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