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Java > Open Source Codes > com > sun > org > apache > bcel > internal > generic > InstructionComparator


1 package com.sun.org.apache.bcel.internal.generic;
2
3 /* ====================================================================
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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 1.1.2.1 2005/07/31 23:46:03 jeffsuttor 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 }
110
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