/*
 * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
 */
/*
 * 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 com.sun.org.apache.xalan.internal.xsltc.compiler.util;
import java.io.DataOutputStream;
import java.io.IOException;

import com.sun.org.apache.bcel.internal.Const;
import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;
import com.sun.org.apache.bcel.internal.generic.Instruction;
import com.sun.org.apache.bcel.internal.generic.Visitor;

A special abstract dummy subclass of Instruction used to mark locations of interest in an InstructionList. It and its subclasses are only used as placeholders, and do not contribute to the actual byte code instruction stream. /**
 * A special abstract dummy subclass of
 * {@link org.apache.bcel.generic.Instruction} used to mark locations of
 * interest in an {@link com.sun.org.apache.bcel.internal.generic.InstructionList}.  It and
 * its subclasses are only used as placeholders, and do not contribute to the
 * actual byte code instruction stream.
 */
abstract class MarkerInstruction extends Instruction {
    
Zero-argument constructor.  Sets the opcode to an invalid value and
sets the length to zero, as it will not be written as part of the
generated byte code.
/**
     * Zero-argument constructor.  Sets the opcode to an invalid value and
     * sets the length to zero, as it will not be written as part of the
     * generated byte code.
     */
    public MarkerInstruction() {
        super(Const.UNDEFINED, (short) 0);
    }

    
Visitors will know nothing about this kind of Instruction, so this method does nothing. /**
     * {@link com.sun.org.apache.bcel.internal.generic.Visitor}s will know nothing about this
     * kind of {@link org.apche.bcel.generic.Instruction}, so this method does
     * nothing.
     */
    public void accept(Visitor v) {
    }

    
The number of JVM stack entries consumed by the instruction.
This instruction is just a place holder, so it does not consume any
stack entries.
Params:
cpg – The ConstantPoolGen for the current ClassGen
Returns:
0 always/**
     * The number of JVM stack entries consumed by the instruction.
     * This instruction is just a place holder, so it does not consume any
     * stack entries.
     * @param cpg The {@link com.sun.org.apache.bcel.internal.generic.ConstantPoolGen} for the
     * current {@link com.sun.org.apache.bcel.internal.generic.ClassGen}
     * @return <code>0</code> always
     */
    final public int consumeStack(ConstantPoolGen cpg) {
        return 0;
    }
    
The number of JVM stack entries produced by the instruction.
This instruction is just a place holder, so it does not produce any
stack entries.
Params:
cpg – The ConstantPoolGen for the current ClassGen
Returns:
0 always/**
     * The number of JVM stack entries produced by the instruction.
     * This instruction is just a place holder, so it does not produce any
     * stack entries.
     * @param cpg The {@link com.sun.org.apache.bcel.internal.generic.ConstantPoolGen} for the
     * current {@link com.sun.org.apache.bcel.internal.generic.ClassGen}
     * @return <code>0</code> always
     */
    final public int produceStack(ConstantPoolGen cpg) {
        return 0;
    }

    
Produce a copy of the instruction. By default a MarkerInstruction has no parameters, so the base implementation of copy() returns the instruction itself. 
Returns:
The instruction itself./**
     * Produce a copy of the instruction.  By default a
     * {@link MarkerInstruction} has no parameters, so the base implementation
     * of {@link #copy()} returns the instruction itself.
     * @return The instruction itself.
     */
    public Instruction copy() {
        return this;
    }
    
Dump instruction as byte code to stream out. A MarkerInstruction has no effect on the generated byte code so it is never emitted to the output stream. 
Params:
out – Output stream/**
     * Dump instruction as byte code to stream out.  A {@link MarkerInstruction}
     * has no effect on the generated byte code so it is never emitted to the
     * output stream.
     * @param out Output stream
     */
    final public void dump(DataOutputStream out) throws IOException {
    }
}