1/*
2 * Copyright (c) 2017, 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 */
20package com.sun.org.apache.bcel.internal.classfile;
21
22import java.io.DataInput;
23import java.io.DataOutputStream;
24import java.io.IOException;
25
26import com.sun.org.apache.bcel.internal.Const;
27import com.sun.org.apache.bcel.internal.util.BCELComparator;
28
29/**
30 * Abstract superclass for classes to represent the different constant types in
31 * the constant pool of a class file. The classes keep closely to the JVM
32 * specification.
33 *
34 * @version $Id: Constant.java 1749603 2016-06-21 20:50:19Z ggregory $
35 */
36public abstract class Constant implements Cloneable, Node {
37
38    private static BCELComparator bcelComparator = new BCELComparator() {
39
40        @Override
41        public boolean equals(final Object o1, final Object o2) {
42            final Constant THIS = (Constant) o1;
43            final Constant THAT = (Constant) o2;
44            return THIS.toString().equals(THAT.toString());
45        }
46
47        @Override
48        public int hashCode(final Object o) {
49            final Constant THIS = (Constant) o;
50            return THIS.toString().hashCode();
51        }
52    };
53
54    /* In fact this tag is redundant since we can distinguish different
55     * `Constant' objects by their type, i.e., via `instanceof'. In some
56     * places we will use the tag for switch()es anyway.
57     *
58     * First, we want match the specification as closely as possible. Second we
59     * need the tag as an index to select the corresponding class name from the
60     * `CONSTANT_NAMES' array.
61     */
62    private byte tag;
63
64    Constant(final byte tag) {
65        this.tag = tag;
66    }
67
68    /**
69     * Called by objects that are traversing the nodes of the tree implicitely
70     * defined by the contents of a Java class. I.e., the hierarchy of methods,
71     * fields, attributes, etc. spawns a tree of objects.
72     *
73     * @param v Visitor object
74     */
75    @Override
76    public abstract void accept(Visitor v);
77
78    public abstract void dump(DataOutputStream file) throws IOException;
79
80    /**
81     * @return Tag of constant, i.e., its type. No setTag() method to avoid
82     * confusion.
83     */
84    public final byte getTag() {
85        return tag;
86    }
87
88    /**
89     * @return String representation.
90     */
91    @Override
92    public String toString() {
93        return Const.getConstantName(tag) + "[" + tag + "]";
94    }
95
96    /**
97     * @return deep copy of this constant
98     */
99    public Constant copy() {
100        try {
101            return (Constant) super.clone();
102        } catch (final CloneNotSupportedException e) {
103            // TODO should this throw?
104        }
105        return null;
106    }
107
108    @Override
109    public Object clone() {
110        try {
111            return super.clone();
112        } catch (final CloneNotSupportedException e) {
113            throw new Error("Clone Not Supported"); // never happens
114        }
115    }
116
117    /**
118     * Read one constant from the given input, the type depends on a tag byte.
119     *
120     * @param input Input stream
121     * @return Constant object
122     * @since 6.0 made public
123     */
124    public static Constant readConstant(final DataInput input) throws IOException,
125            ClassFormatException {
126        final byte b = input.readByte(); // Read tag byte
127        switch (b) {
128            case Const.CONSTANT_Class:
129                return new ConstantClass(input);
130            case Const.CONSTANT_Fieldref:
131                return new ConstantFieldref(input);
132            case Const.CONSTANT_Methodref:
133                return new ConstantMethodref(input);
134            case Const.CONSTANT_InterfaceMethodref:
135                return new ConstantInterfaceMethodref(input);
136            case Const.CONSTANT_String:
137                return new ConstantString(input);
138            case Const.CONSTANT_Integer:
139                return new ConstantInteger(input);
140            case Const.CONSTANT_Float:
141                return new ConstantFloat(input);
142            case Const.CONSTANT_Long:
143                return new ConstantLong(input);
144            case Const.CONSTANT_Double:
145                return new ConstantDouble(input);
146            case Const.CONSTANT_NameAndType:
147                return new ConstantNameAndType(input);
148            case Const.CONSTANT_Utf8:
149                return ConstantUtf8.getInstance(input);
150            case Const.CONSTANT_MethodHandle:
151                return new ConstantMethodHandle(input);
152            case Const.CONSTANT_MethodType:
153                return new ConstantMethodType(input);
154            case Const.CONSTANT_InvokeDynamic:
155                return new ConstantInvokeDynamic(input);
156            default:
157                throw new ClassFormatException("Invalid byte tag in constant pool: " + b);
158        }
159    }
160
161    /**
162     * @return Comparison strategy object
163     */
164    public static BCELComparator getComparator() {
165        return bcelComparator;
166    }
167
168    /**
169     * @param comparator Comparison strategy object
170     */
171    public static void setComparator(final BCELComparator comparator) {
172        bcelComparator = comparator;
173    }
174
175    /**
176     * Return value as defined by given BCELComparator strategy. By default two
177     * Constant objects are said to be equal when the result of toString() is
178     * equal.
179     *
180     * @see java.lang.Object#equals(java.lang.Object)
181     */
182    @Override
183    public boolean equals(final Object obj) {
184        return bcelComparator.equals(this, obj);
185    }
186
187    /**
188     * Return value as defined by given BCELComparator strategy. By default
189     * return the hashcode of the result of toString().
190     *
191     * @see java.lang.Object#hashCode()
192     */
193    @Override
194    public int hashCode() {
195        return bcelComparator.hashCode(this);
196    }
197}
198