1 package org.apache.bcel.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 org.apache.bcel.Constants;
58 import java.io.*;
59
60 /***
61 * Abstract superclass for classes to represent the different constant types
62 * in the constant pool of a class file. The classes keep closely to
63 * the JVM specification.
64 *
65 * @version $Id: Constant.java,v 1.3 2002/07/11 19:39:04 mdahm Exp $
66 * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
67 */
68 public abstract class Constant implements Cloneable, Node, Serializable {
69 /* In fact this tag is redundant since we can distinguish different
70 * `Constant' objects by their type, i.e., via `instanceof'. In some
71 * places we will use the tag for switch()es anyway.
72 *
73 * First, we want match the specification as closely as possible. Second we
74 * need the tag as an index to select the corresponding class name from the
75 * `CONSTANT_NAMES' array.
76 */
77 protected byte tag;
78
79 Constant(byte tag) { this.tag = tag; }
80
81 /***
82 * Called by objects that are traversing the nodes of the tree implicitely
83 * defined by the contents of a Java class. I.e., the hierarchy of methods,
84 * fields, attributes, etc. spawns a tree of objects.
85 *
86 * @param v Visitor object
87 */
88 public abstract void accept(Visitor v);
89
90 public abstract void dump(DataOutputStream file) throws IOException;
91
92 /***
93 * @return Tag of constant, i.e., its type. No setTag() method to avoid
94 * confusion.
95 */
96 public final byte getTag() { return tag; }
97
98 /***
99 * @return String representation.
100 */
101 public String toString() {
102 return Constants.CONSTANT_NAMES[tag] + "[" + tag + "]";
103 }
104
105 /***
106 * @return deep copy of this constant
107 */
108 public Constant copy() {
109 try {
110 return (Constant)super.clone();
111 } catch(CloneNotSupportedException e) {}
112
113 return null;
114 }
115
116 public Object clone() throws CloneNotSupportedException {
117 return super.clone();
118 }
119
120 /***
121 * Read one constant from the given file, the type depends on a tag byte.
122 *
123 * @param file Input stream
124 * @return Constant object
125 */
126 static final Constant readConstant(DataInputStream file)
127 throws IOException, ClassFormatException
128 {
129 byte b = file.readByte(); // Read tag byte
130
131 switch(b) {
132 case Constants.CONSTANT_Class: return new ConstantClass(file);
133 case Constants.CONSTANT_Fieldref: return new ConstantFieldref(file);
134 case Constants.CONSTANT_Methodref: return new ConstantMethodref(file);
135 case Constants.CONSTANT_InterfaceMethodref: return new
136 ConstantInterfaceMethodref(file);
137 case Constants.CONSTANT_String: return new ConstantString(file);
138 case Constants.CONSTANT_Integer: return new ConstantInteger(file);
139 case Constants.CONSTANT_Float: return new ConstantFloat(file);
140 case Constants.CONSTANT_Long: return new ConstantLong(file);
141 case Constants.CONSTANT_Double: return new ConstantDouble(file);
142 case Constants.CONSTANT_NameAndType: return new ConstantNameAndType(file);
143 case Constants.CONSTANT_Utf8: return new ConstantUtf8(file);
144 default:
145 throw new ClassFormatException("Invalid byte tag in constant pool: " + b);
146 }
147 }
148 }
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