    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}