    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.
    025 * <p>
    026 * The DEFAULT comparator however, considers two instructions
    027 * to be equal if they have same opcode and point to the same indexes
    028 * (if any) in the constant pool or the same local variable index. Branch
    029 * instructions must have the same target.
    030 * </p>
    031 *
    032 * @see Instruction
    033 */
    034public interface InstructionComparator {
    035
    036    InstructionComparator DEFAULT = (i1, i2) -> {
    037        if (i1.getOpcode() == i2.getOpcode()) {
    038            if (i1 instanceof BranchInstruction) {
    039             // BIs are never equal to make targeters work correctly (BCEL-195)
    040                return false;
    041//                } else if (i1 == i2) { TODO consider adding this shortcut
    042//                    return true; // this must be AFTER the BI test
    043            } else if (i1 instanceof ConstantPushInstruction) {
    044                return ((ConstantPushInstruction) i1).getValue().equals(
    045                        ((ConstantPushInstruction) i2).getValue());
    046            } else if (i1 instanceof IndexedInstruction) {
    047                return ((IndexedInstruction) i1).getIndex() == ((IndexedInstruction) i2)
    048                        .getIndex();
    049            } else if (i1 instanceof NEWARRAY) {
    050                return ((NEWARRAY) i1).getTypecode() == ((NEWARRAY) i2).getTypecode();
    051            } else {
    052                return true;
    053            }
    054        }
    055        return false;
    056    };
    057
    058
    059    boolean equals( Instruction i1, Instruction i2 );
    060}