001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 *  Unless required by applicable law or agreed to in writing, software
012 *  distributed under the License is distributed on an "AS IS" BASIS,
013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 *  See the License for the specific language governing permissions and
015 *  limitations under the License.
016 *
017 */
018package org.apache.bcel.generic;
019
020/**
021 * Equality of instructions isn't clearly to be defined. You might
022 * wish, for example, to compare whether instructions have the same
023 * meaning. E.g., whether two INVOKEVIRTUALs describe the same
024 * call.<br>The DEFAULT comparator however, considers two instructions
025 * to be equal if they have same opcode and point to the same indexes
026 * (if any) in the constant pool or the same local variable index. Branch
027 * instructions must have the same target.
028 *
029 * @see Instruction
030 * @version $Id: InstructionComparator.java 1749597 2016-06-21 20:28:51Z ggregory $
031 */
032public interface InstructionComparator {
033
034    InstructionComparator DEFAULT = new InstructionComparator() {
035
036        @Override
037        public boolean equals( final Instruction i1, final Instruction i2 ) {
038            if (i1.getOpcode() == i2.getOpcode()) {
039                if (i1 instanceof BranchInstruction) {
040                 // BIs are never equal to make targeters work correctly (BCEL-195)
041                    return false;
042//                } else if (i1 == i2) { TODO consider adding this shortcut
043//                    return true; // this must be AFTER the BI test
044                } else if (i1 instanceof ConstantPushInstruction) {
045                    return ((ConstantPushInstruction) i1).getValue().equals(
046                            ((ConstantPushInstruction) i2).getValue());
047                } else if (i1 instanceof IndexedInstruction) {
048                    return ((IndexedInstruction) i1).getIndex() == ((IndexedInstruction) i2)
049                            .getIndex();
050                } else if (i1 instanceof NEWARRAY) {
051                    return ((NEWARRAY) i1).getTypecode() == ((NEWARRAY) i2).getTypecode();
052                } else {
053                    return true;
054                }
055            }
056            return false;
057        }
058    };
059
060
061    boolean equals( Instruction i1, Instruction i2 );
062}