    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;
    024import org.apache.bcel.util.Args;
    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 nameIndex 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 constantPool The constant pool this attribute is associated with.
    043     */
    044    public Synthetic(final int nameIndex, final int length, final byte[] bytes, final ConstantPool constantPool) {
    045        super(Const.ATTR_SYNTHETIC, nameIndex, Args.require0(length, "Synthetic attribute length"), constantPool);
    046        this.bytes = bytes;
    047    }
    048
    049    /**
    050     * Constructs object from input stream.
    051     *
    052     * @param nameIndex Index in constant pool to CONSTANT_Utf8
    053     * @param length Content length in bytes
    054     * @param input Input stream
    055     * @param constantPool Array of constants
    056     * @throws IOException if an I/O error occurs.
    057     */
    058    Synthetic(final int nameIndex, final int length, final DataInput input, final ConstantPool constantPool) throws IOException {
    059        this(nameIndex, length, (byte[]) null, constantPool);
    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     * @param c Source to copy.
    072     */
    073    public Synthetic(final Synthetic c) {
    074        this(c.getNameIndex(), c.getLength(), c.getBytes(), c.getConstantPool());
    075    }
    076
    077    /**
    078     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    079     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    080     *
    081     * @param v Visitor object
    082     */
    083    @Override
    084    public void accept(final Visitor v) {
    085        v.visitSynthetic(this);
    086    }
    087
    088    /**
    089     * @return deep copy of this attribute
    090     */
    091    @Override
    092    public Attribute copy(final ConstantPool constantPool) {
    093        final Synthetic c = (Synthetic) clone();
    094        if (bytes != null) {
    095            c.bytes = bytes.clone();
    096        }
    097        c.setConstantPool(constantPool);
    098        return c;
    099    }
    100
    101    /**
    102     * Dump source file attribute to file stream in binary format.
    103     *
    104     * @param file Output file stream
    105     * @throws IOException if an I/O error occurs.
    106     */
    107    @Override
    108    public void dump(final DataOutputStream file) throws IOException {
    109        super.dump(file);
    110        if (super.getLength() > 0) {
    111            file.write(bytes, 0, super.getLength());
    112        }
    113    }
    114
    115    /**
    116     * @return data bytes.
    117     */
    118    public byte[] getBytes() {
    119        return bytes;
    120    }
    121
    122    /**
    123     * @param bytes
    124     */
    125    public void setBytes(final byte[] bytes) {
    126        this.bytes = bytes;
    127    }
    128
    129    /**
    130     * @return String representation.
    131     */
    132    @Override
    133    public String toString() {
    134        final StringBuilder buf = new StringBuilder("Synthetic");
    135        if (super.getLength() > 0) {
    136            buf.append(" ").append(Utility.toHexString(bytes));
    137        }
    138        return buf.toString();
    139    }
    140}