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.*;
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 */
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 */
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 */
56 JavaConstant readArrayElement(JavaConstant array, int index);
57
58 /**
59 * Reads a value from the given array at the given index if it is a stable array. Returns
60 * {@code null} if the constant is not a stable array, if it is a default value, if the index is
61 * out of bounds, or if the value is not available at this point.
62 */
63 JavaConstant readConstantArrayElement(JavaConstant array, int index);
64
65 /**
66 * Reads a value from the given array at the given offset if it is a stable array. The offset
67 * will be decoded relative to the platform addressing into an index into the array. Returns
68 * {@code null} if the constant is not a stable array, if it is a default value, if the offset
69 * is out of bounds, or if the value is not available at this point.
70 */
71 JavaConstant readConstantArrayElementForOffset(JavaConstant array, long offset);
72
73 /**
74 * Gets the constant value of this field. Note that a {@code static final} field may not be
75 * considered constant if its declaring class is not yet initialized or if it is a well known
76 * field that can be updated via other means (e.g., {@link System#setOut(java.io.PrintStream)}).
77 *
78 * @param receiver object from which this field's value is to be read. This value is ignored if
79 * this field is static.
80 * @return the constant value of this field or {@code null} if this field is not considered
81 * constant by the runtime
82 */
83 JavaConstant readConstantFieldValue(JavaField field, JavaConstant receiver);
84
85 /**
86 * Gets the current value of this field for a given object, if available.
87 *
88 * There is no guarantee that the same value will be returned by this method for a field unless
89 * the field is considered to be {@linkplain #readConstantFieldValue(JavaField, JavaConstant)
90 * constant} by the runtime.
91 *
92 * @param receiver object from which this field's value is to be read. This value is ignored if
93 * this field is static.
94 * @return the value of this field or {@code null} if the value is not available (e.g., because
95 * the field holder is not yet initialized).
96 */
97 JavaConstant readFieldValue(JavaField field, JavaConstant receiver);
98
99 /**
100 * Gets the current value of this field for a given object, if available. Like
101 * {@link #readFieldValue(JavaField, JavaConstant)} but treats array fields as stable.
102 *
103 * There is no guarantee that the same value will be returned by this method for a field unless
104 * the field is considered to be {@linkplain #readConstantFieldValue(JavaField, JavaConstant)
105 * constant} by the runtime.
106 *
107 * @param receiver object from which this field's value is to be read. This value is ignored if
108 * this field is static.
109 * @param isDefaultStable if {@code true}, default values are considered stable
110 * @return the value of this field or {@code null} if the value is not available (e.g., because
111 * the field holder is not yet initialized).
112 */
113 JavaConstant readStableFieldValue(JavaField field, JavaConstant receiver, boolean isDefaultStable);
114
115 /**
116 * Converts the given {@link JavaKind#isPrimitive() primitive} constant to a boxed
117 * {@link JavaKind#Object object} constant, according to the Java boxing rules. Returns
118 * {@code null} if the source is is not a primitive constant, or the boxed value is not
119 * available at this point.
120 */
121 JavaConstant boxPrimitive(JavaConstant source);
122
123 /**
124 * Converts the given {@link JavaKind#Object object} constant to a
125 * {@link JavaKind#isPrimitive() primitive} constant, according to the Java unboxing rules.
126 * Returns {@code null} if the source is is not an object constant that can be unboxed, or the
127 * unboxed value is not available at this point.
128 */
129 JavaConstant unboxPrimitive(JavaConstant source);
130
131 /**
132 * Gets a string as a {@link JavaConstant}.
133 */
134 JavaConstant forString(String value);
135
136 /**
137 * Returns the {@link ResolvedJavaType} for a {@link Class} object (or any other object regarded
138 * as a class by the VM) encapsulated in the given constant. Returns {@code null} if the
139 * constant does not encapsulate a class, or if the type is not available at this point.
140 */
141 ResolvedJavaType asJavaType(Constant constant);
142
143 /**
144 * Check if the constant is embeddable in the code.
145 */
146 boolean isEmbeddable(Constant constant);
147
148 /**
149 * Gets access to the internals of {@link MethodHandle}.
150 */
151 MethodHandleAccessProvider getMethodHandleAccess();
152
153 /**
154 * Gets raw memory access.
155 */
156 MemoryAccessProvider getMemoryAccessProvider();
157 }