001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   https://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.bcel.classfile;
020
021import java.io.DataInput;
022import java.io.DataOutputStream;
023import java.io.IOException;
024
025import org.apache.bcel.Const;
026import org.apache.bcel.util.Args;
027
028/**
029 * This class is derived from <em>Attribute</em> and declares this class as 'synthetic', i.e., it needs special
030 * handling. The JVM specification states "A class member that does not appear in the source code must be marked using a
031 * Synthetic attribute." It may appear in the ClassFile attribute table, a field_info table or a method_info table. This
032 * class is intended to be instantiated from the <em>Attribute.readAttribute()</em> method.
033 *
034 * @see Attribute
035 */
036public final class Synthetic extends Attribute {
037
038    private byte[] bytes;
039
040    /**
041     * @param nameIndex Index in constant pool to CONSTANT_Utf8, which should represent the string "Synthetic".
042     * @param length Content length in bytes - should be zero.
043     * @param bytes Attribute contents
044     * @param constantPool The constant pool this attribute is associated with.
045     */
046    public Synthetic(final int nameIndex, final int length, final byte[] bytes, final ConstantPool constantPool) {
047        super(Const.ATTR_SYNTHETIC, nameIndex, Args.require0(length, "Synthetic attribute length"), constantPool);
048        this.bytes = bytes;
049    }
050
051    /**
052     * Constructs object from input stream.
053     *
054     * @param nameIndex Index in constant pool to CONSTANT_Utf8
055     * @param length Content length in bytes
056     * @param input Input stream
057     * @param constantPool Array of constants
058     * @throws IOException if an I/O error occurs.
059     */
060    Synthetic(final int nameIndex, final int length, final DataInput input, final ConstantPool constantPool) throws IOException {
061        this(nameIndex, length, (byte[]) null, constantPool);
062        if (length > 0) {
063            bytes = new byte[length];
064            input.readFully(bytes);
065            println("Synthetic attribute with length > 0");
066        }
067    }
068
069    /**
070     * Initialize from another object. Note that both objects use the same references (shallow copy). Use copy() for a
071     * physical copy.
072     *
073     * @param c Source to copy.
074     */
075    public Synthetic(final Synthetic c) {
076        this(c.getNameIndex(), c.getLength(), c.getBytes(), c.getConstantPool());
077    }
078
079    /**
080     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
081     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
082     *
083     * @param v Visitor object
084     */
085    @Override
086    public void accept(final Visitor v) {
087        v.visitSynthetic(this);
088    }
089
090    /**
091     * @return deep copy of this attribute
092     */
093    @Override
094    public Attribute copy(final ConstantPool constantPool) {
095        final Synthetic c = (Synthetic) clone();
096        if (bytes != null) {
097            c.bytes = bytes.clone();
098        }
099        c.setConstantPool(constantPool);
100        return c;
101    }
102
103    /**
104     * Dump source file attribute to file stream in binary format.
105     *
106     * @param file Output file stream
107     * @throws IOException if an I/O error occurs.
108     */
109    @Override
110    public void dump(final DataOutputStream file) throws IOException {
111        super.dump(file);
112        if (super.getLength() > 0) {
113            file.write(bytes, 0, super.getLength());
114        }
115    }
116
117    /**
118     * @return data bytes.
119     */
120    public byte[] getBytes() {
121        return bytes;
122    }
123
124    /**
125     * @param bytes
126     */
127    public void setBytes(final byte[] bytes) {
128        this.bytes = bytes;
129    }
130
131    /**
132     * @return String representation.
133     */
134    @Override
135    public String toString() {
136        final StringBuilder buf = new StringBuilder("Synthetic");
137        if (super.getLength() > 0) {
138            buf.append(" ").append(Utility.toHexString(bytes));
139        }
140        return buf.toString();
141    }
142}