001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   https://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.bcel.classfile;
020
021import java.io.DataInput;
022import java.io.DataOutputStream;
023import java.io.IOException;
024
025import org.apache.bcel.util.Args;
026
027/**
028 * This class represents a (PC offset, line number) pair, i.e., a line number in the source that corresponds to a
029 * relative address in the byte code. This is used for debugging purposes.
030 *
031 * @see LineNumberTable
032 */
033public final class LineNumber implements Cloneable, Node {
034
035    static final LineNumber[] EMPTY_ARRAY = {};
036
037    /** Program Counter (PC) corresponds to line */
038    private int startPc;
039
040    /** Number in source file */
041    private int lineNumber;
042
043    /**
044     * Constructs object from file stream.
045     *
046     * @param file Input stream
047     * @throws IOException if an I/O Exception occurs in readUnsignedShort
048     */
049    LineNumber(final DataInput file) throws IOException {
050        this(file.readUnsignedShort(), file.readUnsignedShort());
051    }
052
053    /**
054     * @param startPc Program Counter (PC) corresponds to
055     * @param lineNumber line number in source file
056     */
057    public LineNumber(final int startPc, final int lineNumber) {
058        this.startPc = Args.requireU2(startPc, "startPc");
059        this.lineNumber = Args.requireU2(lineNumber, "lineNumber");
060    }
061
062    /**
063     * Initialize from another object.
064     *
065     * @param c the object to copy
066     */
067    public LineNumber(final LineNumber c) {
068        this(c.getStartPC(), c.getLineNumber());
069    }
070
071    /**
072     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
073     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
074     *
075     * @param v Visitor object
076     */
077    @Override
078    public void accept(final Visitor v) {
079        v.visitLineNumber(this);
080    }
081
082    /**
083     * @return deep copy of this object
084     */
085    public LineNumber copy() {
086        try {
087            return (LineNumber) clone();
088        } catch (final CloneNotSupportedException e) {
089            // TODO should this throw?
090        }
091        return null;
092    }
093
094    /**
095     * Dump line number/pc pair to file stream in binary format.
096     *
097     * @param file Output file stream
098     * @throws IOException if an I/O Exception occurs in writeShort
099     */
100    public void dump(final DataOutputStream file) throws IOException {
101        file.writeShort(startPc);
102        file.writeShort(lineNumber);
103    }
104
105    /**
106     * @return Corresponding source line
107     */
108    public int getLineNumber() {
109        return lineNumber & 0xffff;
110    }
111
112    /**
113     * @return PC in code
114     */
115    public int getStartPC() {
116        return startPc & 0xffff;
117    }
118
119    /**
120     * @param lineNumber the source line number
121     */
122    public void setLineNumber(final int lineNumber) {
123        this.lineNumber = (short) lineNumber;
124    }
125
126    /**
127     * @param startPc the pc for this line number
128     */
129    public void setStartPC(final int startPc) {
130        this.startPc = (short) startPc;
131    }
132
133    /**
134     * @return String representation
135     */
136    @Override
137    public String toString() {
138        return "LineNumber(" + getStartPC() + ", " + getLineNumber() + ")";
139    }
140}