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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */
package org.apache.bcel.generic;

/**
 * Equality of instructions isn't clearly to be defined. You might
 * wish, for example, to compare whether instructions have the same
 * meaning. E.g., whether two INVOKEVIRTUALs describe the same
 * call.
The DEFAULT comparator however, considers two instructions
 * to be equal if they have same opcode and point to the same indexes
 * (if any) in the constant pool or the same local variable index. Branch
 * instructions must have the same target.
 *
 * @see Instruction
 * @version $Id$
 */
public interface InstructionComparator {

    InstructionComparator DEFAULT = new InstructionComparator() {

        @Override
        public boolean equals( final Instruction i1, final Instruction i2 ) {
            if (i1.getOpcode() == i2.getOpcode()) {
                if (i1 instanceof BranchInstruction) {
                 // BIs are never equal to make targeters work correctly (BCEL-195)
                    return false;
//                } else if (i1 == i2) { TODO consider adding this shortcut
//                    return true; // this must be AFTER the BI test
                } else if (i1 instanceof ConstantPushInstruction) {
                    return ((ConstantPushInstruction) i1).getValue().equals(
                            ((ConstantPushInstruction) i2).getValue());
                } else if (i1 instanceof IndexedInstruction) {
                    return ((IndexedInstruction) i1).getIndex() == ((IndexedInstruction) i2)
                            .getIndex();
                } else if (i1 instanceof NEWARRAY) {
                    return ((NEWARRAY) i1).getTypecode() == ((NEWARRAY) i2).getTypecode();
                } else {
                    return true;
                }
            }
            return false;
        }
    };


    boolean equals( Instruction i1, Instruction i2 );
}