1 /* 2 * reserved comment block 3 * DO NOT REMOVE OR ALTER! 4 */ 5 /* 6 * Copyright 2001-2004 The Apache Software Foundation. 7 * 8 * Licensed under the Apache License, Version 2.0 (the "License"); 9 * you may not use this file except in compliance with the License. 10 * You may obtain a copy of the License at 11 * 12 * http://www.apache.org/licenses/LICENSE-2.0 13 * 14 * Unless required by applicable law or agreed to in writing, software 15 * distributed under the License is distributed on an "AS IS" BASIS, 16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 17 * See the License for the specific language governing permissions and 18 * limitations under the License. 19 */ 20 21 /* 22 * $Id: MethodGenerator.java,v 1.10 2010-11-01 04:34:19 joehw Exp $ 23 */ 24 package com.sun.org.apache.xalan.internal.xsltc.compiler.util; 25 import java.io.DataOutputStream; 26 import java.io.IOException; 27 28 import com.sun.org.apache.bcel.internal.Constants; 29 import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen; 30 import com.sun.org.apache.bcel.internal.generic.Instruction; 31 import com.sun.org.apache.bcel.internal.generic.Visitor; 32 33 /** 34 * A special abstract dummy subclass of 35 * {@link org.apache.bcel.generic.Instruction} used to mark locations of 36 * interest in an {@link com.sun.org.apache.bcel.internal.generic.InstructionList}. It and 37 * its subclasses are only used as placeholders, and do not contribute to the 38 * actual byte code instruction stream. 39 */ 40 abstract class MarkerInstruction extends Instruction { 41 /** 42 * Zero-argument constructor. Sets the opcode to an invalid value and 43 * sets the length to zero, as it will not be written as part of the 44 * generated byte code. 45 */ 46 public MarkerInstruction() { 47 super(Constants.UNDEFINED, (short) 0); 48 } 49 50 /** 51 * {@link com.sun.org.apache.bcel.internal.generic.Visitor}s will know nothing about this 52 * kind of {@link org.apche.bcel.generic.Instruction}, so this method does 53 * nothing. 54 */ 55 public void accept(Visitor v) { 56 } 57 58 /** 59 * The number of JVM stack entries consumed by the instruction. 60 * This instruction is just a place holder, so it does not consume any 61 * stack entries. 62 * @param cpg The {@link com.sun.org.apache.bcel.internal.generic.ConstantPoolGen} for the 63 * current {@link com.sun.org.apache.bcel.internal.generic.ClassGen} 64 * @return <code>0</code> always 65 */ 66 final public int consumeStack(ConstantPoolGen cpg) { 67 return 0; 68 } 69 /** 70 * The number of JVM stack entries produced by the instruction. 71 * This instruction is just a place holder, so it does not produce any 72 * stack entries. 73 * @param cpg The {@link com.sun.org.apache.bcel.internal.generic.ConstantPoolGen} for the 74 * current {@link com.sun.org.apache.bcel.internal.generic.ClassGen} 75 * @return <code>0</code> always 76 */ 77 final public int produceStack(ConstantPoolGen cpg) { 78 return 0; 79 } 80 81 /** 82 * Produce a copy of the instruction. By default a 83 * {@link MarkerInstruction} has no parameters, so the base implementation 84 * of {@link #copy()} returns the instruction itself. 85 * @return The instruction itself. 86 */ 87 public Instruction copy() { 88 return this; 89 } 90 /** 91 * Dump instruction as byte code to stream out. A {@link MarkerInstruction} 92 * has no effect on the generated byte code so it is never emitted to the 93 * output stream. 94 * @param out Output stream 95 */ 96 final public void dump(DataOutputStream out) throws IOException { 97 } 98 }