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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 the table of exceptions that are thrown by a
28   * method. This attribute may be used once per method.  The name of
29   * this class is <em>ExceptionTable</em> for historical reasons; The
30   * Java Virtual Machine Specification, Second Edition defines this
31   * attribute using the name <em>Exceptions</em> (which is inconsistent
32   * with the other classes).
33   *
34   * @version $Id: ExceptionTable.html 1018313 2017-09-18 09:03:04Z britter $
35   * @see     Code
36   */
37  public final class ExceptionTable extends Attribute {
38  
39      private int[] exception_index_table; // constant pool
40  
41  
42      /**
43       * Initialize from another object. Note that both objects use the same
44       * references (shallow copy). Use copy() for a physical copy.
45       */
46      public ExceptionTable(final ExceptionTable c) {
47          this(c.getNameIndex(), c.getLength(), c.getExceptionIndexTable(), c.getConstantPool());
48      }
49  
50  
51      /**
52       * @param name_index Index in constant pool
53       * @param length Content length in bytes
54       * @param exception_index_table Table of indices in constant pool
55       * @param constant_pool Array of constants
56       */
57      public ExceptionTable(final int name_index, final int length, final int[] exception_index_table,
58              final ConstantPool constant_pool) {
59          super(Const.ATTR_EXCEPTIONS, name_index, length, constant_pool);
60          this.exception_index_table = exception_index_table != null ? exception_index_table : new int[0];
61      }
62  
63  
64      /**
65       * Construct object from input stream.
66       * @param name_index Index in constant pool
67       * @param length Content length in bytes
68       * @param input Input stream
69       * @param constant_pool Array of constants
70       * @throws IOException
71       */
72      ExceptionTable(final int name_index, final int length, final DataInput input, final ConstantPool constant_pool) throws IOException {
73          this(name_index, length, (int[]) null, constant_pool);
74          final int number_of_exceptions = input.readUnsignedShort();
75          exception_index_table = new int[number_of_exceptions];
76          for (int i = 0; i < number_of_exceptions; i++) {
77              exception_index_table[i] = input.readUnsignedShort();
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.visitExceptionTable(this);
92      }
93  
94  
95      /**
96       * Dump exceptions attribute to file stream in binary format.
97       *
98       * @param file Output file stream
99       * @throws IOException
100      */
101     @Override
102     public final void dump( final DataOutputStream file ) throws IOException {
103         super.dump(file);
104         file.writeShort(exception_index_table.length);
105         for (final int index : exception_index_table) {
106             file.writeShort(index);
107         }
108     }
109 
110 
111     /**
112      * @return Array of indices into constant pool of thrown exceptions.
113      */
114     public final int[] getExceptionIndexTable() {
115         return exception_index_table;
116     }
117 
118 
119     /**
120      * @return Length of exception table.
121      */
122     public final int getNumberOfExceptions() {
123         return exception_index_table == null ? 0 : exception_index_table.length;
124     }
125 
126 
127     /**
128      * @return class names of thrown exceptions
129      */
130     public final String[] getExceptionNames() {
131         final String[] names = new String[exception_index_table.length];
132         for (int i = 0; i < exception_index_table.length; i++) {
133             names[i] = super.getConstantPool().getConstantString(exception_index_table[i],
134                     Const.CONSTANT_Class).replace('/', '.');
135         }
136         return names;
137     }
138 
139 
140     /**
141      * @param exception_index_table the list of exception indexes
142      * Also redefines number_of_exceptions according to table length.
143      */
144     public final void setExceptionIndexTable( final int[] exception_index_table ) {
145         this.exception_index_table = exception_index_table != null ? exception_index_table : new int[0];
146     }
147 
148 
149     /**
150      * @return String representation, i.e., a list of thrown exceptions.
151      */
152     @Override
153     public final String toString() {
154         final StringBuilder buf = new StringBuilder();
155         String str;
156         buf.append("Exceptions: ");
157         for (int i = 0; i < exception_index_table.length; i++) {
158             str = super.getConstantPool().getConstantString(exception_index_table[i], Const.CONSTANT_Class);
159             buf.append(Utility.compactClassName(str, false));
160             if (i < exception_index_table.length - 1) {
161                 buf.append(", ");
162             }
163         }
164         return buf.toString();
165     }
166 
167 
168     /**
169      * @return deep copy of this attribute
170      */
171     @Override
172     public Attribute copy( final ConstantPool _constant_pool ) {
173         final ExceptionTable c = (ExceptionTable) clone();
174         if (exception_index_table != null) {
175             c.exception_index_table = new int[exception_index_table.length];
176             System.arraycopy(exception_index_table, 0, c.exception_index_table, 0,
177                     exception_index_table.length);
178         }
179         c.setConstantPool(_constant_pool);
180         return c;
181     }
182 }