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}