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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   *  Unless required by applicable law or agreed to in writing, software
12   *  distributed under the License is distributed on an "AS IS" BASIS,
13   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   *  See the License for the specific language governing permissions and
15   *  limitations under the License.
16   *
17   */
18  package org.apache.bcel.classfile;
19  
20  import java.io.DataInput;
21  import java.io.DataOutputStream;
22  import java.io.IOException;
23  
24  import org.apache.bcel.Const;
25  
26  /**
27   * This class is derived from the abstract {@link Constant}
28   * and represents a reference to a (external) class.
29   *
30   * @version $Id: ConstantClass.html 1018313 2017-09-18 09:03:04Z britter $
31   * @see     Constant
32   */
33  public final class ConstantClass extends Constant implements ConstantObject {
34  
35      private int name_index; // Identical to ConstantString except for the name
36  
37  
38      /**
39       * Initialize from another object.
40       */
41      public ConstantClass(final ConstantClass c) {
42          this(c.getNameIndex());
43      }
44  
45  
46      /**
47       * Initialize instance from file data.
48       *
49       * @param file Input stream
50       * @throws IOException
51       */
52      ConstantClass(final DataInput file) throws IOException {
53          this(file.readUnsignedShort());
54      }
55  
56  
57      /**
58       * @param name_index Name index in constant pool.  Should refer to a
59       * ConstantUtf8.
60       */
61      public ConstantClass(final int name_index) {
62          super(Const.CONSTANT_Class);
63          this.name_index = name_index;
64      }
65  
66  
67      /**
68       * Called by objects that are traversing the nodes of the tree implicitely
69       * defined by the contents of a Java class. I.e., the hierarchy of methods,
70       * fields, attributes, etc. spawns a tree of objects.
71       *
72       * @param v Visitor object
73       */
74      @Override
75      public void accept( final Visitor v ) {
76          v.visitConstantClass(this);
77      }
78  
79  
80      /**
81       * Dump constant class to file stream in binary format.
82       *
83       * @param file Output file stream
84       * @throws IOException
85       */
86      @Override
87      public final void dump( final DataOutputStream file ) throws IOException {
88          file.writeByte(super.getTag());
89          file.writeShort(name_index);
90      }
91  
92  
93      /**
94       * @return Name index in constant pool of class name.
95       */
96      public final int getNameIndex() {
97          return name_index;
98      }
99  
100 
101     /**
102      * @param name_index the name index in the constant pool of this Constant Class
103      */
104     public final void setNameIndex( final int name_index ) {
105         this.name_index = name_index;
106     }
107 
108 
109     /** @return String object
110      */
111     @Override
112     public Object getConstantValue( final ConstantPool cp ) {
113         final Constant c = cp.getConstant(name_index, Const.CONSTANT_Utf8);
114         return ((ConstantUtf8) c).getBytes();
115     }
116 
117 
118     /** @return dereferenced string
119      */
120     public String getBytes( final ConstantPool cp ) {
121         return (String) getConstantValue(cp);
122     }
123 
124 
125     /**
126      * @return String representation.
127      */
128     @Override
129     public final String toString() {
130         return super.toString() + "(name_index = " + name_index + ")";
131     }
132 }