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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 String object.
29   *
30   * @version $Id: ConstantString.html 1018313 2017-09-18 09:03:04Z britter $
31   * @see     Constant
32   */
33  public final class ConstantString extends Constant implements ConstantObject {
34  
35      private int string_index; // Identical to ConstantClass except for this name
36  
37  
38      /**
39       * Initialize from another object.
40       */
41      public ConstantString(final ConstantString c) {
42          this(c.getStringIndex());
43      }
44  
45  
46      /**
47       * Initialize instance from file data.
48       *
49       * @param file Input stream
50       * @throws IOException
51       */
52      ConstantString(final DataInput file) throws IOException {
53          this(file.readUnsignedShort());
54      }
55  
56  
57      /**
58       * @param string_index Index of Constant_Utf8 in constant pool
59       */
60      public ConstantString(final int string_index) {
61          super(Const.CONSTANT_String);
62          this.string_index = string_index;
63      }
64  
65  
66      /**
67       * Called by objects that are traversing the nodes of the tree implicitely
68       * defined by the contents of a Java class. I.e., the hierarchy of methods,
69       * fields, attributes, etc. spawns a tree of objects.
70       *
71       * @param v Visitor object
72       */
73      @Override
74      public void accept( final Visitor v ) {
75          v.visitConstantString(this);
76      }
77  
78  
79      /**
80       * Dump constant field reference to file stream in binary format.
81       *
82       * @param file Output file stream
83       * @throws IOException
84       */
85      @Override
86      public final void dump( final DataOutputStream file ) throws IOException {
87          file.writeByte(super.getTag());
88          file.writeShort(string_index);
89      }
90  
91  
92      /**
93       * @return Index in constant pool of the string (ConstantUtf8).
94       */
95      public final int getStringIndex() {
96          return string_index;
97      }
98  
99  
100     /**
101      * @param string_index the index into the constant of the string value
102      */
103     public final void setStringIndex( final int string_index ) {
104         this.string_index = string_index;
105     }
106 
107 
108     /**
109      * @return String representation.
110      */
111     @Override
112     public final String toString() {
113         return super.toString() + "(string_index = " + string_index + ")";
114     }
115 
116 
117     /** @return String object
118      */
119     @Override
120     public Object getConstantValue( final ConstantPool cp ) {
121         final Constant c = cp.getConstant(string_index, Const.CONSTANT_Utf8);
122         return ((ConstantUtf8) c).getBytes();
123     }
124 
125 
126     /** @return dereferenced string
127      */
128     public String getBytes( final ConstantPool cp ) {
129         return (String) getConstantValue(cp);
130     }
131 }