    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}