1 /*
2 * Copyright (c) 2022, 2025, 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.lang.classfile.ClassFile.PREVIEW_MINOR_VERSION;
39 import static java.util.Objects.requireNonNull;
40
41 public final class DirectClassBuilder
42 extends AbstractDirectBuilder<ClassModel>
43 implements ClassBuilder {
44
45 /** The value of default class access flags */
46 static final int DEFAULT_CLASS_FLAGS = ClassFile.ACC_PUBLIC | ClassFile.ACC_SUPER;
47 static final Util.Writable[] EMPTY_WRITABLE_ARRAY = {};
48 static final WritableField[] EMPTY_WRITABLE_FIELD_ARRAY = {};
49 static final ClassEntry[] EMPTY_CLASS_ENTRY_ARRAY = {};
50 final ClassEntry thisClassEntry;
51 private WritableField[] fields = EMPTY_WRITABLE_FIELD_ARRAY;
52 private Util.Writable[] methods = EMPTY_WRITABLE_ARRAY;
53 private int fieldsCount = 0;
54 private int methodsCount = 0;
55 private ClassEntry superclassEntry;
56 private List<ClassEntry> interfaceEntries;
57 private int majorVersion;
58 private int minorVersion;
59 private int flags;
60 private int sizeHint;
61
62 public DirectClassBuilder(SplitConstantPool constantPool,
63 ClassFileImpl context,
64 ClassEntry thisClass) {
65 super(constantPool, context);
66 this.thisClassEntry = AbstractPoolEntry.maybeClone(constantPool, thisClass);
67 this.flags = DEFAULT_CLASS_FLAGS;
68 this.superclassEntry = null;
69 this.interfaceEntries = Collections.emptyList();
70 this.majorVersion = ClassFile.latestMajorVersion();
71 this.minorVersion = ClassFile.latestMinorVersion();
72 }
73
74 @Override
75 public ClassBuilder with(ClassElement element) {
76 if (element instanceof AbstractElement ae) {
77 ae.writeTo(this);
78 } else {
79 writeAttribute((CustomAttribute<?>) requireNonNull(element));
80 }
81 return this;
82 }
83
84 @Override
85 public ClassBuilder withFlags(int flags) {
86 setFlags(Util.checkFlags(flags));
87 return this;
88 }
89
90 @Override
91 public ClassBuilder withField(Utf8Entry name,
92 Utf8Entry descriptor,
93 int flags) {
94 return withField(new DirectFieldBuilder(constantPool, context, name, descriptor, flags, null));
95 }
96
97 @Override
98 public ClassBuilder withField(Utf8Entry name,
99 Utf8Entry descriptor,
100 Consumer<? super FieldBuilder> handler) {
101 return withField(new DirectFieldBuilder(constantPool, context, name, descriptor, 0, null)
102 .run(handler));
103 }
104
105 @Override
106 public ClassBuilder transformField(FieldModel field, FieldTransform transform) {
107 DirectFieldBuilder builder = new DirectFieldBuilder(constantPool, context, field.fieldName(),
108 field.fieldType(), 0, field);
109 builder.transform(field, transform);
110 return withField(builder);
111 }
112
113 @Override
114 public ClassBuilder withMethod(Utf8Entry name,
115 Utf8Entry descriptor,
116 int flags,
117 Consumer<? super MethodBuilder> handler) {
118 return withMethod(new DirectMethodBuilder(constantPool, context, name, descriptor, flags, null)
119 .run(handler));
120 }
121
122 @Override
123 public ClassBuilder transformMethod(MethodModel method, MethodTransform transform) {
124 DirectMethodBuilder builder = new DirectMethodBuilder(constantPool, context, method.methodName(),
125 method.methodType(),
126 method.flags().flagsMask(),
127 method);
128 builder.transform(method, transform);
129 return withMethod(builder);
130 }
131
132 // internal / for use by elements
133
134 ClassBuilder withField(WritableField field) {
135 if (fieldsCount >= fields.length) {
136 int newCapacity = fieldsCount + 8;
137 this.fields = Arrays.copyOf(fields, newCapacity);
138 }
139 fields[fieldsCount++] = field;
140 return this;
141 }
142
143 ClassBuilder withMethod(Util.Writable method) {
144 if (methodsCount >= methods.length) {
145 int newCapacity = methodsCount + 8;
146 this.methods = Arrays.copyOf(methods, newCapacity);
147 }
148 methods[methodsCount++] = method;
149 return this;
150 }
151
152 void setSuperclass(ClassEntry superclassEntry) {
153 this.superclassEntry = superclassEntry;
154 }
155
156 void setInterfaces(List<ClassEntry> interfaces) {
157 this.interfaceEntries = interfaces;
158 }
159
160 void setVersion(int major, int minor) {
161 this.majorVersion = major;
162 this.minorVersion = minor;
163 }
164
165 void setFlags(int flags) {
166 this.flags = flags;
167 }
168
169 public void setSizeHint(int sizeHint) {
170 this.sizeHint = sizeHint;
171 }
172
173 public byte[] build() {
174
175 // The logic of this is very carefully ordered. We want to avoid
176 // repeated buffer copyings, so we accumulate lists of writers which
177 // all get written later into the same buffer. But, writing can often
178 // trigger CP / BSM insertions, so we cannot run the CP writer or
179 // BSM writers until everything else is written.
180
181 // Do this early because it might trigger CP activity
182 var constantPool = this.constantPool;
183 ClassEntry superclass = superclassEntry;
184 if (superclass != null)
185 superclass = AbstractPoolEntry.maybeClone(constantPool, superclass);
186 else if ((flags & ClassFile.ACC_MODULE) == 0 && !"java/lang/Object".equals(thisClassEntry.asInternalName()))
187 superclass = constantPool.classEntry(ConstantDescs.CD_Object);
188 int interfaceEntriesSize = interfaceEntries.size();
189 ClassEntry[] ies = interfaceEntriesSize == 0 ? EMPTY_CLASS_ENTRY_ARRAY : buildInterfaceEnties(interfaceEntriesSize);
190
191 // We maintain two writers, and then we join them at the end
192 int size = sizeHint == 0 ? 256 : sizeHint;
193 BufWriterImpl head = new BufWriterImpl(constantPool, context, size);
194 BufWriterImpl tail = new BufWriterImpl(constantPool, context, size, thisClassEntry, majorVersion);
195
196 // The tail consists of fields and methods, and attributes
197 // This should trigger all the CP/BSM mutation
198 Util.writeList(tail, fields, fieldsCount);
199 WritableField.UnsetField[] strictInstanceFields;
200 if (minorVersion == PREVIEW_MINOR_VERSION && majorVersion >= Util.VALUE_OBJECTS_MAJOR) {
201 strictInstanceFields = WritableField.filterStrictInstanceFields(constantPool, fields, fieldsCount);
202 } else {
203 strictInstanceFields = WritableField.UnsetField.EMPTY_ARRAY;
204 }
205 tail.setStrictInstanceFields(strictInstanceFields);
206 Util.writeList(tail, methods, methodsCount);
207 int attributesOffset = tail.size();
208 attributes.writeTo(tail);
209
210 // Now we have to append the BSM, if there is one
211 if (constantPool.writeBootstrapMethods(tail)) {
212 // Update attributes count
213 tail.patchU2(attributesOffset, attributes.size() + 1);
214 }
215
216 // Now we can make the head
217 head.writeInt(ClassFile.MAGIC_NUMBER);
218 head.writeU2U2(minorVersion, majorVersion);
219 constantPool.writeTo(head);
220 head.writeU2U2U2(flags, head.cpIndex(thisClassEntry), head.cpIndexOrZero(superclass));
221 head.writeU2(interfaceEntriesSize);
222 for (int i = 0; i < interfaceEntriesSize; i++) {
223 head.writeIndex(ies[i]);
224 }
225
226 // Join head and tail into an exact-size buffer
227 return BufWriterImpl.join(head, tail);
228 }
229
230 private ClassEntry[] buildInterfaceEnties(int interfaceEntriesSize) {
231 var ies = new ClassEntry[interfaceEntriesSize];
232 for (int i = 0; i < interfaceEntriesSize; i++)
233 ies[i] = AbstractPoolEntry.maybeClone(constantPool, interfaceEntries.get(i));
234 return ies;
235 }
236 }