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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  package org.apache.bcel.classfile;
18  
19  import java.io.DataInput;
20  import java.io.DataOutputStream;
21  import java.io.IOException;
22  
23  import org.apache.bcel.Const;
24  import org.apache.bcel.Constants;
25  import org.apache.bcel.util.Args;
26  
27  /**
28   * This class represents an entry in the exception table of the <em>Code</em> attribute and is used only there. It
29   * contains a range in which a particular exception handler is active.
30   *
31   * <pre>
32   * Code_attribute {
33   *   u2 attribute_name_index;
34   *   u4 attribute_length;
35   *   u2 max_stack;
36   *   u2 max_locals;
37   *   u4 code_length;
38   *   u1 code[code_length];
39   *   u2 exception_table_length;
40   *   {
41   *     u2 start_pc;
42   *     u2 end_pc;
43   *     u2 handler_pc;
44   *     u2 catch_type;
45   *   } exception_table[exception_table_length];
46   *   u2 attributes_count;
47   *   attribute_info attributes[attributes_count];
48   * }
49   * </pre>
50   *
51   * @see Code
52   */
53  public final class CodeException implements Cloneable, Node, Constants {
54  
55      /**
56       * Empty array.
57       */
58      static final CodeException[] EMPTY_CODE_EXCEPTION_ARRAY = {};
59  
60      /** Range in the code the exception handler. */
61      private int startPc;
62  
63      /** Active. startPc is inclusive, endPc exclusive. */
64      private int endPc;
65  
66      /**
67       * Starting address of exception handler, i.e., an offset from start of code.
68       */
69      private int handlerPc;
70  
71      /*
72       * If this is zero the handler catches any exception, otherwise it points to the exception class which is to be caught.
73       */
74      private int catchType;
75  
76      /**
77       * Constructs a new instance from another instance.
78       *
79       * @param c Source for copying.
80       */
81      public CodeException(final CodeException c) {
82          this(c.getStartPC(), c.getEndPC(), c.getHandlerPC(), c.getCatchType());
83      }
84  
85      /**
86       * Constructs a new instance from a DataInput.
87       *
88       * @param file Input stream
89       * @throws IOException if an I/O error occurs.
90       */
91      CodeException(final DataInput file) throws IOException {
92          this(file.readUnsignedShort(), file.readUnsignedShort(), file.readUnsignedShort(), file.readUnsignedShort());
93      }
94  
95      /**
96       * Constructs a new instance.
97       *
98       * @param startPc Range in the code the exception handler is active, startPc is inclusive while
99       * @param endPc is exclusive
100      * @param handlerPc Starting address of exception handler, i.e., an offset from start of code.
101      * @param catchType If zero the handler catches any exception, otherwise it points to the exception class which is to be
102      *        caught.
103      */
104     public CodeException(final int startPc, final int endPc, final int handlerPc, final int catchType) {
105         this.startPc = Args.requireU2(startPc, "startPc");
106         this.endPc = Args.requireU2(endPc, "endPc");
107         this.handlerPc = Args.requireU2(handlerPc, "handlerPc");
108         this.catchType = Args.requireU2(catchType, "catchType");
109     }
110 
111     /**
112      * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
113      * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
114      *
115      * @param v Visitor object
116      */
117     @Override
118     public void accept(final Visitor v) {
119         v.visitCodeException(this);
120     }
121 
122     /**
123      * @return deep copy of this object
124      */
125     public CodeException copy() {
126         try {
127             return (CodeException) clone();
128         } catch (final CloneNotSupportedException e) {
129             // TODO should this throw?
130         }
131         return null;
132     }
133 
134     /**
135      * Dumps code exception to file stream in binary format.
136      *
137      * @param file Output file stream
138      * @throws IOException if an I/O error occurs.
139      */
140     public void dump(final DataOutputStream file) throws IOException {
141         file.writeShort(startPc);
142         file.writeShort(endPc);
143         file.writeShort(handlerPc);
144         file.writeShort(catchType);
145     }
146 
147     /**
148      * @return 0, if the handler catches any exception, otherwise it points to the exception class which is to be caught.
149      */
150     public int getCatchType() {
151         return catchType;
152     }
153 
154     /**
155      * @return Exclusive end index of the region where the handler is active.
156      */
157     public int getEndPC() {
158         return endPc;
159     }
160 
161     /**
162      * @return Starting address of exception handler, relative to the code.
163      */
164     public int getHandlerPC() {
165         return handlerPc;
166     }
167 
168     /**
169      * @return Inclusive start index of the region where the handler is active.
170      */
171     public int getStartPC() {
172         return startPc;
173     }
174 
175     /**
176      * @param catchType the type of exception that is caught
177      */
178     public void setCatchType(final int catchType) {
179         this.catchType = catchType;
180     }
181 
182     /**
183      * @param endPc end of handled block
184      */
185     public void setEndPC(final int endPc) {
186         this.endPc = endPc;
187     }
188 
189     /**
190      * @param handlerPc where the actual code is
191      */
192     public void setHandlerPC(final int handlerPc) { // TODO unused
193         this.handlerPc = handlerPc;
194     }
195 
196     /**
197      * @param startPc start of handled block
198      */
199     public void setStartPC(final int startPc) { // TODO unused
200         this.startPc = startPc;
201     }
202 
203     /**
204      * @return String representation.
205      */
206     @Override
207     public String toString() {
208         return "CodeException(startPc = " + startPc + ", endPc = " + endPc + ", handlerPc = " + handlerPc + ", catchType = " + catchType + ")";
209     }
210 
211     public String toString(final ConstantPool cp) {
212         return toString(cp, true);
213     }
214 
215     /**
216      * @param cp constant pool source.
217      * @param verbose Output more if true.
218      * @return String representation.
219      */
220     public String toString(final ConstantPool cp, final boolean verbose) {
221         String str;
222         if (catchType == 0) {
223             str = "<Any exception>(0)";
224         } else {
225             str = Utility.compactClassName(cp.getConstantString(catchType, Const.CONSTANT_Class), false) + (verbose ? "(" + catchType + ")" : "");
226         }
227         return startPc + "\t" + endPc + "\t" + handlerPc + "\t" + str;
228     }
229 }