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