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., application-specific) attribute of a class. It is instantiated
030 * from the {@link Attribute#readAttribute(java.io.DataInput, ConstantPool)} method. Applications that need to read in
031 * application-specific attributes should create an {@link UnknownAttributeReader} implementation and attach it via
032 * {@link Attribute#addAttributeReader(String, UnknownAttributeReader)}.
033 *
034 *
035 * @see Attribute
036 * @see UnknownAttributeReader
037 */
038public final class Unknown extends Attribute {
039
040    private static final Unknown[] EMPTY_ARRAY = {};
041
042    private static final Map<String, Unknown> UNKNOWN_ATTRIBUTES = new HashMap<>();
043
044    /**
045     * @return array of unknown attributes, but just one for each kind.
046     */
047    static Unknown[] getUnknownAttributes() {
048        try {
049            return UNKNOWN_ATTRIBUTES.values().toArray(EMPTY_ARRAY);
050        } finally {
051            // TODO Does this really make sense?
052            UNKNOWN_ATTRIBUTES.clear();
053        }
054    }
055
056    private byte[] bytes;
057
058    private final String name;
059
060    /**
061     * Create a non-standard attribute.
062     *
063     * @param name_index Index in constant pool
064     * @param length Content length in bytes
065     * @param bytes Attribute contents
066     * @param constant_pool Array of constants
067     */
068    public Unknown(final int name_index, final int length, final byte[] bytes, final ConstantPool constant_pool) {
069        super(Const.ATTR_UNKNOWN, name_index, length, constant_pool);
070        this.bytes = bytes;
071        name = constant_pool.getConstantUtf8(name_index).getBytes();
072        UNKNOWN_ATTRIBUTES.put(name, this);
073    }
074
075    /**
076     * Construct object from input stream.
077     *
078     * @param name_index Index in constant pool
079     * @param length Content length in bytes
080     * @param input Input stream
081     * @param constant_pool Array of constants
082     * @throws IOException if an I/O error occurs.
083     */
084    Unknown(final int name_index, final int length, final DataInput input, final ConstantPool constant_pool) throws IOException {
085        this(name_index, length, (byte[]) null, constant_pool);
086        if (length > 0) {
087            bytes = new byte[length];
088            input.readFully(bytes);
089        }
090    }
091
092    /**
093     * Initialize from another object. Note that both objects use the same references (shallow copy). Use clone() for a
094     * physical copy.
095     */
096    public Unknown(final Unknown c) {
097        this(c.getNameIndex(), c.getLength(), c.getBytes(), c.getConstantPool());
098    }
099
100    /**
101     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
102     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
103     *
104     * @param v Visitor object
105     */
106    @Override
107    public void accept(final Visitor v) {
108        v.visitUnknown(this);
109    }
110
111    /**
112     * @return deep copy of this attribute
113     */
114    @Override
115    public Attribute copy(final ConstantPool constantPool) {
116        final Unknown c = (Unknown) clone();
117        if (bytes != null) {
118            c.bytes = new byte[bytes.length];
119            System.arraycopy(bytes, 0, c.bytes, 0, bytes.length);
120        }
121        c.setConstantPool(constantPool);
122        return c;
123    }
124
125    /**
126     * Dump unknown bytes to file stream.
127     *
128     * @param file Output file stream
129     * @throws IOException if an I/O error occurs.
130     */
131    @Override
132    public void dump(final DataOutputStream file) throws IOException {
133        super.dump(file);
134        if (super.getLength() > 0) {
135            file.write(bytes, 0, super.getLength());
136        }
137    }
138
139    /**
140     * @return data bytes.
141     */
142    public byte[] getBytes() {
143        return bytes;
144    }
145
146    /**
147     * @return name of attribute.
148     */
149    @Override
150    public String getName() {
151        return name;
152    }
153
154    /**
155     * @param bytes the bytes to set
156     */
157    public void setBytes(final byte[] bytes) {
158        this.bytes = bytes;
159    }
160
161    /**
162     * @return String representation.
163     */
164    @Override
165    public String toString() {
166        if (super.getLength() == 0 || bytes == null) {
167            return "(Unknown attribute " + name + ")";
168        }
169        String hex;
170        if (super.getLength() > 10) {
171            final byte[] tmp = new byte[10];
172            System.arraycopy(bytes, 0, tmp, 0, 10);
173            hex = Utility.toHexString(tmp) + "... (truncated)";
174        } else {
175            hex = Utility.toHexString(bytes);
176        }
177        return "(Unknown attribute " + name + ": " + hex + ")";
178    }
179}