1 /*
2 * Copyright (c) 2023, 2024, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package jdk.internal.value;
27
28 import jdk.internal.access.JavaLangReflectAccess;
29 import jdk.internal.access.SharedSecrets;
30 import jdk.internal.misc.Unsafe;
31 import jdk.internal.vm.annotation.IntrinsicCandidate;
32
33 import java.lang.reflect.Array;
34 import java.lang.reflect.Field;
35
36 /**
37 * Utilities to access
38 */
39 public class ValueClass {
40 private static final Unsafe UNSAFE = Unsafe.getUnsafe();
41 private static final JavaLangReflectAccess JLRA = SharedSecrets.getJavaLangReflectAccess();
42
43 /**
44 * {@return true if the given {@code Class} object is implicitly constructible}
45 */
46 public static native boolean isImplicitlyConstructible(Class<?> cls);
47
48 /**
49 * {@return the default value of the given value class type}
50 *
51 * @throws IllegalArgumentException if {@code cls} is not a
52 * value class type or is not annotated with
53 * {@link jdk.internal.vm.annotation.ImplicitlyConstructible}
54 */
55 public static <T> T zeroInstance(Class<T> cls) {
56 if (!cls.isValue()) {
57 throw new IllegalArgumentException(cls.getName() + " not a value class");
58 }
59 if (!isImplicitlyConstructible(cls)) {
60 throw new IllegalArgumentException(cls.getName() + " not implicitly constructible");
61 }
62 UNSAFE.ensureClassInitialized(cls);
63 return UNSAFE.uninitializedDefaultValue(cls);
64 }
65
66 /**
67 * {@return {@code CheckedType} representing the type of the given field}
68 */
69 public static CheckedType checkedType(Field f) {
70 return JLRA.isNullRestrictedField(f) ? NullRestrictedCheckedType.of(f.getType())
71 : NormalCheckedType.of(f.getType());
72 }
73
74 /**
75 * {@return {@code CheckedType} representing the component type of the given array}
76 */
77 public static CheckedType componentCheckedType(Object array) {
78 Class<?> componentType = array.getClass().getComponentType();
79 return isNullRestrictedArray(array) ? NullRestrictedCheckedType.of(componentType)
80 : NormalCheckedType.of(componentType);
81 }
82
83 /**
84 * Allocate an array of a value class type with components that behave in
85 * the same way as a {@link jdk.internal.vm.annotation.NullRestricted}
86 * field.
87 * <p>
88 * Because these behaviors are not specified by Java SE, arrays created with
89 * this method should only be used by internal JDK code for experimental
90 * purposes and should not affect user-observable outcomes.
91 *
92 * @throws IllegalArgumentException if {@code componentType} is not a
93 * value class type or is not annotated with
94 * {@link jdk.internal.vm.annotation.ImplicitlyConstructible}
95 */
96 @SuppressWarnings("unchecked")
97 public static Object[] newArrayInstance(CheckedType componentType, int length) {
98 if (componentType instanceof NullRestrictedCheckedType) {
99 return newNullRestrictedArray(componentType.boundingClass(), length);
100 } else {
101 return (Object[]) Array.newInstance(componentType.boundingClass(), length);
102 }
103 }
104
105 /**
106 * Allocate an array of a value class type with components that behave in
107 * the same way as a {@link jdk.internal.vm.annotation.NullRestricted}
108 * field.
109 * <p>
110 * Because these behaviors are not specified by Java SE, arrays created with
111 * this method should only be used by internal JDK code for experimental
112 * purposes and should not affect user-observable outcomes.
113 *
114 * @throws IllegalArgumentException if {@code componentType} is not a
115 * value class type or is not annotated with
116 * {@link jdk.internal.vm.annotation.ImplicitlyConstructible}
117 */
118 @IntrinsicCandidate
119 public static native Object[] newNullRestrictedArray(Class<?> componentType,
120 int length);
121
122 /**
123 * {@return true if the given array is a null-restricted array}
124 */
125 public static native boolean isNullRestrictedArray(Object array);
126 }