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 * Licensed to the Apache Software Foundation (ASF) under one or more
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 * this work for additional information regarding copyright ownership.
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 * (the "License"); you may not use this file except in compliance with
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package com.sun.org.apache.bcel.internal.generic;


Equality of instructions isn't clearly to be defined. You might
wish, for example, to compare whether instructions have the same
meaning. E.g., whether two INVOKEVIRTUALs describe the same
call.
The DEFAULT comparator however, considers two instructions
to be equal if they have same opcode and point to the same indexes
(if any) in the constant pool or the same local variable index. Branch
instructions must have the same target.
Author:
M. Dahm
See Also:
Instruction/**
 * Equality of instructions isn't clearly to be defined. You might
 * wish, for example, to compare whether instructions have the same
 * meaning. E.g., whether two INVOKEVIRTUALs describe the same
 * call.<br>The DEFAULT comparator however, considers two instructions
 * to be equal if they have same opcode and point to the same indexes
 * (if any) in the constant pool or the same local variable index. Branch
 * instructions must have the same target.
 *
 * @see Instruction
 * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
 */
public interface InstructionComparator {
  public static final InstructionComparator DEFAULT =
    new InstructionComparator() {
        public boolean equals(Instruction i1, Instruction i2) {
          if(i1.opcode == i2.opcode) {
            if(i1 instanceof Select) {
              InstructionHandle[] t1 = ((Select)i1).getTargets();
              InstructionHandle[] t2 = ((Select)i2).getTargets();

              if(t1.length == t2.length) {
                for(int i = 0; i < t1.length; i++) {
                  if(t1[i] != t2[i]) {
                    return false;
                  }
                }

                return true;
              }
            } else if(i1 instanceof BranchInstruction) {
              return ((BranchInstruction)i1).target ==
                ((BranchInstruction)i2).target;
            } else if(i1 instanceof ConstantPushInstruction) {
              return ((ConstantPushInstruction)i1).getValue().
                equals(((ConstantPushInstruction)i2).getValue());
            } else if(i1 instanceof IndexedInstruction) {
              return ((IndexedInstruction)i1).getIndex() ==
                ((IndexedInstruction)i2).getIndex();
            } else if(i1 instanceof NEWARRAY) {
              return ((NEWARRAY)i1).getTypecode() == ((NEWARRAY)i2).getTypecode();
            } else {
              return true;
            }
          }

          return false;
        }
      };

  public boolean equals(Instruction i1, Instruction i2);
}