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