    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;
    024import java.util.Arrays;
    025import java.util.Iterator;
    026import java.util.stream.Stream;
    027
    028import org.apache.bcel.Const;
    029import org.apache.bcel.util.Args;
    030import org.apache.commons.lang3.SystemProperties;
    031
    032/**
    033 * This class represents a table of line numbers for debugging purposes. This attribute is used by the <em>Code</em>
    034 * attribute. It contains pairs of PCs and line numbers.
    035 *
    036 * @see Code
    037 * @see LineNumber
    038 */
    039public final class LineNumberTable extends Attribute implements Iterable<LineNumber> {
    040
    041    private static final int MAX_LINE_LENGTH = 72;
    042    private LineNumber[] lineNumberTable; // Table of line/numbers pairs
    043
    044    /**
    045     * Constructs a new instance from a data input stream.
    046     *
    047     * @param nameIndex Index of name.
    048     * @param length Content length in bytes.
    049     * @param input Input stream.
    050     * @param constantPool Array of constants.
    051     * @throws IOException if an I/O Exception occurs in readUnsignedShort.
    052     */
    053    LineNumberTable(final int nameIndex, final int length, final DataInput input, final ConstantPool constantPool) throws IOException {
    054        this(nameIndex, length, (LineNumber[]) null, constantPool);
    055        final int lineNumberTableLength = input.readUnsignedShort();
    056        lineNumberTable = new LineNumber[lineNumberTableLength];
    057        for (int i = 0; i < lineNumberTableLength; i++) {
    058            lineNumberTable[i] = new LineNumber(input);
    059        }
    060    }
    061
    062    /**
    063     * Constructs a new instance.
    064     *
    065     * @param nameIndex Index of name.
    066     * @param length Content length in bytes.
    067     * @param lineNumberTable Table of line/numbers pairs.
    068     * @param constantPool Array of constants.
    069     */
    070    public LineNumberTable(final int nameIndex, final int length, final LineNumber[] lineNumberTable, final ConstantPool constantPool) {
    071        super(Const.ATTR_LINE_NUMBER_TABLE, nameIndex, length, constantPool);
    072        this.lineNumberTable = lineNumberTable != null ? lineNumberTable : LineNumber.EMPTY_ARRAY;
    073        Args.requireU2(this.lineNumberTable.length, "lineNumberTable.length");
    074    }
    075
    076    /**
    077     * Constructs a new instance from another.
    078     * <p>
    079     * Note that both objects use the same references (shallow copy). Use copy() for a physical copy.
    080     * </p>
    081     */
    082    public LineNumberTable(final LineNumberTable c) {
    083        this(c.getNameIndex(), c.getLength(), c.getLineNumberTable(), c.getConstantPool());
    084    }
    085
    086    /**
    087     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    088     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    089     *
    090     * @param v Visitor object.
    091     */
    092    @Override
    093    public void accept(final Visitor v) {
    094        v.visitLineNumberTable(this);
    095    }
    096
    097    /**
    098     * @return deep copy of this attribute.
    099     */
    100    @Override
    101    public Attribute copy(final ConstantPool constantPool) {
    102        // TODO could use the lower level constructor and thereby allow
    103        // lineNumberTable to be made final
    104        final LineNumberTable c = (LineNumberTable) clone();
    105        c.lineNumberTable = new LineNumber[lineNumberTable.length];
    106        Arrays.setAll(c.lineNumberTable, i -> lineNumberTable[i].copy());
    107        c.setConstantPool(constantPool);
    108        return c;
    109    }
    110
    111    /**
    112     * Dumps line number table attribute to file stream in binary format.
    113     *
    114     * @param file Output file stream.
    115     * @throws IOException if an I/O Exception occurs in writeShort.
    116     */
    117    @Override
    118    public void dump(final DataOutputStream file) throws IOException {
    119        super.dump(file);
    120        file.writeShort(lineNumberTable.length);
    121        for (final LineNumber lineNumber : lineNumberTable) {
    122            lineNumber.dump(file);
    123        }
    124    }
    125
    126    /**
    127     * @return Array of (pc offset, line number) pairs.
    128     */
    129    public LineNumber[] getLineNumberTable() {
    130        return lineNumberTable;
    131    }
    132
    133    /**
    134     * Map byte code positions to source code lines.
    135     *
    136     * @param pos byte code offset.
    137     * @return corresponding line in source code.
    138     */
    139    public int getSourceLine(final int pos) {
    140        int l = 0;
    141        int r = lineNumberTable.length - 1;
    142        if (r < 0) {
    143            return -1;
    144        }
    145        int minIndex = -1;
    146        int min = -1;
    147        /*
    148         * Do a binary search since the array is ordered.
    149         */
    150        do {
    151            final int i = l + r >>> 1;
    152            final int j = lineNumberTable[i].getStartPC();
    153            if (j == pos) {
    154                return lineNumberTable[i].getLineNumber();
    155            }
    156            if (pos < j) {
    157                r = i - 1;
    158            } else {
    159                l = i + 1;
    160            }
    161            /*
    162             * If exact match can't be found (which is the most common case) return the line number that corresponds to the greatest
    163             * index less than pos.
    164             */
    165            if (j < pos && j > min) {
    166                min = j;
    167                minIndex = i;
    168            }
    169        } while (l <= r);
    170        /*
    171         * It's possible that we did not find any valid entry for the bytecode offset we were looking for.
    172         */
    173        if (minIndex < 0) {
    174            return -1;
    175        }
    176        return lineNumberTable[minIndex].getLineNumber();
    177    }
    178
    179    public int getTableLength() {
    180        return lineNumberTable.length;
    181    }
    182
    183    @Override
    184    public Iterator<LineNumber> iterator() {
    185        return Stream.of(lineNumberTable).iterator();
    186    }
    187
    188    /**
    189     * @param lineNumberTable the line number entries for this table.
    190     */
    191    public void setLineNumberTable(final LineNumber[] lineNumberTable) {
    192        this.lineNumberTable = lineNumberTable != null ? lineNumberTable : LineNumber.EMPTY_ARRAY;
    193    }
    194
    195    /**
    196     * @return String representation.
    197     */
    198    @Override
    199    public String toString() {
    200        final StringBuilder buf = new StringBuilder();
    201        final StringBuilder line = new StringBuilder();
    202        final String newLine = SystemProperties.getLineSeparator(() -> "\n");
    203        for (int i = 0; i < lineNumberTable.length; i++) {
    204            line.append(lineNumberTable[i].toString());
    205            if (i < lineNumberTable.length - 1) {
    206                line.append(", ");
    207            }
    208            if (line.length() > MAX_LINE_LENGTH && i < lineNumberTable.length - 1) {
    209                line.append(newLine);
    210                buf.append(line);
    211                line.setLength(0);
    212            }
    213        }
    214        buf.append(line);
    215        return buf.toString();
    216    }
    217}