1   package org.apache.bcel.classfile;
2   
3   /* ====================================================================
4    * The Apache Software License, Version 1.1
5    *
6    * Copyright (c) 2001 The Apache Software Foundation.  All rights
7    * reserved.
8    *
9    * Redistribution and use in source and binary forms, with or without
10   * modification, are permitted provided that the following conditions
11   * are met:
12   *
13   * 1. Redistributions of source code must retain the above copyright
14   *    notice, this list of conditions and the following disclaimer.
15   *
16   * 2. Redistributions in binary form must reproduce the above copyright
17   *    notice, this list of conditions and the following disclaimer in
18   *    the documentation and/or other materials provided with the
19   *    distribution.
20   *
21   * 3. The end-user documentation included with the redistribution,
22   *    if any, must include the following acknowledgment:
23   *       "This product includes software developed by the
24   *        Apache Software Foundation (http://www.apache.org/)."
25   *    Alternately, this acknowledgment may appear in the software itself,
26   *    if and wherever such third-party acknowledgments normally appear.
27   *
28   * 4. The names "Apache" and "Apache Software Foundation" and
29   *    "Apache BCEL" must not be used to endorse or promote products
30   *    derived from this software without prior written permission. For
31   *    written permission, please contact apache@apache.org.
32   *
33   * 5. Products derived from this software may not be called "Apache",
34   *    "Apache BCEL", nor may "Apache" appear in their name, without
35   *    prior written permission of the Apache Software Foundation.
36   *
37   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
38   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
39   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
40   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
41   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
42   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
43   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
44   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
45   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
46   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
47   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
48   * SUCH DAMAGE.
49   * ====================================================================
50   *
51   * This software consists of voluntary contributions made by many
52   * individuals on behalf of the Apache Software Foundation.  For more
53   * information on the Apache Software Foundation, please see
54   * <http://www.apache.org/>.
55   */
56  
57  import  org.apache.bcel.Constants;
58  import  java.io.*;
59  
60  /*** 
61   * This class is derived from the abstract 
62   * <A HREF="org.apache.bcel.classfile.Constant.html">Constant</A> class 
63   * and represents a reference to a String object.
64   *
65   * @version $Id: ConstantString.java,v 1.2 2002/03/11 16:16:35 mdahm Exp $
66   * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
67   * @see     Constant
68   */
69  public final class ConstantString extends Constant implements ConstantObject {
70    private int string_index; // Identical to ConstantClass except for this name
71  
72    /***
73     * Initialize from another object.
74     */
75    public ConstantString(ConstantString c) {
76      this(c.getStringIndex());
77    }    
78    /*** 
79     * Initialize instance from file data.
80     *
81     * @param file Input stream
82     * @throws IOException
83     */
84    ConstantString(DataInputStream file) throws IOException
85    {    
86      this((int)file.readUnsignedShort());
87    }    
88    /***
89     * @param string_index Index of Constant_Utf8 in constant pool
90     */
91    public ConstantString(int string_index)
92    {    
93      super(Constants.CONSTANT_String);
94      this.string_index = string_index;
95    }    
96    /***
97     * Called by objects that are traversing the nodes of the tree implicitely
98     * defined by the contents of a Java class. I.e., the hierarchy of methods,
99     * fields, attributes, etc. spawns a tree of objects.
100    *
101    * @param v Visitor object
102    */
103   public void accept(Visitor v) {
104     v.visitConstantString(this);
105   }    
106   /***
107    * Dump constant field reference to file stream in binary format.
108    *
109    * @param file Output file stream
110    * @throws IOException
111    */ 
112   public final void dump(DataOutputStream file) throws IOException
113   {
114     file.writeByte(tag);
115     file.writeShort(string_index);
116   }    
117   /***
118    * @return Index in constant pool of the string (ConstantUtf8).
119    */  
120   public final int getStringIndex() { return string_index; }    
121   /***
122    * @param string_index.
123    */
124   public final void setStringIndex(int string_index) {
125     this.string_index = string_index;
126   }    
127   /***
128    * @return String representation.
129    */
130   public final String toString()
131   {
132     return super.toString() + "(string_index = " + string_index + ")";
133   }    
134 
135   /*** @return String object
136    */
137   public Object getConstantValue(ConstantPool cp) {
138     Constant c = cp.getConstant(string_index, Constants.CONSTANT_Utf8);
139     return ((ConstantUtf8)c).getBytes();
140   }
141 
142   /*** @return dereferenced string
143    */
144   public String getBytes(ConstantPool cp) {
145     return (String)getConstantValue(cp);
146   }
147 }
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