1 /* 2 * Copyright (c) 2023, 2025, 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.vm.annotation.IntrinsicCandidate; 32 33 import java.lang.reflect.Field; 34 import java.lang.reflect.Modifier; 35 36 /** 37 * Utilities to access package private methods of java.lang.Class and related reflection classes. 38 */ 39 public final class ValueClass { 40 private static final JavaLangReflectAccess JLRA = SharedSecrets.getJavaLangReflectAccess(); 41 42 /// {@return whether this field type may store value objects} 43 /// This excludes primitives and includes Object. 44 public static boolean isValueObjectCompatible(Class<?> fieldType) { 45 return PreviewFeatures.isEnabled() 46 && !fieldType.isPrimitive() // non-primitive 47 && (!fieldType.isIdentity() || fieldType == Object.class); // AVC or Object 48 } 49 50 /// {@return whether an object of this exact class is a value object} 51 /// This excludes abstract value classes and primitives. 52 public static boolean isConcreteValueClass(Class<?> clazz) { 53 return clazz.isValue() && !Modifier.isAbstract(clazz.getModifiers()); 54 } 55 56 /** 57 * {@return {@code true} if the field is NullRestricted} 58 */ 59 public static boolean isNullRestrictedField(Field f) { 60 return JLRA.isNullRestrictedField(f); 61 } 62 63 /** 64 * Allocate an array of a value class type with components that behave in 65 * the same way as a {@link jdk.internal.vm.annotation.NullRestricted} 66 * field. 67 * <p> 68 * Because these behaviors are not specified by Java SE, arrays created with 69 * this method should only be used by internal JDK code for experimental 70 * purposes and should not affect user-observable outcomes. 71 * 72 * @throws IllegalArgumentException if {@code componentType} is not a 73 * value class type. 74 */ 75 @IntrinsicCandidate 76 public static native Object[] newNullRestrictedAtomicArray(Class<?> componentType, 77 int length, Object initVal); 78 79 @IntrinsicCandidate 80 public static native Object[] newNullRestrictedNonAtomicArray(Class<?> componentType, 81 int length, Object initVal); 82 83 @IntrinsicCandidate 84 public static native Object[] newNullableAtomicArray(Class<?> componentType, 85 int length); 86 87 public static native boolean isFlatArray(Object array); 88 89 public static Object[] copyOfSpecialArray(Object[] array, int from, int to) { 90 return copyOfSpecialArray0(array, from, to); 91 } 92 93 private static native Object[] copyOfSpecialArray0(Object[] array, int from, int to); 94 95 /** 96 * {@return true if the given array is a null-restricted array} 97 */ 98 public static native boolean isNullRestrictedArray(Object array); 99 100 /** 101 * {@return true if the given array uses a layout designed for atomic accesses } 102 */ 103 public static native boolean isAtomicArray(Object array); 104 }