    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 value, i.e., a default value for initializing
    028 * a class field. This class is instantiated by the <em>Attribute.readAttribute()</em> method.
    029 *
    030 * @see Attribute
    031 */
    032public final class ConstantValue extends Attribute {
    033
    034    private int constantValueIndex;
    035
    036    /**
    037     * Initialize from another object. Note that both objects use the same references (shallow copy). Use clone() for a
    038     * physical copy.
    039     */
    040    public ConstantValue(final ConstantValue c) {
    041        this(c.getNameIndex(), c.getLength(), c.getConstantValueIndex(), c.getConstantPool());
    042    }
    043
    044    /**
    045     * Construct object from input stream.
    046     *
    047     * @param name_index Name index in constant pool
    048     * @param length Content length in bytes
    049     * @param input Input stream
    050     * @param constant_pool Array of constants
    051     * @throws IOException if an I/O error occurs.
    052     */
    053    ConstantValue(final int name_index, final int length, final DataInput input, final ConstantPool constant_pool) throws IOException {
    054        this(name_index, length, input.readUnsignedShort(), constant_pool);
    055    }
    056
    057    /**
    058     * @param name_index Name index in constant pool
    059     * @param length Content length in bytes
    060     * @param constantValueIndex Index in constant pool
    061     * @param constant_pool Array of constants
    062     */
    063    public ConstantValue(final int name_index, final int length, final int constantValueIndex, final ConstantPool constant_pool) {
    064        super(Const.ATTR_CONSTANT_VALUE, name_index, length, constant_pool);
    065        this.constantValueIndex = constantValueIndex;
    066    }
    067
    068    /**
    069     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    070     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    071     *
    072     * @param v Visitor object
    073     */
    074    @Override
    075    public void accept(final Visitor v) {
    076        v.visitConstantValue(this);
    077    }
    078
    079    /**
    080     * @return deep copy of this attribute
    081     */
    082    @Override
    083    public Attribute copy(final ConstantPool constantPool) {
    084        final ConstantValue c = (ConstantValue) clone();
    085        c.setConstantPool(constantPool);
    086        return c;
    087    }
    088
    089    /**
    090     * Dump constant value attribute to file stream on binary format.
    091     *
    092     * @param file Output file stream
    093     * @throws IOException if an I/O error occurs.
    094     */
    095    @Override
    096    public void dump(final DataOutputStream file) throws IOException {
    097        super.dump(file);
    098        file.writeShort(constantValueIndex);
    099    }
    100
    101    /**
    102     * @return Index in constant pool of constant value.
    103     */
    104    public int getConstantValueIndex() {
    105        return constantValueIndex;
    106    }
    107
    108    /**
    109     * @param constantValueIndex the index info the constant pool of this constant value
    110     */
    111    public void setConstantValueIndex(final int constantValueIndex) {
    112        this.constantValueIndex = constantValueIndex;
    113    }
    114
    115    /**
    116     * @return String representation of constant value.
    117     */
    118    @Override
    119    public String toString() {
    120        Constant c = super.getConstantPool().getConstant(constantValueIndex);
    121        String buf;
    122        int i;
    123        // Print constant to string depending on its type
    124        switch (c.getTag()) {
    125        case Const.CONSTANT_Long:
    126            buf = String.valueOf(((ConstantLong) c).getBytes());
    127            break;
    128        case Const.CONSTANT_Float:
    129            buf = String.valueOf(((ConstantFloat) c).getBytes());
    130            break;
    131        case Const.CONSTANT_Double:
    132            buf = String.valueOf(((ConstantDouble) c).getBytes());
    133            break;
    134        case Const.CONSTANT_Integer:
    135            buf = String.valueOf(((ConstantInteger) c).getBytes());
    136            break;
    137        case Const.CONSTANT_String:
    138            i = ((ConstantString) c).getStringIndex();
    139            c = super.getConstantPool().getConstantUtf8(i);
    140            buf = "\"" + Utility.convertString(((ConstantUtf8) c).getBytes()) + "\"";
    141            break;
    142        default:
    143            throw new IllegalStateException("Type of ConstValue invalid: " + c);
    144        }
    145        return buf;
    146    }
    147}