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