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
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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.
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37   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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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  
57  /***
58   * Equality of instructions isn't clearly to be defined. You might
59   * wish, for example, to compare whether instructions have the same
60   * meaning. E.g., whether two INVOKEVIRTUALs describe the same
61   * call.<br>The DEFAULT comparator however, considers two instructions
62   * to be equal if they have same opcode and point to the same indexes
63   * (if any) in the constant pool or the same local variable index. Branch
64   * instructions must have the same target.
65   *
66   * @see Instruction
67   * @version $Id: InstructionComparator.java,v 1.3 2002/10/11 20:33:07 mdahm Exp $
68   * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
69   */
70  public interface InstructionComparator {
71    public static final InstructionComparator DEFAULT =
72      new InstructionComparator() {
73  	public boolean equals(Instruction i1, Instruction i2) {
74  	  if(i1.opcode == i2.opcode) {
75  	    if(i1 instanceof Select) {
76  	      InstructionHandle[] t1 = ((Select)i1).getTargets();
77  	      InstructionHandle[] t2 = ((Select)i2).getTargets();
78  
79  	      if(t1.length == t2.length) {
80  		for(int i = 0; i < t1.length; i++) {
81  		  if(t1[i] != t2[i]) {
82  		    return false;
83  		  }
84  		}
85  		
86  		return true;
87  	      }
88  	    } else if(i1 instanceof BranchInstruction) {
89  	      return ((BranchInstruction)i1).target == 
90  		((BranchInstruction)i2).target;
91  	    } else if(i1 instanceof ConstantPushInstruction) {
92  	      return ((ConstantPushInstruction)i1).getValue().
93  		equals(((ConstantPushInstruction)i2).getValue());
94  	    } else if(i1 instanceof IndexedInstruction) {
95  	      return ((IndexedInstruction)i1).getIndex() == 
96  		((IndexedInstruction)i2).getIndex();
97  	    } else if(i1 instanceof NEWARRAY) {
98  	      return ((NEWARRAY)i1).getTypecode() == ((NEWARRAY)i2).getTypecode();
99  	    } else {
100 	      return true;
101 	    }
102 	  }
103 
104 	  return false;
105 	}
106       };
107 
108   public boolean equals(Instruction i1, Instruction i2);
109 }
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