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 * @version $Id: ConstantClass.java 1749603 2016-06-21 20:50:19Z ggregory $
031 * @see     Constant
032 */
033public final class ConstantClass extends Constant implements ConstantObject {
034
035    private int name_index; // Identical to ConstantString except for the name
036
037
038    /**
039     * Initialize from another object.
040     */
041    public ConstantClass(final ConstantClass c) {
042        this(c.getNameIndex());
043    }
044
045
046    /**
047     * Initialize instance from file data.
048     *
049     * @param file Input stream
050     * @throws IOException
051     */
052    ConstantClass(final DataInput file) throws IOException {
053        this(file.readUnsignedShort());
054    }
055
056
057    /**
058     * @param name_index Name index in constant pool.  Should refer to a
059     * ConstantUtf8.
060     */
061    public ConstantClass(final int name_index) {
062        super(Const.CONSTANT_Class);
063        this.name_index = name_index;
064    }
065
066
067    /**
068     * Called by objects that are traversing the nodes of the tree implicitely
069     * defined by the contents of a Java class. I.e., the hierarchy of methods,
070     * fields, attributes, etc. spawns a tree of objects.
071     *
072     * @param v Visitor object
073     */
074    @Override
075    public void accept( final Visitor v ) {
076        v.visitConstantClass(this);
077    }
078
079
080    /** 
081     * Dump constant class to file stream in binary format.
082     *
083     * @param file Output file stream
084     * @throws IOException
085     */
086    @Override
087    public final void dump( final DataOutputStream file ) throws IOException {
088        file.writeByte(super.getTag());
089        file.writeShort(name_index);
090    }
091
092
093    /**
094     * @return Name index in constant pool of class name.
095     */
096    public final int getNameIndex() {
097        return name_index;
098    }
099
100
101    /**
102     * @param name_index the name index in the constant pool of this Constant Class
103     */
104    public final void setNameIndex( final int name_index ) {
105        this.name_index = name_index;
106    }
107
108
109    /** @return String object
110     */
111    @Override
112    public Object getConstantValue( final ConstantPool cp ) {
113        final Constant c = cp.getConstant(name_index, Const.CONSTANT_Utf8);
114        return ((ConstantUtf8) c).getBytes();
115    }
116
117
118    /** @return dereferenced string
119     */
120    public String getBytes( final ConstantPool cp ) {
121        return (String) getConstantValue(cp);
122    }
123
124
125    /**
126     * @return String representation.
127     */
128    @Override
129    public final String toString() {
130        return super.toString() + "(name_index = " + name_index + ")";
131    }
132}