    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 *
    017 */
    018package org.apache.bcel.classfile;
    019
    020import java.io.DataInput;
    021import java.io.DataOutputStream;
    022import java.io.IOException;
    023import java.util.Arrays;
    024import java.util.Iterator;
    025import java.util.stream.Stream;
    026
    027import org.apache.bcel.Const;
    028
    029/**
    030 * This class represents a table of line numbers for debugging purposes. This attribute is used by the <em>Code</em>
    031 * attribute. It contains pairs of PCs and line numbers.
    032 *
    033 * @see Code
    034 * @see LineNumber
    035 */
    036public final class LineNumberTable extends Attribute implements Iterable<LineNumber> {
    037
    038    private static final int MAX_LINE_LENGTH = 72;
    039    private LineNumber[] lineNumberTable; // Table of line/numbers pairs
    040
    041    /**
    042     * Construct object from input stream.
    043     *
    044     * @param name_index Index of name
    045     * @param length Content length in bytes
    046     * @param input Input stream
    047     * @param constant_pool Array of constants
    048     * @throws IOException if an I/O Exception occurs in readUnsignedShort
    049     */
    050    LineNumberTable(final int name_index, final int length, final DataInput input, final ConstantPool constant_pool) throws IOException {
    051        this(name_index, length, (LineNumber[]) null, constant_pool);
    052        final int line_number_table_length = input.readUnsignedShort();
    053        lineNumberTable = new LineNumber[line_number_table_length];
    054        for (int i = 0; i < line_number_table_length; i++) {
    055            lineNumberTable[i] = new LineNumber(input);
    056        }
    057    }
    058
    059    /*
    060     * @param name_index Index of name
    061     *
    062     * @param length Content length in bytes
    063     *
    064     * @param lineNumberTable Table of line/numbers pairs
    065     *
    066     * @param constant_pool Array of constants
    067     */
    068    public LineNumberTable(final int name_index, final int length, final LineNumber[] line_number_table, final ConstantPool constant_pool) {
    069        super(Const.ATTR_LINE_NUMBER_TABLE, name_index, length, constant_pool);
    070        this.lineNumberTable = line_number_table;
    071    }
    072
    073    /*
    074     * Initialize from another object. Note that both objects use the same references (shallow copy). Use copy() for a
    075     * physical copy.
    076     */
    077    public LineNumberTable(final LineNumberTable c) {
    078        this(c.getNameIndex(), c.getLength(), c.getLineNumberTable(), c.getConstantPool());
    079    }
    080
    081    /**
    082     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    083     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    084     *
    085     * @param v Visitor object
    086     */
    087    @Override
    088    public void accept(final Visitor v) {
    089        v.visitLineNumberTable(this);
    090    }
    091
    092    /**
    093     * @return deep copy of this attribute
    094     */
    095    @Override
    096    public Attribute copy(final ConstantPool constantPool) {
    097        // TODO could use the lower level constructor and thereby allow
    098        // lineNumberTable to be made final
    099        final LineNumberTable c = (LineNumberTable) clone();
    100        c.lineNumberTable = new LineNumber[lineNumberTable.length];
    101        Arrays.setAll(c.lineNumberTable, i -> lineNumberTable[i].copy());
    102        c.setConstantPool(constantPool);
    103        return c;
    104    }
    105
    106    /**
    107     * Dump line number table attribute to file stream in binary format.
    108     *
    109     * @param file Output file stream
    110     * @throws IOException if an I/O Exception occurs in writeShort
    111     */
    112    @Override
    113    public void dump(final DataOutputStream file) throws IOException {
    114        super.dump(file);
    115        file.writeShort(lineNumberTable.length);
    116        for (final LineNumber lineNumber : lineNumberTable) {
    117            lineNumber.dump(file);
    118        }
    119    }
    120
    121    /**
    122     * @return Array of (pc offset, line number) pairs.
    123     */
    124    public LineNumber[] getLineNumberTable() {
    125        return lineNumberTable;
    126    }
    127
    128    /**
    129     * Map byte code positions to source code lines.
    130     *
    131     * @param pos byte code offset
    132     * @return corresponding line in source code
    133     */
    134    public int getSourceLine(final int pos) {
    135        int l = 0;
    136        int r = lineNumberTable.length - 1;
    137        if (r < 0) {
    138            return -1;
    139        }
    140        int min_index = -1;
    141        int min = -1;
    142        /*
    143         * Do a binary search since the array is ordered.
    144         */
    145        do {
    146            final int i = l + r >>> 1;
    147            final int j = lineNumberTable[i].getStartPC();
    148            if (j == pos) {
    149                return lineNumberTable[i].getLineNumber();
    150            }
    151            if (pos < j) {
    152                r = i - 1;
    153            } else {
    154                l = i + 1;
    155            }
    156            /*
    157             * If exact match can't be found (which is the most common case) return the line number that corresponds to the greatest
    158             * index less than pos.
    159             */
    160            if (j < pos && j > min) {
    161                min = j;
    162                min_index = i;
    163            }
    164        } while (l <= r);
    165        /*
    166         * It's possible that we did not find any valid entry for the bytecode offset we were looking for.
    167         */
    168        if (min_index < 0) {
    169            return -1;
    170        }
    171        return lineNumberTable[min_index].getLineNumber();
    172    }
    173
    174    public int getTableLength() {
    175        return lineNumberTable == null ? 0 : lineNumberTable.length;
    176    }
    177
    178    @Override
    179    public Iterator<LineNumber> iterator() {
    180        return Stream.of(lineNumberTable).iterator();
    181    }
    182
    183    /**
    184     * @param lineNumberTable the line number entries for this table
    185     */
    186    public void setLineNumberTable(final LineNumber[] lineNumberTable) {
    187        this.lineNumberTable = lineNumberTable;
    188    }
    189
    190    /**
    191     * @return String representation.
    192     */
    193    @Override
    194    public String toString() {
    195        final StringBuilder buf = new StringBuilder();
    196        final StringBuilder line = new StringBuilder();
    197        final String newLine = System.getProperty("line.separator", "\n");
    198        for (int i = 0; i < lineNumberTable.length; i++) {
    199            line.append(lineNumberTable[i].toString());
    200            if (i < lineNumberTable.length - 1) {
    201                line.append(", ");
    202            }
    203            if (line.length() > MAX_LINE_LENGTH && i < lineNumberTable.length - 1) {
    204                line.append(newLine);
    205                buf.append(line);
    206                line.setLength(0);
    207            }
    208        }
    209        buf.append(line);
    210        return buf.toString();
    211    }
    212}