    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 the abstract {@link Constant}
    028 * and represents a reference to a (external) class.
    029 *
    030 * @see     Constant
    031 */
    032public final class ConstantClass extends Constant implements ConstantObject {
    033
    034    private int name_index; // Identical to ConstantString except for the name
    035
    036
    037    /**
    038     * Initialize from another object.
    039     */
    040    public ConstantClass(final ConstantClass c) {
    041        this(c.getNameIndex());
    042    }
    043
    044
    045    /**
    046     * Constructs an instance from file data.
    047     *
    048     * @param dataInput Input stream
    049     * @throws IOException if an I/O error occurs reading from the given {@code dataInput}.
    050     */
    051    ConstantClass(final DataInput dataInput) throws IOException {
    052        this(dataInput.readUnsignedShort());
    053    }
    054
    055
    056    /**
    057     * @param name_index Name index in constant pool.  Should refer to a
    058     * ConstantUtf8.
    059     */
    060    public ConstantClass(final int name_index) {
    061        super(Const.CONSTANT_Class);
    062        this.name_index = name_index;
    063    }
    064
    065
    066    /**
    067     * Called by objects that are traversing the nodes of the tree implicitely
    068     * defined by the contents of a Java class. I.e., the hierarchy of methods,
    069     * fields, attributes, etc. spawns a tree of objects.
    070     *
    071     * @param v Visitor object
    072     */
    073    @Override
    074    public void accept( final Visitor v ) {
    075        v.visitConstantClass(this);
    076    }
    077
    078
    079    /**
    080     * Dumps constant class to file stream in binary format.
    081     *
    082     * @param file Output file stream
    083     * @throws IOException if an I/O error occurs writing to the DataOutputStream.
    084     */
    085    @Override
    086    public void dump( final DataOutputStream file ) throws IOException {
    087        file.writeByte(super.getTag());
    088        file.writeShort(name_index);
    089    }
    090
    091
    092    /**
    093     * @return Name index in constant pool of class name.
    094     */
    095    public int getNameIndex() {
    096        return name_index;
    097    }
    098
    099
    100    /**
    101     * @param name_index the name index in the constant pool of this Constant Class
    102     */
    103    public void setNameIndex( final int name_index ) {
    104        this.name_index = name_index;
    105    }
    106
    107
    108    /** @return String object
    109     */
    110    @Override
    111    public Object getConstantValue( final ConstantPool cp ) {
    112        final Constant c = cp.getConstant(name_index, Const.CONSTANT_Utf8);
    113        return ((ConstantUtf8) c).getBytes();
    114    }
    115
    116
    117    /** @return dereferenced string
    118     */
    119    public String getBytes( final ConstantPool cp ) {
    120        return (String) getConstantValue(cp);
    121    }
    122
    123
    124    /**
    125     * @return String representation.
    126     */
    127    @Override
    128    public String toString() {
    129        return super.toString() + "(name_index = " + name_index + ")";
    130    }
    131}