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}