001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   https://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.bcel.classfile;
020
021import java.io.DataInput;
022import java.io.DataOutputStream;
023import java.io.IOException;
024
025import org.apache.bcel.Const;
026
027/**
028 * This class is derived from the abstract {@link Constant} and represents a reference to a String object.
029 *
030 * @see Constant
031 */
032public final class ConstantString extends Constant implements ConstantObject {
033
034    private int stringIndex; // Identical to ConstantClass except for this name
035
036    /**
037     * Initialize from another object.
038     *
039     * @param c Source to copy.
040     */
041    public ConstantString(final ConstantString c) {
042        this(c.getStringIndex());
043    }
044
045    /**
046     * Initialize instance from file data.
047     *
048     * @param file Input stream.
049     * @throws IOException if an I/O error occurs.
050     */
051    ConstantString(final DataInput file) throws IOException {
052        this(file.readUnsignedShort());
053    }
054
055    /**
056     * Constructs a ConstantString.
057     *
058     * @param stringIndex Index of Constant_Utf8 in constant pool.
059     */
060    public ConstantString(final int stringIndex) {
061        super(Const.CONSTANT_String);
062        this.stringIndex = stringIndex;
063    }
064
065    /**
066     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
067     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
068     *
069     * @param v Visitor object.
070     */
071    @Override
072    public void accept(final Visitor v) {
073        v.visitConstantString(this);
074    }
075
076    /**
077     * Dumps constant field reference to file stream in binary format.
078     *
079     * @param file Output file stream.
080     * @throws IOException if an I/O error occurs.
081     */
082    @Override
083    public void dump(final DataOutputStream file) throws IOException {
084        file.writeByte(super.getTag());
085        file.writeShort(stringIndex);
086    }
087
088    /**
089     * Gets the dereferenced string.
090     *
091     * @param cp the constant pool.
092     * @return dereferenced string.
093     */
094    public String getBytes(final ConstantPool cp) {
095        return (String) getConstantValue(cp);
096    }
097
098    /**
099     * Gets the String object.
100     *
101     * @param cp the constant pool.
102     * @return String object.
103     */
104    @Override
105    public Object getConstantValue(final ConstantPool cp) {
106        return cp.getConstantUtf8(stringIndex).getBytes();
107    }
108
109    /**
110     * Gets the index in constant pool of the string.
111     *
112     * @return Index in constant pool of the string (ConstantUtf8).
113     */
114    public int getStringIndex() {
115        return stringIndex;
116    }
117
118    /**
119     * Sets the string index.
120     *
121     * @param stringIndex the index into the constant of the string value.
122     */
123    public void setStringIndex(final int stringIndex) {
124        this.stringIndex = stringIndex;
125    }
126
127    /**
128     * @return String representation.
129     */
130    @Override
131    public String toString() {
132        return super.toString() + "(stringIndex = " + stringIndex + ")";
133    }
134}