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 <em>Attribute</em> and represents a constant
028 * value, i.e., a default value for initializing a class field.
029 * This class is instantiated by the <em>Attribute.readAttribute()</em> method.
030 *
031 * @version $Id: ConstantValue.java 1806200 2017-08-25 16:33:06Z ggregory $
032 * @see     Attribute
033 */
034public final class ConstantValue extends Attribute {
035
036    private int constantvalue_index;
037
038
039    /**
040     * Initialize from another object. Note that both objects use the same
041     * references (shallow copy). Use clone() for a physical copy.
042     */
043    public ConstantValue(final ConstantValue c) {
044        this(c.getNameIndex(), c.getLength(), c.getConstantValueIndex(), c.getConstantPool());
045    }
046
047
048    /**
049     * Construct object from input stream.
050     * @param name_index Name index in constant pool
051     * @param length Content length in bytes
052     * @param input Input stream
053     * @param constant_pool Array of constants
054     * @throws IOException
055     */
056    ConstantValue(final int name_index, final int length, final DataInput input, final ConstantPool constant_pool)
057            throws IOException {
058        this(name_index, length, input.readUnsignedShort(), constant_pool);
059    }
060
061
062    /**
063     * @param name_index Name index in constant pool
064     * @param length Content length in bytes
065     * @param constantvalue_index Index in constant pool
066     * @param constant_pool Array of constants
067     */
068    public ConstantValue(final int name_index, final int length, final int constantvalue_index,
069            final ConstantPool constant_pool) {
070        super(Const.ATTR_CONSTANT_VALUE, name_index, length, constant_pool);
071        this.constantvalue_index = constantvalue_index;
072    }
073
074
075    /**
076     * Called by objects that are traversing the nodes of the tree implicitely
077     * defined by the contents of a Java class. I.e., the hierarchy of methods,
078     * fields, attributes, etc. spawns a tree of objects.
079     *
080     * @param v Visitor object
081     */
082    @Override
083    public void accept( final Visitor v ) {
084        v.visitConstantValue(this);
085    }
086
087
088    /**
089     * Dump constant value attribute to file stream on binary format.
090     *
091     * @param file Output file stream
092     * @throws IOException
093     */
094    @Override
095    public final void dump( final DataOutputStream file ) throws IOException {
096        super.dump(file);
097        file.writeShort(constantvalue_index);
098    }
099
100
101    /**
102     * @return Index in constant pool of constant value.
103     */
104    public final int getConstantValueIndex() {
105        return constantvalue_index;
106    }
107
108
109    /**
110     * @param constantvalue_index the index info the constant pool of this constant value
111     */
112    public final void setConstantValueIndex( final int constantvalue_index ) {
113        this.constantvalue_index = constantvalue_index;
114    }
115
116
117    /**
118     * @return String representation of constant value.
119     */
120    @Override
121    public final String toString() {
122        Constant c = super.getConstantPool().getConstant(constantvalue_index);
123        String buf;
124        int i;
125        // Print constant to string depending on its type
126        switch (c.getTag()) {
127            case Const.CONSTANT_Long:
128                buf = String.valueOf(((ConstantLong) c).getBytes());
129                break;
130            case Const.CONSTANT_Float:
131                buf = String.valueOf(((ConstantFloat) c).getBytes());
132                break;
133            case Const.CONSTANT_Double:
134                buf = String.valueOf(((ConstantDouble) c).getBytes());
135                break;
136            case Const.CONSTANT_Integer:
137                buf = String.valueOf(((ConstantInteger) c).getBytes());
138                break;
139            case Const.CONSTANT_String:
140                i = ((ConstantString) c).getStringIndex();
141                c = super.getConstantPool().getConstant(i, Const.CONSTANT_Utf8);
142                buf = "\"" + Utility.convertString(((ConstantUtf8) c).getBytes()) + "\"";
143                break;
144            default:
145                throw new IllegalStateException("Type of ConstValue invalid: " + c);
146        }
147        return buf;
148    }
149
150
151    /**
152     * @return deep copy of this attribute
153     */
154    @Override
155    public Attribute copy( final ConstantPool _constant_pool ) {
156        final ConstantValue c = (ConstantValue) clone();
157        c.setConstantPool(_constant_pool);
158        return c;
159    }
160}