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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  import java.util.HashMap;
24  import java.util.Map;
25  
26  import org.apache.bcel.Const;
27  
28  /**
29   * This class represents a reference to an unknown (i.e.,
30   * application-specific) attribute of a class.  It is instantiated from the
31   * {@link Attribute#readAttribute(java.io.DataInput, ConstantPool)} method.
32   * Applications that need to read in application-specific attributes should create an
33   * {@link UnknownAttributeReader} implementation and attach it via
34   * {@link Attribute#addAttributeReader(String, UnknownAttributeReader)}.
35  
36   *
37   * @version $Id: Unknown.html 1018313 2017-09-18 09:03:04Z britter $
38   * @see Attribute
39   * @see UnknownAttributeReader
40   */
41  public final class Unknown extends Attribute {
42  
43      private byte[] bytes;
44      private final String name;
45      private static final Map<String, Unknown> unknown_attributes = new HashMap<>();
46  
47  
48      /** @return array of unknown attributes, but just one for each kind.
49       */
50      static Unknown[] getUnknownAttributes() {
51          final Unknown[] unknowns = new Unknown[unknown_attributes.size()];
52          unknown_attributes.values().toArray(unknowns);
53          unknown_attributes.clear();
54          return unknowns;
55      }
56  
57  
58      /**
59       * Initialize from another object. Note that both objects use the same
60       * references (shallow copy). Use clone() for a physical copy.
61       */
62      public Unknown(final Unknown c) {
63          this(c.getNameIndex(), c.getLength(), c.getBytes(), c.getConstantPool());
64      }
65  
66  
67      /**
68       * Create a non-standard attribute.
69       *
70       * @param name_index Index in constant pool
71       * @param length Content length in bytes
72       * @param bytes Attribute contents
73       * @param constant_pool Array of constants
74       */
75      public Unknown(final int name_index, final int length, final byte[] bytes, final ConstantPool constant_pool) {
76          super(Const.ATTR_UNKNOWN, name_index, length, constant_pool);
77          this.bytes = bytes;
78          name = ((ConstantUtf8) constant_pool.getConstant(name_index, Const.CONSTANT_Utf8))
79                  .getBytes();
80          unknown_attributes.put(name, this);
81      }
82  
83  
84      /**
85       * Construct object from input stream.
86       *
87       * @param name_index Index in constant pool
88       * @param length Content length in bytes
89       * @param input Input stream
90       * @param constant_pool Array of constants
91       * @throws IOException
92       */
93      Unknown(final int name_index, final int length, final DataInput input, final ConstantPool constant_pool)
94              throws IOException {
95          this(name_index, length, (byte[]) null, constant_pool);
96          if (length > 0) {
97              bytes = new byte[length];
98              input.readFully(bytes);
99          }
100     }
101 
102 
103     /**
104      * Called by objects that are traversing the nodes of the tree implicitely
105      * defined by the contents of a Java class. I.e., the hierarchy of methods,
106      * fields, attributes, etc. spawns a tree of objects.
107      *
108      * @param v Visitor object
109      */
110     @Override
111     public void accept( final Visitor v ) {
112         v.visitUnknown(this);
113     }
114 
115 
116     /**
117      * Dump unknown bytes to file stream.
118      *
119      * @param file Output file stream
120      * @throws IOException
121      */
122     @Override
123     public final void dump( final DataOutputStream file ) throws IOException {
124         super.dump(file);
125         if (super.getLength() > 0) {
126             file.write(bytes, 0, super.getLength());
127         }
128     }
129 
130 
131     /**
132      * @return data bytes.
133      */
134     public final byte[] getBytes() {
135         return bytes;
136     }
137 
138 
139     /**
140      * @return name of attribute.
141      */
142     @Override
143     public final String getName() {
144         return name;
145     }
146 
147 
148     /**
149      * @param bytes the bytes to set
150      */
151     public final void setBytes( final byte[] bytes ) {
152         this.bytes = bytes;
153     }
154 
155 
156     /**
157      * @return String representation.
158      */
159     @Override
160     public final String toString() {
161         if (super.getLength() == 0 || bytes == null) {
162             return "(Unknown attribute " + name + ")";
163         }
164         String hex;
165         if (super.getLength() > 10) {
166             final byte[] tmp = new byte[10];
167             System.arraycopy(bytes, 0, tmp, 0, 10);
168             hex = Utility.toHexString(tmp) + "... (truncated)";
169         } else {
170             hex = Utility.toHexString(bytes);
171         }
172         return "(Unknown attribute " + name + ": " + hex + ")";
173     }
174 
175 
176     /**
177      * @return deep copy of this attribute
178      */
179     @Override
180     public Attribute copy( final ConstantPool _constant_pool ) {
181         final Unknown c = (Unknown) clone();
182         if (bytes != null) {
183             c.bytes = new byte[bytes.length];
184             System.arraycopy(bytes, 0, c.bytes, 0, bytes.length);
185         }
186         c.setConstantPool(_constant_pool);
187         return c;
188     }
189 }