1/* 2 * ProGuard -- shrinking, optimization, obfuscation, and preverification 3 * of Java bytecode. 4 * 5 * Copyright (c) 2002-2013 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 */ 21package proguard.classfile.instruction; 22 23import proguard.classfile.*; 24import proguard.classfile.attribute.CodeAttribute; 25import proguard.classfile.constant.*; 26import proguard.classfile.constant.visitor.ConstantVisitor; 27import proguard.classfile.instruction.visitor.InstructionVisitor; 28import 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 */ 36public class ConstantInstruction extends Instruction 37implements 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 return 97 opcode == InstructionConstants.OP_LDC_W ? InstructionConstants.OP_LDC : 98 opcode; 99 } 100 101 public Instruction shrink() 102 { 103 // Do we need a short index or a long index? 104 if (requiredConstantIndexSize() == 1) 105 { 106 // Can we replace the long instruction by a short instruction? 107 if (opcode == InstructionConstants.OP_LDC_W) 108 { 109 opcode = InstructionConstants.OP_LDC; 110 } 111 } 112 else 113 { 114 // Should we replace the short instruction by a long instruction? 115 if (opcode == InstructionConstants.OP_LDC) 116 { 117 opcode = InstructionConstants.OP_LDC_W; 118 } 119 } 120 121 return this; 122 } 123 124 protected void readInfo(byte[] code, int offset) 125 { 126 int constantIndexSize = constantIndexSize(); 127 int constantSize = constantSize(); 128 129 constantIndex = readValue(code, offset, constantIndexSize); offset += constantIndexSize; 130 constant = readValue(code, offset, constantSize); 131 } 132 133 134 protected void writeInfo(byte[] code, int offset) 135 { 136 int constantIndexSize = constantIndexSize(); 137 int constantSize = constantSize(); 138 139 if (requiredConstantIndexSize() > constantIndexSize) 140 { 141 throw new IllegalArgumentException("Instruction has invalid constant index size ("+this.toString(offset)+")"); 142 } 143 144 writeValue(code, offset, constantIndex, constantIndexSize); offset += constantIndexSize; 145 writeValue(code, offset, constant, constantSize); 146 } 147 148 149 public int length(int offset) 150 { 151 return 1 + constantIndexSize() + constantSize(); 152 } 153 154 155 public void accept(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, InstructionVisitor instructionVisitor) 156 { 157 instructionVisitor.visitConstantInstruction(clazz, method, codeAttribute, offset, this); 158 } 159 160 161 public int stackPopCount(Clazz clazz) 162 { 163 int stackPopCount = super.stackPopCount(clazz); 164 165 // Some special cases. 166 switch (opcode) 167 { 168 case InstructionConstants.OP_MULTIANEWARRAY: 169 // For each dimension, an integer size is popped from the stack. 170 stackPopCount += constant; 171 break; 172 173 case InstructionConstants.OP_PUTSTATIC: 174 case InstructionConstants.OP_PUTFIELD: 175 // The field value is be popped from the stack. 176 clazz.constantPoolEntryAccept(constantIndex, this); 177 stackPopCount += typeStackDelta; 178 break; 179 180 case InstructionConstants.OP_INVOKEVIRTUAL: 181 case InstructionConstants.OP_INVOKESPECIAL: 182 case InstructionConstants.OP_INVOKESTATIC: 183 case InstructionConstants.OP_INVOKEINTERFACE: 184 case InstructionConstants.OP_INVOKEDYNAMIC: 185 // Some parameters may be popped from the stack. 186 clazz.constantPoolEntryAccept(constantIndex, this); 187 stackPopCount += parameterStackDelta; 188 break; 189 } 190 191 return stackPopCount; 192 } 193 194 195 public int stackPushCount(Clazz clazz) 196 { 197 int stackPushCount = super.stackPushCount(clazz); 198 199 // Some special cases. 200 switch (opcode) 201 { 202 case InstructionConstants.OP_GETSTATIC: 203 case InstructionConstants.OP_GETFIELD: 204 case InstructionConstants.OP_INVOKEVIRTUAL: 205 case InstructionConstants.OP_INVOKESPECIAL: 206 case InstructionConstants.OP_INVOKESTATIC: 207 case InstructionConstants.OP_INVOKEINTERFACE: 208 case InstructionConstants.OP_INVOKEDYNAMIC: 209 // The field value or a return value may be pushed onto the stack. 210 clazz.constantPoolEntryAccept(constantIndex, this); 211 stackPushCount += typeStackDelta; 212 break; 213 } 214 215 return stackPushCount; 216 } 217 218 219 // Implementations for ConstantVisitor. 220 221 public void visitIntegerConstant(Clazz clazz, IntegerConstant integerConstant) {} 222 public void visitLongConstant(Clazz clazz, LongConstant longConstant) {} 223 public void visitFloatConstant(Clazz clazz, FloatConstant floatConstant) {} 224 public void visitDoubleConstant(Clazz clazz, DoubleConstant doubleConstant) {} 225 public void visitStringConstant(Clazz clazz, StringConstant stringConstant) {} 226 public void visitUtf8Constant(Clazz clazz, Utf8Constant utf8Constant) {} 227 public void visitMethodHandleConstant(Clazz clazz, MethodHandleConstant methodHandleConstant) {} 228 public void visitClassConstant(Clazz clazz, ClassConstant classConstant) {} 229 public void visitMethodTypeConstant(Clazz clazz, MethodTypeConstant methodTypeConstant) {} 230 231 232 public void visitFieldrefConstant(Clazz clazz, FieldrefConstant fieldrefConstant) 233 { 234 String type = fieldrefConstant.getType(clazz); 235 236 typeStackDelta = ClassUtil.internalTypeSize(ClassUtil.internalMethodReturnType(type)); 237 } 238 239 240 public void visitInvokeDynamicConstant(Clazz clazz, InvokeDynamicConstant invokeDynamicConstant) 241 { 242 clazz.constantPoolEntryAccept(invokeDynamicConstant.u2nameAndTypeIndex, this); 243 } 244 245 246 public void visitInterfaceMethodrefConstant(Clazz clazz, InterfaceMethodrefConstant interfaceMethodrefConstant) 247 { 248 clazz.constantPoolEntryAccept(interfaceMethodrefConstant.u2nameAndTypeIndex, this); 249 } 250 251 252 public void visitMethodrefConstant(Clazz clazz, MethodrefConstant methodrefConstant) 253 { 254 clazz.constantPoolEntryAccept(methodrefConstant.u2nameAndTypeIndex, this); 255 } 256 257 258 public void visitNameAndTypeConstant(Clazz clazz, NameAndTypeConstant nameAndTypeConstant) 259 { 260 String type = nameAndTypeConstant.getType(clazz); 261 262 parameterStackDelta = ClassUtil.internalMethodParameterSize(type); 263 typeStackDelta = ClassUtil.internalTypeSize(ClassUtil.internalMethodReturnType(type)); 264 } 265 266 267 // Implementations for Object. 268 269 public String toString() 270 { 271 return getName()+" #"+constantIndex+(constantSize() == 0 ? "" : ", "+constant); 272 } 273 274 275 // Small utility methods. 276 277 /** 278 * Returns the constant pool index size for this instruction. 279 */ 280 private int constantIndexSize() 281 { 282 return opcode == InstructionConstants.OP_LDC ? 1 : 283 2; 284 } 285 286 287 /** 288 * Returns the constant size for this instruction. 289 */ 290 private int constantSize() 291 { 292 return opcode == InstructionConstants.OP_MULTIANEWARRAY ? 1 : 293 opcode == InstructionConstants.OP_INVOKEDYNAMIC || 294 opcode == InstructionConstants.OP_INVOKEINTERFACE ? 2 : 295 0; 296 } 297 298 299 /** 300 * Computes the required constant pool index size for this instruction's 301 * constant pool index. 302 */ 303 private int requiredConstantIndexSize() 304 { 305 return (constantIndex & 0xff) == constantIndex ? 1 : 306 (constantIndex & 0xffff) == constantIndex ? 2 : 307 4; 308 } 309} 310