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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.
40   *
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
44   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
45   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
46   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
47   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
48   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
49   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
50   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
51   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
52   * SUCH DAMAGE.
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  
61  /**
62   * Equality of instructions isn't clearly to be defined. You might
63   * wish, for example, to compare whether instructions have the same
64   * meaning. E.g., whether two INVOKEVIRTUALs describe the same
65   * call.<br>The DEFAULT comparator however, considers two instructions
66   * to be equal if they have same opcode and point to the same indexes
67   * (if any) in the constant pool or the same local variable index. Branch
68   * instructions must have the same target.
69   *
70   * @see Instruction
71   * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
72   */
73  public interface InstructionComparator {
74    public static final InstructionComparator DEFAULT =
75      new InstructionComparator() {
76          public boolean equals(Instruction i1, Instruction i2) {
77            if(i1.opcode == i2.opcode) {
78              if(i1 instanceof Select) {
79                InstructionHandle[] t1 = ((Select)i1).getTargets();
80                InstructionHandle[] t2 = ((Select)i2).getTargets();
81  
82                if(t1.length == t2.length) {
83                  for(int i = 0; i < t1.length; i++) {
84                    if(t1[i] != t2[i]) {
85                      return false;
86                    }
87                  }
88  
89                  return true;
90                }
91              } else if(i1 instanceof BranchInstruction) {
92                return ((BranchInstruction)i1).target ==
93                  ((BranchInstruction)i2).target;
94              } else if(i1 instanceof ConstantPushInstruction) {
95                return ((ConstantPushInstruction)i1).getValue().
96                  equals(((ConstantPushInstruction)i2).getValue());
97              } else if(i1 instanceof IndexedInstruction) {
98                return ((IndexedInstruction)i1).getIndex() ==
99                  ((IndexedInstruction)i2).getIndex();
100             } else if(i1 instanceof NEWARRAY) {
101               return ((NEWARRAY)i1).getTypecode() == ((NEWARRAY)i2).getTypecode();
102             } else {
103               return true;
104             }
105           }
106 
107           return false;
108         }
109       };
110 
111   public boolean equals(Instruction i1, Instruction i2);
112 }