1 /*
2 * Copyright (c) 2014, 2023, 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
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24 */
25
26 package java.lang.invoke;
27
28 import java.lang.constant.ClassDesc;
29 import java.lang.constant.Constable;
30 import java.lang.constant.ConstantDesc;
31 import java.lang.constant.ConstantDescs;
32 import java.lang.constant.DirectMethodHandleDesc;
33 import java.lang.constant.DynamicConstantDesc;
34 import java.util.List;
35 import java.util.Objects;
36 import java.util.Optional;
37
38 import jdk.internal.vm.annotation.DontInline;
39 import jdk.internal.vm.annotation.ForceInline;
40 import jdk.internal.vm.annotation.IntrinsicCandidate;
41 import jdk.internal.vm.annotation.Stable;
42
43 import static java.lang.invoke.MethodHandleStatics.UNSAFE;
44
45 /**
46 * A VarHandle is a dynamically strongly typed reference to a variable, or to a
47 * parametrically-defined family of variables, including static fields,
48 * non-static fields, array elements, or components of an off-heap data
49 * structure. Access to such variables is supported under various
50 * <em>access modes</em>, including plain read/write access, volatile
51 * read/write access, and compare-and-set.
52 *
53 * <p>VarHandles are immutable and have no visible state. VarHandles cannot be
54 * subclassed by the user.
55 *
56 * <p>A VarHandle has:
57 * <ul>
58 * <li>a {@link #varType variable type} T, the type of every variable referenced
59 * by this VarHandle; and
60 * <li>a list of {@link #coordinateTypes coordinate types}
61 * {@code CT1, CT2, ..., CTn}, the types of <em>coordinate expressions</em> that
62 * jointly locate a variable referenced by this VarHandle.
63 * </ul>
64 * Variable and coordinate types may be primitive or reference, and are
65 * represented by {@code Class} objects. The list of coordinate types may be
66 * empty.
67 *
68 * <p>Factory methods that produce or {@link java.lang.invoke.MethodHandles.Lookup
69 * lookup} VarHandle instances document the supported variable type and the list
70 * of coordinate types.
71 *
72 * <p>Each access mode is associated with one <em>access mode method</em>, a
73 * <a href="MethodHandle.html#sigpoly">signature polymorphic</a> method named
74 * for the access mode. When an access mode method is invoked on a VarHandle
75 * instance, the initial arguments to the invocation are coordinate expressions
76 * that indicate in precisely which object the variable is to be accessed.
77 * Trailing arguments to the invocation represent values of importance to the
78 * access mode. For example, the various compare-and-set or compare-and-exchange
79 * access modes require two trailing arguments for the variable's expected value
80 * and new value.
81 *
82 * <p>The arity and types of arguments to the invocation of an access mode
83 * method are not checked statically. Instead, each access mode method
84 * specifies an {@link #accessModeType(AccessMode) access mode type},
85 * represented as an instance of {@link MethodType}, that serves as a kind of
86 * method signature against which the arguments are checked dynamically. An
87 * access mode type gives formal parameter types in terms of the coordinate
88 * types of a VarHandle instance and the types for values of importance to the
89 * access mode. An access mode type also gives a return type, often in terms of
90 * the variable type of a VarHandle instance. When an access mode method is
91 * invoked on a VarHandle instance, the symbolic type descriptor at the
92 * call site, the run time types of arguments to the invocation, and the run
93 * time type of the return value, must <a href="#invoke">match</a> the types
94 * given in the access mode type. A runtime exception will be thrown if the
95 * match fails.
96 *
97 * For example, the access mode method {@link #compareAndSet} specifies that if
98 * its receiver is a VarHandle instance with coordinate types
99 * {@code CT1, ..., CTn} and variable type {@code T}, then its access mode type
100 * is {@code (CT1 c1, ..., CTn cn, T expectedValue, T newValue)boolean}.
101 * Suppose that a VarHandle instance can access array elements, and that its
102 * coordinate types are {@code String[]} and {@code int} while its variable type
103 * is {@code String}. The access mode type for {@code compareAndSet} on this
104 * VarHandle instance would be
105 * {@code (String[] c1, int c2, String expectedValue, String newValue)boolean}.
106 * Such a VarHandle instance may be produced by the
107 * {@link MethodHandles#arrayElementVarHandle(Class) array factory method} and
108 * access array elements as follows:
109 * <pre> {@code
110 * String[] sa = ...
111 * VarHandle avh = MethodHandles.arrayElementVarHandle(String[].class);
112 * boolean r = avh.compareAndSet(sa, 10, "expected", "new");
113 * }</pre>
114 *
115 * <p>Access modes control atomicity and consistency properties.
116 * <em>Plain</em> read ({@code get}) and write ({@code set})
117 * accesses are guaranteed to be bitwise atomic only for references
118 * and for primitive values of at most 32 bits, and impose no observable
119 * ordering constraints with respect to threads other than the
120 * executing thread. <em>Opaque</em> operations are bitwise atomic and
121 * coherently ordered with respect to accesses to the same variable.
122 * In addition to obeying Opaque properties, <em>Acquire</em> mode
123 * reads and their subsequent accesses are ordered after matching
124 * <em>Release</em> mode writes and their previous accesses. In
125 * addition to obeying Acquire and Release properties, all
126 * <em>Volatile</em> operations are totally ordered with respect to
127 * each other.
128 *
129 * <p>Access modes are grouped into the following categories:
130 * <ul>
131 * <li>read access modes that get the value of a variable under specified
132 * memory ordering effects.
133 * The set of corresponding access mode methods belonging to this group
134 * consists of the methods
135 * {@link #get get},
136 * {@link #getVolatile getVolatile},
137 * {@link #getAcquire getAcquire},
138 * {@link #getOpaque getOpaque}.
139 * <li>write access modes that set the value of a variable under specified
140 * memory ordering effects.
141 * The set of corresponding access mode methods belonging to this group
142 * consists of the methods
143 * {@link #set set},
144 * {@link #setVolatile setVolatile},
145 * {@link #setRelease setRelease},
146 * {@link #setOpaque setOpaque}.
147 * <li>atomic update access modes that, for example, atomically compare and set
148 * the value of a variable under specified memory ordering effects.
149 * The set of corresponding access mode methods belonging to this group
150 * consists of the methods
151 * {@link #compareAndSet compareAndSet},
152 * {@link #weakCompareAndSetPlain weakCompareAndSetPlain},
153 * {@link #weakCompareAndSet weakCompareAndSet},
154 * {@link #weakCompareAndSetAcquire weakCompareAndSetAcquire},
155 * {@link #weakCompareAndSetRelease weakCompareAndSetRelease},
156 * {@link #compareAndExchangeAcquire compareAndExchangeAcquire},
157 * {@link #compareAndExchange compareAndExchange},
158 * {@link #compareAndExchangeRelease compareAndExchangeRelease},
159 * {@link #getAndSet getAndSet},
160 * {@link #getAndSetAcquire getAndSetAcquire},
161 * {@link #getAndSetRelease getAndSetRelease}.
162 * <li>numeric atomic update access modes that, for example, atomically get and
163 * set with addition the value of a variable under specified memory ordering
164 * effects.
165 * The set of corresponding access mode methods belonging to this group
166 * consists of the methods
167 * {@link #getAndAdd getAndAdd},
168 * {@link #getAndAddAcquire getAndAddAcquire},
169 * {@link #getAndAddRelease getAndAddRelease},
170 * <li>bitwise atomic update access modes that, for example, atomically get and
171 * bitwise OR the value of a variable under specified memory ordering
172 * effects.
173 * The set of corresponding access mode methods belonging to this group
174 * consists of the methods
175 * {@link #getAndBitwiseOr getAndBitwiseOr},
176 * {@link #getAndBitwiseOrAcquire getAndBitwiseOrAcquire},
177 * {@link #getAndBitwiseOrRelease getAndBitwiseOrRelease},
178 * {@link #getAndBitwiseAnd getAndBitwiseAnd},
179 * {@link #getAndBitwiseAndAcquire getAndBitwiseAndAcquire},
180 * {@link #getAndBitwiseAndRelease getAndBitwiseAndRelease},
181 * {@link #getAndBitwiseXor getAndBitwiseXor},
182 * {@link #getAndBitwiseXorAcquire getAndBitwiseXorAcquire},
183 * {@link #getAndBitwiseXorRelease getAndBitwiseXorRelease}.
184 * </ul>
185 *
186 * <p>Factory methods that produce or {@link java.lang.invoke.MethodHandles.Lookup
187 * lookup} VarHandle instances document the set of access modes that are
188 * supported, which may also include documenting restrictions based on the
189 * variable type and whether a variable is read-only. If an access mode is not
190 * supported then the corresponding access mode method will on invocation throw
191 * an {@code UnsupportedOperationException}. Factory methods should document
192 * any additional undeclared exceptions that may be thrown by access mode
193 * methods.
194 * The {@link #get get} access mode is supported for all
195 * VarHandle instances and the corresponding method never throws
196 * {@code UnsupportedOperationException}.
197 * If a VarHandle references a read-only variable (for example a {@code final}
198 * field) then write, atomic update, numeric atomic update, and bitwise atomic
199 * update access modes are not supported and corresponding methods throw
200 * {@code UnsupportedOperationException}.
201 * Read/write access modes (if supported), with the exception of
202 * {@code get} and {@code set}, provide atomic access for
203 * reference types and all primitive types.
204 * Unless stated otherwise in the documentation of a factory method, the access
205 * modes {@code get} and {@code set} (if supported) provide atomic access for
206 * reference types and all primitives types, with the exception of {@code long}
207 * and {@code double} on 32-bit platforms.
208 *
209 * <p>Access modes will override any memory ordering effects specified at
210 * the declaration site of a variable. For example, a VarHandle accessing
211 * a field using the {@code get} access mode will access the field as
212 * specified <em>by its access mode</em> even if that field is declared
213 * {@code volatile}. When mixed access is performed extreme care should be
214 * taken since the Java Memory Model may permit surprising results.
215 *
216 * <p>In addition to supporting access to variables under various access modes,
217 * a set of static methods, referred to as memory fence methods, is also
218 * provided for fine-grained control of memory ordering.
219 *
220 * The Java Language Specification permits other threads to observe operations
221 * as if they were executed in orders different than are apparent in program
222 * source code, subject to constraints arising, for example, from the use of
223 * locks, {@code volatile} fields or VarHandles. The static methods,
224 * {@link #fullFence fullFence}, {@link #acquireFence acquireFence},
225 * {@link #releaseFence releaseFence}, {@link #loadLoadFence loadLoadFence} and
226 * {@link #storeStoreFence storeStoreFence}, can also be used to impose
227 * constraints. Their specifications, as is the case for certain access modes,
228 * are phrased in terms of the lack of "reorderings" -- observable ordering
229 * effects that might otherwise occur if the fence was not present. More
230 * precise phrasing of the specification of access mode methods and memory fence
231 * methods may accompany future updates of the Java Language Specification.
232 *
233 * <h2>Compiling invocation of access mode methods</h2>
234 * A Java method call expression naming an access mode method can invoke a
235 * VarHandle from Java source code. From the viewpoint of source code, these
236 * methods can take any arguments and their polymorphic result (if expressed)
237 * can be cast to any return type. Formally this is accomplished by giving the
238 * access mode methods variable arity {@code Object} arguments and
239 * {@code Object} return types (if the return type is polymorphic), but they
240 * have an additional quality called <em>signature polymorphism</em> which
241 * connects this freedom of invocation directly to the JVM execution stack.
242 * <p>
243 * As is usual with virtual methods, source-level calls to access mode methods
244 * compile to an {@code invokevirtual} instruction. More unusually, the
245 * compiler must record the actual argument types, and may not perform method
246 * invocation conversions on the arguments. Instead, it must generate
247 * instructions to push them on the stack according to their own unconverted
248 * types. The VarHandle object itself will be pushed on the stack before the
249 * arguments. The compiler then generates an {@code invokevirtual} instruction
250 * that invokes the access mode method with a symbolic type descriptor which
251 * describes the argument and return types.
252 * <p>
253 * To issue a complete symbolic type descriptor, the compiler must also
254 * determine the return type (if polymorphic). This is based on a cast on the
255 * method invocation expression, if there is one, or else {@code Object} if the
256 * invocation is an expression, or else {@code void} if the invocation is a
257 * statement. The cast may be to a primitive type (but not {@code void}).
258 * <p>
259 * As a corner case, an uncasted {@code null} argument is given a symbolic type
260 * descriptor of {@code java.lang.Void}. The ambiguity with the type
261 * {@code Void} is harmless, since there are no references of type {@code Void}
262 * except the null reference.
263 *
264 *
265 * <h2><a id="invoke">Performing invocation of access mode methods</a></h2>
266 * The first time an {@code invokevirtual} instruction is executed it is linked
267 * by symbolically resolving the names in the instruction and verifying that
268 * the method call is statically legal. This also holds for calls to access mode
269 * methods. In this case, the symbolic type descriptor emitted by the compiler
270 * is checked for correct syntax, and names it contains are resolved. Thus, an
271 * {@code invokevirtual} instruction which invokes an access mode method will
272 * always link, as long as the symbolic type descriptor is syntactically
273 * well-formed and the types exist.
274 * <p>
275 * When the {@code invokevirtual} is executed after linking, the receiving
276 * VarHandle's access mode type is first checked by the JVM to ensure that it
277 * matches the symbolic type descriptor. If the type
278 * match fails, it means that the access mode method which the caller is
279 * invoking is not present on the individual VarHandle being invoked.
280 *
281 * <p id="invoke-behavior">
282 * Invocation of an access mode method behaves, by default, as if an invocation of
283 * {@link MethodHandle#invoke}, where the receiving method handle accepts the
284 * VarHandle instance as the leading argument. More specifically, the
285 * following, where {@code {access-mode}} corresponds to the access mode method
286 * name:
287 * <pre> {@code
288 * VarHandle vh = ..
289 * R r = (R) vh.{access-mode}(p1, p2, ..., pN);
290 * }</pre>
291 * behaves as if:
292 * <pre> {@code
293 * VarHandle vh = ..
294 * VarHandle.AccessMode am = VarHandle.AccessMode.valueFromMethodName("{access-mode}");
295 * MethodHandle mh = MethodHandles.varHandleExactInvoker(
296 * am,
297 * vh.accessModeType(am));
298 *
299 * R r = (R) mh.invoke(vh, p1, p2, ..., pN)
300 * }</pre>
301 * (modulo access mode methods do not declare throwing of {@code Throwable}).
302 * This is equivalent to:
303 * <pre> {@code
304 * MethodHandle mh = MethodHandles.lookup().findVirtual(
305 * VarHandle.class,
306 * "{access-mode}",
307 * MethodType.methodType(R, p1, p2, ..., pN));
308 *
309 * R r = (R) mh.invokeExact(vh, p1, p2, ..., pN)
310 * }</pre>
311 * where the desired method type is the symbolic type descriptor and a
312 * {@link MethodHandle#invokeExact} is performed, since before invocation of the
313 * target, the handle will apply reference casts as necessary and box, unbox, or
314 * widen primitive values, as if by {@link MethodHandle#asType asType} (see also
315 * {@link MethodHandles#varHandleInvoker}).
316 *
317 * More concisely, such behavior is equivalent to:
318 * <pre> {@code
319 * VarHandle vh = ..
320 * VarHandle.AccessMode am = VarHandle.AccessMode.valueFromMethodName("{access-mode}");
321 * MethodHandle mh = vh.toMethodHandle(am);
322 *
323 * R r = (R) mh.invoke(p1, p2, ..., pN)
324 * }</pre>
325 * Where, in this case, the method handle is bound to the VarHandle instance.
326 *
327 * <p id="invoke-exact-behavior">
328 * A VarHandle's invocation behavior can be adjusted (see {@link #withInvokeExactBehavior}) such that invocation of
329 * an access mode method behaves as if invocation of {@link MethodHandle#invokeExact},
330 * where the receiving method handle accepts the VarHandle instance as the leading argument.
331 * More specifically, the following, where {@code {access-mode}} corresponds to the access mode method
332 * name:
333 * <pre> {@code
334 * VarHandle vh = ..
335 * R r = (R) vh.{access-mode}(p1, p2, ..., pN);
336 * }</pre>
337 * behaves as if:
338 * <pre> {@code
339 * VarHandle vh = ..
340 * VarHandle.AccessMode am = VarHandle.AccessMode.valueFromMethodName("{access-mode}");
341 * MethodHandle mh = MethodHandles.varHandleExactInvoker(
342 * am,
343 * vh.accessModeType(am));
344 *
345 * R r = (R) mh.invokeExact(vh, p1, p2, ..., pN)
346 * }</pre>
347 * (modulo access mode methods do not declare throwing of {@code Throwable}).
348 *
349 * More concisely, such behavior is equivalent to:
350 * <pre> {@code
351 * VarHandle vh = ..
352 * VarHandle.AccessMode am = VarHandle.AccessMode.valueFromMethodName("{access-mode}");
353 * MethodHandle mh = vh.toMethodHandle(am);
354 *
355 * R r = (R) mh.invokeExact(p1, p2, ..., pN)
356 * }</pre>
357 * Where, in this case, the method handle is bound to the VarHandle instance.
358 *
359 * <h2>Invocation checking</h2>
360 * In typical programs, VarHandle access mode type matching will usually
361 * succeed. But if a match fails, the JVM will throw a
362 * {@link WrongMethodTypeException}.
363 * <p>
364 * Thus, an access mode type mismatch which might show up as a linkage error
365 * in a statically typed program can show up as a dynamic
366 * {@code WrongMethodTypeException} in a program which uses VarHandles.
367 * <p>
368 * Because access mode types contain "live" {@code Class} objects, method type
369 * matching takes into account both type names and class loaders.
370 * Thus, even if a VarHandle {@code VH} is created in one class loader
371 * {@code L1} and used in another {@code L2}, VarHandle access mode method
372 * calls are type-safe, because the caller's symbolic type descriptor, as
373 * resolved in {@code L2}, is matched against the original callee method's
374 * symbolic type descriptor, as resolved in {@code L1}. The resolution in
375 * {@code L1} happens when {@code VH} is created and its access mode types are
376 * assigned, while the resolution in {@code L2} happens when the
377 * {@code invokevirtual} instruction is linked.
378 * <p>
379 * Apart from type descriptor checks, a VarHandles's capability to
380 * access its variables is unrestricted.
381 * If a VarHandle is formed on a non-public variable by a class that has access
382 * to that variable, the resulting VarHandle can be used in any place by any
383 * caller who receives a reference to it.
384 * <p>
385 * Unlike with the Core Reflection API, where access is checked every time a
386 * reflective method is invoked, VarHandle access checking is performed
387 * <a href="MethodHandles.Lookup.html#access">when the VarHandle is
388 * created</a>.
389 * Thus, VarHandles to non-public variables, or to variables in non-public
390 * classes, should generally be kept secret. They should not be passed to
391 * untrusted code unless their use from the untrusted code would be harmless.
392 *
393 *
394 * <h2>VarHandle creation</h2>
395 * Java code can create a VarHandle that directly accesses any field that is
396 * accessible to that code. This is done via a reflective, capability-based
397 * API called {@link java.lang.invoke.MethodHandles.Lookup
398 * MethodHandles.Lookup}.
399 * For example, a VarHandle for a non-static field can be obtained
400 * from {@link java.lang.invoke.MethodHandles.Lookup#findVarHandle
401 * Lookup.findVarHandle}.
402 * There is also a conversion method from Core Reflection API objects,
403 * {@link java.lang.invoke.MethodHandles.Lookup#unreflectVarHandle
404 * Lookup.unreflectVarHandle}.
405 * <p>
406 * Access to protected field members is restricted to receivers only of the
407 * accessing class, or one of its subclasses, and the accessing class must in
408 * turn be a subclass (or package sibling) of the protected member's defining
409 * class. If a VarHandle refers to a protected non-static field of a declaring
410 * class outside the current package, the receiver argument will be narrowed to
411 * the type of the accessing class.
412 *
413 * <h2>Interoperation between VarHandles and the Core Reflection API</h2>
414 * Using factory methods in the {@link java.lang.invoke.MethodHandles.Lookup
415 * Lookup} API, any field represented by a Core Reflection API object
416 * can be converted to a behaviorally equivalent VarHandle.
417 * For example, a reflective {@link java.lang.reflect.Field Field} can
418 * be converted to a VarHandle using
419 * {@link java.lang.invoke.MethodHandles.Lookup#unreflectVarHandle
420 * Lookup.unreflectVarHandle}.
421 * The resulting VarHandles generally provide more direct and efficient
422 * access to the underlying fields.
423 * <p>
424 * As a special case, when the Core Reflection API is used to view the
425 * signature polymorphic access mode methods in this class, they appear as
426 * ordinary non-polymorphic methods. Their reflective appearance, as viewed by
427 * {@link java.lang.Class#getDeclaredMethod Class.getDeclaredMethod},
428 * is unaffected by their special status in this API.
429 * For example, {@link java.lang.reflect.Method#getModifiers
430 * Method.getModifiers}
431 * will report exactly those modifier bits required for any similarly
432 * declared method, including in this case {@code native} and {@code varargs}
433 * bits.
434 * <p>
435 * As with any reflected method, these methods (when reflected) may be invoked
436 * directly via {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke},
437 * via JNI, or indirectly via
438 * {@link java.lang.invoke.MethodHandles.Lookup#unreflect Lookup.unreflect}.
439 * However, such reflective calls do not result in access mode method
440 * invocations. Such a call, if passed the required argument (a single one, of
441 * type {@code Object[]}), will ignore the argument and will throw an
442 * {@code UnsupportedOperationException}.
443 * <p>
444 * Since {@code invokevirtual} instructions can natively invoke VarHandle
445 * access mode methods under any symbolic type descriptor, this reflective view
446 * conflicts with the normal presentation of these methods via bytecodes.
447 * Thus, these native methods, when reflectively viewed by
448 * {@code Class.getDeclaredMethod}, may be regarded as placeholders only.
449 * <p>
450 * In order to obtain an invoker method for a particular access mode type,
451 * use {@link java.lang.invoke.MethodHandles#varHandleExactInvoker} or
452 * {@link java.lang.invoke.MethodHandles#varHandleInvoker}. The
453 * {@link java.lang.invoke.MethodHandles.Lookup#findVirtual Lookup.findVirtual}
454 * API is also able to return a method handle to call an access mode method for
455 * any specified access mode type and is equivalent in behavior to
456 * {@link java.lang.invoke.MethodHandles#varHandleInvoker}.
457 *
458 * <h2>Interoperation between VarHandles and Java generics</h2>
459 * A VarHandle can be obtained for a variable, such as a field, which is
460 * declared with Java generic types. As with the Core Reflection API, the
461 * VarHandle's variable type will be constructed from the erasure of the
462 * source-level type. When a VarHandle access mode method is invoked, the
463 * types
464 * of its arguments or the return value cast type may be generic types or type
465 * instances. If this occurs, the compiler will replace those types by their
466 * erasures when it constructs the symbolic type descriptor for the
467 * {@code invokevirtual} instruction.
468 *
469 * @see MethodHandle
470 * @see MethodHandles
471 * @see MethodType
472 * @since 9
473 */
474 public abstract sealed class VarHandle implements Constable
475 permits IndirectVarHandle, LazyInitializingVarHandle,
476 VarHandleSegmentViewBase,
477 VarHandleByteArrayAsChars.ByteArrayViewVarHandle,
478 VarHandleByteArrayAsDoubles.ByteArrayViewVarHandle,
479 VarHandleByteArrayAsFloats.ByteArrayViewVarHandle,
480 VarHandleByteArrayAsInts.ByteArrayViewVarHandle,
481 VarHandleByteArrayAsLongs.ByteArrayViewVarHandle,
482 VarHandleByteArrayAsShorts.ByteArrayViewVarHandle,
483 VarHandleBooleans.Array,
484 VarHandleBooleans.FieldInstanceReadOnly,
485 VarHandleBooleans.FieldStaticReadOnly,
486 VarHandleBytes.Array,
487 VarHandleBytes.FieldInstanceReadOnly,
488 VarHandleBytes.FieldStaticReadOnly,
489 VarHandleChars.Array,
490 VarHandleChars.FieldInstanceReadOnly,
491 VarHandleChars.FieldStaticReadOnly,
492 VarHandleDoubles.Array,
493 VarHandleDoubles.FieldInstanceReadOnly,
494 VarHandleDoubles.FieldStaticReadOnly,
495 VarHandleFloats.Array,
496 VarHandleFloats.FieldInstanceReadOnly,
497 VarHandleFloats.FieldStaticReadOnly,
498 VarHandleInts.Array,
499 VarHandleInts.FieldInstanceReadOnly,
500 VarHandleInts.FieldStaticReadOnly,
501 VarHandleLongs.Array,
502 VarHandleLongs.FieldInstanceReadOnly,
503 VarHandleLongs.FieldStaticReadOnly,
504 VarHandleReferences.Array,
505 VarHandleReferences.FieldInstanceReadOnly,
506 VarHandleReferences.FieldStaticReadOnly,
507 VarHandleShorts.Array,
508 VarHandleShorts.FieldInstanceReadOnly,
509 VarHandleShorts.FieldStaticReadOnly {
510 final VarForm vform;
511 final boolean exact;
512
513 VarHandle(VarForm vform) {
514 this(vform, false);
515 }
516
517 VarHandle(VarForm vform, boolean exact) {
518 this.vform = vform;
519 this.exact = exact;
520 }
521
522 /**
523 * Returns the target VarHandle. Subclasses may override this method to implement
524 * additional logic for example lazily initializing the declaring class of a static field var handle.
525 */
526 @ForceInline
527 VarHandle target() {
528 return asDirect();
529 }
530
531 /**
532 * Returns the direct target VarHandle. Indirect VarHandle subclasses should implement
533 * this method.
534 *
535 * @see #getMethodHandle(int)
536 * @see #checkAccessModeThenIsDirect(AccessDescriptor)
537 */
538 @ForceInline
539 VarHandle asDirect() {
540 return this;
541 }
542
543 /**
544 * Returns {@code true} if this VarHandle has <a href="#invoke-exact-behavior"><em>invoke-exact behavior</em></a>.
545 *
546 * @see #withInvokeExactBehavior()
547 * @see #withInvokeBehavior()
548 * @return {@code true} if this VarHandle has <a href="#invoke-exact-behavior"><em>invoke-exact behavior</em></a>.
549 * @since 16
550 */
551 public boolean hasInvokeExactBehavior() {
552 return exact;
553 }
554
555 // Plain accessors
556
557 /**
558 * Returns the value of a variable, with memory semantics of reading as
559 * if the variable was declared non-{@code volatile}. Commonly referred to
560 * as plain read access.
561 *
562 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn)T}.
563 *
564 * <p>The symbolic type descriptor at the call site of {@code get}
565 * must match the access mode type that is the result of calling
566 * {@code accessModeType(VarHandle.AccessMode.GET)} on this VarHandle.
567 *
568 * <p>This access mode is supported by all VarHandle instances and never
569 * throws {@code UnsupportedOperationException}.
570 *
571 * @param args the signature-polymorphic parameter list of the form
572 * {@code (CT1 ct1, ..., CTn)}
573 * , statically represented using varargs.
574 * @return the signature-polymorphic result that is the value of the
575 * variable
576 * , statically represented using {@code Object}.
577 * @throws WrongMethodTypeException if the access mode type does not
578 * match the caller's symbolic type descriptor.
579 * @throws ClassCastException if the access mode type matches the caller's
580 * symbolic type descriptor, but a reference cast fails.
581 */
582 public final native
583 @MethodHandle.PolymorphicSignature
584 @IntrinsicCandidate
585 Object get(Object... args);
586
587 /**
588 * Sets the value of a variable to the {@code newValue}, with memory
589 * semantics of setting as if the variable was declared non-{@code volatile}
590 * and non-{@code final}. Commonly referred to as plain write access.
591 *
592 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T newValue)void}
593 *
594 * <p>The symbolic type descriptor at the call site of {@code set}
595 * must match the access mode type that is the result of calling
596 * {@code accessModeType(VarHandle.AccessMode.SET)} on this VarHandle.
597 *
598 * @param args the signature-polymorphic parameter list of the form
599 * {@code (CT1 ct1, ..., CTn ctn, T newValue)}
600 * , statically represented using varargs.
601 * @throws UnsupportedOperationException if the access mode is unsupported
602 * for this VarHandle.
603 * @throws WrongMethodTypeException if the access mode type does not
604 * match the caller's symbolic type descriptor.
605 * @throws ClassCastException if the access mode type matches the caller's
606 * symbolic type descriptor, but a reference cast fails.
607 */
608 public final native
609 @MethodHandle.PolymorphicSignature
610 @IntrinsicCandidate
611 void set(Object... args);
612
613
614 // Volatile accessors
615
616 /**
617 * Returns the value of a variable, with memory semantics of reading as if
618 * the variable was declared {@code volatile}.
619 *
620 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn)T}.
621 *
622 * <p>The symbolic type descriptor at the call site of {@code getVolatile}
623 * must match the access mode type that is the result of calling
624 * {@code accessModeType(VarHandle.AccessMode.GET_VOLATILE)} on this
625 * VarHandle.
626 *
627 * @param args the signature-polymorphic parameter list of the form
628 * {@code (CT1 ct1, ..., CTn ctn)}
629 * , statically represented using varargs.
630 * @return the signature-polymorphic result that is the value of the
631 * variable
632 * , statically represented using {@code Object}.
633 * @throws UnsupportedOperationException if the access mode is unsupported
634 * for this VarHandle.
635 * @throws WrongMethodTypeException if the access mode type does not
636 * match the caller's symbolic type descriptor.
637 * @throws ClassCastException if the access mode type matches the caller's
638 * symbolic type descriptor, but a reference cast fails.
639 */
640 public final native
641 @MethodHandle.PolymorphicSignature
642 @IntrinsicCandidate
643 Object getVolatile(Object... args);
644
645 /**
646 * Sets the value of a variable to the {@code newValue}, with memory
647 * semantics of setting as if the variable was declared {@code volatile}.
648 *
649 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T newValue)void}.
650 *
651 * <p>The symbolic type descriptor at the call site of {@code setVolatile}
652 * must match the access mode type that is the result of calling
653 * {@code accessModeType(VarHandle.AccessMode.SET_VOLATILE)} on this
654 * VarHandle.
655 *
656 * @apiNote
657 * Ignoring the many semantic differences from C and C++, this method has
658 * memory ordering effects compatible with {@code memory_order_seq_cst}.
659 *
660 * @param args the signature-polymorphic parameter list of the form
661 * {@code (CT1 ct1, ..., CTn ctn, T newValue)}
662 * , statically represented using varargs.
663 * @throws UnsupportedOperationException if the access mode is unsupported
664 * for this VarHandle.
665 * @throws WrongMethodTypeException if the access mode type does not
666 * match the caller's symbolic type descriptor.
667 * @throws ClassCastException if the access mode type matches the caller's
668 * symbolic type descriptor, but a reference cast fails.
669 */
670 public final native
671 @MethodHandle.PolymorphicSignature
672 @IntrinsicCandidate
673 void setVolatile(Object... args);
674
675
676 /**
677 * Returns the value of a variable, accessed in program order, but with no
678 * assurance of memory ordering effects with respect to other threads.
679 *
680 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn)T}.
681 *
682 * <p>The symbolic type descriptor at the call site of {@code getOpaque}
683 * must match the access mode type that is the result of calling
684 * {@code accessModeType(VarHandle.AccessMode.GET_OPAQUE)} on this
685 * VarHandle.
686 *
687 * @param args the signature-polymorphic parameter list of the form
688 * {@code (CT1 ct1, ..., CTn ctn)}
689 * , statically represented using varargs.
690 * @return the signature-polymorphic result that is the value of the
691 * variable
692 * , statically represented using {@code Object}.
693 * @throws UnsupportedOperationException if the access mode is unsupported
694 * for this VarHandle.
695 * @throws WrongMethodTypeException if the access mode type does not
696 * match the caller's symbolic type descriptor.
697 * @throws ClassCastException if the access mode type matches the caller's
698 * symbolic type descriptor, but a reference cast fails.
699 */
700 public final native
701 @MethodHandle.PolymorphicSignature
702 @IntrinsicCandidate
703 Object getOpaque(Object... args);
704
705 /**
706 * Sets the value of a variable to the {@code newValue}, in program order,
707 * but with no assurance of memory ordering effects with respect to other
708 * threads.
709 *
710 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T newValue)void}.
711 *
712 * <p>The symbolic type descriptor at the call site of {@code setOpaque}
713 * must match the access mode type that is the result of calling
714 * {@code accessModeType(VarHandle.AccessMode.SET_OPAQUE)} on this
715 * VarHandle.
716 *
717 * @param args the signature-polymorphic parameter list of the form
718 * {@code (CT1 ct1, ..., CTn ctn, T newValue)}
719 * , statically represented using varargs.
720 * @throws UnsupportedOperationException if the access mode is unsupported
721 * for this VarHandle.
722 * @throws WrongMethodTypeException if the access mode type does not
723 * match the caller's symbolic type descriptor.
724 * @throws ClassCastException if the access mode type matches the caller's
725 * symbolic type descriptor, but a reference cast fails.
726 */
727 public final native
728 @MethodHandle.PolymorphicSignature
729 @IntrinsicCandidate
730 void setOpaque(Object... args);
731
732
733 // Lazy accessors
734
735 /**
736 * Returns the value of a variable, and ensures that subsequent loads and
737 * stores are not reordered before this access.
738 *
739 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn)T}.
740 *
741 * <p>The symbolic type descriptor at the call site of {@code getAcquire}
742 * must match the access mode type that is the result of calling
743 * {@code accessModeType(VarHandle.AccessMode.GET_ACQUIRE)} on this
744 * VarHandle.
745 *
746 * @apiNote
747 * Ignoring the many semantic differences from C and C++, this method has
748 * memory ordering effects compatible with {@code memory_order_acquire}
749 * ordering.
750 *
751 * @param args the signature-polymorphic parameter list of the form
752 * {@code (CT1 ct1, ..., CTn ctn)}
753 * , statically represented using varargs.
754 * @return the signature-polymorphic result that is the value of the
755 * variable
756 * , statically represented using {@code Object}.
757 * @throws UnsupportedOperationException if the access mode is unsupported
758 * for this VarHandle.
759 * @throws WrongMethodTypeException if the access mode type does not
760 * match the caller's symbolic type descriptor.
761 * @throws ClassCastException if the access mode type matches the caller's
762 * symbolic type descriptor, but a reference cast fails.
763 */
764 public final native
765 @MethodHandle.PolymorphicSignature
766 @IntrinsicCandidate
767 Object getAcquire(Object... args);
768
769 /**
770 * Sets the value of a variable to the {@code newValue}, and ensures that
771 * prior loads and stores are not reordered after this access.
772 *
773 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T newValue)void}.
774 *
775 * <p>The symbolic type descriptor at the call site of {@code setRelease}
776 * must match the access mode type that is the result of calling
777 * {@code accessModeType(VarHandle.AccessMode.SET_RELEASE)} on this
778 * VarHandle.
779 *
780 * @apiNote
781 * Ignoring the many semantic differences from C and C++, this method has
782 * memory ordering effects compatible with {@code memory_order_release}
783 * ordering.
784 *
785 * @param args the signature-polymorphic parameter list of the form
786 * {@code (CT1 ct1, ..., CTn ctn, T newValue)}
787 * , statically represented using varargs.
788 * @throws UnsupportedOperationException if the access mode is unsupported
789 * for this VarHandle.
790 * @throws WrongMethodTypeException if the access mode type does not
791 * match the caller's symbolic type descriptor.
792 * @throws ClassCastException if the access mode type matches the caller's
793 * symbolic type descriptor, but a reference cast fails.
794 */
795 public final native
796 @MethodHandle.PolymorphicSignature
797 @IntrinsicCandidate
798 void setRelease(Object... args);
799
800
801 // Compare and set accessors
802
803 /**
804 * Atomically sets the value of a variable to the {@code newValue} with the
805 * memory semantics of {@link #setVolatile} if the variable's current value,
806 * referred to as the <em>witness value</em>, {@code ==} the
807 * {@code expectedValue}, as accessed with the memory semantics of
808 * {@link #getVolatile}.
809 *
810 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)boolean}.
811 *
812 * <p>The symbolic type descriptor at the call site of {@code
813 * compareAndSet} must match the access mode type that is the result of
814 * calling {@code accessModeType(VarHandle.AccessMode.COMPARE_AND_SET)} on
815 * this VarHandle.
816 *
817 * @param args the signature-polymorphic parameter list of the form
818 * {@code (CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)}
819 * , statically represented using varargs.
820 * @return {@code true} if successful, otherwise {@code false} if the
821 * <em>witness value</em> was not the same as the {@code expectedValue}.
822 * @throws UnsupportedOperationException if the access mode is unsupported
823 * for this VarHandle.
824 * @throws WrongMethodTypeException if the access mode type does not
825 * match the caller's symbolic type descriptor.
826 * @throws ClassCastException if the access mode type matches the caller's
827 * symbolic type descriptor, but a reference cast fails.
828 * @see #setVolatile(Object...)
829 * @see #getVolatile(Object...)
830 */
831 public final native
832 @MethodHandle.PolymorphicSignature
833 @IntrinsicCandidate
834 boolean compareAndSet(Object... args);
835
836 /**
837 * Atomically sets the value of a variable to the {@code newValue} with the
838 * memory semantics of {@link #setVolatile} if the variable's current value,
839 * referred to as the <em>witness value</em>, {@code ==} the
840 * {@code expectedValue}, as accessed with the memory semantics of
841 * {@link #getVolatile}.
842 *
843 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)T}.
844 *
845 * <p>The symbolic type descriptor at the call site of {@code
846 * compareAndExchange}
847 * must match the access mode type that is the result of calling
848 * {@code accessModeType(VarHandle.AccessMode.COMPARE_AND_EXCHANGE)}
849 * on this VarHandle.
850 *
851 * @param args the signature-polymorphic parameter list of the form
852 * {@code (CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)}
853 * , statically represented using varargs.
854 * @return the signature-polymorphic result that is the <em>witness value</em>, which
855 * will be the same as the {@code expectedValue} if successful
856 * , statically represented using {@code Object}.
857 * @throws UnsupportedOperationException if the access mode is unsupported
858 * for this VarHandle.
859 * @throws WrongMethodTypeException if the access mode type is not
860 * compatible with the caller's symbolic type descriptor.
861 * @throws ClassCastException if the access mode type is compatible with the
862 * caller's symbolic type descriptor, but a reference cast fails.
863 * @see #setVolatile(Object...)
864 * @see #getVolatile(Object...)
865 */
866 public final native
867 @MethodHandle.PolymorphicSignature
868 @IntrinsicCandidate
869 Object compareAndExchange(Object... args);
870
871 /**
872 * Atomically sets the value of a variable to the {@code newValue} with the
873 * memory semantics of {@link #set} if the variable's current value,
874 * referred to as the <em>witness value</em>, {@code ==} the
875 * {@code expectedValue}, as accessed with the memory semantics of
876 * {@link #getAcquire}.
877 *
878 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)T}.
879 *
880 * <p>The symbolic type descriptor at the call site of {@code
881 * compareAndExchangeAcquire}
882 * must match the access mode type that is the result of calling
883 * {@code accessModeType(VarHandle.AccessMode.COMPARE_AND_EXCHANGE_ACQUIRE)} on
884 * this VarHandle.
885 *
886 * @param args the signature-polymorphic parameter list of the form
887 * {@code (CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)}
888 * , statically represented using varargs.
889 * @return the signature-polymorphic result that is the <em>witness value</em>, which
890 * will be the same as the {@code expectedValue} if successful
891 * , statically represented using {@code Object}.
892 * @throws UnsupportedOperationException if the access mode is unsupported
893 * for this VarHandle.
894 * @throws WrongMethodTypeException if the access mode type does not
895 * match the caller's symbolic type descriptor.
896 * @throws ClassCastException if the access mode type matches the caller's
897 * symbolic type descriptor, but a reference cast fails.
898 * @see #set(Object...)
899 * @see #getAcquire(Object...)
900 */
901 public final native
902 @MethodHandle.PolymorphicSignature
903 @IntrinsicCandidate
904 Object compareAndExchangeAcquire(Object... args);
905
906 /**
907 * Atomically sets the value of a variable to the {@code newValue} with the
908 * memory semantics of {@link #setRelease} if the variable's current value,
909 * referred to as the <em>witness value</em>, {@code ==} the
910 * {@code expectedValue}, as accessed with the memory semantics of
911 * {@link #get}.
912 *
913 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)T}.
914 *
915 * <p>The symbolic type descriptor at the call site of {@code
916 * compareAndExchangeRelease}
917 * must match the access mode type that is the result of calling
918 * {@code accessModeType(VarHandle.AccessMode.COMPARE_AND_EXCHANGE_RELEASE)}
919 * on this VarHandle.
920 *
921 * @param args the signature-polymorphic parameter list of the form
922 * {@code (CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)}
923 * , statically represented using varargs.
924 * @return the signature-polymorphic result that is the <em>witness value</em>, which
925 * will be the same as the {@code expectedValue} if successful
926 * , statically represented using {@code Object}.
927 * @throws UnsupportedOperationException if the access mode is unsupported
928 * for this VarHandle.
929 * @throws WrongMethodTypeException if the access mode type does not
930 * match the caller's symbolic type descriptor.
931 * @throws ClassCastException if the access mode type matches the caller's
932 * symbolic type descriptor, but a reference cast fails.
933 * @see #setRelease(Object...)
934 * @see #get(Object...)
935 */
936 public final native
937 @MethodHandle.PolymorphicSignature
938 @IntrinsicCandidate
939 Object compareAndExchangeRelease(Object... args);
940
941 // Weak (spurious failures allowed)
942
943 /**
944 * Possibly atomically sets the value of a variable to the {@code newValue}
945 * with the semantics of {@link #set} if the variable's current value,
946 * referred to as the <em>witness value</em>, {@code ==} the
947 * {@code expectedValue}, as accessed with the memory semantics of
948 * {@link #get}.
949 *
950 * <p>This operation may fail spuriously (typically, due to memory
951 * contention) even if the <em>witness value</em> does match the expected value.
952 *
953 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)boolean}.
954 *
955 * <p>The symbolic type descriptor at the call site of {@code
956 * weakCompareAndSetPlain} must match the access mode type that is the result of
957 * calling {@code accessModeType(VarHandle.AccessMode.WEAK_COMPARE_AND_SET_PLAIN)}
958 * on this VarHandle.
959 *
960 * @param args the signature-polymorphic parameter list of the form
961 * {@code (CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)}
962 * , statically represented using varargs.
963 * @return {@code true} if successful, otherwise {@code false} if the
964 * <em>witness value</em> was not the same as the {@code expectedValue} or if this
965 * operation spuriously failed.
966 * @throws UnsupportedOperationException if the access mode is unsupported
967 * for this VarHandle.
968 * @throws WrongMethodTypeException if the access mode type does not
969 * match the caller's symbolic type descriptor.
970 * @throws ClassCastException if the access mode type matches the caller's
971 * symbolic type descriptor, but a reference cast fails.
972 * @see #set(Object...)
973 * @see #get(Object...)
974 */
975 public final native
976 @MethodHandle.PolymorphicSignature
977 @IntrinsicCandidate
978 boolean weakCompareAndSetPlain(Object... args);
979
980 /**
981 * Possibly atomically sets the value of a variable to the {@code newValue}
982 * with the memory semantics of {@link #setVolatile} if the variable's
983 * current value, referred to as the <em>witness value</em>, {@code ==} the
984 * {@code expectedValue}, as accessed with the memory semantics of
985 * {@link #getVolatile}.
986 *
987 * <p>This operation may fail spuriously (typically, due to memory
988 * contention) even if the <em>witness value</em> does match the expected value.
989 *
990 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)boolean}.
991 *
992 * <p>The symbolic type descriptor at the call site of {@code
993 * weakCompareAndSet} must match the access mode type that is the
994 * result of calling {@code accessModeType(VarHandle.AccessMode.WEAK_COMPARE_AND_SET)}
995 * on this VarHandle.
996 *
997 * @param args the signature-polymorphic parameter list of the form
998 * {@code (CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)}
999 * , statically represented using varargs.
1000 * @return {@code true} if successful, otherwise {@code false} if the
1001 * <em>witness value</em> was not the same as the {@code expectedValue} or if this
1002 * operation spuriously failed.
1003 * @throws UnsupportedOperationException if the access mode is unsupported
1004 * for this VarHandle.
1005 * @throws WrongMethodTypeException if the access mode type does not
1006 * match the caller's symbolic type descriptor.
1007 * @throws ClassCastException if the access mode type matches the caller's
1008 * symbolic type descriptor, but a reference cast fails.
1009 * @see #setVolatile(Object...)
1010 * @see #getVolatile(Object...)
1011 */
1012 public final native
1013 @MethodHandle.PolymorphicSignature
1014 @IntrinsicCandidate
1015 boolean weakCompareAndSet(Object... args);
1016
1017 /**
1018 * Possibly atomically sets the value of a variable to the {@code newValue}
1019 * with the semantics of {@link #set} if the variable's current value,
1020 * referred to as the <em>witness value</em>, {@code ==} the
1021 * {@code expectedValue}, as accessed with the memory semantics of
1022 * {@link #getAcquire}.
1023 *
1024 * <p>This operation may fail spuriously (typically, due to memory
1025 * contention) even if the <em>witness value</em> does match the expected value.
1026 *
1027 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)boolean}.
1028 *
1029 * <p>The symbolic type descriptor at the call site of {@code
1030 * weakCompareAndSetAcquire}
1031 * must match the access mode type that is the result of calling
1032 * {@code accessModeType(VarHandle.AccessMode.WEAK_COMPARE_AND_SET_ACQUIRE)}
1033 * on this VarHandle.
1034 *
1035 * @param args the signature-polymorphic parameter list of the form
1036 * {@code (CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)}
1037 * , statically represented using varargs.
1038 * @return {@code true} if successful, otherwise {@code false} if the
1039 * <em>witness value</em> was not the same as the {@code expectedValue} or if this
1040 * operation spuriously failed.
1041 * @throws UnsupportedOperationException if the access mode is unsupported
1042 * for this VarHandle.
1043 * @throws WrongMethodTypeException if the access mode type does not
1044 * match the caller's symbolic type descriptor.
1045 * @throws ClassCastException if the access mode type matches the caller's
1046 * symbolic type descriptor, but a reference cast fails.
1047 * @see #set(Object...)
1048 * @see #getAcquire(Object...)
1049 */
1050 public final native
1051 @MethodHandle.PolymorphicSignature
1052 @IntrinsicCandidate
1053 boolean weakCompareAndSetAcquire(Object... args);
1054
1055 /**
1056 * Possibly atomically sets the value of a variable to the {@code newValue}
1057 * with the semantics of {@link #setRelease} if the variable's current
1058 * value, referred to as the <em>witness value</em>, {@code ==} the
1059 * {@code expectedValue}, as accessed with the memory semantics of
1060 * {@link #get}.
1061 *
1062 * <p>This operation may fail spuriously (typically, due to memory
1063 * contention) even if the <em>witness value</em> does match the expected value.
1064 *
1065 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)boolean}.
1066 *
1067 * <p>The symbolic type descriptor at the call site of {@code
1068 * weakCompareAndSetRelease}
1069 * must match the access mode type that is the result of calling
1070 * {@code accessModeType(VarHandle.AccessMode.WEAK_COMPARE_AND_SET_RELEASE)}
1071 * on this VarHandle.
1072 *
1073 * @param args the signature-polymorphic parameter list of the form
1074 * {@code (CT1 ct1, ..., CTn ctn, T expectedValue, T newValue)}
1075 * , statically represented using varargs.
1076 * @return {@code true} if successful, otherwise {@code false} if the
1077 * <em>witness value</em> was not the same as the {@code expectedValue} or if this
1078 * operation spuriously failed.
1079 * @throws UnsupportedOperationException if the access mode is unsupported
1080 * for this VarHandle.
1081 * @throws WrongMethodTypeException if the access mode type does not
1082 * match the caller's symbolic type descriptor.
1083 * @throws ClassCastException if the access mode type matches the caller's
1084 * symbolic type descriptor, but a reference cast fails.
1085 * @see #setRelease(Object...)
1086 * @see #get(Object...)
1087 */
1088 public final native
1089 @MethodHandle.PolymorphicSignature
1090 @IntrinsicCandidate
1091 boolean weakCompareAndSetRelease(Object... args);
1092
1093 /**
1094 * Atomically sets the value of a variable to the {@code newValue} with the
1095 * memory semantics of {@link #setVolatile} and returns the variable's
1096 * previous value, as accessed with the memory semantics of
1097 * {@link #getVolatile}.
1098 *
1099 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T newValue)T}.
1100 *
1101 * <p>The symbolic type descriptor at the call site of {@code getAndSet}
1102 * must match the access mode type that is the result of calling
1103 * {@code accessModeType(VarHandle.AccessMode.GET_AND_SET)} on this
1104 * VarHandle.
1105 *
1106 * @param args the signature-polymorphic parameter list of the form
1107 * {@code (CT1 ct1, ..., CTn ctn, T newValue)}
1108 * , statically represented using varargs.
1109 * @return the signature-polymorphic result that is the previous value of
1110 * the variable
1111 * , statically represented using {@code Object}.
1112 * @throws UnsupportedOperationException if the access mode is unsupported
1113 * for this VarHandle.
1114 * @throws WrongMethodTypeException if the access mode type does not
1115 * match the caller's symbolic type descriptor.
1116 * @throws ClassCastException if the access mode type matches the caller's
1117 * symbolic type descriptor, but a reference cast fails.
1118 * @see #setVolatile(Object...)
1119 * @see #getVolatile(Object...)
1120 */
1121 public final native
1122 @MethodHandle.PolymorphicSignature
1123 @IntrinsicCandidate
1124 Object getAndSet(Object... args);
1125
1126 /**
1127 * Atomically sets the value of a variable to the {@code newValue} with the
1128 * memory semantics of {@link #set} and returns the variable's
1129 * previous value, as accessed with the memory semantics of
1130 * {@link #getAcquire}.
1131 *
1132 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T newValue)T}.
1133 *
1134 * <p>The symbolic type descriptor at the call site of {@code getAndSetAcquire}
1135 * must match the access mode type that is the result of calling
1136 * {@code accessModeType(VarHandle.AccessMode.GET_AND_SET_ACQUIRE)} on this
1137 * VarHandle.
1138 *
1139 * @param args the signature-polymorphic parameter list of the form
1140 * {@code (CT1 ct1, ..., CTn ctn, T newValue)}
1141 * , statically represented using varargs.
1142 * @return the signature-polymorphic result that is the previous value of
1143 * the variable
1144 * , statically represented using {@code Object}.
1145 * @throws UnsupportedOperationException if the access mode is unsupported
1146 * for this VarHandle.
1147 * @throws WrongMethodTypeException if the access mode type does not
1148 * match the caller's symbolic type descriptor.
1149 * @throws ClassCastException if the access mode type matches the caller's
1150 * symbolic type descriptor, but a reference cast fails.
1151 * @see #setVolatile(Object...)
1152 * @see #getVolatile(Object...)
1153 */
1154 public final native
1155 @MethodHandle.PolymorphicSignature
1156 @IntrinsicCandidate
1157 Object getAndSetAcquire(Object... args);
1158
1159 /**
1160 * Atomically sets the value of a variable to the {@code newValue} with the
1161 * memory semantics of {@link #setRelease} and returns the variable's
1162 * previous value, as accessed with the memory semantics of
1163 * {@link #get}.
1164 *
1165 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T newValue)T}.
1166 *
1167 * <p>The symbolic type descriptor at the call site of {@code getAndSetRelease}
1168 * must match the access mode type that is the result of calling
1169 * {@code accessModeType(VarHandle.AccessMode.GET_AND_SET_RELEASE)} on this
1170 * VarHandle.
1171 *
1172 * @param args the signature-polymorphic parameter list of the form
1173 * {@code (CT1 ct1, ..., CTn ctn, T newValue)}
1174 * , statically represented using varargs.
1175 * @return the signature-polymorphic result that is the previous value of
1176 * the variable
1177 * , statically represented using {@code Object}.
1178 * @throws UnsupportedOperationException if the access mode is unsupported
1179 * for this VarHandle.
1180 * @throws WrongMethodTypeException if the access mode type does not
1181 * match the caller's symbolic type descriptor.
1182 * @throws ClassCastException if the access mode type matches the caller's
1183 * symbolic type descriptor, but a reference cast fails.
1184 * @see #setVolatile(Object...)
1185 * @see #getVolatile(Object...)
1186 */
1187 public final native
1188 @MethodHandle.PolymorphicSignature
1189 @IntrinsicCandidate
1190 Object getAndSetRelease(Object... args);
1191
1192 // Primitive adders
1193 // Throw UnsupportedOperationException for refs
1194
1195 /**
1196 * Atomically adds the {@code value} to the current value of a variable with
1197 * the memory semantics of {@link #setVolatile}, and returns the variable's
1198 * previous value, as accessed with the memory semantics of
1199 * {@link #getVolatile}.
1200 *
1201 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T value)T}.
1202 *
1203 * <p>The symbolic type descriptor at the call site of {@code getAndAdd}
1204 * must match the access mode type that is the result of calling
1205 * {@code accessModeType(VarHandle.AccessMode.GET_AND_ADD)} on this
1206 * VarHandle.
1207 *
1208 * @param args the signature-polymorphic parameter list of the form
1209 * {@code (CT1 ct1, ..., CTn ctn, T value)}
1210 * , statically represented using varargs.
1211 * @return the signature-polymorphic result that is the previous value of
1212 * the variable
1213 * , statically represented using {@code Object}.
1214 * @throws UnsupportedOperationException if the access mode is unsupported
1215 * for this VarHandle.
1216 * @throws WrongMethodTypeException if the access mode type does not
1217 * match the caller's symbolic type descriptor.
1218 * @throws ClassCastException if the access mode type matches the caller's
1219 * symbolic type descriptor, but a reference cast fails.
1220 * @see #setVolatile(Object...)
1221 * @see #getVolatile(Object...)
1222 */
1223 public final native
1224 @MethodHandle.PolymorphicSignature
1225 @IntrinsicCandidate
1226 Object getAndAdd(Object... args);
1227
1228 /**
1229 * Atomically adds the {@code value} to the current value of a variable with
1230 * the memory semantics of {@link #set}, and returns the variable's
1231 * previous value, as accessed with the memory semantics of
1232 * {@link #getAcquire}.
1233 *
1234 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T value)T}.
1235 *
1236 * <p>The symbolic type descriptor at the call site of {@code getAndAddAcquire}
1237 * must match the access mode type that is the result of calling
1238 * {@code accessModeType(VarHandle.AccessMode.GET_AND_ADD_ACQUIRE)} on this
1239 * VarHandle.
1240 *
1241 * @param args the signature-polymorphic parameter list of the form
1242 * {@code (CT1 ct1, ..., CTn ctn, T value)}
1243 * , statically represented using varargs.
1244 * @return the signature-polymorphic result that is the previous value of
1245 * the variable
1246 * , statically represented using {@code Object}.
1247 * @throws UnsupportedOperationException if the access mode is unsupported
1248 * for this VarHandle.
1249 * @throws WrongMethodTypeException if the access mode type does not
1250 * match the caller's symbolic type descriptor.
1251 * @throws ClassCastException if the access mode type matches the caller's
1252 * symbolic type descriptor, but a reference cast fails.
1253 * @see #setVolatile(Object...)
1254 * @see #getVolatile(Object...)
1255 */
1256 public final native
1257 @MethodHandle.PolymorphicSignature
1258 @IntrinsicCandidate
1259 Object getAndAddAcquire(Object... args);
1260
1261 /**
1262 * Atomically adds the {@code value} to the current value of a variable with
1263 * the memory semantics of {@link #setRelease}, and returns the variable's
1264 * previous value, as accessed with the memory semantics of
1265 * {@link #get}.
1266 *
1267 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T value)T}.
1268 *
1269 * <p>The symbolic type descriptor at the call site of {@code getAndAddRelease}
1270 * must match the access mode type that is the result of calling
1271 * {@code accessModeType(VarHandle.AccessMode.GET_AND_ADD_RELEASE)} on this
1272 * VarHandle.
1273 *
1274 * @param args the signature-polymorphic parameter list of the form
1275 * {@code (CT1 ct1, ..., CTn ctn, T value)}
1276 * , statically represented using varargs.
1277 * @return the signature-polymorphic result that is the previous value of
1278 * the variable
1279 * , statically represented using {@code Object}.
1280 * @throws UnsupportedOperationException if the access mode is unsupported
1281 * for this VarHandle.
1282 * @throws WrongMethodTypeException if the access mode type does not
1283 * match the caller's symbolic type descriptor.
1284 * @throws ClassCastException if the access mode type matches the caller's
1285 * symbolic type descriptor, but a reference cast fails.
1286 * @see #setVolatile(Object...)
1287 * @see #getVolatile(Object...)
1288 */
1289 public final native
1290 @MethodHandle.PolymorphicSignature
1291 @IntrinsicCandidate
1292 Object getAndAddRelease(Object... args);
1293
1294
1295 // Bitwise operations
1296 // Throw UnsupportedOperationException for refs
1297
1298 /**
1299 * Atomically sets the value of a variable to the result of
1300 * bitwise OR between the variable's current value and the {@code mask}
1301 * with the memory semantics of {@link #setVolatile} and returns the
1302 * variable's previous value, as accessed with the memory semantics of
1303 * {@link #getVolatile}.
1304 *
1305 * <p>If the variable type is the non-integral {@code boolean} type then a
1306 * logical OR is performed instead of a bitwise OR.
1307 *
1308 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T mask)T}.
1309 *
1310 * <p>The symbolic type descriptor at the call site of {@code getAndBitwiseOr}
1311 * must match the access mode type that is the result of calling
1312 * {@code accessModeType(VarHandle.AccessMode.GET_AND_BITWISE_OR)} on this
1313 * VarHandle.
1314 *
1315 * @param args the signature-polymorphic parameter list of the form
1316 * {@code (CT1 ct1, ..., CTn ctn, T mask)}
1317 * , statically represented using varargs.
1318 * @return the signature-polymorphic result that is the previous value of
1319 * the variable
1320 * , statically represented using {@code Object}.
1321 * @throws UnsupportedOperationException if the access mode is unsupported
1322 * for this VarHandle.
1323 * @throws WrongMethodTypeException if the access mode type does not
1324 * match the caller's symbolic type descriptor.
1325 * @throws ClassCastException if the access mode type matches the caller's
1326 * symbolic type descriptor, but a reference cast fails.
1327 * @see #setVolatile(Object...)
1328 * @see #getVolatile(Object...)
1329 */
1330 public final native
1331 @MethodHandle.PolymorphicSignature
1332 @IntrinsicCandidate
1333 Object getAndBitwiseOr(Object... args);
1334
1335 /**
1336 * Atomically sets the value of a variable to the result of
1337 * bitwise OR between the variable's current value and the {@code mask}
1338 * with the memory semantics of {@link #set} and returns the
1339 * variable's previous value, as accessed with the memory semantics of
1340 * {@link #getAcquire}.
1341 *
1342 * <p>If the variable type is the non-integral {@code boolean} type then a
1343 * logical OR is performed instead of a bitwise OR.
1344 *
1345 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T mask)T}.
1346 *
1347 * <p>The symbolic type descriptor at the call site of {@code getAndBitwiseOrAcquire}
1348 * must match the access mode type that is the result of calling
1349 * {@code accessModeType(VarHandle.AccessMode.GET_AND_BITWISE_OR_ACQUIRE)} on this
1350 * VarHandle.
1351 *
1352 * @param args the signature-polymorphic parameter list of the form
1353 * {@code (CT1 ct1, ..., CTn ctn, T mask)}
1354 * , statically represented using varargs.
1355 * @return the signature-polymorphic result that is the previous value of
1356 * the variable
1357 * , statically represented using {@code Object}.
1358 * @throws UnsupportedOperationException if the access mode is unsupported
1359 * for this VarHandle.
1360 * @throws WrongMethodTypeException if the access mode type does not
1361 * match the caller's symbolic type descriptor.
1362 * @throws ClassCastException if the access mode type matches the caller's
1363 * symbolic type descriptor, but a reference cast fails.
1364 * @see #set(Object...)
1365 * @see #getAcquire(Object...)
1366 */
1367 public final native
1368 @MethodHandle.PolymorphicSignature
1369 @IntrinsicCandidate
1370 Object getAndBitwiseOrAcquire(Object... args);
1371
1372 /**
1373 * Atomically sets the value of a variable to the result of
1374 * bitwise OR between the variable's current value and the {@code mask}
1375 * with the memory semantics of {@link #setRelease} and returns the
1376 * variable's previous value, as accessed with the memory semantics of
1377 * {@link #get}.
1378 *
1379 * <p>If the variable type is the non-integral {@code boolean} type then a
1380 * logical OR is performed instead of a bitwise OR.
1381 *
1382 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T mask)T}.
1383 *
1384 * <p>The symbolic type descriptor at the call site of {@code getAndBitwiseOrRelease}
1385 * must match the access mode type that is the result of calling
1386 * {@code accessModeType(VarHandle.AccessMode.GET_AND_BITWISE_OR_RELEASE)} on this
1387 * VarHandle.
1388 *
1389 * @param args the signature-polymorphic parameter list of the form
1390 * {@code (CT1 ct1, ..., CTn ctn, T mask)}
1391 * , statically represented using varargs.
1392 * @return the signature-polymorphic result that is the previous value of
1393 * the variable
1394 * , statically represented using {@code Object}.
1395 * @throws UnsupportedOperationException if the access mode is unsupported
1396 * for this VarHandle.
1397 * @throws WrongMethodTypeException if the access mode type does not
1398 * match the caller's symbolic type descriptor.
1399 * @throws ClassCastException if the access mode type matches the caller's
1400 * symbolic type descriptor, but a reference cast fails.
1401 * @see #setRelease(Object...)
1402 * @see #get(Object...)
1403 */
1404 public final native
1405 @MethodHandle.PolymorphicSignature
1406 @IntrinsicCandidate
1407 Object getAndBitwiseOrRelease(Object... args);
1408
1409 /**
1410 * Atomically sets the value of a variable to the result of
1411 * bitwise AND between the variable's current value and the {@code mask}
1412 * with the memory semantics of {@link #setVolatile} and returns the
1413 * variable's previous value, as accessed with the memory semantics of
1414 * {@link #getVolatile}.
1415 *
1416 * <p>If the variable type is the non-integral {@code boolean} type then a
1417 * logical AND is performed instead of a bitwise AND.
1418 *
1419 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T mask)T}.
1420 *
1421 * <p>The symbolic type descriptor at the call site of {@code getAndBitwiseAnd}
1422 * must match the access mode type that is the result of calling
1423 * {@code accessModeType(VarHandle.AccessMode.GET_AND_BITWISE_AND)} on this
1424 * VarHandle.
1425 *
1426 * @param args the signature-polymorphic parameter list of the form
1427 * {@code (CT1 ct1, ..., CTn ctn, T mask)}
1428 * , statically represented using varargs.
1429 * @return the signature-polymorphic result that is the previous value of
1430 * the variable
1431 * , statically represented using {@code Object}.
1432 * @throws UnsupportedOperationException if the access mode is unsupported
1433 * for this VarHandle.
1434 * @throws WrongMethodTypeException if the access mode type does not
1435 * match the caller's symbolic type descriptor.
1436 * @throws ClassCastException if the access mode type matches the caller's
1437 * symbolic type descriptor, but a reference cast fails.
1438 * @see #setVolatile(Object...)
1439 * @see #getVolatile(Object...)
1440 */
1441 public final native
1442 @MethodHandle.PolymorphicSignature
1443 @IntrinsicCandidate
1444 Object getAndBitwiseAnd(Object... args);
1445
1446 /**
1447 * Atomically sets the value of a variable to the result of
1448 * bitwise AND between the variable's current value and the {@code mask}
1449 * with the memory semantics of {@link #set} and returns the
1450 * variable's previous value, as accessed with the memory semantics of
1451 * {@link #getAcquire}.
1452 *
1453 * <p>If the variable type is the non-integral {@code boolean} type then a
1454 * logical AND is performed instead of a bitwise AND.
1455 *
1456 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T mask)T}.
1457 *
1458 * <p>The symbolic type descriptor at the call site of {@code getAndBitwiseAndAcquire}
1459 * must match the access mode type that is the result of calling
1460 * {@code accessModeType(VarHandle.AccessMode.GET_AND_BITWISE_AND_ACQUIRE)} on this
1461 * VarHandle.
1462 *
1463 * @param args the signature-polymorphic parameter list of the form
1464 * {@code (CT1 ct1, ..., CTn ctn, T mask)}
1465 * , statically represented using varargs.
1466 * @return the signature-polymorphic result that is the previous value of
1467 * the variable
1468 * , statically represented using {@code Object}.
1469 * @throws UnsupportedOperationException if the access mode is unsupported
1470 * for this VarHandle.
1471 * @throws WrongMethodTypeException if the access mode type does not
1472 * match the caller's symbolic type descriptor.
1473 * @throws ClassCastException if the access mode type matches the caller's
1474 * symbolic type descriptor, but a reference cast fails.
1475 * @see #set(Object...)
1476 * @see #getAcquire(Object...)
1477 */
1478 public final native
1479 @MethodHandle.PolymorphicSignature
1480 @IntrinsicCandidate
1481 Object getAndBitwiseAndAcquire(Object... args);
1482
1483 /**
1484 * Atomically sets the value of a variable to the result of
1485 * bitwise AND between the variable's current value and the {@code mask}
1486 * with the memory semantics of {@link #setRelease} and returns the
1487 * variable's previous value, as accessed with the memory semantics of
1488 * {@link #get}.
1489 *
1490 * <p>If the variable type is the non-integral {@code boolean} type then a
1491 * logical AND is performed instead of a bitwise AND.
1492 *
1493 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T mask)T}.
1494 *
1495 * <p>The symbolic type descriptor at the call site of {@code getAndBitwiseAndRelease}
1496 * must match the access mode type that is the result of calling
1497 * {@code accessModeType(VarHandle.AccessMode.GET_AND_BITWISE_AND_RELEASE)} on this
1498 * VarHandle.
1499 *
1500 * @param args the signature-polymorphic parameter list of the form
1501 * {@code (CT1 ct1, ..., CTn ctn, T mask)}
1502 * , statically represented using varargs.
1503 * @return the signature-polymorphic result that is the previous value of
1504 * the variable
1505 * , statically represented using {@code Object}.
1506 * @throws UnsupportedOperationException if the access mode is unsupported
1507 * for this VarHandle.
1508 * @throws WrongMethodTypeException if the access mode type does not
1509 * match the caller's symbolic type descriptor.
1510 * @throws ClassCastException if the access mode type matches the caller's
1511 * symbolic type descriptor, but a reference cast fails.
1512 * @see #setRelease(Object...)
1513 * @see #get(Object...)
1514 */
1515 public final native
1516 @MethodHandle.PolymorphicSignature
1517 @IntrinsicCandidate
1518 Object getAndBitwiseAndRelease(Object... args);
1519
1520 /**
1521 * Atomically sets the value of a variable to the result of
1522 * bitwise XOR between the variable's current value and the {@code mask}
1523 * with the memory semantics of {@link #setVolatile} and returns the
1524 * variable's previous value, as accessed with the memory semantics of
1525 * {@link #getVolatile}.
1526 *
1527 * <p>If the variable type is the non-integral {@code boolean} type then a
1528 * logical XOR is performed instead of a bitwise XOR.
1529 *
1530 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T mask)T}.
1531 *
1532 * <p>The symbolic type descriptor at the call site of {@code getAndBitwiseXor}
1533 * must match the access mode type that is the result of calling
1534 * {@code accessModeType(VarHandle.AccessMode.GET_AND_BITWISE_XOR)} on this
1535 * VarHandle.
1536 *
1537 * @param args the signature-polymorphic parameter list of the form
1538 * {@code (CT1 ct1, ..., CTn ctn, T mask)}
1539 * , statically represented using varargs.
1540 * @return the signature-polymorphic result that is the previous value of
1541 * the variable
1542 * , statically represented using {@code Object}.
1543 * @throws UnsupportedOperationException if the access mode is unsupported
1544 * for this VarHandle.
1545 * @throws WrongMethodTypeException if the access mode type does not
1546 * match the caller's symbolic type descriptor.
1547 * @throws ClassCastException if the access mode type matches the caller's
1548 * symbolic type descriptor, but a reference cast fails.
1549 * @see #setVolatile(Object...)
1550 * @see #getVolatile(Object...)
1551 */
1552 public final native
1553 @MethodHandle.PolymorphicSignature
1554 @IntrinsicCandidate
1555 Object getAndBitwiseXor(Object... args);
1556
1557 /**
1558 * Atomically sets the value of a variable to the result of
1559 * bitwise XOR between the variable's current value and the {@code mask}
1560 * with the memory semantics of {@link #set} and returns the
1561 * variable's previous value, as accessed with the memory semantics of
1562 * {@link #getAcquire}.
1563 *
1564 * <p>If the variable type is the non-integral {@code boolean} type then a
1565 * logical XOR is performed instead of a bitwise XOR.
1566 *
1567 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T mask)T}.
1568 *
1569 * <p>The symbolic type descriptor at the call site of {@code getAndBitwiseXorAcquire}
1570 * must match the access mode type that is the result of calling
1571 * {@code accessModeType(VarHandle.AccessMode.GET_AND_BITWISE_XOR_ACQUIRE)} on this
1572 * VarHandle.
1573 *
1574 * @param args the signature-polymorphic parameter list of the form
1575 * {@code (CT1 ct1, ..., CTn ctn, T mask)}
1576 * , statically represented using varargs.
1577 * @return the signature-polymorphic result that is the previous value of
1578 * the variable
1579 * , statically represented using {@code Object}.
1580 * @throws UnsupportedOperationException if the access mode is unsupported
1581 * for this VarHandle.
1582 * @throws WrongMethodTypeException if the access mode type does not
1583 * match the caller's symbolic type descriptor.
1584 * @throws ClassCastException if the access mode type matches the caller's
1585 * symbolic type descriptor, but a reference cast fails.
1586 * @see #set(Object...)
1587 * @see #getAcquire(Object...)
1588 */
1589 public final native
1590 @MethodHandle.PolymorphicSignature
1591 @IntrinsicCandidate
1592 Object getAndBitwiseXorAcquire(Object... args);
1593
1594 /**
1595 * Atomically sets the value of a variable to the result of
1596 * bitwise XOR between the variable's current value and the {@code mask}
1597 * with the memory semantics of {@link #setRelease} and returns the
1598 * variable's previous value, as accessed with the memory semantics of
1599 * {@link #get}.
1600 *
1601 * <p>If the variable type is the non-integral {@code boolean} type then a
1602 * logical XOR is performed instead of a bitwise XOR.
1603 *
1604 * <p>The method signature is of the form {@code (CT1 ct1, ..., CTn ctn, T mask)T}.
1605 *
1606 * <p>The symbolic type descriptor at the call site of {@code getAndBitwiseXorRelease}
1607 * must match the access mode type that is the result of calling
1608 * {@code accessModeType(VarHandle.AccessMode.GET_AND_BITWISE_XOR_RELEASE)} on this
1609 * VarHandle.
1610 *
1611 * @param args the signature-polymorphic parameter list of the form
1612 * {@code (CT1 ct1, ..., CTn ctn, T mask)}
1613 * , statically represented using varargs.
1614 * @return the signature-polymorphic result that is the previous value of
1615 * the variable
1616 * , statically represented using {@code Object}.
1617 * @throws UnsupportedOperationException if the access mode is unsupported
1618 * for this VarHandle.
1619 * @throws WrongMethodTypeException if the access mode type does not
1620 * match the caller's symbolic type descriptor.
1621 * @throws ClassCastException if the access mode type matches the caller's
1622 * symbolic type descriptor, but a reference cast fails.
1623 * @see #setRelease(Object...)
1624 * @see #get(Object...)
1625 */
1626 public final native
1627 @MethodHandle.PolymorphicSignature
1628 @IntrinsicCandidate
1629 Object getAndBitwiseXorRelease(Object... args);
1630
1631 /**
1632 * Returns a VarHandle, with access to the same variable(s) as this VarHandle, but whose
1633 * invocation behavior of access mode methods is adjusted to
1634 * <a href="#invoke-exact-behavior"><em>invoke-exact behavior</em></a>.
1635 * <p>
1636 * If this VarHandle already has invoke-exact behavior this VarHandle is returned.
1637 * <p>
1638 * Invoking {@link #hasInvokeExactBehavior()} on the returned var handle
1639 * is guaranteed to return {@code true}.
1640 *
1641 * @apiNote
1642 * Invoke-exact behavior guarantees that upon invocation of an access mode method
1643 * the types and arity of the arguments must match the {@link #accessModeType(AccessMode) access mode type},
1644 * otherwise a {@link WrongMethodTypeException} is thrown.
1645 *
1646 * @see #withInvokeBehavior()
1647 * @see #hasInvokeExactBehavior()
1648 * @return a VarHandle with invoke-exact behavior
1649 * @since 16
1650 */
1651 public abstract VarHandle withInvokeExactBehavior();
1652
1653 /**
1654 * Returns a VarHandle, with access to the same variable(s) as this VarHandle, but whose
1655 * invocation behavior of access mode methods is adjusted to
1656 * <a href="#invoke-behavior"><em>invoke behavior</em></a>.
1657 * <p>
1658 * If this VarHandle already has invoke behavior this VarHandle is returned.
1659 * <p>
1660 * Invoking {@link #hasInvokeExactBehavior()} on the returned var handle
1661 * is guaranteed to return {@code false}.
1662 *
1663 * @see #withInvokeExactBehavior()
1664 * @see #hasInvokeExactBehavior()
1665 * @return a VarHandle with invoke behavior
1666 * @since 16
1667 */
1668 public abstract VarHandle withInvokeBehavior();
1669
1670 enum AccessType {
1671 GET(Object.class),
1672 SET(void.class),
1673 COMPARE_AND_SET(boolean.class),
1674 COMPARE_AND_EXCHANGE(Object.class),
1675 GET_AND_UPDATE(Object.class);
1676
1677 static final int COUNT = GET_AND_UPDATE.ordinal() + 1;
1678 static {
1679 assert (COUNT == values().length);
1680 }
1681 final Class<?> returnType;
1682 final boolean isMonomorphicInReturnType;
1683
1684 AccessType(Class<?> returnType) {
1685 this.returnType = returnType;
1686 isMonomorphicInReturnType = returnType != Object.class;
1687 }
1688
1689 MethodType accessModeType(Class<?> receiver, Class<?> value,
1690 Class<?>... intermediate) {
1691 Class<?>[] ps;
1692 int i;
1693 switch (this) {
1694 case GET:
1695 ps = allocateParameters(0, receiver, intermediate);
1696 fillParameters(ps, receiver, intermediate);
1697 return MethodType.methodType(value, ps);
1698 case SET:
1699 ps = allocateParameters(1, receiver, intermediate);
1700 i = fillParameters(ps, receiver, intermediate);
1701 ps[i] = value;
1702 return MethodType.methodType(void.class, ps);
1703 case COMPARE_AND_SET:
1704 ps = allocateParameters(2, receiver, intermediate);
1705 i = fillParameters(ps, receiver, intermediate);
1706 ps[i++] = value;
1707 ps[i] = value;
1708 return MethodType.methodType(boolean.class, ps);
1709 case COMPARE_AND_EXCHANGE:
1710 ps = allocateParameters(2, receiver, intermediate);
1711 i = fillParameters(ps, receiver, intermediate);
1712 ps[i++] = value;
1713 ps[i] = value;
1714 return MethodType.methodType(value, ps);
1715 case GET_AND_UPDATE:
1716 ps = allocateParameters(1, receiver, intermediate);
1717 i = fillParameters(ps, receiver, intermediate);
1718 ps[i] = value;
1719 return MethodType.methodType(value, ps);
1720 default:
1721 throw new InternalError("Unknown AccessType");
1722 }
1723 }
1724
1725 private static Class<?>[] allocateParameters(int values,
1726 Class<?> receiver, Class<?>... intermediate) {
1727 int size = ((receiver != null) ? 1 : 0) + intermediate.length + values;
1728 return new Class<?>[size];
1729 }
1730
1731 private static int fillParameters(Class<?>[] ps,
1732 Class<?> receiver, Class<?>... intermediate) {
1733 int i = 0;
1734 if (receiver != null)
1735 ps[i++] = receiver;
1736 for (int j = 0; j < intermediate.length; j++)
1737 ps[i++] = intermediate[j];
1738 return i;
1739 }
1740 }
1741
1742 /**
1743 * The set of access modes that specify how a variable, referenced by a
1744 * VarHandle, is accessed.
1745 */
1746 public enum AccessMode {
1747 /**
1748 * The access mode whose access is specified by the corresponding
1749 * method
1750 * {@link VarHandle#get VarHandle.get}
1751 */
1752 GET("get", AccessType.GET),
1753 /**
1754 * The access mode whose access is specified by the corresponding
1755 * method
1756 * {@link VarHandle#set VarHandle.set}
1757 */
1758 SET("set", AccessType.SET),
1759 /**
1760 * The access mode whose access is specified by the corresponding
1761 * method
1762 * {@link VarHandle#getVolatile VarHandle.getVolatile}
1763 */
1764 GET_VOLATILE("getVolatile", AccessType.GET),
1765 /**
1766 * The access mode whose access is specified by the corresponding
1767 * method
1768 * {@link VarHandle#setVolatile VarHandle.setVolatile}
1769 */
1770 SET_VOLATILE("setVolatile", AccessType.SET),
1771 /**
1772 * The access mode whose access is specified by the corresponding
1773 * method
1774 * {@link VarHandle#getAcquire VarHandle.getAcquire}
1775 */
1776 GET_ACQUIRE("getAcquire", AccessType.GET),
1777 /**
1778 * The access mode whose access is specified by the corresponding
1779 * method
1780 * {@link VarHandle#setRelease VarHandle.setRelease}
1781 */
1782 SET_RELEASE("setRelease", AccessType.SET),
1783 /**
1784 * The access mode whose access is specified by the corresponding
1785 * method
1786 * {@link VarHandle#getOpaque VarHandle.getOpaque}
1787 */
1788 GET_OPAQUE("getOpaque", AccessType.GET),
1789 /**
1790 * The access mode whose access is specified by the corresponding
1791 * method
1792 * {@link VarHandle#setOpaque VarHandle.setOpaque}
1793 */
1794 SET_OPAQUE("setOpaque", AccessType.SET),
1795 /**
1796 * The access mode whose access is specified by the corresponding
1797 * method
1798 * {@link VarHandle#compareAndSet VarHandle.compareAndSet}
1799 */
1800 COMPARE_AND_SET("compareAndSet", AccessType.COMPARE_AND_SET),
1801 /**
1802 * The access mode whose access is specified by the corresponding
1803 * method
1804 * {@link VarHandle#compareAndExchange VarHandle.compareAndExchange}
1805 */
1806 COMPARE_AND_EXCHANGE("compareAndExchange", AccessType.COMPARE_AND_EXCHANGE),
1807 /**
1808 * The access mode whose access is specified by the corresponding
1809 * method
1810 * {@link VarHandle#compareAndExchangeAcquire VarHandle.compareAndExchangeAcquire}
1811 */
1812 COMPARE_AND_EXCHANGE_ACQUIRE("compareAndExchangeAcquire", AccessType.COMPARE_AND_EXCHANGE),
1813 /**
1814 * The access mode whose access is specified by the corresponding
1815 * method
1816 * {@link VarHandle#compareAndExchangeRelease VarHandle.compareAndExchangeRelease}
1817 */
1818 COMPARE_AND_EXCHANGE_RELEASE("compareAndExchangeRelease", AccessType.COMPARE_AND_EXCHANGE),
1819 /**
1820 * The access mode whose access is specified by the corresponding
1821 * method
1822 * {@link VarHandle#weakCompareAndSetPlain VarHandle.weakCompareAndSetPlain}
1823 */
1824 WEAK_COMPARE_AND_SET_PLAIN("weakCompareAndSetPlain", AccessType.COMPARE_AND_SET),
1825 /**
1826 * The access mode whose access is specified by the corresponding
1827 * method
1828 * {@link VarHandle#weakCompareAndSet VarHandle.weakCompareAndSet}
1829 */
1830 WEAK_COMPARE_AND_SET("weakCompareAndSet", AccessType.COMPARE_AND_SET),
1831 /**
1832 * The access mode whose access is specified by the corresponding
1833 * method
1834 * {@link VarHandle#weakCompareAndSetAcquire VarHandle.weakCompareAndSetAcquire}
1835 */
1836 WEAK_COMPARE_AND_SET_ACQUIRE("weakCompareAndSetAcquire", AccessType.COMPARE_AND_SET),
1837 /**
1838 * The access mode whose access is specified by the corresponding
1839 * method
1840 * {@link VarHandle#weakCompareAndSetRelease VarHandle.weakCompareAndSetRelease}
1841 */
1842 WEAK_COMPARE_AND_SET_RELEASE("weakCompareAndSetRelease", AccessType.COMPARE_AND_SET),
1843 /**
1844 * The access mode whose access is specified by the corresponding
1845 * method
1846 * {@link VarHandle#getAndSet VarHandle.getAndSet}
1847 */
1848 GET_AND_SET("getAndSet", AccessType.GET_AND_UPDATE),
1849 /**
1850 * The access mode whose access is specified by the corresponding
1851 * method
1852 * {@link VarHandle#getAndSetAcquire VarHandle.getAndSetAcquire}
1853 */
1854 GET_AND_SET_ACQUIRE("getAndSetAcquire", AccessType.GET_AND_UPDATE),
1855 /**
1856 * The access mode whose access is specified by the corresponding
1857 * method
1858 * {@link VarHandle#getAndSetRelease VarHandle.getAndSetRelease}
1859 */
1860 GET_AND_SET_RELEASE("getAndSetRelease", AccessType.GET_AND_UPDATE),
1861 /**
1862 * The access mode whose access is specified by the corresponding
1863 * method
1864 * {@link VarHandle#getAndAdd VarHandle.getAndAdd}
1865 */
1866 GET_AND_ADD("getAndAdd", AccessType.GET_AND_UPDATE),
1867 /**
1868 * The access mode whose access is specified by the corresponding
1869 * method
1870 * {@link VarHandle#getAndAddAcquire VarHandle.getAndAddAcquire}
1871 */
1872 GET_AND_ADD_ACQUIRE("getAndAddAcquire", AccessType.GET_AND_UPDATE),
1873 /**
1874 * The access mode whose access is specified by the corresponding
1875 * method
1876 * {@link VarHandle#getAndAddRelease VarHandle.getAndAddRelease}
1877 */
1878 GET_AND_ADD_RELEASE("getAndAddRelease", AccessType.GET_AND_UPDATE),
1879 /**
1880 * The access mode whose access is specified by the corresponding
1881 * method
1882 * {@link VarHandle#getAndBitwiseOr VarHandle.getAndBitwiseOr}
1883 */
1884 GET_AND_BITWISE_OR("getAndBitwiseOr", AccessType.GET_AND_UPDATE),
1885 /**
1886 * The access mode whose access is specified by the corresponding
1887 * method
1888 * {@link VarHandle#getAndBitwiseOrRelease VarHandle.getAndBitwiseOrRelease}
1889 */
1890 GET_AND_BITWISE_OR_RELEASE("getAndBitwiseOrRelease", AccessType.GET_AND_UPDATE),
1891 /**
1892 * The access mode whose access is specified by the corresponding
1893 * method
1894 * {@link VarHandle#getAndBitwiseOrAcquire VarHandle.getAndBitwiseOrAcquire}
1895 */
1896 GET_AND_BITWISE_OR_ACQUIRE("getAndBitwiseOrAcquire", AccessType.GET_AND_UPDATE),
1897 /**
1898 * The access mode whose access is specified by the corresponding
1899 * method
1900 * {@link VarHandle#getAndBitwiseAnd VarHandle.getAndBitwiseAnd}
1901 */
1902 GET_AND_BITWISE_AND("getAndBitwiseAnd", AccessType.GET_AND_UPDATE),
1903 /**
1904 * The access mode whose access is specified by the corresponding
1905 * method
1906 * {@link VarHandle#getAndBitwiseAndRelease VarHandle.getAndBitwiseAndRelease}
1907 */
1908 GET_AND_BITWISE_AND_RELEASE("getAndBitwiseAndRelease", AccessType.GET_AND_UPDATE),
1909 /**
1910 * The access mode whose access is specified by the corresponding
1911 * method
1912 * {@link VarHandle#getAndBitwiseAndAcquire VarHandle.getAndBitwiseAndAcquire}
1913 */
1914 GET_AND_BITWISE_AND_ACQUIRE("getAndBitwiseAndAcquire", AccessType.GET_AND_UPDATE),
1915 /**
1916 * The access mode whose access is specified by the corresponding
1917 * method
1918 * {@link VarHandle#getAndBitwiseXor VarHandle.getAndBitwiseXor}
1919 */
1920 GET_AND_BITWISE_XOR("getAndBitwiseXor", AccessType.GET_AND_UPDATE),
1921 /**
1922 * The access mode whose access is specified by the corresponding
1923 * method
1924 * {@link VarHandle#getAndBitwiseXorRelease VarHandle.getAndBitwiseXorRelease}
1925 */
1926 GET_AND_BITWISE_XOR_RELEASE("getAndBitwiseXorRelease", AccessType.GET_AND_UPDATE),
1927 /**
1928 * The access mode whose access is specified by the corresponding
1929 * method
1930 * {@link VarHandle#getAndBitwiseXorAcquire VarHandle.getAndBitwiseXorAcquire}
1931 */
1932 GET_AND_BITWISE_XOR_ACQUIRE("getAndBitwiseXorAcquire", AccessType.GET_AND_UPDATE),
1933 ;
1934
1935 static final int COUNT = GET_AND_BITWISE_XOR_ACQUIRE.ordinal() + 1;
1936 static {
1937 assert (COUNT == values().length);
1938 }
1939 final String methodName;
1940 final AccessType at;
1941
1942 AccessMode(final String methodName, AccessType at) {
1943 this.methodName = methodName;
1944 this.at = at;
1945 }
1946
1947 /**
1948 * Returns the {@code VarHandle} signature-polymorphic method name
1949 * associated with this {@code AccessMode} value.
1950 *
1951 * @return the signature-polymorphic method name
1952 * @see #valueFromMethodName
1953 */
1954 public String methodName() {
1955 return methodName;
1956 }
1957
1958 /**
1959 * Returns the {@code AccessMode} value associated with the specified
1960 * {@code VarHandle} signature-polymorphic method name.
1961 *
1962 * @param methodName the signature-polymorphic method name
1963 * @return the {@code AccessMode} value
1964 * @throws IllegalArgumentException if there is no {@code AccessMode}
1965 * value associated with method name (indicating the method
1966 * name does not correspond to a {@code VarHandle}
1967 * signature-polymorphic method name).
1968 * @see #methodName()
1969 */
1970 public static AccessMode valueFromMethodName(String methodName) {
1971 return switch (methodName) {
1972 case "get" -> GET;
1973 case "set" -> SET;
1974 case "getVolatile" -> GET_VOLATILE;
1975 case "setVolatile" -> SET_VOLATILE;
1976 case "getAcquire" -> GET_ACQUIRE;
1977 case "setRelease" -> SET_RELEASE;
1978 case "getOpaque" -> GET_OPAQUE;
1979 case "setOpaque" -> SET_OPAQUE;
1980 case "compareAndSet" -> COMPARE_AND_SET;
1981 case "compareAndExchange" -> COMPARE_AND_EXCHANGE;
1982 case "compareAndExchangeAcquire" -> COMPARE_AND_EXCHANGE_ACQUIRE;
1983 case "compareAndExchangeRelease" -> COMPARE_AND_EXCHANGE_RELEASE;
1984 case "weakCompareAndSet" -> WEAK_COMPARE_AND_SET;
1985 case "weakCompareAndSetPlain" -> WEAK_COMPARE_AND_SET_PLAIN;
1986 case "weakCompareAndSetAcquire" -> WEAK_COMPARE_AND_SET_ACQUIRE;
1987 case "weakCompareAndSetRelease" -> WEAK_COMPARE_AND_SET_RELEASE;
1988 case "getAndSet" -> GET_AND_SET;
1989 case "getAndSetAcquire" -> GET_AND_SET_ACQUIRE;
1990 case "getAndSetRelease" -> GET_AND_SET_RELEASE;
1991 case "getAndAdd" -> GET_AND_ADD;
1992 case "getAndAddAcquire" -> GET_AND_ADD_ACQUIRE;
1993 case "getAndAddRelease" -> GET_AND_ADD_RELEASE;
1994 case "getAndBitwiseOr" -> GET_AND_BITWISE_OR;
1995 case "getAndBitwiseOrRelease" -> GET_AND_BITWISE_OR_RELEASE;
1996 case "getAndBitwiseOrAcquire" -> GET_AND_BITWISE_OR_ACQUIRE;
1997 case "getAndBitwiseAnd" -> GET_AND_BITWISE_AND;
1998 case "getAndBitwiseAndRelease" -> GET_AND_BITWISE_AND_RELEASE;
1999 case "getAndBitwiseAndAcquire" -> GET_AND_BITWISE_AND_ACQUIRE;
2000 case "getAndBitwiseXor" -> GET_AND_BITWISE_XOR;
2001 case "getAndBitwiseXorRelease" -> GET_AND_BITWISE_XOR_RELEASE;
2002 case "getAndBitwiseXorAcquire" -> GET_AND_BITWISE_XOR_ACQUIRE;
2003 default -> throw new IllegalArgumentException("No AccessMode value for method name " + methodName);
2004 };
2005 }
2006
2007 private static final @Stable AccessMode[] VALUES = values();
2008 static AccessMode valueFromOrdinal(int mode) {
2009 return VALUES[mode];
2010 }
2011 }
2012
2013 static final class AccessDescriptor {
2014 final MethodType symbolicMethodTypeExact;
2015 final MethodType symbolicMethodTypeErased;
2016 final MethodType symbolicMethodTypeInvoker;
2017 final Class<?> returnType;
2018 final int type;
2019 final int mode;
2020
2021 public AccessDescriptor(MethodType symbolicMethodType, int type, int mode) {
2022 this.symbolicMethodTypeExact = symbolicMethodType;
2023 this.symbolicMethodTypeErased = symbolicMethodType.erase();
2024 this.symbolicMethodTypeInvoker = symbolicMethodType.insertParameterTypes(0, VarHandle.class);
2025 this.returnType = symbolicMethodType.returnType();
2026 this.type = type;
2027 this.mode = mode;
2028 }
2029 }
2030
2031 /**
2032 * Returns a compact textual description of this {@linkplain VarHandle},
2033 * including the type of variable described, and a description of its coordinates.
2034 *
2035 * @return A compact textual description of this {@linkplain VarHandle}
2036 */
2037 @Override
2038 public final String toString() {
2039 return String.format("VarHandle[varType=%s, coord=%s]",
2040 varType().getName(),
2041 coordinateTypes());
2042 }
2043
2044 /**
2045 * Returns the variable type of variables referenced by this VarHandle.
2046 *
2047 * @return the variable type of variables referenced by this VarHandle
2048 */
2049 public Class<?> varType() {
2050 MethodType typeSet = accessModeType(AccessMode.SET);
2051 return typeSet.parameterType(typeSet.parameterCount() - 1);
2052 }
2053
2054 /**
2055 * Returns the coordinate types for this VarHandle.
2056 *
2057 * @return the coordinate types for this VarHandle. The returned
2058 * list is unmodifiable
2059 */
2060 public List<Class<?>> coordinateTypes() {
2061 MethodType typeGet = accessModeType(AccessMode.GET);
2062 return typeGet.parameterList();
2063 }
2064
2065 /**
2066 * Obtains the access mode type for this VarHandle and a given access mode.
2067 *
2068 * <p>The access mode type's parameter types will consist of a prefix that
2069 * is the coordinate types of this VarHandle followed by further
2070 * types as defined by the access mode method.
2071 * The access mode type's return type is defined by the return type of the
2072 * access mode method.
2073 *
2074 * @param accessMode the access mode, corresponding to the
2075 * signature-polymorphic method of the same name
2076 * @return the access mode type for the given access mode
2077 */
2078 public final MethodType accessModeType(AccessMode accessMode) {
2079 return accessModeType(accessMode.at.ordinal());
2080 }
2081
2082 /**
2083 * Validates that the given access descriptors method type matches up with
2084 * the access mode of this VarHandle, then returns if this is direct.
2085 * These operations were grouped together to slightly
2086 * improve efficiency during startup/warmup.
2087 *
2088 * A direct VarHandle's VarForm has implementation MemberNames that can
2089 * be linked directly. If a VarHandle is indirect, it must override
2090 * {@link #isAccessModeSupported} and {@link #getMethodHandleUncached}
2091 * which access MemberNames.
2092 *
2093 * @return true if this is a direct VarHandle, false if it's an indirect
2094 * VarHandle.
2095 * @throws WrongMethodTypeException if there's an access type mismatch
2096 * @see #asDirect()
2097 */
2098 @ForceInline
2099 boolean checkAccessModeThenIsDirect(VarHandle.AccessDescriptor ad) {
2100 if (exact && accessModeType(ad.type) != ad.symbolicMethodTypeExact) {
2101 throwWrongMethodTypeException(ad);
2102 }
2103 // return true unless overridden in an IndirectVarHandle
2104 return true;
2105 }
2106
2107 @DontInline
2108 private final void throwWrongMethodTypeException(VarHandle.AccessDescriptor ad) {
2109 throw new WrongMethodTypeException("handle's method type " + accessModeType(ad.type)
2110 + " but found " + ad.symbolicMethodTypeExact);
2111 }
2112
2113 @ForceInline
2114 final MethodType accessModeType(int accessTypeOrdinal) {
2115 MethodType[] mtTable = methodTypeTable;
2116 if (mtTable == null) {
2117 mtTable = methodTypeTable = new MethodType[VarHandle.AccessType.COUNT];
2118 }
2119 MethodType mt = mtTable[accessTypeOrdinal];
2120 if (mt == null) {
2121 mt = mtTable[accessTypeOrdinal] =
2122 accessModeTypeUncached(accessTypeOrdinal);
2123 }
2124 return mt;
2125 }
2126
2127 final MethodType accessModeTypeUncached(int accessTypeOrdinal) {
2128 return accessModeTypeUncached(AccessType.values()[accessTypeOrdinal]);
2129 }
2130
2131 abstract MethodType accessModeTypeUncached(AccessType accessMode);
2132
2133 /**
2134 * Returns {@code true} if the given access mode is supported, otherwise
2135 * {@code false}.
2136 *
2137 * <p>The return of a {@code false} value for a given access mode indicates
2138 * that an {@code UnsupportedOperationException} is thrown on invocation
2139 * of the corresponding access mode method.
2140 *
2141 * @param accessMode the access mode, corresponding to the
2142 * signature-polymorphic method of the same name
2143 * @return {@code true} if the given access mode is supported, otherwise
2144 * {@code false}.
2145 */
2146 public boolean isAccessModeSupported(AccessMode accessMode) {
2147 return vform.getMemberNameOrNull(accessMode.ordinal()) != null;
2148 }
2149
2150 /**
2151 * Obtains a method handle bound to this VarHandle and the given access
2152 * mode.
2153 *
2154 * @apiNote This method, for a VarHandle {@code vh} and access mode
2155 * {@code {access-mode}}, returns a method handle that is equivalent to
2156 * method handle {@code bmh} in the following code (though it may be more
2157 * efficient):
2158 * <pre>{@code
2159 * MethodHandle mh = MethodHandles.varHandleExactInvoker(
2160 * vh.accessModeType(VarHandle.AccessMode.{access-mode}));
2161 *
2162 * MethodHandle bmh = mh.bindTo(vh);
2163 * }</pre>
2164 *
2165 * @param accessMode the access mode, corresponding to the
2166 * signature-polymorphic method of the same name
2167 * @return a method handle bound to this VarHandle and the given access mode
2168 */
2169 public MethodHandle toMethodHandle(AccessMode accessMode) {
2170 if (isAccessModeSupported(accessMode)) {
2171 MethodHandle mh = getMethodHandle(accessMode.ordinal());
2172 return mh.bindTo(asDirect());
2173 }
2174 else {
2175 // Ensure an UnsupportedOperationException is thrown
2176 return MethodHandles.varHandleInvoker(accessMode, accessModeType(accessMode)).
2177 bindTo(this);
2178 }
2179 }
2180
2181 /**
2182 * Return a nominal descriptor for this instance, if one can be
2183 * constructed, or an empty {@link Optional} if one cannot be.
2184 *
2185 * @return An {@link Optional} containing the resulting nominal descriptor,
2186 * or an empty {@link Optional} if one cannot be constructed.
2187 * @since 12
2188 */
2189 @Override
2190 public Optional<VarHandleDesc> describeConstable() {
2191 // partial function for field and array only
2192 return Optional.empty();
2193 }
2194
2195 @Stable
2196 MethodType[] methodTypeTable;
2197
2198 @Stable
2199 MethodHandle[] methodHandleTable;
2200
2201 @ForceInline
2202 final MethodHandle getMethodHandle(int mode) {
2203 MethodHandle[] mhTable = methodHandleTable;
2204 if (mhTable == null) {
2205 mhTable = methodHandleTable = new MethodHandle[AccessMode.COUNT];
2206 }
2207 MethodHandle mh = mhTable[mode];
2208 if (mh == null) {
2209 mh = mhTable[mode] = getMethodHandleUncached(mode);
2210 }
2211 return mh;
2212 }
2213
2214 /**
2215 * Computes a method handle that can be passed the {@linkplain #asDirect() direct}
2216 * var handle of this var handle with the given access mode. Pre/postprocessing
2217 * such as argument or return value filtering should be done by the returned
2218 * method handle.
2219 *
2220 * @throws UnsupportedOperationException if the access mode is not supported
2221 */
2222 MethodHandle getMethodHandleUncached(int mode) {
2223 MethodType mt = accessModeType(AccessMode.valueFromOrdinal(mode)).
2224 insertParameterTypes(0, VarHandle.class);
2225 MemberName mn = vform.getMemberName(mode);
2226 DirectMethodHandle dmh = DirectMethodHandle.make(mn);
2227 // Such a method handle must not be publicly exposed directly
2228 // otherwise it can be cracked, it must be transformed or rebound
2229 // before exposure
2230 MethodHandle mh = dmh.copyWith(mt, dmh.form);
2231 assert mh.type().erase() == mn.getMethodType().erase();
2232 return mh;
2233 }
2234
2235
2236 /*non-public*/
2237 final void updateVarForm(VarForm newVForm) {
2238 if (vform == newVForm) return;
2239 UNSAFE.putReference(this, VFORM_OFFSET, newVForm);
2240 UNSAFE.fullFence();
2241 }
2242
2243 private static final long VFORM_OFFSET;
2244
2245 static {
2246 VFORM_OFFSET = UNSAFE.objectFieldOffset(VarHandle.class, "vform");
2247
2248 // The VarHandleGuards must be initialized to ensure correct
2249 // compilation of the guard methods
2250 UNSAFE.ensureClassInitialized(VarHandleGuards.class);
2251 }
2252
2253
2254 // Fence methods
2255
2256 /**
2257 * Ensures that loads and stores before the fence will not be reordered
2258 * with
2259 * loads and stores after the fence.
2260 *
2261 * @apiNote Ignoring the many semantic differences from C and C++, this
2262 * method has memory ordering effects compatible with
2263 * {@code atomic_thread_fence(memory_order_seq_cst)}
2264 */
2265 @ForceInline
2266 public static void fullFence() {
2267 UNSAFE.fullFence();
2268 }
2269
2270 /**
2271 * Ensures that loads before the fence will not be reordered with loads and
2272 * stores after the fence.
2273 *
2274 * @apiNote Ignoring the many semantic differences from C and C++, this
2275 * method has memory ordering effects compatible with
2276 * {@code atomic_thread_fence(memory_order_acquire)}
2277 */
2278 @ForceInline
2279 public static void acquireFence() {
2280 UNSAFE.loadFence();
2281 }
2282
2283 /**
2284 * Ensures that loads and stores before the fence will not be
2285 * reordered with stores after the fence.
2286 *
2287 * @apiNote Ignoring the many semantic differences from C and C++, this
2288 * method has memory ordering effects compatible with
2289 * {@code atomic_thread_fence(memory_order_release)}
2290 */
2291 @ForceInline
2292 public static void releaseFence() {
2293 UNSAFE.storeFence();
2294 }
2295
2296 /**
2297 * Ensures that loads before the fence will not be reordered with
2298 * loads after the fence.
2299 */
2300 @ForceInline
2301 public static void loadLoadFence() {
2302 UNSAFE.loadLoadFence();
2303 }
2304
2305 /**
2306 * Ensures that stores before the fence will not be reordered with
2307 * stores after the fence.
2308 */
2309 @ForceInline
2310 public static void storeStoreFence() {
2311 UNSAFE.storeStoreFence();
2312 }
2313
2314 /**
2315 * A <a href="{@docRoot}/java.base/java/lang/constant/package-summary.html#nominal">nominal descriptor</a> for a
2316 * {@link VarHandle} constant.
2317 *
2318 * @since 12
2319 */
2320 public static final class VarHandleDesc extends DynamicConstantDesc<VarHandle> {
2321
2322 /**
2323 * Kinds of variable handle descs
2324 */
2325 private enum Kind {
2326 FIELD(ConstantDescs.BSM_VARHANDLE_FIELD),
2327 STATIC_FIELD(ConstantDescs.BSM_VARHANDLE_STATIC_FIELD),
2328 ARRAY(ConstantDescs.BSM_VARHANDLE_ARRAY);
2329
2330 final DirectMethodHandleDesc bootstrapMethod;
2331
2332 Kind(DirectMethodHandleDesc bootstrapMethod) {
2333 this.bootstrapMethod = bootstrapMethod;
2334 }
2335
2336 ConstantDesc[] toBSMArgs(ClassDesc declaringClass, ClassDesc varType) {
2337 return switch (this) {
2338 case FIELD, STATIC_FIELD -> new ConstantDesc[]{declaringClass, varType};
2339 case ARRAY -> new ConstantDesc[]{declaringClass};
2340 default -> throw new InternalError("Cannot reach here");
2341 };
2342 }
2343 }
2344
2345 private final Kind kind;
2346 private final ClassDesc declaringClass;
2347 private final ClassDesc varType;
2348
2349 /**
2350 * Construct a {@linkplain VarHandleDesc} given a kind, name, and declaring
2351 * class.
2352 *
2353 * @param kind the kind of the var handle
2354 * @param name the unqualified name of the field, for field var handles; otherwise ignored
2355 * @param declaringClass a {@link ClassDesc} describing the declaring class,
2356 * for field var handles
2357 * @param varType a {@link ClassDesc} describing the type of the variable
2358 * @throws NullPointerException if any required argument is null
2359 * @jvms 4.2.2 Unqualified Names
2360 */
2361 private VarHandleDesc(Kind kind, String name, ClassDesc declaringClass, ClassDesc varType) {
2362 super(kind.bootstrapMethod, name,
2363 ConstantDescs.CD_VarHandle,
2364 kind.toBSMArgs(declaringClass, varType));
2365 this.kind = kind;
2366 this.declaringClass = declaringClass;
2367 this.varType = varType;
2368 }
2369
2370 /**
2371 * Returns a {@linkplain VarHandleDesc} corresponding to a {@link VarHandle}
2372 * for an instance field.
2373 *
2374 * @param name the unqualified name of the field
2375 * @param declaringClass a {@link ClassDesc} describing the declaring class,
2376 * for field var handles
2377 * @param fieldType a {@link ClassDesc} describing the type of the field
2378 * @return the {@linkplain VarHandleDesc}
2379 * @throws NullPointerException if any of the arguments are null
2380 * @jvms 4.2.2 Unqualified Names
2381 */
2382 public static VarHandleDesc ofField(ClassDesc declaringClass, String name, ClassDesc fieldType) {
2383 Objects.requireNonNull(declaringClass);
2384 Objects.requireNonNull(name);
2385 Objects.requireNonNull(fieldType);
2386 return new VarHandleDesc(Kind.FIELD, name, declaringClass, fieldType);
2387 }
2388
2389 /**
2390 * Returns a {@linkplain VarHandleDesc} corresponding to a {@link VarHandle}
2391 * for a static field.
2392 *
2393 * @param name the unqualified name of the field
2394 * @param declaringClass a {@link ClassDesc} describing the declaring class,
2395 * for field var handles
2396 * @param fieldType a {@link ClassDesc} describing the type of the field
2397 * @return the {@linkplain VarHandleDesc}
2398 * @throws NullPointerException if any of the arguments are null
2399 * @jvms 4.2.2 Unqualified Names
2400 */
2401 public static VarHandleDesc ofStaticField(ClassDesc declaringClass, String name, ClassDesc fieldType) {
2402 Objects.requireNonNull(declaringClass);
2403 Objects.requireNonNull(name);
2404 Objects.requireNonNull(fieldType);
2405 return new VarHandleDesc(Kind.STATIC_FIELD, name, declaringClass, fieldType);
2406 }
2407
2408 /**
2409 * Returns a {@linkplain VarHandleDesc} corresponding to a {@link VarHandle}
2410 * for an array type.
2411 *
2412 * @param arrayClass a {@link ClassDesc} describing the type of the array
2413 * @return the {@linkplain VarHandleDesc}
2414 * @throws NullPointerException if any of the arguments are null
2415 */
2416 public static VarHandleDesc ofArray(ClassDesc arrayClass) {
2417 Objects.requireNonNull(arrayClass);
2418 if (!arrayClass.isArray())
2419 throw new IllegalArgumentException("Array class argument not an array: " + arrayClass);
2420 return new VarHandleDesc(Kind.ARRAY, ConstantDescs.DEFAULT_NAME, arrayClass, arrayClass.componentType());
2421 }
2422
2423 /**
2424 * Returns a {@link ClassDesc} describing the type of the variable described
2425 * by this descriptor.
2426 *
2427 * @return the variable type
2428 */
2429 public ClassDesc varType() {
2430 return varType;
2431 }
2432
2433 @Override
2434 public VarHandle resolveConstantDesc(MethodHandles.Lookup lookup)
2435 throws ReflectiveOperationException {
2436 return switch (kind) {
2437 case FIELD -> lookup.findVarHandle(declaringClass.resolveConstantDesc(lookup),
2438 constantName(),
2439 varType.resolveConstantDesc(lookup));
2440 case STATIC_FIELD -> lookup.findStaticVarHandle(declaringClass.resolveConstantDesc(lookup),
2441 constantName(),
2442 varType.resolveConstantDesc(lookup));
2443 case ARRAY -> MethodHandles.arrayElementVarHandle(declaringClass.resolveConstantDesc(lookup));
2444 default -> throw new InternalError("Cannot reach here");
2445 };
2446 }
2447
2448 /**
2449 * Returns a compact textual description of this constant description.
2450 * For a field {@linkplain VarHandle}, includes the owner, name, and type
2451 * of the field, and whether it is static; for an array {@linkplain VarHandle},
2452 * the name of the component type.
2453 *
2454 * @return A compact textual description of this descriptor
2455 */
2456 @Override
2457 public String toString() {
2458 return switch (kind) {
2459 case FIELD, STATIC_FIELD -> String.format("VarHandleDesc[%s%s.%s:%s]",
2460 (kind == Kind.STATIC_FIELD) ? "static " : "",
2461 declaringClass.displayName(), constantName(), varType.displayName());
2462 case ARRAY -> String.format("VarHandleDesc[%s[]]", declaringClass.displayName());
2463 default -> throw new InternalError("Cannot reach here");
2464 };
2465 }
2466 }
2467
2468 }