The field value is be popped from the stack. 180 clazz.constantPoolEntryAccept(constantIndex, this); 181 stackPopCount += typeStackDelta; 182 break; 183 184 case InstructionConstants.OP_INVOKEVIRTUAL: 185 case InstructionConstants.OP_INVOKESPECIAL: 186 case InstructionConstants.OP_INVOKESTATIC: 187 case InstructionConstants.OP_INVOKEINTERFACE: 188 // The some parameters may be popped from the stack. 189 clazz.constantPoolEntryAccept(constantIndex, this); 190 stackPopCount += parameterStackDelta; 191 break; 192 } 193 194 return stackPopCount; 195 } 196 197 198 public int stackPushCount(Clazz clazz) 199 { 200 int stackPushCount = super.stackPushCount(clazz); 201 202 // Some special cases. 203 switch (opcode) 204 { 205 case InstructionConstants.OP_GETSTATIC: 206 case InstructionConstants.OP_GETFIELD: 207 case InstructionConstants.OP_INVOKEVIRTUAL: 208 case InstructionConstants.OP_INVOKESPECIAL: 209 case InstructionConstants.OP_INVOKESTATIC: 210 case InstructionConstants.OP_INVOKEINTERFACE: 211 // The field value or a return value may be pushed onto the stack. 212 clazz.constantPoolEntryAccept(constantIndex, this); 213 stackPushCount += typeStackDelta; 214 break; 215 } 216 217 return stackPushCount; 218 } 219 220 221 // Implementations for ConstantVisitor. 222 223 public void visitIntegerConstant(Clazz clazz, IntegerConstant integerConstant) {} 224 public void visitLongConstant(Clazz clazz, LongConstant longConstant) {} 225 public void visitFloatConstant(Clazz clazz, FloatConstant floatConstant) {} 226 public void visitDoubleConstant(Clazz clazz, DoubleConstant doubleConstant) {} 227 public void visitStringConstant(Clazz clazz, StringConstant stringConstant) {} 228 public void visitUtf8Constant(Clazz clazz, Utf8Constant utf8Constant) {} 229 public void visitClassConstant(Clazz clazz, ClassConstant classConstant) {} 230 public void visitNameAndTypeConstant(Clazz clazz, NameAndTypeConstant nameAndTypeConstant) {} 231 232 233 public void visitFieldrefConstant(Clazz clazz, FieldrefConstant fieldrefConstant) 234 { 235 String type = fieldrefConstant.getType(clazz); 236 237 typeStackDelta = ClassUtil.internalTypeSize(ClassUtil.internalMethodReturnType(type)); 238 } 239 240 241 public void visitInterfaceMethodrefConstant(Clazz clazz, InterfaceMethodrefConstant interfaceMethodrefConstant) 242 { 243 visitRefConstant(clazz, interfaceMethodrefConstant); 244 } 245 246 247 public void visitMethodrefConstant(Clazz clazz, MethodrefConstant methodrefConstant) 248 { 249 visitRefConstant(clazz, methodrefConstant); 250 } 251 252 253 private void visitRefConstant(Clazz clazz, RefConstant methodrefConstant) 254 { 255 String type = methodrefConstant.getType(clazz); 256 257 parameterStackDelta = ClassUtil.internalMethodParameterSize(type); 258 typeStackDelta = ClassUtil.internalTypeSize(ClassUtil.internalMethodReturnType(type)); 259 } 260 261 262 // Implementations for Object. 263 264 public String toString() 265 { 266 return getName()+" #"+constantIndex; 267 } 268 269 270 // Small utility methods. 271 272 /** 273 * Returns the constant pool index size for this instruction. 274 */ 275 private int constantIndexSize() 276 { 277 return opcode == InstructionConstants.OP_LDC ? 1 : 278 2; 279 } 280 281 282 /** 283 * Returns the constant size for this instruction. 284 */ 285 private int constantSize() 286 { 287 return opcode == InstructionConstants.OP_MULTIANEWARRAY ? 1 : 288 opcode == InstructionConstants.OP_INVOKEINTERFACE ? 2 : 289 0; 290 } 291 292 293 /** 294 * Computes the required constant pool index size for this instruction's 295 * constant pool index. 296 */ 297 private int requiredConstantIndexSize() 298 { 299 return (constantIndex & 0xff) == constantIndex ? 1 : 300 (constantIndex & 0xffff) == constantIndex ? 2 : 301 4; 302 } 303 } 304