1 /* 2 * Copyright (c) 2012, 2015, 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. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 package jdk.vm.ci.meta; 24 25 import java.lang.invoke.MethodHandle; 26 27 /** 28 * Reflection operations on values represented as {@linkplain JavaConstant constants}. All methods 29 * in this interface require the VM to access the actual object encapsulated in 30 * {@link JavaKind#Object object} constants. This access is not always possible, depending on kind 31 * of VM and the state that the VM is in. Therefore, all methods can return {@code null} at any 32 * time, to indicate that the result is not available at this point. The caller is responsible to 33 * check for {@code null} results and handle them properly, e.g., not perform an optimization. 34 */ 35 public interface ConstantReflectionProvider { 36 37 /** 38 * Compares two constants for equality. The equality relationship is symmetric. Returns 39 * {@link Boolean#TRUE true} if the two constants represent the same run time value, 40 * {@link Boolean#FALSE false} if they are different. Returns {@code null} if the constants 41 * cannot be compared at this point. 42 */ constantEquals(Constant x, Constant y)43 Boolean constantEquals(Constant x, Constant y); 44 45 /** 46 * Returns the length of the array constant. Returns {@code null} if the constant is not an 47 * array, or if the array length is not available at this point. 48 */ readArrayLength(JavaConstant array)49 Integer readArrayLength(JavaConstant array); 50 51 /** 52 * Reads a value from the given array at the given index. Returns {@code null} if the constant 53 * is not an array, if the index is out of bounds, or if the value is not available at this 54 * point. 55 */ readArrayElement(JavaConstant array, int index)56 JavaConstant readArrayElement(JavaConstant array, int index); 57 58 /** 59 * Gets the current value of this field for a given object, if available. 60 * 61 * There is no guarantee that the same value will be returned by this method for a field unless 62 * the field is considered to be constant by the runtime. 63 * 64 * @param receiver object from which this field's value is to be read. This value is ignored if 65 * this field is static. 66 * @return the value of this field or {@code null} if the value is not available (e.g., because 67 * the field holder is not yet initialized). 68 */ readFieldValue(ResolvedJavaField field, JavaConstant receiver)69 JavaConstant readFieldValue(ResolvedJavaField field, JavaConstant receiver); 70 71 /** 72 * Converts the given {@link JavaKind#isPrimitive() primitive} constant to a boxed 73 * {@link JavaKind#Object object} constant, according to the Java boxing rules. Returns 74 * {@code null} if the source is is not a primitive constant, or the boxed value is not 75 * available at this point. 76 */ boxPrimitive(JavaConstant source)77 JavaConstant boxPrimitive(JavaConstant source); 78 79 /** 80 * Converts the given {@link JavaKind#Object object} constant to a {@link JavaKind#isPrimitive() 81 * primitive} constant, according to the Java unboxing rules. Returns {@code null} if the source 82 * is is not an object constant that can be unboxed, or the unboxed value is not available at 83 * this point. 84 */ unboxPrimitive(JavaConstant source)85 JavaConstant unboxPrimitive(JavaConstant source); 86 87 /** 88 * Gets a string as a {@link JavaConstant}. 89 */ forString(String value)90 JavaConstant forString(String value); 91 92 /** 93 * Returns the {@link ResolvedJavaType} for a {@link Class} object (or any other object regarded 94 * as a class by the VM) encapsulated in the given constant. Returns {@code null} if the 95 * constant does not encapsulate a class, or if the type is not available at this point. 96 */ asJavaType(Constant constant)97 ResolvedJavaType asJavaType(Constant constant); 98 99 /** 100 * Gets access to the internals of {@link MethodHandle}. 101 */ getMethodHandleAccess()102 MethodHandleAccessProvider getMethodHandleAccess(); 103 104 /** 105 * Gets raw memory access. 106 */ getMemoryAccessProvider()107 MemoryAccessProvider getMemoryAccessProvider(); 108 109 /** 110 * Gets the runtime representation of the {@link Class} object of this type. 111 */ asJavaClass(ResolvedJavaType type)112 JavaConstant asJavaClass(ResolvedJavaType type); 113 114 /** 115 * Gets the runtime representation of the "hub" of this type--that is, the closest part of the 116 * type representation which is typically stored in the object header. 117 */ asObjectHub(ResolvedJavaType type)118 Constant asObjectHub(ResolvedJavaType type); 119 } 120