    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;
    025import org.apache.bcel.util.Args;
    026
    027/**
    028 * This class is derived from <em>Attribute</em> and indicates the main class of a module. There may be at most one
    029 * ModuleMainClass attribute in a ClassFile structure.
    030 *
    031 * @see Attribute
    032 */
    033public final class ModuleMainClass extends Attribute {
    034
    035    private int mainClassIndex;
    036
    037    /**
    038     * Constructs object from input stream.
    039     *
    040     * @param nameIndex Index in constant pool
    041     * @param length Content length in bytes
    042     * @param input Input stream
    043     * @param constantPool Array of constants
    044     * @throws IOException if an I/O error occurs.
    045     */
    046    ModuleMainClass(final int nameIndex, final int length, final DataInput input, final ConstantPool constantPool) throws IOException {
    047        this(nameIndex, length, 0, constantPool);
    048        mainClassIndex = input.readUnsignedShort();
    049    }
    050
    051    /**
    052     * @param nameIndex Index in constant pool
    053     * @param length Content length in bytes
    054     * @param mainClassIndex Host class index
    055     * @param constantPool Array of constants
    056     */
    057    public ModuleMainClass(final int nameIndex, final int length, final int mainClassIndex, final ConstantPool constantPool) {
    058        super(Const.ATTR_NEST_MEMBERS, nameIndex, length, constantPool);
    059        this.mainClassIndex = Args.requireU2(mainClassIndex, "mainClassIndex");
    060    }
    061
    062    /**
    063     * Initialize from another object. Note that both objects use the same references (shallow copy). Use copy() for a
    064     * physical copy.
    065     *
    066     * @param c Source to copy.
    067     */
    068    public ModuleMainClass(final ModuleMainClass c) {
    069        this(c.getNameIndex(), c.getLength(), c.getHostClassIndex(), c.getConstantPool());
    070    }
    071
    072    /**
    073     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class. I.e.,
    074     * the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    075     *
    076     * @param v Visitor object
    077     */
    078    @Override
    079    public void accept(final Visitor v) {
    080        v.visitModuleMainClass(this);
    081    }
    082
    083    /**
    084     * @return deep copy of this attribute
    085     */
    086    @Override
    087    public Attribute copy(final ConstantPool constantPool) {
    088        final ModuleMainClass c = (ModuleMainClass) clone();
    089        c.setConstantPool(constantPool);
    090        return c;
    091    }
    092
    093    /**
    094     * Dump ModuleMainClass attribute to file stream in binary format.
    095     *
    096     * @param file Output file stream
    097     * @throws IOException if an I/O error occurs.
    098     */
    099    @Override
    100    public void dump(final DataOutputStream file) throws IOException {
    101        super.dump(file);
    102        file.writeShort(mainClassIndex);
    103    }
    104
    105    /**
    106     * @return index into constant pool of host class name.
    107     */
    108    public int getHostClassIndex() {
    109        return mainClassIndex;
    110    }
    111
    112    /**
    113     * @param mainClassIndex the host class index
    114     */
    115    public void setHostClassIndex(final int mainClassIndex) {
    116        this.mainClassIndex = mainClassIndex;
    117    }
    118
    119    /**
    120     * @return String representation
    121     */
    122    @Override
    123    public String toString() {
    124        final StringBuilder buf = new StringBuilder();
    125        buf.append("ModuleMainClass: ");
    126        final String className = super.getConstantPool().getConstantString(mainClassIndex, Const.CONSTANT_Class);
    127        buf.append(Utility.compactClassName(className, false));
    128        return buf.toString();
    129    }
    130}