    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 */
    017package org.apache.bcel.classfile;
    018
    019import java.io.DataInput;
    020import java.io.DataOutputStream;
    021import java.io.IOException;
    022
    023import org.apache.bcel.Const;
    024
    025/**
    026 * This class is derived from the abstract {@link Constant} and represents a reference to a (external) class.
    027 *
    028 * @see Constant
    029 */
    030public final class ConstantClass extends Constant implements ConstantObject {
    031
    032    private int nameIndex; // Identical to ConstantString except for the name
    033
    034    /**
    035     * Initialize from another object.
    036     *
    037     * @param c Source to copy.
    038     */
    039    public ConstantClass(final ConstantClass c) {
    040        this(c.getNameIndex());
    041    }
    042
    043    /**
    044     * Constructs an instance from file data.
    045     *
    046     * @param dataInput Input stream
    047     * @throws IOException if an I/O error occurs reading from the given {@code dataInput}.
    048     */
    049    ConstantClass(final DataInput dataInput) throws IOException {
    050        this(dataInput.readUnsignedShort());
    051    }
    052
    053    /**
    054     * @param nameIndex Name index in constant pool. Should refer to a ConstantUtf8.
    055     */
    056    public ConstantClass(final int nameIndex) {
    057        super(Const.CONSTANT_Class);
    058        this.nameIndex = nameIndex;
    059    }
    060
    061    /**
    062     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    063     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    064     *
    065     * @param v Visitor object
    066     */
    067    @Override
    068    public void accept(final Visitor v) {
    069        v.visitConstantClass(this);
    070    }
    071
    072    /**
    073     * Dumps constant class to file stream in binary format.
    074     *
    075     * @param file Output file stream
    076     * @throws IOException if an I/O error occurs writing to the DataOutputStream.
    077     */
    078    @Override
    079    public void dump(final DataOutputStream file) throws IOException {
    080        file.writeByte(super.getTag());
    081        file.writeShort(nameIndex);
    082    }
    083
    084    /**
    085     * @return dereferenced string
    086     */
    087    public String getBytes(final ConstantPool cp) {
    088        return (String) getConstantValue(cp);
    089    }
    090
    091    /**
    092     * @return String object
    093     */
    094    @Override
    095    public Object getConstantValue(final ConstantPool cp) {
    096        return cp.getConstantUtf8(nameIndex).getBytes();
    097    }
    098
    099    /**
    100     * @return Name index in constant pool of class name.
    101     */
    102    public int getNameIndex() {
    103        return nameIndex;
    104    }
    105
    106    /**
    107     * @param nameIndex the name index in the constant pool of this Constant Class
    108     */
    109    public void setNameIndex(final int nameIndex) {
    110        this.nameIndex = nameIndex;
    111    }
    112
    113    /**
    114     * @return String representation.
    115     */
    116    @Override
    117    public String toString() {
    118        return super.toString() + "(nameIndex = " + nameIndex + ")";
    119    }
    120}