1 /*
2 * Copyright (c) 2017, 2020, Oracle and/or its affiliates. All rights reserved.
3 */
4 /*
5 * Licensed to the Apache Software Foundation (ASF) under one or more
6 * contributor license agreements. See the NOTICE file distributed with
7 * this work for additional information regarding copyright ownership.
8 * The ASF licenses this file to You under the Apache License, Version 2.0
9 * (the "License"); you may not use this file except in compliance with
10 * the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing, software
15 * distributed under the License is distributed on an "AS IS" BASIS,
16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17 * See the License for the specific language governing permissions and
18 * limitations under the License.
19 */
20 package com.sun.org.apache.bcel.internal.classfile;
21
22 import java.io.DataInput;
23 import java.io.DataOutputStream;
24 import java.io.IOException;
25 import java.util.Objects;
26
27 import com.sun.org.apache.bcel.internal.Const;
28 import com.sun.org.apache.bcel.internal.util.BCELComparator;
29
30 /**
31 * Abstract superclass for classes to represent the different constant types
32 * in the constant pool of a class file. The classes keep closely to
33 * the JVM specification.
34 *
35 * @LastModified: Jan 2020
36 */
37 public abstract class Constant implements Cloneable, Node {
38
39 private static BCELComparator bcelComparator = new BCELComparator() {
40
41 @Override
42 public boolean equals( final Object o1, final Object o2 ) {
43 final Constant THIS = (Constant) o1;
44 final Constant THAT = (Constant) o2;
45 return Objects.equals(THIS.toString(), THAT.toString());
46 }
47
48
49 @Override
50 public int hashCode( final Object o ) {
51 final Constant THIS = (Constant) o;
52 return THIS.toString().hashCode();
53 }
54 };
55
56 /* In fact this tag is redundant since we can distinguish different
57 * `Constant' objects by their type, i.e., via `instanceof'. In some
58 * places we will use the tag for switch()es anyway.
59 *
60 * First, we want match the specification as closely as possible. Second we
61 * need the tag as an index to select the corresponding class name from the
62 * `CONSTANT_NAMES' array.
63 */
64 private byte tag;
65
66 Constant(final byte tag) {
67 this.tag = tag;
68 }
69
70 /**
71 * Called by objects that are traversing the nodes of the tree implicitely
72 * defined by the contents of a Java class. I.e., the hierarchy of methods,
73 * fields, attributes, etc. spawns a tree of objects.
74 *
75 * @param v Visitor object
76 */
77 @Override
78 public abstract void accept( Visitor v );
79
80 public abstract void dump( DataOutputStream file ) throws IOException;
81
82 /**
83 * @return Tag of constant, i.e., its type. No setTag() method to avoid
84 * confusion.
85 */
86 public final byte getTag() {
87 return tag;
88 }
89
90 /**
91 * @return String representation.
92 */
93 @Override
94 public String toString() {
95 return Const.getConstantName(tag) + "[" + tag + "]";
96 }
97
98 /**
99 * @return deep copy of this constant
100 */
101 public Constant copy() {
102 try {
103 return (Constant) super.clone();
104 } catch (final CloneNotSupportedException e) {
105 // TODO should this throw?
106 }
107 return null;
108 }
109
110 @Override
111 public Object clone() {
112 try {
113 return super.clone();
114 } catch (final CloneNotSupportedException e) {
115 throw new Error("Clone Not Supported"); // never happens
116 }
117 }
118
119 /**
120 * Reads one constant from the given input, the type depends on a tag byte.
121 *
122 * @param dataInput Input stream
123 * @return Constant object
124 * @throws IOException if an I/O error occurs reading from the given {@code dataInput}.
125 * @throws ClassFormatException if the next byte is not recognized
126 * @since 6.0 made public
127 */
128 public static Constant readConstant(final DataInput dataInput) throws IOException, ClassFormatException {
129 final byte b = dataInput.readByte(); // Read tag byte
130 switch (b) {
131 case Const.CONSTANT_Class:
132 return new ConstantClass(dataInput);
133 case Const.CONSTANT_Fieldref:
134 return new ConstantFieldref(dataInput);
135 case Const.CONSTANT_Methodref:
136 return new ConstantMethodref(dataInput);
137 case Const.CONSTANT_InterfaceMethodref:
138 return new ConstantInterfaceMethodref(dataInput);
139 case Const.CONSTANT_String:
140 return new ConstantString(dataInput);
141 case Const.CONSTANT_Integer:
142 return new ConstantInteger(dataInput);
143 case Const.CONSTANT_Float:
144 return new ConstantFloat(dataInput);
145 case Const.CONSTANT_Long:
146 return new ConstantLong(dataInput);
147 case Const.CONSTANT_Double:
148 return new ConstantDouble(dataInput);
149 case Const.CONSTANT_NameAndType:
150 return new ConstantNameAndType(dataInput);
151 case Const.CONSTANT_Utf8:
152 return ConstantUtf8.getInstance(dataInput);
153 case Const.CONSTANT_MethodHandle:
154 return new ConstantMethodHandle(dataInput);
155 case Const.CONSTANT_MethodType:
156 return new ConstantMethodType(dataInput);
157 case Const.CONSTANT_Dynamic:
158 return new ConstantDynamic(dataInput);
159 case Const.CONSTANT_InvokeDynamic:
160 return new ConstantInvokeDynamic(dataInput);
161 case Const.CONSTANT_Module:
162 return new ConstantModule(dataInput);
163 case Const.CONSTANT_Package:
164 return new ConstantPackage(dataInput);
165 default:
166 throw new ClassFormatException("Invalid byte tag in constant pool: " + b);
167 }
168 }
169
170 /**
171 * @return Comparison strategy object
172 */
173 public static BCELComparator getComparator() {
174 return bcelComparator;
175 }
176
177 /**
178 * @param comparator Comparison strategy object
179 */
180 public static void setComparator( final BCELComparator comparator ) {
181 bcelComparator = comparator;
182 }
183
184 /**
185 * Returns value as defined by given BCELComparator strategy.
186 * By default two Constant objects are said to be equal when
187 * the result of toString() is equal.
188 *
189 * @see java.lang.Object#equals(java.lang.Object)
190 */
191 @Override
192 public boolean equals( final Object obj ) {
193 return bcelComparator.equals(this, obj);
194 }
195
196 /**
197 * Returns value as defined by given BCELComparator strategy.
198 * By default return the hashcode of the result of toString().
199 *
200 * @see java.lang.Object#hashCode()
201 */
202 @Override
203 public int hashCode() {
204 return bcelComparator.hashCode(this);
205 }
206 }