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}