View Javadoc
1   /*
2    * reserved comment block
3    * DO NOT REMOVE OR ALTER!
4    */
5   package com.sun.org.apache.bcel.internal.classfile;
6   
7   /* ====================================================================
8    * The Apache Software License, Version 1.1
9    *
10   * Copyright (c) 2001 The Apache Software Foundation.  All rights
11   * reserved.
12   *
13   * Redistribution and use in source and binary forms, with or without
14   * modification, are permitted provided that the following conditions
15   * are met:
16   *
17   * 1. Redistributions of source code must retain the above copyright
18   *    notice, this list of conditions and the following disclaimer.
19   *
20   * 2. Redistributions in binary form must reproduce the above copyright
21   *    notice, this list of conditions and the following disclaimer in
22   *    the documentation and/or other materials provided with the
23   *    distribution.
24   *
25   * 3. The end-user documentation included with the redistribution,
26   *    if any, must include the following acknowledgment:
27   *       "This product includes software developed by the
28   *        Apache Software Foundation (http://www.apache.org/)."
29   *    Alternately, this acknowledgment may appear in the software itself,
30   *    if and wherever such third-party acknowledgments normally appear.
31   *
32   * 4. The names "Apache" and "Apache Software Foundation" and
33   *    "Apache BCEL" must not be used to endorse or promote products
34   *    derived from this software without prior written permission. For
35   *    written permission, please contact apache@apache.org.
36   *
37   * 5. Products derived from this software may not be called "Apache",
38   *    "Apache BCEL", nor may "Apache" appear in their name, without
39   *    prior written permission of the Apache Software Foundation.
40   *
41   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
42   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
43   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
44   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
45   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
46   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
47   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
48   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
49   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
50   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
51   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
52   * SUCH DAMAGE.
53   * ====================================================================
54   *
55   * This software consists of voluntary contributions made by many
56   * individuals on behalf of the Apache Software Foundation.  For more
57   * information on the Apache Software Foundation, please see
58   * <http://www.apache.org/>.
59   */
60  
61  import  com.sun.org.apache.bcel.internal.Constants;
62  import  java.io.*;
63  
64  /**
65   * This class is derived from <em>Attribute</em> and represents a constant
66   * value, i.e., a default value for initializing a class field.
67   * This class is instantiated by the <em>Attribute.readAttribute()</em> method.
68   *
69   * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
70   * @see     Attribute
71   */
72  public final class ConstantValue extends Attribute {
73    private int constantvalue_index;
74  
75    /**
76     * Initialize from another object. Note that both objects use the same
77     * references (shallow copy). Use clone() for a physical copy.
78     */
79    public ConstantValue(ConstantValue c) {
80      this(c.getNameIndex(), c.getLength(), c.getConstantValueIndex(),
81           c.getConstantPool());
82    }
83  
84    /**
85     * Construct object from file stream.
86     * @param name_index Name index in constant pool
87     * @param length Content length in bytes
88     * @param file Input stream
89     * @param constant_pool Array of constants
90     * @throw IOException
91     */
92    ConstantValue(int name_index, int length, DataInputStream file,
93                  ConstantPool constant_pool) throws IOException
94    {
95      this(name_index, length, (int)file.readUnsignedShort(), constant_pool);
96    }
97  
98    /**
99     * @param name_index Name index in constant pool
100    * @param length Content length in bytes
101    * @param constantvalue_index Index in constant pool
102    * @param constant_pool Array of constants
103    */
104   public ConstantValue(int name_index, int length,
105                        int constantvalue_index,
106                        ConstantPool constant_pool)
107   {
108     super(Constants.ATTR_CONSTANT_VALUE, name_index, length, constant_pool);
109     this.constantvalue_index = constantvalue_index;
110   }
111 
112   /**
113    * Called by objects that are traversing the nodes of the tree implicitely
114    * defined by the contents of a Java class. I.e., the hierarchy of methods,
115    * fields, attributes, etc. spawns a tree of objects.
116    *
117    * @param v Visitor object
118    */
119   public void accept(Visitor v) {
120     v.visitConstantValue(this);
121   }
122   /**
123    * Dump constant value attribute to file stream on binary format.
124    *
125    * @param file Output file stream
126    * @throws IOException
127    */
128   public final void dump(DataOutputStream file) throws IOException
129   {
130     super.dump(file);
131     file.writeShort(constantvalue_index);
132   }
133   /**
134    * @return Index in constant pool of constant value.
135    */
136   public final int getConstantValueIndex() { return constantvalue_index; }
137 
138   /**
139    * @param constantvalue_index.
140    */
141   public final void setConstantValueIndex(int constantvalue_index) {
142     this.constantvalue_index = constantvalue_index;
143   }
144 
145   /**
146    * @return String representation of constant value.
147    */
148   public final String toString() {
149     Constant c = constant_pool.getConstant(constantvalue_index);
150 
151     String   buf;
152     int    i;
153 
154     // Print constant to string depending on its type
155     switch(c.getTag()) {
156     case Constants.CONSTANT_Long:    buf = "" + ((ConstantLong)c).getBytes();    break;
157     case Constants.CONSTANT_Float:   buf = "" + ((ConstantFloat)c).getBytes();   break;
158     case Constants.CONSTANT_Double:  buf = "" + ((ConstantDouble)c).getBytes();  break;
159     case Constants.CONSTANT_Integer: buf = "" + ((ConstantInteger)c).getBytes(); break;
160     case Constants.CONSTANT_String:
161       i   = ((ConstantString)c).getStringIndex();
162       c   = constant_pool.getConstant(i, Constants.CONSTANT_Utf8);
163       buf = "\"" + Utility.convertString(((ConstantUtf8)c).getBytes()) + "\"";
164       break;
165 
166     default:
167       throw new IllegalStateException("Type of ConstValue invalid: " + c);
168     }
169 
170     return buf;
171   }
172 
173   /**
174    * @return deep copy of this attribute
175    */
176   public Attribute copy(ConstantPool constant_pool) {
177     ConstantValue c = (ConstantValue)clone();
178     c.constant_pool = constant_pool;
179     return c;
180   }
181 }