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