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      1 /*
      2  * Licensed to the Apache Software Foundation (ASF) under one or more
      3  * contributor license agreements.  See the NOTICE file distributed with
      4  * this work for additional information regarding copyright ownership.
      5  * The ASF licenses this file to You under the Apache License, Version 2.0
      6  * (the "License"); you may not use this file except in compliance with
      7  * the License.  You may obtain a copy of the License at
      8  *
      9  *      http://www.apache.org/licenses/LICENSE-2.0
     10  *
     11  *  Unless required by applicable law or agreed to in writing, software
     12  *  distributed under the License is distributed on an "AS IS" BASIS,
     13  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14  *  See the License for the specific language governing permissions and
     15  *  limitations under the License.
     16  *
     17  */
     18 package org.apache.bcel.generic;
     19 
     20 /**
     21  * Equality of instructions isn't clearly to be defined. You might
     22  * wish, for example, to compare whether instructions have the same
     23  * meaning. E.g., whether two INVOKEVIRTUALs describe the same
     24  * call.<br>The DEFAULT comparator however, considers two instructions
     25  * to be equal if they have same opcode and point to the same indexes
     26  * (if any) in the constant pool or the same local variable index. Branch
     27  * instructions must have the same target.
     28  *
     29  * @see Instruction
     30  * @version $Id$
     31  */
     32 public interface InstructionComparator {
     33 
     34     InstructionComparator DEFAULT = new InstructionComparator() {
     35 
     36         @Override
     37         public boolean equals( final Instruction i1, final Instruction i2 ) {
     38             if (i1.getOpcode() == i2.getOpcode()) {
     39                 if (i1 instanceof BranchInstruction) {
     40                  // BIs are never equal to make targeters work correctly (BCEL-195)
     41                     return false;
     42 //                } else if (i1 == i2) { TODO consider adding this shortcut
     43 //                    return true; // this must be AFTER the BI test
     44                 } else if (i1 instanceof ConstantPushInstruction) {
     45                     return ((ConstantPushInstruction) i1).getValue().equals(
     46                             ((ConstantPushInstruction) i2).getValue());
     47                 } else if (i1 instanceof IndexedInstruction) {
     48                     return ((IndexedInstruction) i1).getIndex() == ((IndexedInstruction) i2)
     49                             .getIndex();
     50                 } else if (i1 instanceof NEWARRAY) {
     51                     return ((NEWARRAY) i1).getTypecode() == ((NEWARRAY) i2).getTypecode();
     52                 } else {
     53                     return true;
     54                 }
     55             }
     56             return false;
     57         }
     58     };
     59 
     60 
     61     boolean equals( Instruction i1, Instruction i2 );
     62 }
     63