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