    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 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     * Dumps 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}