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;
023
024import org.apache.bcel.Const;
025
026/**
027 * This class is derived from <em>Attribute</em> and declares this class as `synthetic', i.e., it needs special
028 * handling. The JVM specification states "A class member that does not appear in the source code must be marked using a
029 * Synthetic attribute." It may appear in the ClassFile attribute table, a field_info table or a method_info table. This
030 * class is intended to be instantiated from the <em>Attribute.readAttribute()</em> method.
031 *
032 * @see Attribute
033 */
034public final class Synthetic extends Attribute {
035
036    private byte[] bytes;
037
038    /**
039     * @param name_index Index in constant pool to CONSTANT_Utf8, which should represent the string "Synthetic".
040     * @param length Content length in bytes - should be zero.
041     * @param bytes Attribute contents
042     * @param constant_pool The constant pool this attribute is associated with.
043     */
044    public Synthetic(final int name_index, final int length, final byte[] bytes, final ConstantPool constant_pool) {
045        super(Const.ATTR_SYNTHETIC, name_index, length, constant_pool);
046        this.bytes = bytes;
047    }
048
049    /**
050     * Construct object from input stream.
051     *
052     * @param name_index Index in constant pool to CONSTANT_Utf8
053     * @param length Content length in bytes
054     * @param input Input stream
055     * @param constant_pool Array of constants
056     * @throws IOException if an I/O error occurs.
057     */
058    Synthetic(final int name_index, final int length, final DataInput input, final ConstantPool constant_pool) throws IOException {
059        this(name_index, length, (byte[]) null, constant_pool);
060        if (length > 0) {
061            bytes = new byte[length];
062            input.readFully(bytes);
063            println("Synthetic attribute with length > 0");
064        }
065    }
066
067    /**
068     * Initialize from another object. Note that both objects use the same references (shallow copy). Use copy() for a
069     * physical copy.
070     */
071    public Synthetic(final Synthetic c) {
072        this(c.getNameIndex(), c.getLength(), c.getBytes(), c.getConstantPool());
073    }
074
075    /**
076     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
077     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
078     *
079     * @param v Visitor object
080     */
081    @Override
082    public void accept(final Visitor v) {
083        v.visitSynthetic(this);
084    }
085
086    /**
087     * @return deep copy of this attribute
088     */
089    @Override
090    public Attribute copy(final ConstantPool constantPool) {
091        final Synthetic c = (Synthetic) clone();
092        if (bytes != null) {
093            c.bytes = new byte[bytes.length];
094            System.arraycopy(bytes, 0, c.bytes, 0, bytes.length);
095        }
096        c.setConstantPool(constantPool);
097        return c;
098    }
099
100    /**
101     * Dump source file attribute to file stream in binary format.
102     *
103     * @param file Output file stream
104     * @throws IOException if an I/O error occurs.
105     */
106    @Override
107    public void dump(final DataOutputStream file) throws IOException {
108        super.dump(file);
109        if (super.getLength() > 0) {
110            file.write(bytes, 0, super.getLength());
111        }
112    }
113
114    /**
115     * @return data bytes.
116     */
117    public byte[] getBytes() {
118        return bytes;
119    }
120
121    /**
122     * @param bytes
123     */
124    public void setBytes(final byte[] bytes) {
125        this.bytes = bytes;
126    }
127
128    /**
129     * @return String representation.
130     */
131    @Override
132    public String toString() {
133        final StringBuilder buf = new StringBuilder("Synthetic");
134        if (super.getLength() > 0) {
135            buf.append(" ").append(Utility.toHexString(bytes));
136        }
137        return buf.toString();
138    }
139}