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1 package org.apache.bcel.generic; 2 3 /* ==================================================================== 4 * The Apache Software License, Version 1.1 5 * 6 * Copyright (c) 2001 The Apache Software Foundation. All rights 7 * reserved. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in 18 * the documentation and/or other materials provided with the 19 * distribution. 20 * 21 * 3. The end-user documentation included with the redistribution, 22 * if any, must include the following acknowledgment: 23 * "This product includes software developed by the 24 * Apache Software Foundation (http://www.apache.org/)." 25 * Alternately, this acknowledgment may appear in the software itself, 26 * if and wherever such third-party acknowledgments normally appear. 27 * 28 * 4. The names "Apache" and "Apache Software Foundation" and 29 * "Apache BCEL" must not be used to endorse or promote products 30 * derived from this software without prior written permission. For 31 * written permission, please contact apache@apache.org. 32 * 33 * 5. Products derived from this software may not be called "Apache", 34 * "Apache BCEL", nor may "Apache" appear in their name, without 35 * prior written permission of the Apache Software Foundation. 36 * 37 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED 38 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 39 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 40 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR 41 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 42 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 43 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF 44 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 45 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 46 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 47 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 48 * SUCH DAMAGE. 49 * ==================================================================== 50 * 51 * This software consists of voluntary contributions made by many 52 * individuals on behalf of the Apache Software Foundation. For more 53 * information on the Apache Software Foundation, please see 54 * <http://www.apache.org/>;. 55 */ 56 import java.io.*; 57 import org.apache.bcel.util.ByteSequence; 58 59 /*** 60 * Select - Abstract super class for LOOKUPSWITCH and TABLESWITCH instructions. 61 * 62 * @version $Id: Select.java,v 1.2 2002/04/26 09:30:11 mdahm Exp $ 63 * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A> 64 * @see LOOKUPSWITCH 65 * @see TABLESWITCH 66 * @see InstructionList 67 */ 68 public abstract class Select extends BranchInstruction 69 implements VariableLengthInstruction, StackProducer 70 { 71 protected int[] match; // matches, i.e., case 1: ... 72 protected int[] indices; // target offsets 73 protected InstructionHandle[] targets; // target objects in instruction list 74 protected int fixed_length; // fixed length defined by subclasses 75 protected int match_length; // number of cases 76 protected int padding = 0; // number of pad bytes for alignment 77 78 /*** 79 * Empty constructor needed for the Class.newInstance() statement in 80 * Instruction.readInstruction(). Not to be used otherwise. 81 */ 82 Select() {} 83 84 /*** 85 * (Match, target) pairs for switch. 86 * `Match' and `targets' must have the same length of course. 87 * 88 * @param match array of matching values 89 * @param targets instruction targets 90 * @param target default instruction target 91 */ 92 Select(short opcode, int[] match, InstructionHandle[] targets, 93 InstructionHandle target) { 94 super(opcode, target); 95 96 this.targets = targets; 97 for(int i=0; i < targets.length; i++) 98 notifyTarget(null, targets[i], this); 99 100 this.match = match; 101 102 if((match_length = match.length) != targets.length) 103 throw new ClassGenException("Match and target array have not the same length"); 104 105 indices = new int[match_length]; 106 } 107 108 /*** 109 * Since this is a variable length instruction, it may shift the following 110 * instructions which then need to update their position. 111 * 112 * Called by InstructionList.setPositions when setting the position for every 113 * instruction. In the presence of variable length instructions `setPositions' 114 * performs multiple passes over the instruction list to calculate the 115 * correct (byte) positions and offsets by calling this function. 116 * 117 * @param offset additional offset caused by preceding (variable length) instructions 118 * @param max_offset the maximum offset that may be caused by these instructions 119 * @return additional offset caused by possible change of this instruction's length 120 */ 121 protected int updatePosition(int offset, int max_offset) { 122 position += offset; // Additional offset caused by preceding SWITCHs, GOTOs, etc. 123 124 short old_length = length; 125 126 /* Alignment on 4-byte-boundary, + 1, because of tag byte. 127 */ 128 padding = (4 - ((position + 1) % 4)) % 4; 129 length = (short)(fixed_length + padding); // Update length 130 131 return length - old_length; 132 } 133 134 /*** 135 * Dump instruction as byte code to stream out. 136 * @param out Output stream 137 */ 138 public void dump(DataOutputStream out) throws IOException { 139 out.writeByte(opcode); 140 141 for(int i=0; i < padding; i++) // Padding bytes 142 out.writeByte(0); 143 144 index = getTargetOffset(); // Write default target offset 145 out.writeInt(index); 146 } 147 148 /*** 149 * Read needed data (e.g. index) from file. 150 */ 151 protected void initFromFile(ByteSequence bytes, boolean wide) throws IOException 152 { 153 padding = (4 - (bytes.getIndex() % 4)) % 4; // Compute number of pad bytes 154 155 for(int i=0; i < padding; i++) { 156 bytes.readByte(); 157 } 158 159 // Default branch target common for both cases (TABLESWITCH, LOOKUPSWITCH) 160 index = bytes.readInt(); 161 } 162 163 /*** 164 * @return mnemonic for instruction 165 */ 166 public String toString(boolean verbose) { 167 StringBuffer buf = new StringBuffer(super.toString(verbose)); 168 169 if(verbose) { 170 for(int i=0; i < match_length; i++) { 171 String s = "null"; 172 173 if(targets[i] != null) 174 s = targets[i].getInstruction().toString(); 175 176 buf.append("(" + match[i] + ", " + s + " = {" + indices[i] + "})"); 177 } 178 } 179 else 180 buf.append(" ..."); 181 182 return buf.toString(); 183 } 184 185 /*** 186 * Set branch target for `i'th case 187 */ 188 public void setTarget(int i, InstructionHandle target) { 189 notifyTarget(targets[i], target, this); 190 targets[i] = target; 191 } 192 193 /*** 194 * @param old_ih old target 195 * @param new_ih new target 196 */ 197 public void updateTarget(InstructionHandle old_ih, InstructionHandle new_ih) { 198 boolean targeted = false; 199 200 if(target == old_ih) { 201 targeted = true; 202 setTarget(new_ih); 203 } 204 205 for(int i=0; i < targets.length; i++) { 206 if(targets[i] == old_ih) { 207 targeted = true; 208 setTarget(i, new_ih); 209 } 210 } 211 212 if(!targeted) 213 throw new ClassGenException("Not targeting " + old_ih); 214 } 215 216 /*** 217 * @return true, if ih is target of this instruction 218 */ 219 public boolean containsTarget(InstructionHandle ih) { 220 if(target == ih) 221 return true; 222 223 for(int i=0; i < targets.length; i++) 224 if(targets[i] == ih) 225 return true; 226 227 return false; 228 } 229 230 /*** 231 * Inform targets that they're not targeted anymore. 232 */ 233 void dispose() { 234 super.dispose(); 235 236 for(int i=0; i < targets.length; i++) 237 targets[i].removeTargeter(this); 238 } 239 240 /*** 241 * @return array of match indices 242 */ 243 public int[] getMatchs() { return match; } 244 245 /*** 246 * @return array of match target offsets 247 */ 248 public int[] getIndices() { return indices; } 249 250 /*** 251 * @return array of match targets 252 */ 253 public InstructionHandle[] getTargets() { return targets; } 254 }

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