1/* Copyright (C) 2003 Vladimir Roubtsov. All rights reserved.
2 *
3 * This program and the accompanying materials are made available under
4 * the terms of the Common Public License v1.0 which accompanies this distribution,
5 * and is available at http://www.eclipse.org/legal/cpl-v10.html
6 *
7 * $Id: ConstantValueAttribute_info.java,v 1.1.1.1 2004/05/09 16:57:47 vlad_r Exp $
8 */
9package com.vladium.jcd.cls.attribute;
10
11import java.io.IOException;
12
13import com.vladium.jcd.cls.ClassDef;
14import com.vladium.jcd.cls.constant.CONSTANT_literal_info;
15import com.vladium.jcd.lib.UDataInputStream;
16import com.vladium.jcd.lib.UDataOutputStream;
17
18// ----------------------------------------------------------------------------
19/**
20 * The ConstantValue attribute is a fixed-length attribute used in the attributes
21 * table of the {@link com.vladium.jcd.cls.Field_info} structures. A ConstantValue
22 * attribute represents the value of a constant field that must be (explicitly or
23 * implicitly) static; that is, the ACC_STATIC bit in the flags item of the
24 * Field_info structure must be set. The field is not required to be final. There
25 * can be no more than one ConstantValue attribute in the attributes table of a
26 * given Field_info structure. The constant field represented by the Field_info
27 * structure is assigned the value referenced by its ConstantValue attribute as
28 * part of its initialization.<P>
29 *
30 * The ConstantValue attribute has the format
31 * <PRE>
32 *  ConstantValue_attribute {
33 *          u2 attribute_name_index;
34 *          u4 attribute_length;
35 *          u2 constantvalue_index;
36 *  }
37 * </PRE>
38 *
39 * The value of the constantvalue_index item must be a valid index into the constant
40 * pool table. The constant pool entry at that index must give the constant value
41 * represented by this attribute.<P>
42 *
43 * The constant pool entry must be of a type appropriate to the field, as shown below:
44 *
45 * <TABLE>
46 * <TR><TH>Field Type</TH>                      <TH>Entry Type</TH></TR>
47 * <TR><TD>long</TD>                            <TD>CONSTANT_Long</TD></TR>
48 * <TR><TD>float</TD>                           <TD>CONSTANT_Float</TD></TR>
49 * <TR><TD>double</TD>                          <TD>CONSTANT_Double</TD></TR>
50 * <TR><TD>int, short, char, byte, boolean</TD> <TD>CONSTANT_Integer</TD></TR>
51 * <TR><TD>java.lang.String</TD>                <TD>CONSTANT_String</TD></TR>
52 * </TABLE>
53 *
54 * @author (C) 2001, Vlad Roubtsov
55 */
56public
57final class ConstantValueAttribute_info extends Attribute_info
58{
59    // public: ................................................................
60
61
62    public int m_value_index;
63
64
65    public ConstantValueAttribute_info (final int attribute_name_index, final int value_index)
66    {
67        super (attribute_name_index, 2);
68
69        m_value_index = value_index;
70    }
71
72    public CONSTANT_literal_info getValue (final ClassDef cls)
73    {
74        return (CONSTANT_literal_info) cls.getConstants ().get (m_value_index);
75    }
76
77    public long length ()
78    {
79        return 8;
80    }
81
82    // Visitor:
83
84    public void accept (final IAttributeVisitor visitor, final Object ctx)
85    {
86        visitor.visit (this, ctx);
87    }
88
89    public String toString ()
90    {
91        // TODO: return more data here
92        return "ConstantValueAttribute_info: [attribute_name_index = " + m_name_index + ", attribute_length = " + m_attribute_length + ']';
93
94    }
95
96    // Cloneable:
97
98    /**
99     * Performs a deep copy.
100     */
101    public Object clone ()
102    {
103        return super.clone ();
104    }
105
106    // IClassFormatOutput:
107
108    public void writeInClassFormat (final UDataOutputStream out) throws IOException
109    {
110        super.writeInClassFormat (out);
111
112        out.writeU2 (m_value_index);
113    }
114
115    // protected: .............................................................
116
117    // package: ...............................................................
118
119
120    ConstantValueAttribute_info (final int attribute_name_index, final long attribute_length,
121                                 final UDataInputStream bytes)
122        throws IOException
123    {
124        super (attribute_name_index, attribute_length);
125
126        m_value_index = bytes.readU2 ();
127        if (DEBUG) System.out.println ("\tconstantvalue_index: " + m_value_index);
128    }
129
130    // private: ...............................................................
131
132
133    private static final boolean DEBUG = false;
134
135} // end of class
136// ----------------------------------------------------------------------------
137