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 * @version $Id: Unknown.java 1749603 2016-06-21 20:50:19Z ggregory $
038 * @see Attribute
039 * @see UnknownAttributeReader
040 */
041public final class Unknown extends Attribute {
042
043    private byte[] bytes;
044    private final String name;
045    private static final Map<String, Unknown> unknown_attributes = new HashMap<>();
046
047
048    /** @return array of unknown attributes, but just one for each kind.
049     */
050    static Unknown[] getUnknownAttributes() {
051        final Unknown[] unknowns = new Unknown[unknown_attributes.size()];
052        unknown_attributes.values().toArray(unknowns);
053        unknown_attributes.clear();
054        return unknowns;
055    }
056
057
058    /**
059     * Initialize from another object. Note that both objects use the same
060     * references (shallow copy). Use clone() for a physical copy.
061     */
062    public Unknown(final Unknown c) {
063        this(c.getNameIndex(), c.getLength(), c.getBytes(), c.getConstantPool());
064    }
065
066
067    /**
068     * Create a non-standard attribute.
069     *
070     * @param name_index Index in constant pool
071     * @param length Content length in bytes
072     * @param bytes Attribute contents
073     * @param constant_pool Array of constants
074     */
075    public Unknown(final int name_index, final int length, final byte[] bytes, final ConstantPool constant_pool) {
076        super(Const.ATTR_UNKNOWN, name_index, length, constant_pool);
077        this.bytes = bytes;
078        name = ((ConstantUtf8) constant_pool.getConstant(name_index, Const.CONSTANT_Utf8))
079                .getBytes();
080        unknown_attributes.put(name, this);
081    }
082
083
084    /**
085     * Construct object from input stream.
086     * 
087     * @param name_index Index in constant pool
088     * @param length Content length in bytes
089     * @param input Input stream
090     * @param constant_pool Array of constants
091     * @throws IOException
092     */
093    Unknown(final int name_index, final int length, final DataInput input, final ConstantPool constant_pool)
094            throws IOException {
095        this(name_index, length, (byte[]) null, constant_pool);
096        if (length > 0) {
097            bytes = new byte[length];
098            input.readFully(bytes);
099        }
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}