View Javadoc
1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   *  Unless required by applicable law or agreed to in writing, software
12   *  distributed under the License is distributed on an "AS IS" BASIS,
13   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   *  See the License for the specific language governing permissions and
15   *  limitations under the License.
16   *
17   */
18  package org.apache.bcel.classfile;
19  
20  import java.io.DataInput;
21  import java.io.DataOutputStream;
22  import java.io.IOException;
23  
24  import org.apache.bcel.Const;
25  
26  /**
27   * This class represents a table of line numbers for debugging
28   * purposes. This attribute is used by the <em>Code</em> attribute. It
29   * contains pairs of PCs and line numbers.
30   *
31   * @version $Id: LineNumberTable.html 1018313 2017-09-18 09:03:04Z britter $
32   * @see     Code
33   * @see LineNumber
34   */
35  public final class LineNumberTable extends Attribute {
36  
37      private static final int MAX_LINE_LENGTH = 72;
38      private LineNumber[] line_number_table; // Table of line/numbers pairs
39  
40  
41      /*
42       * Initialize from another object. Note that both objects use the same
43       * references (shallow copy). Use copy() for a physical copy.
44       */
45      public LineNumberTable(final LineNumberTable c) {
46          this(c.getNameIndex(), c.getLength(), c.getLineNumberTable(), c.getConstantPool());
47      }
48  
49  
50      /*
51       * @param name_index Index of name
52       * @param length Content length in bytes
53       * @param line_number_table Table of line/numbers pairs
54       * @param constant_pool Array of constants
55       */
56      public LineNumberTable(final int name_index, final int length, final LineNumber[] line_number_table,
57              final ConstantPool constant_pool) {
58          super(Const.ATTR_LINE_NUMBER_TABLE, name_index, length, constant_pool);
59          this.line_number_table = line_number_table;
60      }
61  
62  
63      /**
64       * Construct object from input stream.
65       * @param name_index Index of name
66       * @param length Content length in bytes
67       * @param input Input stream
68       * @param constant_pool Array of constants
69       * @throws IOEXception if an I/O Exception occurs in readUnsignedShort
70       */
71      LineNumberTable(final int name_index, final int length, final DataInput input, final ConstantPool constant_pool)
72              throws IOException {
73          this(name_index, length, (LineNumber[]) null, constant_pool);
74          final int line_number_table_length = input.readUnsignedShort();
75          line_number_table = new LineNumber[line_number_table_length];
76          for (int i = 0; i < line_number_table_length; i++) {
77              line_number_table[i] = new LineNumber(input);
78          }
79      }
80  
81  
82      /**
83       * Called by objects that are traversing the nodes of the tree implicitely
84       * defined by the contents of a Java class. I.e., the hierarchy of methods,
85       * fields, attributes, etc. spawns a tree of objects.
86       *
87       * @param v Visitor object
88       */
89      @Override
90      public void accept( final Visitor v ) {
91          v.visitLineNumberTable(this);
92      }
93  
94  
95      /**
96       * Dump line number table attribute to file stream in binary format.
97       *
98       * @param file Output file stream
99       * @throws IOEXception if an I/O Exception occurs in writeShort
100      */
101     @Override
102     public final void dump( final DataOutputStream file ) throws IOException {
103         super.dump(file);
104         file.writeShort(line_number_table.length);
105         for (final LineNumber lineNumber : line_number_table) {
106             lineNumber.dump(file);
107         }
108     }
109 
110 
111     /**
112      * @return Array of (pc offset, line number) pairs.
113      */
114     public final LineNumber[] getLineNumberTable() {
115         return line_number_table;
116     }
117 
118 
119     /**
120      * @param line_number_table the line number entries for this table
121      */
122     public final void setLineNumberTable( final LineNumber[] line_number_table ) {
123         this.line_number_table = line_number_table;
124     }
125 
126 
127     /**
128      * @return String representation.
129      */
130     @Override
131     public final String toString() {
132         final StringBuilder buf = new StringBuilder();
133         final StringBuilder line = new StringBuilder();
134         final String newLine = System.getProperty("line.separator", "\n");
135         for (int i = 0; i < line_number_table.length; i++) {
136             line.append(line_number_table[i].toString());
137             if (i < line_number_table.length - 1) {
138                 line.append(", ");
139             }
140             if ((line.length() > MAX_LINE_LENGTH) && (i < line_number_table.length - 1)) {
141                 line.append(newLine);
142                 buf.append(line);
143                 line.setLength(0);
144             }
145         }
146         buf.append(line);
147         return buf.toString();
148     }
149 
150 
151     /**
152      * Map byte code positions to source code lines.
153      *
154      * @param pos byte code offset
155      * @return corresponding line in source code
156      */
157     public int getSourceLine( final int pos ) {
158         int l = 0;
159         int r = line_number_table.length - 1;
160         if (r < 0) {
161             return -1;
162         }
163         int min_index = -1;
164         int min = -1;
165         /* Do a binary search since the array is ordered.
166          */
167         do {
168             final int i = (l + r) / 2;
169             final int j = line_number_table[i].getStartPC();
170             if (j == pos) {
171                 return line_number_table[i].getLineNumber();
172             } else if (pos < j) {
173                 r = i - 1;
174             } else {
175                 l = i + 1;
176             }
177             /* If exact match can't be found (which is the most common case)
178              * return the line number that corresponds to the greatest index less
179              * than pos.
180              */
181             if (j < pos && j > min) {
182                 min = j;
183                 min_index = i;
184             }
185         } while (l <= r);
186         /* It's possible that we did not find any valid entry for the bytecode
187          * offset we were looking for.
188          */
189         if (min_index < 0) {
190             return -1;
191         }
192         return line_number_table[min_index].getLineNumber();
193     }
194 
195 
196     /**
197      * @return deep copy of this attribute
198      */
199     @Override
200     public Attribute copy( final ConstantPool _constant_pool ) {
201         // TODO could use the lower level constructor and thereby allow
202         // line_number_table to be made final
203         final LineNumberTable c = (LineNumberTable) clone();
204         c.line_number_table = new LineNumber[line_number_table.length];
205         for (int i = 0; i < line_number_table.length; i++) {
206             c.line_number_table[i] = line_number_table[i].copy();
207         }
208         c.setConstantPool(_constant_pool);
209         return c;
210     }
211 
212 
213     public final int getTableLength() {
214         return line_number_table == null ? 0 : line_number_table.length;
215     }
216 }