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Java > Open Source Codes > com > vladium > jcd > cls > attribute > LineNumberTableAttribute_info


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: LineNumberTableAttribute_info.java,v 1.1.1.1 2004/05/09 16:57:48 vlad_r Exp $
8  */
9 package com.vladium.jcd.cls.attribute;
10
11 import java.io.IOException JavaDoc;
12 import java.util.ArrayList JavaDoc;
13 import java.util.List JavaDoc;
14
15 import com.vladium.jcd.lib.UDataInputStream;
16 import com.vladium.jcd.lib.UDataOutputStream;
17
18 // ----------------------------------------------------------------------------
19 /**
20  * The LineNumberTable attribute is an optional variable-length attribute in
21  * the attributes table of a {@link CodeAttribute_info} attribute. It may be
22  * used by debuggers to determine which part of the JVM code array corresponds
23  * to a given line number in the original source file. If LineNumberTable
24  * attributes are present in the attributes table of a given Code attribute,
25  * then they may appear in any order. Furthermore, multiple LineNumberTable
26  * attributes may together represent a given line of a source file; that is,
27  * LineNumberTable attributes need not be one-to-one with source lines.<P>
28  *
29  * The LineNumberTable attribute has the following format:
30  * <PRE>
31  * LineNumberTable_attribute {
32  * u2 attribute_name_index;
33  * u4 attribute_length;
34  * u2 line_number_table_length;
35  * { u2 start_pc;
36  * u2 line_number;
37  * } line_number_table[line_number_table_length];
38  * }
39  * <PRE>
40  *
41  * LineNumberTable_attribute structure contains the following items:
42  * <PRE>
43  * line_number_table_length
44  * </PRE>
45  * The value of the line_number_table_length item indicates the number of
46  * entries in the line_number_table array.
47  * <PRE>
48  * line_number_table[]
49  * </PRE>
50  * Each entry in the line_number_table array indicates that the line number
51  * in the original source file changes at a given point in the code array.<P>
52  *
53  * Each line_number_table entry must contain the following two items:
54  * <PRE>
55  * start_pc
56  * </PRE>
57  * The value of the start_pc item must indicate the index into the code array
58  * at which the code for a new line in the original source file begins. The
59  * value of start_pc must be less than the value of the code_length item of
60  * the {@link CodeAttribute_info} attribute of which this LineNumberTable
61  * is an attribute.<P>
62  * <PRE>
63  * line_number
64  * </PRE>
65  * The value of the line_number item must give the corresponding line number
66  * in the original source file.
67  *
68  * @author Vlad Roubtsov, (C) 2003
69  */
70 public
71 final class LineNumberTableAttribute_info extends Attribute_info
72 {
73     // public: ................................................................
74
75     // ACCESSORS:
76
77     /**
78      * Returns {@link LineNumber_info} descriptor at a given offset.
79      *
80      * @param offset line number entry offset [must be in [0, size()) range;
81      * input not checked]
82      * @return LineNumber_info descriptor [never null]
83      *
84      * @throws IndexOutOfBoundsException if 'offset' is outside of valid range
85      */
86     public LineNumber_info get (final int offset)
87     {
88         return (LineNumber_info) m_lines.get (offset);
89     }
90     
91     /**
92      * Returns the number of descriptors in this collection [can be 0].
93      */
94     public int size ()
95     {
96         return m_lines.size ();
97     }
98     
99     public long length ()
100     {
101         return 8 + (m_lines.size () << 2); // use size() if class becomes non-final
102 }
103     
104     // Visitor:
105
106     public void accept (final IAttributeVisitor visitor, final Object JavaDoc ctx)
107     {
108         visitor.visit (this, ctx);
109     }
110     
111     public String JavaDoc toString ()
112     {
113         final StringBuffer JavaDoc s = new StringBuffer JavaDoc ("LineNumberTableAttribute_info: [attribute_name_index = " + m_name_index + ", attribute_length = " + length () + "]\n");
114
115         for (int l = 0; l < size (); ++ l)
116         {
117             s.append (" " + get (l));
118             s.append ("\n"); // TODO: proper EOL const
119 }
120         
121         return s.toString ();
122     }
123     
124     // Cloneable:
125
126     /**
127      * Performs a deep copy.
128      */
129     public Object JavaDoc clone ()
130     {
131         final LineNumberTableAttribute_info _clone = (LineNumberTableAttribute_info) super.clone ();
132         
133         // do deep copy:
134 final int lines_count = m_lines.size (); // use size() if class becomes non-final
135 _clone.m_lines = new ArrayList JavaDoc (lines_count);
136         for (int e = 0; e < lines_count; ++ e)
137         {
138             _clone.m_lines.add (((LineNumber_info) m_lines.get (e)).clone ());
139         }
140         
141         return _clone;
142     }
143
144     // IClassFormatOutput:
145
146     public void writeInClassFormat (final UDataOutputStream out) throws IOException JavaDoc
147     {
148         super.writeInClassFormat (out);
149         
150         final int lines_count = m_lines.size (); // use size() if class becomes non-final
151 out.writeU2 (lines_count);
152         
153         for (int l = 0; l < lines_count; ++ l)
154         {
155             ((LineNumber_info) m_lines.get (l)).writeInClassFormat (out);
156         }
157     }
158     
159     // protected: .............................................................
160
161     // package: ...............................................................
162
163
164     LineNumberTableAttribute_info (final int attribute_name_index, final long attribute_length,
165                                    final UDataInputStream bytes)
166         throws IOException JavaDoc
167     {
168         super (attribute_name_index, attribute_length);
169         
170         final int lines_count = bytes.readU2 ();
171         m_lines = new ArrayList JavaDoc (lines_count);
172         
173         for (int i = 0; i < lines_count; i++)
174         {
175             m_lines.add (new LineNumber_info (bytes));
176         }
177     }
178     
179     // private: ...............................................................
180
181     
182     private List JavaDoc/* LineNumber_info */ m_lines; // never null
183
184 } // end of class
185 // ----------------------------------------------------------------------------
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