1 /*
2 * reserved comment block
3 * DO NOT REMOVE OR ALTER!
4 */
5 package com.sun.org.apache.bcel.internal.classfile;
6
7 /* ====================================================================
8 * The Apache Software License, Version 1.1
9 *
10 * Copyright (c) 2001 The Apache Software Foundation. All rights
11 * reserved.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 *
17 * 1. Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 *
20 * 2. Redistributions in binary form must reproduce the above copyright
21 * notice, this list of conditions and the following disclaimer in
22 * the documentation and/or other materials provided with the
23 * distribution.
24 *
25 * 3. The end-user documentation included with the redistribution,
26 * if any, must include the following acknowledgment:
27 * "This product includes software developed by the
28 * Apache Software Foundation (http://www.apache.org/)."
29 * Alternately, this acknowledgment may appear in the software itself,
30 * if and wherever such third-party acknowledgments normally appear.
31 *
32 * 4. The names "Apache" and "Apache Software Foundation" and
33 * "Apache BCEL" must not be used to endorse or promote products
34 * derived from this software without prior written permission. For
35 * written permission, please contact apache@apache.org.
36 *
37 * 5. Products derived from this software may not be called "Apache",
38 * "Apache BCEL", nor may "Apache" appear in their name, without
39 * prior written permission of the Apache Software Foundation.
40 *
41 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
42 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
43 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
44 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
45 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
46 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
47 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
48 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
49 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
50 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
51 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
52 * SUCH DAMAGE.
53 * ====================================================================
54 *
55 * This software consists of voluntary contributions made by many
56 * individuals on behalf of the Apache Software Foundation. For more
57 * information on the Apache Software Foundation, please see
58 * <http://www.apache.org/>.
59 */
60
61 import com.sun.org.apache.bcel.internal.Constants;
62 import java.io.*;
63
64 /**
65 * Abstract superclass for classes to represent the different constant types
66 * in the constant pool of a class file. The classes keep closely to
67 * the JVM specification.
68 *
69 * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
70 */
71 public abstract class Constant implements Cloneable, Node, Serializable {
72 /* In fact this tag is redundant since we can distinguish different
73 * `Constant' objects by their type, i.e., via `instanceof'. In some
74 * places we will use the tag for switch()es anyway.
75 *
76 * First, we want match the specification as closely as possible. Second we
77 * need the tag as an index to select the corresponding class name from the
78 * `CONSTANT_NAMES' array.
79 */
80 protected byte tag;
81
82 Constant(byte tag) { this.tag = tag; }
83
84 /**
85 * Called by objects that are traversing the nodes of the tree implicitely
86 * defined by the contents of a Java class. I.e., the hierarchy of methods,
87 * fields, attributes, etc. spawns a tree of objects.
88 *
89 * @param v Visitor object
90 */
91 public abstract void accept(Visitor v);
92
93 public abstract void dump(DataOutputStream file) throws IOException;
94
95 /**
96 * @return Tag of constant, i.e., its type. No setTag() method to avoid
97 * confusion.
98 */
99 public final byte getTag() { return tag; }
100
101 /**
102 * @return String representation.
103 */
104 public String toString() {
105 return Constants.CONSTANT_NAMES[tag] + "[" + tag + "]";
106 }
107
108 /**
109 * @return deep copy of this constant
110 */
111 public Constant copy() {
112 try {
113 return (Constant)super.clone();
114 } catch(CloneNotSupportedException e) {}
115
116 return null;
117 }
118
119 public Object clone() throws CloneNotSupportedException {
120 return super.clone();
121 }
122
123 /**
124 * Read one constant from the given file, the type depends on a tag byte.
125 *
126 * @param file Input stream
127 * @return Constant object
128 */
129 static final Constant readConstant(DataInputStream file)
130 throws IOException, ClassFormatException
131 {
132 byte b = file.readByte(); // Read tag byte
133
134 switch(b) {
135 case Constants.CONSTANT_Class: return new ConstantClass(file);
136 case Constants.CONSTANT_Fieldref: return new ConstantFieldref(file);
137 case Constants.CONSTANT_Methodref: return new ConstantMethodref(file);
138 case Constants.CONSTANT_InterfaceMethodref: return new
139 ConstantInterfaceMethodref(file);
140 case Constants.CONSTANT_String: return new ConstantString(file);
141 case Constants.CONSTANT_Integer: return new ConstantInteger(file);
142 case Constants.CONSTANT_Float: return new ConstantFloat(file);
143 case Constants.CONSTANT_Long: return new ConstantLong(file);
144 case Constants.CONSTANT_Double: return new ConstantDouble(file);
145 case Constants.CONSTANT_NameAndType: return new ConstantNameAndType(file);
146 case Constants.CONSTANT_Utf8: return new ConstantUtf8(file);
147 default:
148 throw new ClassFormatException("Invalid byte tag in constant pool: " + b);
149 }
150 }
151 }