1 /*

     2  * reserved comment block

     3  * DO NOT REMOVE OR ALTER!

     4  */

     5 package com.sun.org.apache.bcel.internal.generic;

     6 

     7 /* ====================================================================

     8  * The Apache Software License, Version 1.1

     9  *

    10  * Copyright (c) 2001 The Apache Software Foundation.  All rights

    11  * reserved.

    12  *

    13  * Redistribution and use in source and binary forms, with or without

    14  * modification, are permitted provided that the following conditions

    15  * are met:

    16  *

    17  * 1. Redistributions of source code must retain the above copyright

    18  *    notice, this list of conditions and the following disclaimer.

    19  *

    20  * 2. Redistributions in binary form must reproduce the above copyright

    21  *    notice, this list of conditions and the following disclaimer in

    22  *    the documentation and/or other materials provided with the

    23  *    distribution.

    24  *

    25  * 3. The end-user documentation included with the redistribution,

    26  *    if any, must include the following acknowledgment:

    27  *       "This product includes software developed by the

    28  *        Apache Software Foundation (http://www.apache.org/)."

    29  *    Alternately, this acknowledgment may appear in the software itself,

    30  *    if and wherever such third-party acknowledgments normally appear.

    31  *

    32  * 4. The names "Apache" and "Apache Software Foundation" and

    33  *    "Apache BCEL" must not be used to endorse or promote products

    34  *    derived from this software without prior written permission. For

    35  *    written permission, please contact apache@apache.org.

    36  *

    37  * 5. Products derived from this software may not be called "Apache",

    38  *    "Apache BCEL", nor may "Apache" appear in their name, without

    39  *    prior written permission of the Apache Software Foundation.

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    41  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED

    42  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

    43  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

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    53  * ====================================================================

    54  *

    55  * This software consists of voluntary contributions made by many

    56  * individuals on behalf of the Apache Software Foundation.  For more

    57  * information on the Apache Software Foundation, please see

    58  * <http://www.apache.org/>.

    59  */

    60 import java.io.*;

    61 import com.sun.org.apache.bcel.internal.util.ByteSequence;

    62 

    63 /**

    64  * Select - Abstract super class for LOOKUPSWITCH and TABLESWITCH instructions.

    65  *

    66  * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>

    67  * @see LOOKUPSWITCH

    68  * @see TABLESWITCH

    69  * @see InstructionList

    70  */

    71 public abstract class Select extends BranchInstruction

    72   implements VariableLengthInstruction, StackProducer

    73 {

    74   protected int[]               match;        // matches, i.e., case 1: ...

    75   protected int[]               indices;      // target offsets

    76   protected InstructionHandle[] targets;      // target objects in instruction list

    77   protected int                 fixed_length; // fixed length defined by subclasses

    78   protected int                 match_length; // number of cases

    79   protected int                 padding = 0;  // number of pad bytes for alignment

    80 

    81   /**

    82    * Empty constructor needed for the Class.newInstance() statement in

    83    * Instruction.readInstruction(). Not to be used otherwise.

    84    */

    85   Select() {}

    86 

    87   /**

    88    * (Match, target) pairs for switch.

    89    * `Match' and `targets' must have the same length of course.

    90    *

    91    * @param match array of matching values

    92    * @param targets instruction targets

    93    * @param target default instruction target

    94    */

    95   Select(short opcode, int[] match, InstructionHandle[] targets,

    96          InstructionHandle target) {

    97     super(opcode, target);

    98 

    99     this.targets = targets;

   100     for(int i=0; i < targets.length; i++)

   101       notifyTarget(null, targets[i], this);

   102 

   103     this.match = match;

   104 

   105     if((match_length = match.length) != targets.length)

   106       throw new ClassGenException("Match and target array have not the same length");

   107 

   108     indices = new int[match_length];

   109   }

   110 

   111   /**

   112    * Since this is a variable length instruction, it may shift the following

   113    * instructions which then need to update their position.

   114    *

   115    * Called by InstructionList.setPositions when setting the position for every

   116    * instruction. In the presence of variable length instructions `setPositions'

   117    * performs multiple passes over the instruction list to calculate the

   118    * correct (byte) positions and offsets by calling this function.

   119    *

   120    * @param offset additional offset caused by preceding (variable length) instructions

   121    * @param max_offset the maximum offset that may be caused by these instructions

   122    * @return additional offset caused by possible change of this instruction's length

   123    */

   124   protected int updatePosition(int offset, int max_offset) {

   125     position += offset; // Additional offset caused by preceding SWITCHs, GOTOs, etc.

   126 

   127     short old_length = length;

   128 

   129     /* Alignment on 4-byte-boundary, + 1, because of tag byte.

   130      */

   131     padding = (4 - ((position + 1) % 4)) % 4;

   132     length  = (short)(fixed_length + padding); // Update length

   133 

   134     return length - old_length;

   135   }

   136 

   137   /**

   138    * Dump instruction as byte code to stream out.

   139    * @param out Output stream

   140    */

   141   public void dump(DataOutputStream out) throws IOException {

   142     out.writeByte(opcode);

   143 

   144     for(int i=0; i < padding; i++) // Padding bytes

   145       out.writeByte(0);

   146 

   147     index = getTargetOffset();     // Write default target offset

   148     out.writeInt(index);

   149   }

   150 

   151   /**

   152    * Read needed data (e.g. index) from file.

   153    */

   154   protected void initFromFile(ByteSequence bytes, boolean wide) throws IOException

   155   {

   156     padding = (4 - (bytes.getIndex() % 4)) % 4; // Compute number of pad bytes

   157 

   158     for(int i=0; i < padding; i++) {

   159       bytes.readByte();

   160     }

   161 

   162     // Default branch target common for both cases (TABLESWITCH, LOOKUPSWITCH)

   163     index = bytes.readInt();

   164   }

   165 

   166   /**

   167    * @return mnemonic for instruction

   168    */

   169   public String toString(boolean verbose) {

   170     StringBuffer buf = new StringBuffer(super.toString(verbose));

   171 

   172     if(verbose) {

   173       for(int i=0; i < match_length; i++) {

   174         String s = "null";

   175 

   176         if(targets[i] != null)

   177           s = targets[i].getInstruction().toString();

   178 

   179         buf.append("(" + match[i] + ", " + s + " = {" + indices[i] + "})");

   180       }

   181     }

   182     else

   183       buf.append(" ...");

   184 

   185     return buf.toString();

   186   }

   187 

   188   /**

   189    * Set branch target for `i'th case

   190    */

   191   public void setTarget(int i, InstructionHandle target) {

   192     notifyTarget(targets[i], target, this);

   193     targets[i] = target;

   194   }

   195 

   196   /**

   197    * @param old_ih old target

   198    * @param new_ih new target

   199    */

   200   public void updateTarget(InstructionHandle old_ih, InstructionHandle new_ih) {

   201     boolean targeted = false;

   202 

   203     if(target == old_ih) {

   204       targeted = true;

   205       setTarget(new_ih);

   206     }

   207 

   208     for(int i=0; i < targets.length; i++) {

   209       if(targets[i] == old_ih) {

   210         targeted = true;

   211         setTarget(i, new_ih);

   212       }

   213     }

   214 

   215     if(!targeted)

   216       throw new ClassGenException("Not targeting " + old_ih);

   217   }

   218 

   219   /**

   220    * @return true, if ih is target of this instruction

   221    */

   222   public boolean containsTarget(InstructionHandle ih) {

   223     if(target == ih)

   224       return true;

   225 

   226     for(int i=0; i < targets.length; i++)

   227       if(targets[i] == ih)

   228         return true;

   229 

   230     return false;

   231   }

   232 

   233   /**

   234    * Inform targets that they're not targeted anymore.

   235    */

   236   void dispose() {

   237     super.dispose();

   238 

   239     for(int i=0; i < targets.length; i++)

   240       targets[i].removeTargeter(this);

   241   }

   242 

   243   /**

   244    * @return array of match indices

   245    */

   246   public int[] getMatchs() { return match; }

   247 

   248   /**

   249    * @return array of match target offsets

   250    */

   251   public int[] getIndices() { return indices; }

   252 

   253   /**

   254    * @return array of match targets

   255    */

   256   public InstructionHandle[] getTargets() { return targets; }

   257 }