001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 *  Unless required by applicable law or agreed to in writing, software
012 *  distributed under the License is distributed on an "AS IS" BASIS,
013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 *  See the License for the specific language governing permissions and
015 *  limitations under the License.
016 *
017 */
018package org.apache.bcel.classfile;
019
020import java.io.DataInput;
021import java.io.DataOutputStream;
022import java.io.IOException;
023import java.util.HashMap;
024import java.util.Map;
025
026import org.apache.bcel.Const;
027
028/**
029 * This class represents a reference to an unknown (i.e.,
030 * application-specific) attribute of a class.  It is instantiated from the
031 * {@link Attribute#readAttribute(java.io.DataInput, ConstantPool)} method.
032 * Applications that need to read in application-specific attributes should create an
033 * {@link UnknownAttributeReader} implementation and attach it via
034 * {@link Attribute#addAttributeReader(String, UnknownAttributeReader)}.
035
036 *
037 * @see Attribute
038 * @see UnknownAttributeReader
039 */
040public final class Unknown extends Attribute {
041
042    private byte[] bytes;
043    private final String name;
044    private static final Map<String, Unknown> unknownAttributes = new HashMap<>();
045
046
047    /** @return array of unknown attributes, but just one for each kind.
048     */
049    static Unknown[] getUnknownAttributes() {
050        final Unknown[] unknowns = new Unknown[unknownAttributes.size()];
051        unknownAttributes.values().toArray(unknowns);
052        unknownAttributes.clear();
053        return unknowns;
054    }
055
056
057    /**
058     * Initialize from another object. Note that both objects use the same
059     * references (shallow copy). Use clone() for a physical copy.
060     */
061    public Unknown(final Unknown c) {
062        this(c.getNameIndex(), c.getLength(), c.getBytes(), c.getConstantPool());
063    }
064
065
066    /**
067     * Create a non-standard attribute.
068     *
069     * @param name_index Index in constant pool
070     * @param length Content length in bytes
071     * @param bytes Attribute contents
072     * @param constant_pool Array of constants
073     */
074    public Unknown(final int name_index, final int length, final byte[] bytes, final ConstantPool constant_pool) {
075        super(Const.ATTR_UNKNOWN, name_index, length, constant_pool);
076        this.bytes = bytes;
077        name = ((ConstantUtf8) constant_pool.getConstant(name_index, Const.CONSTANT_Utf8))
078                .getBytes();
079        unknownAttributes.put(name, this);
080    }
081
082
083    /**
084     * Construct object from input stream.
085     *
086     * @param name_index Index in constant pool
087     * @param length Content length in bytes
088     * @param input Input stream
089     * @param constant_pool Array of constants
090     * @throws IOException
091     */
092    Unknown(final int name_index, final int length, final DataInput input, final ConstantPool constant_pool)
093            throws IOException {
094        this(name_index, length, (byte[]) null, constant_pool);
095        if (length > 0) {
096            bytes = new byte[length];
097            input.readFully(bytes);
098        }
099    }
100
101
102    /**
103     * Called by objects that are traversing the nodes of the tree implicitely
104     * defined by the contents of a Java class. I.e., the hierarchy of methods,
105     * fields, attributes, etc. spawns a tree of objects.
106     *
107     * @param v Visitor object
108     */
109    @Override
110    public void accept( final Visitor v ) {
111        v.visitUnknown(this);
112    }
113
114
115    /**
116     * Dump unknown bytes to file stream.
117     *
118     * @param file Output file stream
119     * @throws IOException
120     */
121    @Override
122    public void dump( final DataOutputStream file ) throws IOException {
123        super.dump(file);
124        if (super.getLength() > 0) {
125            file.write(bytes, 0, super.getLength());
126        }
127    }
128
129
130    /**
131     * @return data bytes.
132     */
133    public byte[] getBytes() {
134        return bytes;
135    }
136
137
138    /**
139     * @return name of attribute.
140     */
141    @Override
142    public String getName() {
143        return name;
144    }
145
146
147    /**
148     * @param bytes the bytes to set
149     */
150    public void setBytes( final byte[] bytes ) {
151        this.bytes = bytes;
152    }
153
154
155    /**
156     * @return String representation.
157     */
158    @Override
159    public String toString() {
160        if (super.getLength() == 0 || bytes == null) {
161            return "(Unknown attribute " + name + ")";
162        }
163        String hex;
164        if (super.getLength() > 10) {
165            final byte[] tmp = new byte[10];
166            System.arraycopy(bytes, 0, tmp, 0, 10);
167            hex = Utility.toHexString(tmp) + "... (truncated)";
168        } else {
169            hex = Utility.toHexString(bytes);
170        }
171        return "(Unknown attribute " + name + ": " + hex + ")";
172    }
173
174
175    /**
176     * @return deep copy of this attribute
177     */
178    @Override
179    public Attribute copy( final ConstantPool _constant_pool ) {
180        final Unknown c = (Unknown) clone();
181        if (bytes != null) {
182            c.bytes = new byte[bytes.length];
183            System.arraycopy(bytes, 0, c.bytes, 0, bytes.length);
184        }
185        c.setConstantPool(_constant_pool);
186        return c;
187    }
188}