instructioncomparator.java

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

/* ====================================================================
 * The Apache Software License, Version 1.1
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 * Copyright (c) 2001 The Apache Software Foundation.  All rights
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 *       "This product includes software developed by the
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 * This software consists of voluntary contributions made by many
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/**
 * 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
 * @version $Id: InstructionComparator.java,v 1.1.2.1 2005/07/31 23:46:03 jeffsuttor Exp $
 * @author <A HREF="mailto:[e-mail]">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);
}