1 /*
2 * Copyright (c) 2023, 2026, 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.PreviewFeatures;
31 import jdk.internal.misc.Unsafe;
32 import jdk.internal.vm.annotation.IntrinsicCandidate;
33
34 import java.lang.reflect.Field;
35 import java.lang.reflect.Modifier;
36
37 /**
38 * Utilities to access package private methods of java.lang.Class and related reflection classes.
39 */
40 public final class ValueClass {
41 private static final JavaLangReflectAccess JLRA = SharedSecrets.getJavaLangReflectAccess();
42
43 /// {@return whether this field type may store value objects}
44 /// This excludes primitives and includes Object.
45 public static boolean isValueObjectCompatible(Class<?> fieldType) {
46 return PreviewFeatures.isEnabled()
47 && !fieldType.isPrimitive() // non-primitive
48 && (!fieldType.isIdentity() || fieldType == Object.class); // AVC or Object
49 }
50
51 /// {@return whether an object of this exact class is a value object}
52 /// This excludes abstract value classes and primitives.
53 public static boolean isConcreteValueClass(Class<?> clazz) {
54 return clazz.isValue() && !Modifier.isAbstract(clazz.getModifiers());
55 }
56
57 /// {@return whether a field of type `c` can be represented with a payload
58 /// without oops} For example, primitive type fields and value classes with
59 /// all primitive fields recursively may be represented by a payload of a
60 /// layout without oops. Returns false if there is no flat layout for a
61 /// field of type `c`.
62 public static boolean hasBinaryPayload(Class<?> c) {
63 // non-concrete value class type field always a reference
64 if (!ValueClass.isConcreteValueClass(c))
65 return c.isPrimitive();
66 // Check the flat layout
67 return Unsafe.getUnsafe().isFlatPayloadBinary(c);
68 }
69
70 /**
71 * {@return {@code true} if the field is NullRestricted}
72 */
73 public static boolean isNullRestrictedField(Field f) {
74 return JLRA.isNullRestrictedField(f);
75 }
76
77 /**
78 * Allocate an array of a value class type with components that behave in
79 * the same way as a {@link jdk.internal.vm.annotation.NullRestricted}
80 * field.
81 * <p>
82 * Because these behaviors are not specified by Java SE, arrays created with
83 * this method should only be used by internal JDK code for experimental
84 * purposes and should not affect user-observable outcomes.
85 *
86 * @throws IllegalArgumentException if {@code componentType} is not a
87 * value class type.
88 */
89 @IntrinsicCandidate
90 public static native Object[] newNullRestrictedAtomicArray(Class<?> componentType,
91 int length, Object initVal);
92
93 @IntrinsicCandidate
94 public static native Object[] newNullRestrictedNonAtomicArray(Class<?> componentType,
95 int length, Object initVal);
96
97 @IntrinsicCandidate
98 public static native Object[] newNullableAtomicArray(Class<?> componentType,
99 int length);
100
101 public static native Object[] newReferenceArray(Class<?> componentType,
102 int length);
103
104 /**
105 * {@return true if the given array is a flat array}
106 */
107 @IntrinsicCandidate
108 public static native boolean isFlatArray(Object array);
109
110 public static Object[] copyOfSpecialArray(Object[] array, int newLength) {
111 if (newLength < 0) {
112 throw new NegativeArraySizeException("" + newLength);
113 }
114 return copyOfSpecialArray0(array, 0, newLength);
115 }
116
117 public static Object[] copyOfRangeSpecialArray(Object[] array, int from, int to) {
118 int length = array.length;
119 if (from < 0 || from > length) {
120 throw new ArrayIndexOutOfBoundsException("source index " + from + " out of bounds for object array[" + length + "]");
121 }
122 if (from > to) {
123 throw new IllegalArgumentException(from + " > " + to);
124 }
125 return copyOfSpecialArray0(array, from, to);
126 }
127
128 private static native Object[] copyOfSpecialArray0(Object[] array, int from, int to);
129
130 /**
131 * {@return true if the given array is a null-restricted array}
132 */
133 @IntrinsicCandidate
134 public static native boolean isNullRestrictedArray(Object array);
135
136 /**
137 * {@return true if the given array uses a layout designed for atomic accesses }
138 */
139 @IntrinsicCandidate
140 public static native boolean isAtomicArray(Object array);
141 }