1 /*
2 * Copyright (c) 2022, 2024, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2024, Alibaba Group Holding Limited. All Rights Reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation. Oracle designates this
9 * particular file as subject to the "Classpath" exception as provided
10 * by Oracle in the LICENSE file that accompanied this code.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
23 * or visit www.oracle.com if you need additional information or have any
24 * questions.
25 */
26
27 package jdk.internal.classfile.impl;
28
29 import java.lang.classfile.*;
30 import java.lang.classfile.constantpool.ClassEntry;
31 import java.lang.classfile.constantpool.Utf8Entry;
32 import java.lang.constant.ConstantDescs;
33 import java.util.Arrays;
34 import java.util.Collections;
35 import java.util.List;
36 import java.util.function.Consumer;
37
38 import static java.util.Objects.requireNonNull;
39
40 public final class DirectClassBuilder
41 extends AbstractDirectBuilder<ClassModel>
42 implements ClassBuilder {
43
44 /** The value of default class access flags */
45 static final int DEFAULT_CLASS_FLAGS = ClassFile.ACC_PUBLIC;
46 static final Util.Writable[] EMPTY_WRITABLE_ARRAY = {};
47 static final ClassEntry[] EMPTY_CLASS_ENTRY_ARRAY = {};
48 final ClassEntry thisClassEntry;
49 private Util.Writable[] fields = EMPTY_WRITABLE_ARRAY;
50 private Util.Writable[] methods = EMPTY_WRITABLE_ARRAY;
51 private int fieldsCount = 0;
52 private int methodsCount = 0;
53 private ClassEntry superclassEntry;
54 private List<ClassEntry> interfaceEntries;
55 private int majorVersion;
56 private int minorVersion;
57 private int flags;
58 private int sizeHint;
59
60 public DirectClassBuilder(SplitConstantPool constantPool,
61 ClassFileImpl context,
62 ClassEntry thisClass) {
63 super(constantPool, context);
64 this.thisClassEntry = AbstractPoolEntry.maybeClone(constantPool, thisClass);
65 this.flags = DEFAULT_CLASS_FLAGS;
66 this.superclassEntry = null;
67 this.interfaceEntries = Collections.emptyList();
68 this.majorVersion = ClassFile.latestMajorVersion();
69 this.minorVersion = ClassFile.latestMinorVersion();
70 }
71
72 @Override
73 public ClassBuilder with(ClassElement element) {
74 if (element instanceof AbstractElement ae) {
75 ae.writeTo(this);
76 } else {
77 writeAttribute((CustomAttribute<?>) requireNonNull(element));
78 }
79 return this;
80 }
81
82 @Override
83 public ClassBuilder withFlags(int flags) {
84 setFlags(flags);
85 return this;
86 }
87
88 @Override
89 public ClassBuilder withField(Utf8Entry name,
90 Utf8Entry descriptor,
91 int flags) {
92 return withField(new DirectFieldBuilder(constantPool, context, name, descriptor, flags, null));
93 }
94
95 @Override
96 public ClassBuilder withField(Utf8Entry name,
97 Utf8Entry descriptor,
98 Consumer<? super FieldBuilder> handler) {
99 return withField(new DirectFieldBuilder(constantPool, context, name, descriptor, 0, null)
100 .run(handler));
101 }
102
103 @Override
104 public ClassBuilder transformField(FieldModel field, FieldTransform transform) {
105 DirectFieldBuilder builder = new DirectFieldBuilder(constantPool, context, field.fieldName(),
106 field.fieldType(), 0, field);
107 builder.transform(field, transform);
108 return withField(builder);
109 }
110
111 @Override
112 public ClassBuilder withMethod(Utf8Entry name,
113 Utf8Entry descriptor,
114 int flags,
115 Consumer<? super MethodBuilder> handler) {
116 return withMethod(new DirectMethodBuilder(constantPool, context, name, descriptor, flags, null)
117 .run(handler));
118 }
119
120 @Override
121 public ClassBuilder transformMethod(MethodModel method, MethodTransform transform) {
122 DirectMethodBuilder builder = new DirectMethodBuilder(constantPool, context, method.methodName(),
123 method.methodType(),
124 method.flags().flagsMask(),
125 method);
126 builder.transform(method, transform);
127 return withMethod(builder);
128 }
129
130 // internal / for use by elements
131
132 ClassBuilder withField(Util.Writable field) {
133 if (fieldsCount >= fields.length) {
134 int newCapacity = fieldsCount + 8;
135 this.fields = Arrays.copyOf(fields, newCapacity);
136 }
137 fields[fieldsCount++] = field;
138 return this;
139 }
140
141 ClassBuilder withMethod(Util.Writable method) {
142 if (methodsCount >= methods.length) {
143 int newCapacity = methodsCount + 8;
144 this.methods = Arrays.copyOf(methods, newCapacity);
145 }
146 methods[methodsCount++] = method;
147 return this;
148 }
149
150 void setSuperclass(ClassEntry superclassEntry) {
151 this.superclassEntry = superclassEntry;
152 }
153
154 void setInterfaces(List<ClassEntry> interfaces) {
155 this.interfaceEntries = interfaces;
156 }
157
158 void setVersion(int major, int minor) {
159 this.majorVersion = major;
160 this.minorVersion = minor;
161 }
162
163 void setFlags(int flags) {
164 this.flags = flags;
165 }
166
167 public void setSizeHint(int sizeHint) {
168 this.sizeHint = sizeHint;
169 }
170
171
172 public byte[] build() {
173
174 // The logic of this is very carefully ordered. We want to avoid
175 // repeated buffer copyings, so we accumulate lists of writers which
176 // all get written later into the same buffer. But, writing can often
177 // trigger CP / BSM insertions, so we cannot run the CP writer or
178 // BSM writers until everything else is written.
179
180 // Do this early because it might trigger CP activity
181 var constantPool = this.constantPool;
182 ClassEntry superclass = superclassEntry;
183 if (superclass != null)
184 superclass = AbstractPoolEntry.maybeClone(constantPool, superclass);
185 else if ((flags & ClassFile.ACC_MODULE) == 0 && !"java/lang/Object".equals(thisClassEntry.asInternalName()))
186 superclass = constantPool.classEntry(ConstantDescs.CD_Object);
187 int interfaceEntriesSize = interfaceEntries.size();
188 ClassEntry[] ies = interfaceEntriesSize == 0 ? EMPTY_CLASS_ENTRY_ARRAY : buildInterfaceEnties(interfaceEntriesSize);
189
190 // We maintain two writers, and then we join them at the end
191 int size = sizeHint == 0 ? 256 : sizeHint;
192 BufWriterImpl head = new BufWriterImpl(constantPool, context, size);
193 BufWriterImpl tail = new BufWriterImpl(constantPool, context, size, thisClassEntry, majorVersion);
194
195 // The tail consists of fields and methods, and attributes
196 // This should trigger all the CP/BSM mutation
197 Util.writeList(tail, fields, fieldsCount);
198 Util.writeList(tail, methods, methodsCount);
199 int attributesOffset = tail.size();
200 attributes.writeTo(tail);
201
202 // Now we have to append the BSM, if there is one
203 if (constantPool.writeBootstrapMethods(tail)) {
204 // Update attributes count
205 tail.patchU2(attributesOffset, attributes.size() + 1);
206 }
207
208 // Now we can make the head
209 head.writeInt(ClassFile.MAGIC_NUMBER);
210 head.writeU2U2(minorVersion, majorVersion);
211 constantPool.writeTo(head);
212 head.writeU2U2U2(flags, head.cpIndex(thisClassEntry), head.cpIndexOrZero(superclass));
213 head.writeU2(interfaceEntriesSize);
214 for (int i = 0; i < interfaceEntriesSize; i++) {
215 head.writeIndex(ies[i]);
216 }
217
218 // Join head and tail into an exact-size buffer
219 return BufWriterImpl.join(head, tail);
220 }
221
222 private ClassEntry[] buildInterfaceEnties(int interfaceEntriesSize) {
223 var ies = new ClassEntry[interfaceEntriesSize];
224 for (int i = 0; i < interfaceEntriesSize; i++)
225 ies[i] = AbstractPoolEntry.maybeClone(constantPool, interfaceEntries.get(i));
226 return ies;
227 }
228 }