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Java > Open Source Codes > com > sun > org > apache > bcel > internal > classfile > ConstantValue


1 package com.sun.org.apache.bcel.internal.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 com.sun.org.apache.bcel.internal.Constants;
58 import java.io.*;
59
60 /**
61  * This class is derived from <em>Attribute</em> and represents a constant
62  * value, i.e., a default value for initializing a class field.
63  * This class is instantiated by the <em>Attribute.readAttribute()</em> method.
64  *
65  * @version $Id: ConstantValue.java,v 1.1.1.1 2001/10/29 20:00:00 jvanzyl Exp $
66  * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
67  * @see Attribute
68  */
69 public final class ConstantValue extends Attribute {
70   private int constantvalue_index;
71
72   /**
73    * Initialize from another object. Note that both objects use the same
74    * references (shallow copy). Use clone() for a physical copy.
75    */
76   public ConstantValue(ConstantValue c) {
77     this(c.getNameIndex(), c.getLength(), c.getConstantValueIndex(),
78      c.getConstantPool());
79   }
80
81   /**
82    * Construct object from file stream.
83    * @param name_index Name index in constant pool
84    * @param length Content length in bytes
85    * @param file Input stream
86    * @param constant_pool Array of constants
87    * @throw IOException
88    */
89   ConstantValue(int name_index, int length, DataInputStream file,
90         ConstantPool constant_pool) throws IOException
91   {
92     this(name_index, length, (int)file.readUnsignedShort(), constant_pool);
93   }
94
95   /**
96    * @param name_index Name index in constant pool
97    * @param length Content length in bytes
98    * @param constantvalue_index Index in constant pool
99    * @param constant_pool Array of constants
100    */
101   public ConstantValue(int name_index, int length,
102                int constantvalue_index,
103                ConstantPool constant_pool)
104   {
105     super(Constants.ATTR_CONSTANT_VALUE, name_index, length, constant_pool);
106     this.constantvalue_index = constantvalue_index;
107   }
108
109   /**
110    * Called by objects that are traversing the nodes of the tree implicitely
111    * defined by the contents of a Java class. I.e., the hierarchy of methods,
112    * fields, attributes, etc. spawns a tree of objects.
113    *
114    * @param v Visitor object
115    */
116   public void accept(Visitor v) {
117     v.visitConstantValue(this);
118   }
119   /**
120    * Dump constant value attribute to file stream on binary format.
121    *
122    * @param file Output file stream
123    * @throw IOException
124    */
125   public final void dump(DataOutputStream file) throws IOException
126   {
127     super.dump(file);
128     file.writeShort(constantvalue_index);
129   }
130   /**
131    * @return Index in constant pool of constant value.
132    */
133   public final int getConstantValueIndex() { return constantvalue_index; }
134
135   /**
136    * @param constantvalue_index.
137    */
138   public final void setConstantValueIndex(int constantvalue_index) {
139     this.constantvalue_index = constantvalue_index;
140   }
141
142   /**
143    * @return String representation of constant value.
144    */
145   public final String JavaDoc toString() throws InternalError JavaDoc
146   {
147     Constant c = constant_pool.getConstant(constantvalue_index);
148     
149     String JavaDoc buf;
150     int i;
151
152     // Print constant to string depending on its type
153 switch(c.getTag()) {
154     case Constants.CONSTANT_Long: buf = "" + ((ConstantLong)c).getBytes(); break;
155     case Constants.CONSTANT_Float: buf = "" + ((ConstantFloat)c).getBytes(); break;
156     case Constants.CONSTANT_Double: buf = "" + ((ConstantDouble)c).getBytes(); break;
157     case Constants.CONSTANT_Integer: buf = "" + ((ConstantInteger)c).getBytes(); break;
158     case Constants.CONSTANT_String:
159       i = ((ConstantString)c).getStringIndex();
160       c = constant_pool.getConstant(i, Constants.CONSTANT_Utf8);
161       buf = "\"" + convertString(((ConstantUtf8)c).getBytes()) + "\"";
162       break;
163     default: throw new InternalError JavaDoc("Type of ConstValue invalid: " + c);
164     }
165
166     return buf;
167   }
168
169   /**
170    * Escape all occurences of newline chars '\n', quotes \", etc.
171    */
172   private static final String JavaDoc convertString(String JavaDoc label) {
173     char[] ch = label.toCharArray();
174     StringBuffer JavaDoc buf = new StringBuffer JavaDoc();
175
176     for(int i=0; i < ch.length; i++) {
177       switch(ch[i]) {
178       case '\n':
179     buf.append("\\n"); break;
180       case '\r':
181     buf.append("\\r"); break;
182       case '\"':
183     buf.append("\\\""); break;
184       case '\'':
185     buf.append("\\'"); break;
186       case '\\':
187     buf.append("\\\\"); break;
188       default:
189     buf.append(ch[i]); break;
190       }
191     }
192
193     return buf.toString();
194   }
195
196   /**
197    * @return deep copy of this attribute
198    */
199   public Attribute copy(ConstantPool constant_pool) {
200     ConstantValue c = (ConstantValue)clone();
201     c.constant_pool = constant_pool;
202     return c;
203   }
204 }
205
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