1 cananian 1.1.2.2 // AttributeConstantValue.java, created Mon Jan 18 22:44:34 1999 by cananian
2 cananian 1.1.2.1 // Copyright (C) 1998 C. Scott Ananian <cananian@alumni.princeton.edu>
3 cananian 1.1.2.1 // Licensed under the terms of the GNU GPL; see COPYING for details.
4 cananian 1.1.2.1 package harpoon.IR.RawClass;
5 cananian 1.1.2.1
6 cananian 1.1.2.1 /**
7 cananian 1.1.2.1 * The <code>ConstantValue</code> attribute is a fixed-length
8 cananian 1.1.2.1 * attribute used in the <code>attributes</code> table of the
9 cananian 1.1.2.1 * <code>field_info</code> structures. A <code>ConstantValue</code>
10 cananian 1.1.2.1 * attribute represents the value of a constant field that must be
11 cananian 1.1.2.1 * (explicitly or implicitly) <code>static</code>; that is, the
12 cananian 1.1.2.1 * <code>ACC_STATIC</code> bit in the <code>flags</code> item of the
13 cananian 1.1.2.1 * <code>field_info</code> structure must be set. The field is not
14 cananian 1.1.2.1 * required to be <code>final</code>. There can be no more than one
15 cananian 1.1.2.1 * <code>ConstantValue</code> attribute in the <code>attributes</code>
16 cananian 1.1.2.1 * table of a given <code>field_info</code> structure. The constant
17 cananian 1.1.2.1 * field represented by the <code>field_info</code> structure is
18 cananian 1.1.2.1 * assigned the value referenced by its <code>ConstantValue</code>
19 cananian 1.1.2.1 * attribute as part of its initialization.<p>
20 cananian 1.1.2.1 * <strong>CORRECTION FROM ERRATA:</strong>
21 cananian 1.1.2.1 * If a non-static field has a <code>ConstantValue</code> attribute, then
22 cananian 1.1.2.1 * the attribute is silently ignored.
23 cananian 1.1.2.1 *
24 cananian 1.1.2.1 * @author C. Scott Ananian <cananian@alumni.princeton.edu>
25 cananian 1.3 * @version $Id: AttributeConstantValue.java,v 1.3 2003/09/05 21:45:15 cananian Exp $
26 cananian 1.1.2.1 * @see Attribute
27 cananian 1.1.2.1 * @see FieldInfo
28 cananian 1.1.2.1 * @see ClassFile
29 cananian 1.1.2.1 */
30 cananian 1.1.2.1 public class AttributeConstantValue extends Attribute {
31 cananian 1.3 /** The string naming this <code>Attribute</code> type. */
32 cananian 1.3 public static final String ATTRIBUTE_NAME = "ConstantValue";
33 cananian 1.1.2.1 /** The value of the <code>constantvalue_index</code> must be a
34 cananian 1.1.2.1 valid index into the <code>constant_pool</code> table. The
35 cananian 1.1.2.1 <code>constant_pool</code> entry at that index must give the
36 cananian 1.1.2.1 constant value represented by this attribute. <p> The
37 cananian 1.1.2.1 <code>constant_pool</code> entry must be of a type appropriate
38 cananian 1.1.2.1 to the field. */
39 cananian 1.1.2.1 public int constantvalue_index;
40 cananian 1.1.2.1
41 cananian 1.1.2.1 /** Constructor. */
42 cananian 1.1.2.1 AttributeConstantValue(ClassFile parent, ClassDataInputStream in,
43 cananian 1.1.2.1 int attribute_name_index) throws java.io.IOException {
44 cananian 1.1.2.1 super(parent, attribute_name_index);
45 cananian 1.1.2.1 long attribute_length = in.read_u4();
46 cananian 1.1.2.1 if (attribute_length != 2)
47 cananian 1.1.2.1 throw new ClassDataException("ConstantValue attribute with length " +
48 cananian 1.1.2.1 attribute_length);
49 cananian 1.1.2.1
50 cananian 1.1.2.1 constantvalue_index = in.read_u2();
51 cananian 1.3 assert ATTRIBUTE_NAME.equals(attribute_name());
52 cananian 1.1.2.1 }
53 cananian 1.1.2.1 /** Constructor. */
54 cananian 1.1.2.1 public AttributeConstantValue(ClassFile parent, int attribute_name_index,
55 cananian 1.1.2.1 int constantvalue_index) {
56 cananian 1.1.2.1 super(parent, attribute_name_index);
57 cananian 1.1.2.1 this.constantvalue_index = constantvalue_index;
58 cananian 1.3 assert ATTRIBUTE_NAME.equals(attribute_name());
59 cananian 1.1.2.1 }
60 cananian 1.1.2.1
61 cananian 1.1.2.1 public long attribute_length() { return 2; }
62 cananian 1.1.2.1
63 cananian 1.1.2.1 // convenience.
64 cananian 1.1.2.1 public Constant constantvalue_index()
65 cananian 1.1.2.1 { return parent.constant_pool[constantvalue_index]; }
66 cananian 1.1.2.1
67 cananian 1.1.2.1 /** Write to bytecode stream. */
68 cananian 1.1.2.1 public void write(ClassDataOutputStream out) throws java.io.IOException {
69 cananian 1.1.2.1 out.write_u2(attribute_name_index);
70 cananian 1.1.2.1 out.write_u4(attribute_length());
71 cananian 1.1.2.1 out.write_u2(constantvalue_index);
72 cananian 1.1.2.1 }
73 cananian 1.1.2.1
74 cananian 1.1.2.1 /** Pretty-print the contents of this attribute.
75 cananian 1.1.2.1 * @param indent the indentation level to use.
76 cananian 1.1.2.1 */
77 cananian 1.1.2.1 public void print(java.io.PrintWriter pw, int indent) {
78 cananian 1.1.2.1 int in = indent;
79 cananian 1.1.2.1 indent(pw, in, "ConstantValue Attribute:");
80 cananian 1.1.2.1 indent(pw, in+1, "Value: " +
81 cananian 1.1.2.1 constantvalue_index().toString() + " {"+constantvalue_index+"}");
82 cananian 1.1.2.1 }
83 cananian 1.2 }