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.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 WritableField[] EMPTY_WRITABLE_FIELD_ARRAY = {};
48 static final ClassEntry[] EMPTY_CLASS_ENTRY_ARRAY = {};
49 final ClassEntry thisClassEntry;
50 private WritableField[] fields = EMPTY_WRITABLE_FIELD_ARRAY;
51 private Util.Writable[] methods = EMPTY_WRITABLE_ARRAY;
52 private int fieldsCount = 0;
53 private int methodsCount = 0;
54 private ClassEntry superclassEntry;
55 private List<ClassEntry> interfaceEntries;
56 private int majorVersion;
57 private int minorVersion;
58 private int flags;
59 private int sizeHint;
60
61 public DirectClassBuilder(SplitConstantPool constantPool,
62 ClassFileImpl context,
63 ClassEntry thisClass) {
64 super(constantPool, context);
65 this.thisClassEntry = AbstractPoolEntry.maybeClone(constantPool, thisClass);
66 this.flags = DEFAULT_CLASS_FLAGS;
67 this.superclassEntry = null;
68 this.interfaceEntries = Collections.emptyList();
69 this.majorVersion = ClassFile.latestMajorVersion();
70 this.minorVersion = ClassFile.latestMinorVersion();
71 }
72
73 @Override
74 public ClassBuilder with(ClassElement element) {
75 if (element instanceof AbstractElement ae) {
76 ae.writeTo(this);
77 } else {
78 writeAttribute((CustomAttribute<?>) requireNonNull(element));
79 }
80 return this;
81 }
82
83 @Override
84 public ClassBuilder withFlags(int flags) {
85 setFlags(flags);
86 return this;
87 }
88
89 @Override
90 public ClassBuilder withField(Utf8Entry name,
91 Utf8Entry descriptor,
92 int flags) {
93 return withField(new DirectFieldBuilder(constantPool, context, name, descriptor, flags, null));
94 }
95
96 @Override
97 public ClassBuilder withField(Utf8Entry name,
98 Utf8Entry descriptor,
99 Consumer<? super FieldBuilder> handler) {
100 return withField(new DirectFieldBuilder(constantPool, context, name, descriptor, 0, null)
101 .run(handler));
102 }
103
104 @Override
105 public ClassBuilder transformField(FieldModel field, FieldTransform transform) {
106 DirectFieldBuilder builder = new DirectFieldBuilder(constantPool, context, field.fieldName(),
107 field.fieldType(), 0, field);
108 builder.transform(field, transform);
109 return withField(builder);
110 }
111
112 @Override
113 public ClassBuilder withMethod(Utf8Entry name,
114 Utf8Entry descriptor,
115 int flags,
116 Consumer<? super MethodBuilder> handler) {
117 return withMethod(new DirectMethodBuilder(constantPool, context, name, descriptor, flags, null)
118 .run(handler));
119 }
120
121 @Override
122 public ClassBuilder transformMethod(MethodModel method, MethodTransform transform) {
123 DirectMethodBuilder builder = new DirectMethodBuilder(constantPool, context, method.methodName(),
124 method.methodType(),
125 method.flags().flagsMask(),
126 method);
127 builder.transform(method, transform);
128 return withMethod(builder);
129 }
130
131 // internal / for use by elements
132
133 ClassBuilder withField(WritableField field) {
134 if (fieldsCount >= fields.length) {
135 int newCapacity = fieldsCount + 8;
136 this.fields = Arrays.copyOf(fields, newCapacity);
137 }
138 fields[fieldsCount++] = field;
139 return this;
140 }
141
142 ClassBuilder withMethod(Util.Writable method) {
143 if (methodsCount >= methods.length) {
144 int newCapacity = methodsCount + 8;
145 this.methods = Arrays.copyOf(methods, newCapacity);
146 }
147 methods[methodsCount++] = method;
148 return this;
149 }
150
151 void setSuperclass(ClassEntry superclassEntry) {
152 this.superclassEntry = superclassEntry;
153 }
154
155 void setInterfaces(List<ClassEntry> interfaces) {
156 this.interfaceEntries = interfaces;
157 }
158
159 void setVersion(int major, int minor) {
160 this.majorVersion = major;
161 this.minorVersion = minor;
162 }
163
164 void setFlags(int flags) {
165 this.flags = flags;
166 }
167
168 public void setSizeHint(int sizeHint) {
169 this.sizeHint = sizeHint;
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 var strictInstanceFields = WritableField.filterStrictInstanceFields(constantPool, fields, fieldsCount);
199 tail.setStrictInstanceFields(strictInstanceFields);
200 Util.writeList(tail, methods, methodsCount);
201 int attributesOffset = tail.size();
202 attributes.writeTo(tail);
203
204 // Now we have to append the BSM, if there is one
205 if (constantPool.writeBootstrapMethods(tail)) {
206 // Update attributes count
207 tail.patchU2(attributesOffset, attributes.size() + 1);
208 }
209
210 // Now we can make the head
211 head.writeInt(ClassFile.MAGIC_NUMBER);
212 head.writeU2U2(minorVersion, majorVersion);
213 constantPool.writeTo(head);
214 head.writeU2U2U2(flags, head.cpIndex(thisClassEntry), head.cpIndexOrZero(superclass));
215 head.writeU2(interfaceEntriesSize);
216 for (int i = 0; i < interfaceEntriesSize; i++) {
217 head.writeIndex(ies[i]);
218 }
219
220 // Join head and tail into an exact-size buffer
221 return BufWriterImpl.join(head, tail);
222 }
223
224 private ClassEntry[] buildInterfaceEnties(int interfaceEntriesSize) {
225 var ies = new ClassEntry[interfaceEntriesSize];
226 for (int i = 0; i < interfaceEntriesSize; i++)
227 ies[i] = AbstractPoolEntry.maybeClone(constantPool, interfaceEntries.get(i));
228 return ies;
229 }
230 }