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;
022
023import org.apache.bcel.Const;
024
025/**
026 * This class is derived from <em>Attribute</em> and declares this class as `synthetic', i.e., it needs special
027 * handling. The JVM specification states "A class member that does not appear in the source code must be marked using a
028 * Synthetic attribute." It may appear in the ClassFile attribute table, a field_info table or a method_info table. This
029 * class is intended to be instantiated from the <em>Attribute.readAttribute()</em> method.
030 *
031 * @see Attribute
032 */
033public final class Synthetic extends Attribute {
034
035    private byte[] bytes;
036
037    /**
038     * @param nameIndex Index in constant pool to CONSTANT_Utf8, which should represent the string "Synthetic".
039     * @param length Content length in bytes - should be zero.
040     * @param bytes Attribute contents
041     * @param constantPool The constant pool this attribute is associated with.
042     */
043    public Synthetic(final int nameIndex, final int length, final byte[] bytes, final ConstantPool constantPool) {
044        super(Const.ATTR_SYNTHETIC, nameIndex, length, constantPool);
045        this.bytes = bytes;
046    }
047
048    /**
049     * Construct object from input stream.
050     *
051     * @param nameIndex Index in constant pool to CONSTANT_Utf8
052     * @param length Content length in bytes
053     * @param input Input stream
054     * @param constantPool Array of constants
055     * @throws IOException if an I/O error occurs.
056     */
057    Synthetic(final int nameIndex, final int length, final DataInput input, final ConstantPool constantPool) throws IOException {
058        this(nameIndex, length, (byte[]) null, constantPool);
059        if (length > 0) {
060            bytes = new byte[length];
061            input.readFully(bytes);
062            println("Synthetic attribute with length > 0");
063        }
064    }
065
066    /**
067     * Initialize from another object. Note that both objects use the same references (shallow copy). Use copy() for a
068     * physical copy.
069     */
070    public Synthetic(final Synthetic c) {
071        this(c.getNameIndex(), c.getLength(), c.getBytes(), c.getConstantPool());
072    }
073
074    /**
075     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
076     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
077     *
078     * @param v Visitor object
079     */
080    @Override
081    public void accept(final Visitor v) {
082        v.visitSynthetic(this);
083    }
084
085    /**
086     * @return deep copy of this attribute
087     */
088    @Override
089    public Attribute copy(final ConstantPool constantPool) {
090        final Synthetic c = (Synthetic) clone();
091        if (bytes != null) {
092            c.bytes = bytes.clone();
093        }
094        c.setConstantPool(constantPool);
095        return c;
096    }
097
098    /**
099     * Dump source file attribute to file stream in binary format.
100     *
101     * @param file Output file stream
102     * @throws IOException if an I/O error occurs.
103     */
104    @Override
105    public void dump(final DataOutputStream file) throws IOException {
106        super.dump(file);
107        if (super.getLength() > 0) {
108            file.write(bytes, 0, super.getLength());
109        }
110    }
111
112    /**
113     * @return data bytes.
114     */
115    public byte[] getBytes() {
116        return bytes;
117    }
118
119    /**
120     * @param bytes
121     */
122    public void setBytes(final byte[] bytes) {
123        this.bytes = bytes;
124    }
125
126    /**
127     * @return String representation.
128     */
129    @Override
130    public String toString() {
131        final StringBuilder buf = new StringBuilder("Synthetic");
132        if (super.getLength() > 0) {
133            buf.append(" ").append(Utility.toHexString(bytes));
134        }
135        return buf.toString();
136    }
137}