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 */
019
020package org.apache.bcel.classfile;
021
022import java.io.DataInput;
023import java.io.DataOutputStream;
024import java.io.IOException;
025
026import org.apache.bcel.Const;
027import org.apache.bcel.util.Args;
028
029/**
030 * This class is derived from <em>Attribute</em> and indicates the main class of a module. There may be at most one
031 * ModuleMainClass attribute in a ClassFile structure.
032 *
033 * @see Attribute
034 */
035public final class ModuleMainClass extends Attribute {
036
037    private int mainClassIndex;
038
039    /**
040     * Constructs object from input stream.
041     *
042     * @param nameIndex Index in constant pool
043     * @param length Content length in bytes
044     * @param input Input stream
045     * @param constantPool Array of constants
046     * @throws IOException if an I/O error occurs.
047     */
048    ModuleMainClass(final int nameIndex, final int length, final DataInput input, final ConstantPool constantPool) throws IOException {
049        this(nameIndex, length, 0, constantPool);
050        mainClassIndex = input.readUnsignedShort();
051    }
052
053    /**
054     * @param nameIndex Index in constant pool
055     * @param length Content length in bytes
056     * @param mainClassIndex Host class index
057     * @param constantPool Array of constants
058     */
059    public ModuleMainClass(final int nameIndex, final int length, final int mainClassIndex, final ConstantPool constantPool) {
060        super(Const.ATTR_NEST_MEMBERS, nameIndex, length, constantPool);
061        this.mainClassIndex = Args.requireU2(mainClassIndex, "mainClassIndex");
062    }
063
064    /**
065     * Initialize from another object. Note that both objects use the same references (shallow copy). Use copy() for a
066     * physical copy.
067     *
068     * @param c Source to copy.
069     */
070    public ModuleMainClass(final ModuleMainClass c) {
071        this(c.getNameIndex(), c.getLength(), c.getHostClassIndex(), 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. I.e.,
076     * 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.visitModuleMainClass(this);
083    }
084
085    /**
086     * @return deep copy of this attribute
087     */
088    @Override
089    public Attribute copy(final ConstantPool constantPool) {
090        final ModuleMainClass c = (ModuleMainClass) clone();
091        c.setConstantPool(constantPool);
092        return c;
093    }
094
095    /**
096     * Dump ModuleMainClass attribute to file stream in binary format.
097     *
098     * @param file Output file stream
099     * @throws IOException if an I/O error occurs.
100     */
101    @Override
102    public void dump(final DataOutputStream file) throws IOException {
103        super.dump(file);
104        file.writeShort(mainClassIndex);
105    }
106
107    /**
108     * @return index into constant pool of host class name.
109     */
110    public int getHostClassIndex() {
111        return mainClassIndex;
112    }
113
114    /**
115     * @param mainClassIndex the host class index
116     */
117    public void setHostClassIndex(final int mainClassIndex) {
118        this.mainClassIndex = mainClassIndex;
119    }
120
121    /**
122     * @return String representation
123     */
124    @Override
125    public String toString() {
126        final StringBuilder buf = new StringBuilder();
127        buf.append("ModuleMainClass: ");
128        final String className = super.getConstantPool().getConstantString(mainClassIndex, Const.CONSTANT_Class);
129        buf.append(Utility.compactClassName(className, false));
130        return buf.toString();
131    }
132}