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 */
017package org.apache.bcel.classfile;
018
019import java.io.DataInput;
020import java.io.DataOutputStream;
021import java.io.IOException;
022import java.util.Arrays;
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 nameIndex Index in constant pool
064     * @param length Content length in bytes
065     * @param bytes Attribute contents
066     * @param constantPool Array of constants
067     */
068    public Unknown(final int nameIndex, final int length, final byte[] bytes, final ConstantPool constantPool) {
069        super(Const.ATTR_UNKNOWN, nameIndex, length, constantPool);
070        this.bytes = bytes;
071        name = constantPool.getConstantUtf8(nameIndex).getBytes();
072        UNKNOWN_ATTRIBUTES.put(name, this);
073    }
074
075    /**
076     * Construct object from input stream.
077     *
078     * @param nameIndex Index in constant pool
079     * @param length Content length in bytes
080     * @param input Input stream
081     * @param constantPool Array of constants
082     * @throws IOException if an I/O error occurs.
083     */
084    Unknown(final int nameIndex, final int length, final DataInput input, final ConstantPool constantPool) throws IOException {
085        this(nameIndex, length, (byte[]) null, constantPool);
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 = bytes.clone();
119        }
120        c.setConstantPool(constantPool);
121        return c;
122    }
123
124    /**
125     * Dump unknown bytes to file stream.
126     *
127     * @param file Output file stream
128     * @throws IOException if an I/O error occurs.
129     */
130    @Override
131    public void dump(final DataOutputStream file) throws IOException {
132        super.dump(file);
133        if (super.getLength() > 0) {
134            file.write(bytes, 0, super.getLength());
135        }
136    }
137
138    /**
139     * @return data bytes.
140     */
141    public byte[] getBytes() {
142        return bytes;
143    }
144
145    /**
146     * @return name of attribute.
147     */
148    @Override
149    public String getName() {
150        return name;
151    }
152
153    /**
154     * @param bytes the bytes to set
155     */
156    public void setBytes(final byte[] bytes) {
157        this.bytes = bytes;
158    }
159
160    /**
161     * @return String representation.
162     */
163    @Override
164    public String toString() {
165        if (super.getLength() == 0 || bytes == null) {
166            return "(Unknown attribute " + name + ")";
167        }
168        String hex;
169        final int limit = 10;
170        if (super.getLength() > limit) {
171            final byte[] tmp = Arrays.copyOf(bytes, limit);
172            hex = Utility.toHexString(tmp) + "... (truncated)";
173        } else {
174            hex = Utility.toHexString(bytes);
175        }
176        return "(Unknown attribute " + name + ": " + hex + ")";
177    }
178}