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, that is, 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 Thrown 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     * Constructs a LineNumber.
055     *
056     * @param startPc Program Counter (PC) corresponds to.
057     * @param lineNumber line number in source file.
058     */
059    public LineNumber(final int startPc, final int lineNumber) {
060        this.startPc = Args.requireU2(startPc, "startPc");
061        this.lineNumber = Args.requireU2(lineNumber, "lineNumber");
062    }
063
064    /**
065     * Initialize from another object.
066     *
067     * @param c The object to copy.
068     */
069    public LineNumber(final LineNumber c) {
070        this(c.getStartPC(), c.getLineNumber());
071    }
072
073    /**
074     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
075     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
076     *
077     * @param v Visitor object.
078     */
079    @Override
080    public void accept(final Visitor v) {
081        v.visitLineNumber(this);
082    }
083
084    /**
085     * Creates a deep copy of this object.
086     *
087     * @return deep copy of this object.
088     */
089    public LineNumber copy() {
090        try {
091            return (LineNumber) clone();
092        } catch (final CloneNotSupportedException e) {
093            // TODO should this throw?
094        }
095        return null;
096    }
097
098    /**
099     * Dumps line number/pc pair to file stream in binary format.
100     *
101     * @param file Output file stream.
102     * @throws IOException Thrown if an I/O Exception occurs in writeShort.
103     */
104    public void dump(final DataOutputStream file) throws IOException {
105        file.writeShort(startPc);
106        file.writeShort(lineNumber);
107    }
108
109    /**
110     * Gets the line number.
111     *
112     * @return Corresponding source line.
113     */
114    public int getLineNumber() {
115        return lineNumber & 0xffff;
116    }
117
118    /**
119     * Gets the program counter.
120     *
121     * @return PC in code.
122     */
123    public int getStartPC() {
124        return startPc & 0xffff;
125    }
126
127    /**
128     * Sets the line number.
129     *
130     * @param lineNumber The source line number.
131     */
132    public void setLineNumber(final int lineNumber) {
133        this.lineNumber = (short) lineNumber;
134    }
135
136    /**
137     * Sets the program counter.
138     *
139     * @param startPc The pc for this line number.
140     */
141    public void setStartPC(final int startPc) {
142        this.startPc = (short) startPc;
143    }
144
145    /**
146     * @return String representation.
147     */
148    @Override
149    public String toString() {
150        return "LineNumber(" + getStartPC() + ", " + getLineNumber() + ")";
151    }
152}