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 the abstract {@link Constant} and represents a reference to a (external) class. 028 * 029 * @see Constant 030 */ 031public final class ConstantClass extends Constant implements ConstantObject { 032 033 private int nameIndex; // Identical to ConstantString except for the name 034 035 /** 036 * Initialize from another object. 037 */ 038 public ConstantClass(final ConstantClass c) { 039 this(c.getNameIndex()); 040 } 041 042 /** 043 * Constructs an instance from file data. 044 * 045 * @param dataInput Input stream 046 * @throws IOException if an I/O error occurs reading from the given {@code dataInput}. 047 */ 048 ConstantClass(final DataInput dataInput) throws IOException { 049 this(dataInput.readUnsignedShort()); 050 } 051 052 /** 053 * @param nameIndex Name index in constant pool. Should refer to a ConstantUtf8. 054 */ 055 public ConstantClass(final int nameIndex) { 056 super(Const.CONSTANT_Class); 057 this.nameIndex = nameIndex; 058 } 059 060 /** 061 * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class. 062 * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects. 063 * 064 * @param v Visitor object 065 */ 066 @Override 067 public void accept(final Visitor v) { 068 v.visitConstantClass(this); 069 } 070 071 /** 072 * Dumps constant class to file stream in binary format. 073 * 074 * @param file Output file stream 075 * @throws IOException if an I/O error occurs writing to the DataOutputStream. 076 */ 077 @Override 078 public void dump(final DataOutputStream file) throws IOException { 079 file.writeByte(super.getTag()); 080 file.writeShort(nameIndex); 081 } 082 083 /** 084 * @return dereferenced string 085 */ 086 public String getBytes(final ConstantPool cp) { 087 return (String) getConstantValue(cp); 088 } 089 090 /** 091 * @return String object 092 */ 093 @Override 094 public Object getConstantValue(final ConstantPool cp) { 095 return cp.getConstantUtf8(nameIndex).getBytes(); 096 } 097 098 /** 099 * @return Name index in constant pool of class name. 100 */ 101 public int getNameIndex() { 102 return nameIndex; 103 } 104 105 /** 106 * @param nameIndex the name index in the constant pool of this Constant Class 107 */ 108 public void setNameIndex(final int nameIndex) { 109 this.nameIndex = nameIndex; 110 } 111 112 /** 113 * @return String representation. 114 */ 115 @Override 116 public String toString() { 117 return super.toString() + "(nameIndex = " + nameIndex + ")"; 118 } 119}