    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} and represents a reference to a (external) class.
    028 *
    029 * @see Constant
    030 */
    031public final class ConstantClass extends Constant implements ConstantObject {
    032
    033    private int nameIndex; // Identical to ConstantString except for the name
    034
    035    /**
    036     * Initialize from another object.
    037     */
    038    public ConstantClass(final ConstantClass c) {
    039        this(c.getNameIndex());
    040    }
    041
    042    /**
    043     * Constructs an instance from file data.
    044     *
    045     * @param dataInput Input stream
    046     * @throws IOException if an I/O error occurs reading from the given {@code dataInput}.
    047     */
    048    ConstantClass(final DataInput dataInput) throws IOException {
    049        this(dataInput.readUnsignedShort());
    050    }
    051
    052    /**
    053     * @param nameIndex Name index in constant pool. Should refer to a ConstantUtf8.
    054     */
    055    public ConstantClass(final int nameIndex) {
    056        super(Const.CONSTANT_Class);
    057        this.nameIndex = nameIndex;
    058    }
    059
    060    /**
    061     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    062     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    063     *
    064     * @param v Visitor object
    065     */
    066    @Override
    067    public void accept(final Visitor v) {
    068        v.visitConstantClass(this);
    069    }
    070
    071    /**
    072     * Dumps constant class to file stream in binary format.
    073     *
    074     * @param file Output file stream
    075     * @throws IOException if an I/O error occurs writing to the DataOutputStream.
    076     */
    077    @Override
    078    public void dump(final DataOutputStream file) throws IOException {
    079        file.writeByte(super.getTag());
    080        file.writeShort(nameIndex);
    081    }
    082
    083    /**
    084     * @return dereferenced string
    085     */
    086    public String getBytes(final ConstantPool cp) {
    087        return (String) getConstantValue(cp);
    088    }
    089
    090    /**
    091     * @return String object
    092     */
    093    @Override
    094    public Object getConstantValue(final ConstantPool cp) {
    095        return cp.getConstantUtf8(nameIndex).getBytes();
    096    }
    097
    098    /**
    099     * @return Name index in constant pool of class name.
    100     */
    101    public int getNameIndex() {
    102        return nameIndex;
    103    }
    104
    105    /**
    106     * @param nameIndex the name index in the constant pool of this Constant Class
    107     */
    108    public void setNameIndex(final int nameIndex) {
    109        this.nameIndex = nameIndex;
    110    }
    111
    112    /**
    113     * @return String representation.
    114     */
    115    @Override
    116    public String toString() {
    117        return super.toString() + "(nameIndex = " + nameIndex + ")";
    118    }
    119}