    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 */
    017package org.apache.bcel.generic;
    018
    019/**
    020 * Equality of instructions isn't clearly to be defined. You might wish, for example, to compare whether instructions
    021 * have the same meaning. E.g., whether two INVOKEVIRTUALs describe the same call.
    022 * <p>
    023 * The DEFAULT comparator however, considers two instructions to be equal if they have same opcode and point to the same
    024 * indexes (if any) in the constant pool or the same local variable index. Branch instructions must have the same
    025 * target.
    026 * </p>
    027 *
    028 * @see Instruction
    029 */
    030public interface InstructionComparator {
    031
    032    InstructionComparator DEFAULT = (i1, i2) -> {
    033        if (i1.getOpcode() == i2.getOpcode()) {
    034            if (i1 instanceof BranchInstruction) {
    035                // BIs are never equal to make targeters work correctly (BCEL-195)
    036                return false;
    037//                } else if (i1 == i2) { TODO consider adding this shortcut
    038//                    return true; // this must be AFTER the BI test
    039            }
    040            if (i1 instanceof ConstantPushInstruction) {
    041                return ((ConstantPushInstruction) i1).getValue().equals(((ConstantPushInstruction) i2).getValue());
    042            }
    043            if (i1 instanceof IndexedInstruction) {
    044                return ((IndexedInstruction) i1).getIndex() == ((IndexedInstruction) i2).getIndex();
    045            }
    046            if (i1 instanceof NEWARRAY) {
    047                return ((NEWARRAY) i1).getTypecode() == ((NEWARRAY) i2).getTypecode();
    048            }
    049            return true;
    050        }
    051        return false;
    052    };
    053
    054    boolean equals(Instruction i1, Instruction i2);
    055}