    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;
    026
    027/**
    028 * This class is derived from the abstract {@link Constant} 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 nameIndex; // Identical to ConstantString except for the name
    035
    036    /**
    037     * Initialize from another object.
    038     *
    039     * @param c Source to copy.
    040     */
    041    public ConstantClass(final ConstantClass c) {
    042        this(c.getNameIndex());
    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     * @param nameIndex Name index in constant pool. Should refer to a ConstantUtf8.
    057     */
    058    public ConstantClass(final int nameIndex) {
    059        super(Const.CONSTANT_Class);
    060        this.nameIndex = nameIndex;
    061    }
    062
    063    /**
    064     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    065     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    066     *
    067     * @param v Visitor object
    068     */
    069    @Override
    070    public void accept(final Visitor v) {
    071        v.visitConstantClass(this);
    072    }
    073
    074    /**
    075     * Dumps constant class to file stream in binary format.
    076     *
    077     * @param file Output file stream
    078     * @throws IOException if an I/O error occurs writing to the DataOutputStream.
    079     */
    080    @Override
    081    public void dump(final DataOutputStream file) throws IOException {
    082        file.writeByte(super.getTag());
    083        file.writeShort(nameIndex);
    084    }
    085
    086    /**
    087     * @return dereferenced string
    088     */
    089    public String getBytes(final ConstantPool cp) {
    090        return (String) getConstantValue(cp);
    091    }
    092
    093    /**
    094     * @return String object
    095     */
    096    @Override
    097    public Object getConstantValue(final ConstantPool cp) {
    098        return cp.getConstantUtf8(nameIndex).getBytes();
    099    }
    100
    101    /**
    102     * @return Name index in constant pool of class name.
    103     */
    104    public int getNameIndex() {
    105        return nameIndex;
    106    }
    107
    108    /**
    109     * @param nameIndex the name index in the constant pool of this Constant Class
    110     */
    111    public void setNameIndex(final int nameIndex) {
    112        this.nameIndex = nameIndex;
    113    }
    114
    115    /**
    116     * @return String representation.
    117     */
    118    @Override
    119    public String toString() {
    120        return super.toString() + "(nameIndex = " + nameIndex + ")";
    121    }
    122}