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 import java.util.Arrays;
23
24 import org.apache.bcel.Const;
25
26 /**
27 * This class represents a reference to an unknown (i.e., application-specific) attribute of a class. It is instantiated
28 * from the {@link Attribute#readAttribute(java.io.DataInput, ConstantPool)} method. Applications that need to read in
29 * application-specific attributes should create an {@link UnknownAttributeReader} implementation and attach it via
30 * {@link Attribute#addAttributeReader(String, UnknownAttributeReader)}.
31 *
32 * @see Attribute
33 * @see UnknownAttributeReader
34 */
35 public final class Unknown extends Attribute {
36
37 private byte[] bytes;
38
39 private final String name;
40
41 /**
42 * Constructs a new instance for a non-standard attribute.
43 *
44 * @param nameIndex Index in constant pool
45 * @param length Content length in bytes
46 * @param bytes Attribute contents
47 * @param constantPool Array of constants
48 */
49 public Unknown(final int nameIndex, final int length, final byte[] bytes, final ConstantPool constantPool) {
50 super(Const.ATTR_UNKNOWN, nameIndex, length, constantPool);
51 this.bytes = bytes;
52 this.name = constantPool.getConstantUtf8(nameIndex).getBytes();
53 }
54
55 /**
56 * Constructs a new instance from an input stream.
57 *
58 * @param nameIndex Index in constant pool
59 * @param length Content length in bytes
60 * @param input Input stream
61 * @param constantPool Array of constants
62 * @throws IOException if an I/O error occurs.
63 */
64 Unknown(final int nameIndex, final int length, final DataInput input, final ConstantPool constantPool) throws IOException {
65 this(nameIndex, length, (byte[]) null, constantPool);
66 if (length > 0) {
67 bytes = new byte[length];
68 input.readFully(bytes);
69 }
70 }
71
72 /**
73 * Constructs a new instance from another instance. Note that both objects use the same references (shallow copy). Use clone() for a physical copy.
74 *
75 * @param unknown Source.
76 */
77 public Unknown(final Unknown unknown) {
78 this(unknown.getNameIndex(), unknown.getLength(), unknown.getBytes(), unknown.getConstantPool());
79 }
80
81 /**
82 * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
83 * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
84 *
85 * @param v Visitor object
86 */
87 @Override
88 public void accept(final Visitor v) {
89 v.visitUnknown(this);
90 }
91
92 /**
93 * @return deep copy of this attribute
94 */
95 @Override
96 public Attribute copy(final ConstantPool constantPool) {
97 final Unknown c = (Unknown) clone();
98 if (bytes != null) {
99 c.bytes = bytes.clone();
100 }
101 c.setConstantPool(constantPool);
102 return c;
103 }
104
105 /**
106 * Dumps unknown bytes to file stream.
107 *
108 * @param file Output file stream
109 * @throws IOException if an I/O error occurs.
110 */
111 @Override
112 public void dump(final DataOutputStream file) throws IOException {
113 super.dump(file);
114 if (super.getLength() > 0) {
115 file.write(bytes, 0, super.getLength());
116 }
117 }
118
119 /**
120 * @return data bytes.
121 */
122 public byte[] getBytes() {
123 return bytes;
124 }
125
126 /**
127 * @return name of attribute.
128 */
129 @Override
130 public String getName() {
131 return name;
132 }
133
134 /**
135 * @param bytes the bytes to set
136 */
137 public void setBytes(final byte[] bytes) {
138 this.bytes = bytes;
139 }
140
141 /**
142 * @return String representation.
143 */
144 @Override
145 public String toString() {
146 if (super.getLength() == 0 || bytes == null) {
147 return "(Unknown attribute " + name + ")";
148 }
149 String hex;
150 final int limit = 10;
151 if (super.getLength() > limit) {
152 final byte[] tmp = Arrays.copyOf(bytes, limit);
153 hex = Utility.toHexString(tmp) + "... (truncated)";
154 } else {
155 hex = Utility.toHexString(bytes);
156 }
157 return "(Unknown attribute " + name + ": " + hex + ")";
158 }
159 }