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1   /*
2    * Copyright  2000-2004 The Apache Software Foundation
3    *
4    *  Licensed under the Apache License, Version 2.0 (the "License");
5    *  you may not use this file except in compliance with the License.
6    *  You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   *  Unless required by applicable law or agreed to in writing, software
11   *  distributed under the License is distributed on an "AS IS" BASIS,
12   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   *  See the License for the specific language governing permissions and
14   *  limitations under the License.
15   *
16   */
17  package org.apache.bcel.classfile;
18  
19  import java.io.DataInputStream;
20  import java.io.DataOutputStream;
21  import java.io.IOException;
22  import org.apache.bcel.Constants;
23  
24  /*** 
25   * This class is derived from the abstract 
26   * <A HREF="org.apache.bcel.classfile.Constant.html">Constant</A> class 
27   * and represents a reference to a (external) class.
28   *
29   * @version $Id: ConstantClass.java 386056 2006-03-15 11:31:56Z tcurdt $
30   * @author  <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
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(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(DataInputStream 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(int name_index) {
62          super(Constants.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      public void accept( Visitor v ) {
75          v.visitConstantClass(this);
76      }
77  
78  
79      /*** 
80       * Dump constant class to file stream in binary format.
81       *
82       * @param file Output file stream
83       * @throws IOException
84       */
85      public final void dump( DataOutputStream file ) throws IOException {
86          file.writeByte(tag);
87          file.writeShort(name_index);
88      }
89  
90  
91      /***
92       * @return Name index in constant pool of class name.
93       */
94      public final int getNameIndex() {
95          return name_index;
96      }
97  
98  
99      /***
100      * @param name_index the name index in the constant pool of this Constant Class
101      */
102     public final void setNameIndex( int name_index ) {
103         this.name_index = name_index;
104     }
105 
106 
107     /*** @return String object
108      */
109     public Object getConstantValue( ConstantPool cp ) {
110         Constant c = cp.getConstant(name_index, Constants.CONSTANT_Utf8);
111         return ((ConstantUtf8) c).getBytes();
112     }
113 
114 
115     /*** @return dereferenced string
116      */
117     public String getBytes( ConstantPool cp ) {
118         return (String) getConstantValue(cp);
119     }
120 
121 
122     /***
123      * @return String representation.
124      */
125     public final String toString() {
126         return super.toString() + "(name_index = " + name_index + ")";
127     }
128 }