1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * https://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19
20 package org.apache.bcel.classfile;
21
22 import java.io.DataInput;
23 import java.io.DataOutputStream;
24 import java.io.IOException;
25
26 import org.apache.bcel.Const;
27 import org.apache.bcel.util.Args;
28
29 /**
30 * This class is derived from <em>Attribute</em> and indicates the main class of a module. There may be at most one
31 * ModuleMainClass attribute in a ClassFile structure.
32 *
33 * @see Attribute
34 */
35 public final class ModuleMainClass extends Attribute {
36
37 private int mainClassIndex;
38
39 /**
40 * Constructs object from input stream.
41 *
42 * @param nameIndex Index in constant pool.
43 * @param length Content length in bytes.
44 * @param input Input stream.
45 * @param constantPool Array of constants.
46 * @throws IOException Thrown if an I/O error occurs.
47 */
48 ModuleMainClass(final int nameIndex, final int length, final DataInput input, final ConstantPool constantPool) throws IOException {
49 this(nameIndex, length, 0, constantPool);
50 mainClassIndex = input.readUnsignedShort();
51 }
52
53 /**
54 * Constructs a new ModuleMainClass.
55 *
56 * @param nameIndex Index in constant pool.
57 * @param length Content length in bytes.
58 * @param mainClassIndex Host class index.
59 * @param constantPool Array of constants.
60 */
61 public ModuleMainClass(final int nameIndex, final int length, final int mainClassIndex, final ConstantPool constantPool) {
62 super(Const.ATTR_MODULE_MAIN_CLASS, nameIndex, length, constantPool);
63 this.mainClassIndex = Args.requireU2(mainClassIndex, "mainClassIndex");
64 }
65
66 /**
67 * Initialize from another object. Note that both objects use the same references (shallow copy). Use copy() for a
68 * physical copy.
69 *
70 * @param c Source to copy.
71 */
72 public ModuleMainClass(final ModuleMainClass c) {
73 this(c.getNameIndex(), c.getLength(), c.getHostClassIndex(), c.getConstantPool());
74 }
75
76 /**
77 * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class. I.e.,
78 * the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
79 *
80 * @param v Visitor object.
81 */
82 @Override
83 public void accept(final Visitor v) {
84 v.visitModuleMainClass(this);
85 }
86
87 /**
88 * @return deep copy of this attribute.
89 */
90 @Override
91 public Attribute copy(final ConstantPool constantPool) {
92 final ModuleMainClass c = (ModuleMainClass) clone();
93 c.setConstantPool(constantPool);
94 return c;
95 }
96
97 /**
98 * Dumps ModuleMainClass attribute to file stream in binary format.
99 *
100 * @param file Output file stream.
101 * @throws IOException Thrown if an I/O error occurs.
102 */
103 @Override
104 public void dump(final DataOutputStream file) throws IOException {
105 super.dump(file);
106 file.writeShort(mainClassIndex);
107 }
108
109 /**
110 * Gets the host class index.
111 *
112 * @return index into constant pool of host class name.
113 */
114 public int getHostClassIndex() {
115 return mainClassIndex;
116 }
117
118 /**
119 * Sets the host class index.
120 *
121 * @param mainClassIndex The host class index.
122 */
123 public void setHostClassIndex(final int mainClassIndex) {
124 this.mainClassIndex = mainClassIndex;
125 }
126
127 /**
128 * @return String representation.
129 */
130 @Override
131 public String toString() {
132 final StringBuilder buf = new StringBuilder();
133 buf.append("ModuleMainClass: ");
134 final String className = super.getConstantPool().getConstantString(mainClassIndex, Const.CONSTANT_Class);
135 buf.append(Utility.compactClassName(className, false));
136 return buf.toString();
137 }
138 }