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.lang.classfile.ClassFile.latestMajorVersion;
40 import static java.util.Objects.requireNonNull;
41
42 public final class DirectClassBuilder
43 extends AbstractDirectBuilder<ClassModel>
44 implements ClassBuilder {
45
46 /** The value of default class access flags */
47 static final int DEFAULT_CLASS_FLAGS = ClassFile.ACC_PUBLIC | ClassFile.ACC_SUPER;
48 static final Util.Writable[] EMPTY_WRITABLE_ARRAY = {};
49 static final WritableField[] EMPTY_WRITABLE_FIELD_ARRAY = {};
50 static final ClassEntry[] EMPTY_CLASS_ENTRY_ARRAY = {};
51 final ClassEntry thisClassEntry;
52 private WritableField[] fields = EMPTY_WRITABLE_FIELD_ARRAY;
53 private Util.Writable[] methods = EMPTY_WRITABLE_ARRAY;
54 private int fieldsCount = 0;
55 private int methodsCount = 0;
56 private ClassEntry superclassEntry;
57 private List<ClassEntry> interfaceEntries;
58 private int majorVersion;
59 private int minorVersion;
60 private int flags;
61 private int sizeHint;
62
63 public DirectClassBuilder(SplitConstantPool constantPool,
64 ClassFileImpl context,
65 ClassEntry thisClass) {
66 super(constantPool, context);
67 this.thisClassEntry = AbstractPoolEntry.maybeClone(constantPool, thisClass);
68 this.flags = DEFAULT_CLASS_FLAGS;
69 this.superclassEntry = null;
70 this.interfaceEntries = Collections.emptyList();
71 this.majorVersion = ClassFile.latestMajorVersion();
72 this.minorVersion = ClassFile.latestMinorVersion();
73 }
74
75 @Override
76 public ClassBuilder with(ClassElement element) {
77 if (element instanceof AbstractElement ae) {
78 ae.writeTo(this);
79 } else {
80 writeAttribute((CustomAttribute<?>) requireNonNull(element));
81 }
82 return this;
83 }
84
85 @Override
86 public ClassBuilder withFlags(int flags) {
87 setFlags(Util.checkFlags(flags));
88 return this;
89 }
90
91 @Override
92 public ClassBuilder withField(Utf8Entry name,
93 Utf8Entry descriptor,
94 int flags) {
95 return withField(new DirectFieldBuilder(constantPool, context, name, descriptor, flags, null));
96 }
97
98 @Override
99 public ClassBuilder withField(Utf8Entry name,
100 Utf8Entry descriptor,
101 Consumer<? super FieldBuilder> handler) {
102 return withField(new DirectFieldBuilder(constantPool, context, name, descriptor, 0, null)
103 .run(handler));
104 }
105
106 @Override
107 public ClassBuilder transformField(FieldModel field, FieldTransform transform) {
108 DirectFieldBuilder builder = new DirectFieldBuilder(constantPool, context, field.fieldName(),
109 field.fieldType(), 0, field);
110 builder.transform(field, transform);
111 return withField(builder);
112 }
113
114 @Override
115 public ClassBuilder withMethod(Utf8Entry name,
116 Utf8Entry descriptor,
117 int flags,
118 Consumer<? super MethodBuilder> handler) {
119 return withMethod(new DirectMethodBuilder(constantPool, context, name, descriptor, flags, null)
120 .run(handler));
121 }
122
123 @Override
124 public ClassBuilder transformMethod(MethodModel method, MethodTransform transform) {
125 DirectMethodBuilder builder = new DirectMethodBuilder(constantPool, context, method.methodName(),
126 method.methodType(),
127 method.flags().flagsMask(),
128 method);
129 builder.transform(method, transform);
130 return withMethod(builder);
131 }
132
133 // internal / for use by elements
134
135 ClassBuilder withField(WritableField field) {
136 if (fieldsCount >= fields.length) {
137 int newCapacity = fieldsCount + 8;
138 this.fields = Arrays.copyOf(fields, newCapacity);
139 }
140 fields[fieldsCount++] = field;
141 return this;
142 }
143
144 ClassBuilder withMethod(Util.Writable method) {
145 if (methodsCount >= methods.length) {
146 int newCapacity = methodsCount + 8;
147 this.methods = Arrays.copyOf(methods, newCapacity);
148 }
149 methods[methodsCount++] = method;
150 return this;
151 }
152
153 void setSuperclass(ClassEntry superclassEntry) {
154 this.superclassEntry = superclassEntry;
155 }
156
157 void setInterfaces(List<ClassEntry> interfaces) {
158 this.interfaceEntries = interfaces;
159 }
160
161 void setVersion(int major, int minor) {
162 this.majorVersion = major;
163 this.minorVersion = minor;
164 }
165
166 void setFlags(int flags) {
167 this.flags = flags;
168 }
169
170 public void setSizeHint(int sizeHint) {
171 this.sizeHint = sizeHint;
172 }
173
174 public byte[] build() {
175
176 // The logic of this is very carefully ordered. We want to avoid
177 // repeated buffer copyings, so we accumulate lists of writers which
178 // all get written later into the same buffer. But, writing can often
179 // trigger CP / BSM insertions, so we cannot run the CP writer or
180 // BSM writers until everything else is written.
181
182 // Do this early because it might trigger CP activity
183 var constantPool = this.constantPool;
184 ClassEntry superclass = superclassEntry;
185 if (superclass != null)
186 superclass = AbstractPoolEntry.maybeClone(constantPool, superclass);
187 else if ((flags & ClassFile.ACC_MODULE) == 0 && !"java/lang/Object".equals(thisClassEntry.asInternalName()))
188 superclass = constantPool.classEntry(ConstantDescs.CD_Object);
189 int interfaceEntriesSize = interfaceEntries.size();
190 ClassEntry[] ies = interfaceEntriesSize == 0 ? EMPTY_CLASS_ENTRY_ARRAY : buildInterfaceEnties(interfaceEntriesSize);
191
192 // We maintain two writers, and then we join them at the end
193 int size = sizeHint == 0 ? 256 : sizeHint;
194 BufWriterImpl head = new BufWriterImpl(constantPool, context, size);
195 BufWriterImpl tail = new BufWriterImpl(constantPool, context, size, thisClassEntry, majorVersion);
196
197 // The tail consists of fields and methods, and attributes
198 // This should trigger all the CP/BSM mutation
199 Util.writeList(tail, fields, fieldsCount);
200 WritableField.UnsetField[] strictInstanceFields;
201 if (minorVersion == PREVIEW_MINOR_VERSION && majorVersion >= Util.VALUE_OBJECTS_MAJOR) {
202 strictInstanceFields = WritableField.filterStrictInstanceFields(constantPool, fields, fieldsCount);
203 } else {
204 strictInstanceFields = WritableField.UnsetField.EMPTY_ARRAY;
205 }
206 tail.setStrictInstanceFields(strictInstanceFields);
207 Util.writeList(tail, methods, methodsCount);
208 int attributesOffset = tail.size();
209 attributes.writeTo(tail);
210
211 // Now we have to append the BSM, if there is one
212 if (constantPool.writeBootstrapMethods(tail)) {
213 // Update attributes count
214 tail.patchU2(attributesOffset, attributes.size() + 1);
215 }
216
217 // Now we can make the head
218 head.writeInt(ClassFile.MAGIC_NUMBER);
219 head.writeU2U2(minorVersion, majorVersion);
220 constantPool.writeTo(head);
221 head.writeU2U2U2(flags, head.cpIndex(thisClassEntry), head.cpIndexOrZero(superclass));
222 head.writeU2(interfaceEntriesSize);
223 for (int i = 0; i < interfaceEntriesSize; i++) {
224 head.writeIndex(ies[i]);
225 }
226
227 // Join head and tail into an exact-size buffer
228 return BufWriterImpl.join(head, tail);
229 }
230
231 private ClassEntry[] buildInterfaceEnties(int interfaceEntriesSize) {
232 var ies = new ClassEntry[interfaceEntriesSize];
233 for (int i = 0; i < interfaceEntriesSize; i++)
234 ies[i] = AbstractPoolEntry.maybeClone(constantPool, interfaceEntries.get(i));
235 return ies;
236 }
237 }