1 /*
2 * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package jdk.internal.misc;
27
28 import jdk.internal.HotSpotIntrinsicCandidate;
29 import jdk.internal.vm.annotation.ForceInline;
30
31 import java.lang.reflect.Field;
32 import java.security.ProtectionDomain;
33
34
35 /**
36 * A collection of methods for performing low-level, unsafe operations.
37 * Although the class and all methods are public, use of this class is
38 * limited because only trusted code can obtain instances of it.
39 *
40 * <em>Note:</em> It is the resposibility of the caller to make sure
41 * arguments are checked before methods of this class are
42 * called. While some rudimentary checks are performed on the input,
43 * the checks are best effort and when performance is an overriding
44 * priority, as when methods of this class are optimized by the
45 * runtime compiler, some or all checks (if any) may be elided. Hence,
46 * the caller must not rely on the checks and corresponding
47 * exceptions!
48 *
49 * @author John R. Rose
50 * @see #getUnsafe
51 */
52
53 public final class Unsafe {
54
55 private static native void registerNatives();
56 static {
57 registerNatives();
58 }
59
60 private Unsafe() {}
61
62 private static final Unsafe theUnsafe = new Unsafe();
63
64 /**
65 * Provides the caller with the capability of performing unsafe
66 * operations.
67 *
68 * <p>The returned {@code Unsafe} object should be carefully guarded
69 * by the caller, since it can be used to read and write data at arbitrary
70 * memory addresses. It must never be passed to untrusted code.
71 *
72 * <p>Most methods in this class are very low-level, and correspond to a
73 * small number of hardware instructions (on typical machines). Compilers
74 * are encouraged to optimize these methods accordingly.
75 *
76 * <p>Here is a suggested idiom for using unsafe operations:
77 *
78 * <pre> {@code
79 * class MyTrustedClass {
80 * private static final Unsafe unsafe = Unsafe.getUnsafe();
81 * ...
82 * private long myCountAddress = ...;
83 * public int getCount() { return unsafe.getByte(myCountAddress); }
84 * }}</pre>
85 *
86 * (It may assist compilers to make the local variable {@code final}.)
87 */
88 public static Unsafe getUnsafe() {
89 return theUnsafe;
90 }
91
92 /// peek and poke operations
93 /// (compilers should optimize these to memory ops)
94
95 // These work on object fields in the Java heap.
96 // They will not work on elements of packed arrays.
97
98 /**
99 * Fetches a value from a given Java variable.
100 * More specifically, fetches a field or array element within the given
101 * object {@code o} at the given offset, or (if {@code o} is null)
102 * from the memory address whose numerical value is the given offset.
103 * <p>
104 * The results are undefined unless one of the following cases is true:
105 * <ul>
106 * <li>The offset was obtained from {@link #objectFieldOffset} on
107 * the {@link java.lang.reflect.Field} of some Java field and the object
108 * referred to by {@code o} is of a class compatible with that
109 * field's class.
110 *
111 * <li>The offset and object reference {@code o} (either null or
112 * non-null) were both obtained via {@link #staticFieldOffset}
113 * and {@link #staticFieldBase} (respectively) from the
114 * reflective {@link Field} representation of some Java field.
115 *
116 * <li>The object referred to by {@code o} is an array, and the offset
117 * is an integer of the form {@code B+N*S}, where {@code N} is
118 * a valid index into the array, and {@code B} and {@code S} are
119 * the values obtained by {@link #arrayBaseOffset} and {@link
120 * #arrayIndexScale} (respectively) from the array's class. The value
121 * referred to is the {@code N}<em>th</em> element of the array.
122 *
123 * </ul>
124 * <p>
125 * If one of the above cases is true, the call references a specific Java
126 * variable (field or array element). However, the results are undefined
127 * if that variable is not in fact of the type returned by this method.
128 * <p>
129 * This method refers to a variable by means of two parameters, and so
130 * it provides (in effect) a <em>double-register</em> addressing mode
131 * for Java variables. When the object reference is null, this method
132 * uses its offset as an absolute address. This is similar in operation
133 * to methods such as {@link #getInt(long)}, which provide (in effect) a
134 * <em>single-register</em> addressing mode for non-Java variables.
135 * However, because Java variables may have a different layout in memory
136 * from non-Java variables, programmers should not assume that these
137 * two addressing modes are ever equivalent. Also, programmers should
138 * remember that offsets from the double-register addressing mode cannot
139 * be portably confused with longs used in the single-register addressing
140 * mode.
141 *
142 * @param o Java heap object in which the variable resides, if any, else
143 * null
144 * @param offset indication of where the variable resides in a Java heap
145 * object, if any, else a memory address locating the variable
146 * statically
147 * @return the value fetched from the indicated Java variable
148 * @throws RuntimeException No defined exceptions are thrown, not even
149 * {@link NullPointerException}
150 */
151 @HotSpotIntrinsicCandidate
152 public native int getInt(Object o, long offset);
153
154 /**
155 * Stores a value into a given Java variable.
156 * <p>
157 * The first two parameters are interpreted exactly as with
158 * {@link #getInt(Object, long)} to refer to a specific
159 * Java variable (field or array element). The given value
160 * is stored into that variable.
161 * <p>
162 * The variable must be of the same type as the method
163 * parameter {@code x}.
164 *
165 * @param o Java heap object in which the variable resides, if any, else
166 * null
167 * @param offset indication of where the variable resides in a Java heap
168 * object, if any, else a memory address locating the variable
169 * statically
170 * @param x the value to store into the indicated Java variable
171 * @throws RuntimeException No defined exceptions are thrown, not even
172 * {@link NullPointerException}
173 */
174 @HotSpotIntrinsicCandidate
175 public native void putInt(Object o, long offset, int x);
176
177 /**
178 * Fetches a reference value from a given Java variable.
179 * @see #getInt(Object, long)
180 */
181 @HotSpotIntrinsicCandidate
182 public native Object getObject(Object o, long offset);
183
184 /**
185 * Stores a reference value into a given Java variable.
186 * <p>
187 * Unless the reference {@code x} being stored is either null
188 * or matches the field type, the results are undefined.
189 * If the reference {@code o} is non-null, card marks or
190 * other store barriers for that object (if the VM requires them)
191 * are updated.
192 * @see #putInt(Object, long, int)
193 */
194 @HotSpotIntrinsicCandidate
195 public native void putObject(Object o, long offset, Object x);
196
197 /** @see #getInt(Object, long) */
198 @HotSpotIntrinsicCandidate
199 public native boolean getBoolean(Object o, long offset);
200
201 /** @see #putInt(Object, long, int) */
202 @HotSpotIntrinsicCandidate
203 public native void putBoolean(Object o, long offset, boolean x);
204
205 /** @see #getInt(Object, long) */
206 @HotSpotIntrinsicCandidate
207 public native byte getByte(Object o, long offset);
208
209 /** @see #putInt(Object, long, int) */
210 @HotSpotIntrinsicCandidate
211 public native void putByte(Object o, long offset, byte x);
212
213 /** @see #getInt(Object, long) */
214 @HotSpotIntrinsicCandidate
215 public native short getShort(Object o, long offset);
216
217 /** @see #putInt(Object, long, int) */
218 @HotSpotIntrinsicCandidate
219 public native void putShort(Object o, long offset, short x);
220
221 /** @see #getInt(Object, long) */
222 @HotSpotIntrinsicCandidate
223 public native char getChar(Object o, long offset);
224
225 /** @see #putInt(Object, long, int) */
226 @HotSpotIntrinsicCandidate
227 public native void putChar(Object o, long offset, char x);
228
229 /** @see #getInt(Object, long) */
230 @HotSpotIntrinsicCandidate
231 public native long getLong(Object o, long offset);
232
233 /** @see #putInt(Object, long, int) */
234 @HotSpotIntrinsicCandidate
235 public native void putLong(Object o, long offset, long x);
236
237 /** @see #getInt(Object, long) */
238 @HotSpotIntrinsicCandidate
239 public native float getFloat(Object o, long offset);
240
241 /** @see #putInt(Object, long, int) */
242 @HotSpotIntrinsicCandidate
243 public native void putFloat(Object o, long offset, float x);
244
245 /** @see #getInt(Object, long) */
246 @HotSpotIntrinsicCandidate
247 public native double getDouble(Object o, long offset);
248
249 /** @see #putInt(Object, long, int) */
250 @HotSpotIntrinsicCandidate
251 public native void putDouble(Object o, long offset, double x);
252
253 /**
254 * Fetches a native pointer from a given memory address. If the address is
255 * zero, or does not point into a block obtained from {@link
256 * #allocateMemory}, the results are undefined.
257 *
258 * <p>If the native pointer is less than 64 bits wide, it is extended as
259 * an unsigned number to a Java long. The pointer may be indexed by any
260 * given byte offset, simply by adding that offset (as a simple integer) to
261 * the long representing the pointer. The number of bytes actually read
262 * from the target address may be determined by consulting {@link
263 * #addressSize}.
264 *
265 * @see #allocateMemory
266 * @see #getInt(Object, long)
267 */
268 @ForceInline
269 public long getAddress(Object o, long offset) {
270 if (ADDRESS_SIZE == 4) {
271 return Integer.toUnsignedLong(getInt(o, offset));
272 } else {
273 return getLong(o, offset);
274 }
275 }
276
277 /**
278 * Stores a native pointer into a given memory address. If the address is
279 * zero, or does not point into a block obtained from {@link
280 * #allocateMemory}, the results are undefined.
281 *
282 * <p>The number of bytes actually written at the target address may be
283 * determined by consulting {@link #addressSize}.
284 *
285 * @see #allocateMemory
286 * @see #putInt(Object, long, int)
287 */
288 @ForceInline
289 public void putAddress(Object o, long offset, long x) {
290 if (ADDRESS_SIZE == 4) {
291 putInt(o, offset, (int)x);
292 } else {
293 putLong(o, offset, x);
294 }
295 }
296
297 // These read VM internal data.
298
299 /**
300 * Fetches an uncompressed reference value from a given native variable
301 * ignoring the VM's compressed references mode.
302 *
303 * @param address a memory address locating the variable
304 * @return the value fetched from the indicated native variable
305 */
306 public native Object getUncompressedObject(long address);
307
308 // These work on values in the C heap.
309
310 /**
311 * Fetches a value from a given memory address. If the address is zero, or
312 * does not point into a block obtained from {@link #allocateMemory}, the
313 * results are undefined.
314 *
315 * @see #allocateMemory
316 */
317 @ForceInline
318 public byte getByte(long address) {
319 return getByte(null, address);
320 }
321
322 /**
323 * Stores a value into a given memory address. If the address is zero, or
324 * does not point into a block obtained from {@link #allocateMemory}, the
325 * results are undefined.
326 *
327 * @see #getByte(long)
328 */
329 @ForceInline
330 public void putByte(long address, byte x) {
331 putByte(null, address, x);
332 }
333
334 /** @see #getByte(long) */
335 @ForceInline
336 public short getShort(long address) {
337 return getShort(null, address);
338 }
339
340 /** @see #putByte(long, byte) */
341 @ForceInline
342 public void putShort(long address, short x) {
343 putShort(null, address, x);
344 }
345
346 /** @see #getByte(long) */
347 @ForceInline
348 public char getChar(long address) {
349 return getChar(null, address);
350 }
351
352 /** @see #putByte(long, byte) */
353 @ForceInline
354 public void putChar(long address, char x) {
355 putChar(null, address, x);
356 }
357
358 /** @see #getByte(long) */
359 @ForceInline
360 public int getInt(long address) {
361 return getInt(null, address);
362 }
363
364 /** @see #putByte(long, byte) */
365 @ForceInline
366 public void putInt(long address, int x) {
367 putInt(null, address, x);
368 }
369
370 /** @see #getByte(long) */
371 @ForceInline
372 public long getLong(long address) {
373 return getLong(null, address);
374 }
375
376 /** @see #putByte(long, byte) */
377 @ForceInline
378 public void putLong(long address, long x) {
379 putLong(null, address, x);
380 }
381
382 /** @see #getByte(long) */
383 @ForceInline
384 public float getFloat(long address) {
385 return getFloat(null, address);
386 }
387
388 /** @see #putByte(long, byte) */
389 @ForceInline
390 public void putFloat(long address, float x) {
391 putFloat(null, address, x);
392 }
393
394 /** @see #getByte(long) */
395 @ForceInline
396 public double getDouble(long address) {
397 return getDouble(null, address);
398 }
399
400 /** @see #putByte(long, byte) */
401 @ForceInline
402 public void putDouble(long address, double x) {
403 putDouble(null, address, x);
404 }
405
406 /** @see #getAddress(Object, long) */
407 @ForceInline
408 public long getAddress(long address) {
409 return getAddress(null, address);
410 }
411
412 /** @see #putAddress(Object, long, long) */
413 @ForceInline
414 public void putAddress(long address, long x) {
415 putAddress(null, address, x);
416 }
417
418
419
420 /// helper methods for validating various types of objects/values
421
422 /**
423 * Create an exception reflecting that some of the input was invalid
424 *
425 * <em>Note:</em> It is the resposibility of the caller to make
426 * sure arguments are checked before the methods are called. While
427 * some rudimentary checks are performed on the input, the checks
428 * are best effort and when performance is an overriding priority,
429 * as when methods of this class are optimized by the runtime
430 * compiler, some or all checks (if any) may be elided. Hence, the
431 * caller must not rely on the checks and corresponding
432 * exceptions!
433 *
434 * @return an exception object
435 */
436 private RuntimeException invalidInput() {
437 return new IllegalArgumentException();
438 }
439
440 /**
441 * Check if a value is 32-bit clean (32 MSB are all zero)
442 *
443 * @param value the 64-bit value to check
444 *
445 * @return true if the value is 32-bit clean
446 */
447 private boolean is32BitClean(long value) {
448 return value >>> 32 == 0;
449 }
450
451 /**
452 * Check the validity of a size (the equivalent of a size_t)
453 *
454 * @throws RuntimeException if the size is invalid
455 * (<em>Note:</em> after optimization, invalid inputs may
456 * go undetected, which will lead to unpredictable
457 * behavior)
458 */
459 private void checkSize(long size) {
460 if (ADDRESS_SIZE == 4) {
461 // Note: this will also check for negative sizes
462 if (!is32BitClean(size)) {
463 throw invalidInput();
464 }
465 } else if (size < 0) {
466 throw invalidInput();
467 }
468 }
469
470 /**
471 * Check the validity of a native address (the equivalent of void*)
472 *
473 * @throws RuntimeException if the address is invalid
474 * (<em>Note:</em> after optimization, invalid inputs may
475 * go undetected, which will lead to unpredictable
476 * behavior)
477 */
478 private void checkNativeAddress(long address) {
479 if (ADDRESS_SIZE == 4) {
480 // Accept both zero and sign extended pointers. A valid
481 // pointer will, after the +1 below, either have produced
482 // the value 0x0 or 0x1. Masking off the low bit allows
483 // for testing against 0.
484 if ((((address >> 32) + 1) & ~1) != 0) {
485 throw invalidInput();
486 }
487 }
488 }
489
490 /**
491 * Check the validity of an offset, relative to a base object
492 *
493 * @param o the base object
494 * @param offset the offset to check
495 *
496 * @throws RuntimeException if the size is invalid
497 * (<em>Note:</em> after optimization, invalid inputs may
498 * go undetected, which will lead to unpredictable
499 * behavior)
500 */
501 private void checkOffset(Object o, long offset) {
502 if (ADDRESS_SIZE == 4) {
503 // Note: this will also check for negative offsets
504 if (!is32BitClean(offset)) {
505 throw invalidInput();
506 }
507 } else if (offset < 0) {
508 throw invalidInput();
509 }
510 }
511
512 /**
513 * Check the validity of a double-register pointer
514 *
515 * Note: This code deliberately does *not* check for NPE for (at
516 * least) three reasons:
517 *
518 * 1) NPE is not just NULL/0 - there is a range of values all
519 * resulting in an NPE, which is not trivial to check for
520 *
521 * 2) It is the responsibility of the callers of Unsafe methods
522 * to verify the input, so throwing an exception here is not really
523 * useful - passing in a NULL pointer is a critical error and the
524 * must not expect an exception to be thrown anyway.
525 *
526 * 3) the actual operations will detect NULL pointers anyway by
527 * means of traps and signals (like SIGSEGV).
528 *
529 * @param o Java heap object, or null
530 * @param offset indication of where the variable resides in a Java heap
531 * object, if any, else a memory address locating the variable
532 * statically
533 *
534 * @throws RuntimeException if the pointer is invalid
535 * (<em>Note:</em> after optimization, invalid inputs may
536 * go undetected, which will lead to unpredictable
537 * behavior)
538 */
539 private void checkPointer(Object o, long offset) {
540 if (o == null) {
541 checkNativeAddress(offset);
542 } else {
543 checkOffset(o, offset);
544 }
545 }
546
547 /**
548 * Check if a type is a primitive array type
549 *
550 * @param c the type to check
551 *
552 * @return true if the type is a primitive array type
553 */
554 private void checkPrimitiveArray(Class<?> c) {
555 Class<?> componentType = c.getComponentType();
556 if (componentType == null || !componentType.isPrimitive()) {
557 throw invalidInput();
558 }
559 }
560
561 /**
562 * Check that a pointer is a valid primitive array type pointer
563 *
564 * Note: pointers off-heap are considered to be primitive arrays
565 *
566 * @throws RuntimeException if the pointer is invalid
567 * (<em>Note:</em> after optimization, invalid inputs may
568 * go undetected, which will lead to unpredictable
569 * behavior)
570 */
571 private void checkPrimitivePointer(Object o, long offset) {
572 checkPointer(o, offset);
573
574 if (o != null) {
575 // If on heap, it it must be a primitive array
576 checkPrimitiveArray(o.getClass());
577 }
578 }
579
580
581 /// wrappers for malloc, realloc, free:
582
583 /**
584 * Allocates a new block of native memory, of the given size in bytes. The
585 * contents of the memory are uninitialized; they will generally be
586 * garbage. The resulting native pointer will never be zero, and will be
587 * aligned for all value types. Dispose of this memory by calling {@link
588 * #freeMemory}, or resize it with {@link #reallocateMemory}.
589 *
590 * <em>Note:</em> It is the resposibility of the caller to make
591 * sure arguments are checked before the methods are called. While
592 * some rudimentary checks are performed on the input, the checks
593 * are best effort and when performance is an overriding priority,
594 * as when methods of this class are optimized by the runtime
595 * compiler, some or all checks (if any) may be elided. Hence, the
596 * caller must not rely on the checks and corresponding
597 * exceptions!
598 *
599 * @throws RuntimeException if the size is negative or too large
600 * for the native size_t type
601 *
602 * @throws OutOfMemoryError if the allocation is refused by the system
603 *
604 * @see #getByte(long)
605 * @see #putByte(long, byte)
606 */
607 public long allocateMemory(long bytes) {
608 allocateMemoryChecks(bytes);
609
610 if (bytes == 0) {
611 return 0;
612 }
613
614 long p = allocateMemory0(bytes);
615 if (p == 0) {
616 throw new OutOfMemoryError();
617 }
618
619 return p;
620 }
621
622 /**
623 * Validate the arguments to allocateMemory
624 *
625 * @throws RuntimeException if the arguments are invalid
626 * (<em>Note:</em> after optimization, invalid inputs may
627 * go undetected, which will lead to unpredictable
628 * behavior)
629 */
630 private void allocateMemoryChecks(long bytes) {
631 checkSize(bytes);
632 }
633
634 /**
635 * Resizes a new block of native memory, to the given size in bytes. The
636 * contents of the new block past the size of the old block are
637 * uninitialized; they will generally be garbage. The resulting native
638 * pointer will be zero if and only if the requested size is zero. The
639 * resulting native pointer will be aligned for all value types. Dispose
640 * of this memory by calling {@link #freeMemory}, or resize it with {@link
641 * #reallocateMemory}. The address passed to this method may be null, in
642 * which case an allocation will be performed.
643 *
644 * <em>Note:</em> It is the resposibility of the caller to make
645 * sure arguments are checked before the methods are called. While
646 * some rudimentary checks are performed on the input, the checks
647 * are best effort and when performance is an overriding priority,
648 * as when methods of this class are optimized by the runtime
649 * compiler, some or all checks (if any) may be elided. Hence, the
650 * caller must not rely on the checks and corresponding
651 * exceptions!
652 *
653 * @throws RuntimeException if the size is negative or too large
654 * for the native size_t type
655 *
656 * @throws OutOfMemoryError if the allocation is refused by the system
657 *
658 * @see #allocateMemory
659 */
660 public long reallocateMemory(long address, long bytes) {
661 reallocateMemoryChecks(address, bytes);
662
663 if (bytes == 0) {
664 freeMemory(address);
665 return 0;
666 }
667
668 long p = (address == 0) ? allocateMemory0(bytes) : reallocateMemory0(address, bytes);
669 if (p == 0) {
670 throw new OutOfMemoryError();
671 }
672
673 return p;
674 }
675
676 /**
677 * Validate the arguments to reallocateMemory
678 *
679 * @throws RuntimeException if the arguments are invalid
680 * (<em>Note:</em> after optimization, invalid inputs may
681 * go undetected, which will lead to unpredictable
682 * behavior)
683 */
684 private void reallocateMemoryChecks(long address, long bytes) {
685 checkPointer(null, address);
686 checkSize(bytes);
687 }
688
689 /**
690 * Sets all bytes in a given block of memory to a fixed value
691 * (usually zero).
692 *
693 * <p>This method determines a block's base address by means of two parameters,
694 * and so it provides (in effect) a <em>double-register</em> addressing mode,
695 * as discussed in {@link #getInt(Object,long)}. When the object reference is null,
696 * the offset supplies an absolute base address.
697 *
698 * <p>The stores are in coherent (atomic) units of a size determined
699 * by the address and length parameters. If the effective address and
700 * length are all even modulo 8, the stores take place in 'long' units.
701 * If the effective address and length are (resp.) even modulo 4 or 2,
702 * the stores take place in units of 'int' or 'short'.
703 *
704 * <em>Note:</em> It is the resposibility of the caller to make
705 * sure arguments are checked before the methods are called. While
706 * some rudimentary checks are performed on the input, the checks
707 * are best effort and when performance is an overriding priority,
708 * as when methods of this class are optimized by the runtime
709 * compiler, some or all checks (if any) may be elided. Hence, the
710 * caller must not rely on the checks and corresponding
711 * exceptions!
712 *
713 * @throws RuntimeException if any of the arguments is invalid
714 *
715 * @since 1.7
716 */
717 public void setMemory(Object o, long offset, long bytes, byte value) {
718 setMemoryChecks(o, offset, bytes, value);
719
720 if (bytes == 0) {
721 return;
722 }
723
724 setMemory0(o, offset, bytes, value);
725 }
726
727 /**
728 * Sets all bytes in a given block of memory to a fixed value
729 * (usually zero). This provides a <em>single-register</em> addressing mode,
730 * as discussed in {@link #getInt(Object,long)}.
731 *
732 * <p>Equivalent to {@code setMemory(null, address, bytes, value)}.
733 */
734 public void setMemory(long address, long bytes, byte value) {
735 setMemory(null, address, bytes, value);
736 }
737
738 /**
739 * Validate the arguments to setMemory
740 *
741 * @throws RuntimeException if the arguments are invalid
742 * (<em>Note:</em> after optimization, invalid inputs may
743 * go undetected, which will lead to unpredictable
744 * behavior)
745 */
746 private void setMemoryChecks(Object o, long offset, long bytes, byte value) {
747 checkPrimitivePointer(o, offset);
748 checkSize(bytes);
749 }
750
751 /**
752 * Sets all bytes in a given block of memory to a copy of another
753 * block.
754 *
755 * <p>This method determines each block's base address by means of two parameters,
756 * and so it provides (in effect) a <em>double-register</em> addressing mode,
757 * as discussed in {@link #getInt(Object,long)}. When the object reference is null,
758 * the offset supplies an absolute base address.
759 *
760 * <p>The transfers are in coherent (atomic) units of a size determined
761 * by the address and length parameters. If the effective addresses and
762 * length are all even modulo 8, the transfer takes place in 'long' units.
763 * If the effective addresses and length are (resp.) even modulo 4 or 2,
764 * the transfer takes place in units of 'int' or 'short'.
765 *
766 * <em>Note:</em> It is the resposibility of the caller to make
767 * sure arguments are checked before the methods are called. While
768 * some rudimentary checks are performed on the input, the checks
769 * are best effort and when performance is an overriding priority,
770 * as when methods of this class are optimized by the runtime
771 * compiler, some or all checks (if any) may be elided. Hence, the
772 * caller must not rely on the checks and corresponding
773 * exceptions!
774 *
775 * @throws RuntimeException if any of the arguments is invalid
776 *
777 * @since 1.7
778 */
779 public void copyMemory(Object srcBase, long srcOffset,
780 Object destBase, long destOffset,
781 long bytes) {
782 copyMemoryChecks(srcBase, srcOffset, destBase, destOffset, bytes);
783
784 if (bytes == 0) {
785 return;
786 }
787
788 copyMemory0(srcBase, srcOffset, destBase, destOffset, bytes);
789 }
790
791 /**
792 * Sets all bytes in a given block of memory to a copy of another
793 * block. This provides a <em>single-register</em> addressing mode,
794 * as discussed in {@link #getInt(Object,long)}.
795 *
796 * Equivalent to {@code copyMemory(null, srcAddress, null, destAddress, bytes)}.
797 */
798 public void copyMemory(long srcAddress, long destAddress, long bytes) {
799 copyMemory(null, srcAddress, null, destAddress, bytes);
800 }
801
802 /**
803 * Validate the arguments to copyMemory
804 *
805 * @throws RuntimeException if any of the arguments is invalid
806 * (<em>Note:</em> after optimization, invalid inputs may
807 * go undetected, which will lead to unpredictable
808 * behavior)
809 */
810 private void copyMemoryChecks(Object srcBase, long srcOffset,
811 Object destBase, long destOffset,
812 long bytes) {
813 checkSize(bytes);
814 checkPrimitivePointer(srcBase, srcOffset);
815 checkPrimitivePointer(destBase, destOffset);
816 }
817
818 /**
819 * Copies all elements from one block of memory to another block,
820 * *unconditionally* byte swapping the elements on the fly.
821 *
822 * <p>This method determines each block's base address by means of two parameters,
823 * and so it provides (in effect) a <em>double-register</em> addressing mode,
824 * as discussed in {@link #getInt(Object,long)}. When the object reference is null,
825 * the offset supplies an absolute base address.
826 *
827 * <em>Note:</em> It is the resposibility of the caller to make
828 * sure arguments are checked before the methods are called. While
829 * some rudimentary checks are performed on the input, the checks
830 * are best effort and when performance is an overriding priority,
831 * as when methods of this class are optimized by the runtime
832 * compiler, some or all checks (if any) may be elided. Hence, the
833 * caller must not rely on the checks and corresponding
834 * exceptions!
835 *
836 * @throws RuntimeException if any of the arguments is invalid
837 *
838 * @since 9
839 */
840 public void copySwapMemory(Object srcBase, long srcOffset,
841 Object destBase, long destOffset,
842 long bytes, long elemSize) {
843 copySwapMemoryChecks(srcBase, srcOffset, destBase, destOffset, bytes, elemSize);
844
845 if (bytes == 0) {
846 return;
847 }
848
849 copySwapMemory0(srcBase, srcOffset, destBase, destOffset, bytes, elemSize);
850 }
851
852 private void copySwapMemoryChecks(Object srcBase, long srcOffset,
853 Object destBase, long destOffset,
854 long bytes, long elemSize) {
855 checkSize(bytes);
856
857 if (elemSize != 2 && elemSize != 4 && elemSize != 8) {
858 throw invalidInput();
859 }
860 if (bytes % elemSize != 0) {
861 throw invalidInput();
862 }
863
864 checkPrimitivePointer(srcBase, srcOffset);
865 checkPrimitivePointer(destBase, destOffset);
866 }
867
868 /**
869 * Copies all elements from one block of memory to another block, byte swapping the
870 * elements on the fly.
871 *
872 * This provides a <em>single-register</em> addressing mode, as
873 * discussed in {@link #getInt(Object,long)}.
874 *
875 * Equivalent to {@code copySwapMemory(null, srcAddress, null, destAddress, bytes, elemSize)}.
876 */
877 public void copySwapMemory(long srcAddress, long destAddress, long bytes, long elemSize) {
878 copySwapMemory(null, srcAddress, null, destAddress, bytes, elemSize);
879 }
880
881 /**
882 * Disposes of a block of native memory, as obtained from {@link
883 * #allocateMemory} or {@link #reallocateMemory}. The address passed to
884 * this method may be null, in which case no action is taken.
885 *
886 * <em>Note:</em> It is the resposibility of the caller to make
887 * sure arguments are checked before the methods are called. While
888 * some rudimentary checks are performed on the input, the checks
889 * are best effort and when performance is an overriding priority,
890 * as when methods of this class are optimized by the runtime
891 * compiler, some or all checks (if any) may be elided. Hence, the
892 * caller must not rely on the checks and corresponding
893 * exceptions!
894 *
895 * @throws RuntimeException if any of the arguments is invalid
896 *
897 * @see #allocateMemory
898 */
899 public void freeMemory(long address) {
900 freeMemoryChecks(address);
901
902 if (address == 0) {
903 return;
904 }
905
906 freeMemory0(address);
907 }
908
909 /**
910 * Validate the arguments to freeMemory
911 *
912 * @throws RuntimeException if the arguments are invalid
913 * (<em>Note:</em> after optimization, invalid inputs may
914 * go undetected, which will lead to unpredictable
915 * behavior)
916 */
917 private void freeMemoryChecks(long address) {
918 checkPointer(null, address);
919 }
920
921 /// random queries
922
923 /**
924 * This constant differs from all results that will ever be returned from
925 * {@link #staticFieldOffset}, {@link #objectFieldOffset},
926 * or {@link #arrayBaseOffset}.
927 */
928 public static final int INVALID_FIELD_OFFSET = -1;
929
930 /**
931 * Reports the location of a given field in the storage allocation of its
932 * class. Do not expect to perform any sort of arithmetic on this offset;
933 * it is just a cookie which is passed to the unsafe heap memory accessors.
934 *
935 * <p>Any given field will always have the same offset and base, and no
936 * two distinct fields of the same class will ever have the same offset
937 * and base.
938 *
939 * <p>As of 1.4.1, offsets for fields are represented as long values,
940 * although the Sun JVM does not use the most significant 32 bits.
941 * However, JVM implementations which store static fields at absolute
942 * addresses can use long offsets and null base pointers to express
943 * the field locations in a form usable by {@link #getInt(Object,long)}.
944 * Therefore, code which will be ported to such JVMs on 64-bit platforms
945 * must preserve all bits of static field offsets.
946 * @see #getInt(Object, long)
947 */
948 public long objectFieldOffset(Field f) {
949 if (f == null) {
950 throw new NullPointerException();
951 }
952
953 return objectFieldOffset0(f);
954 }
955
956 /**
957 * Reports the location of a given static field, in conjunction with {@link
958 * #staticFieldBase}.
959 * <p>Do not expect to perform any sort of arithmetic on this offset;
960 * it is just a cookie which is passed to the unsafe heap memory accessors.
961 *
962 * <p>Any given field will always have the same offset, and no two distinct
963 * fields of the same class will ever have the same offset.
964 *
965 * <p>As of 1.4.1, offsets for fields are represented as long values,
966 * although the Sun JVM does not use the most significant 32 bits.
967 * It is hard to imagine a JVM technology which needs more than
968 * a few bits to encode an offset within a non-array object,
969 * However, for consistency with other methods in this class,
970 * this method reports its result as a long value.
971 * @see #getInt(Object, long)
972 */
973 public long staticFieldOffset(Field f) {
974 if (f == null) {
975 throw new NullPointerException();
976 }
977
978 return staticFieldOffset0(f);
979 }
980
981 /**
982 * Reports the location of a given static field, in conjunction with {@link
983 * #staticFieldOffset}.
984 * <p>Fetch the base "Object", if any, with which static fields of the
985 * given class can be accessed via methods like {@link #getInt(Object,
986 * long)}. This value may be null. This value may refer to an object
987 * which is a "cookie", not guaranteed to be a real Object, and it should
988 * not be used in any way except as argument to the get and put routines in
989 * this class.
990 */
991 public Object staticFieldBase(Field f) {
992 if (f == null) {
993 throw new NullPointerException();
994 }
995
996 return staticFieldBase0(f);
997 }
998
999 /**
1000 * Detects if the given class may need to be initialized. This is often
1001 * needed in conjunction with obtaining the static field base of a
1002 * class.
1003 * @return false only if a call to {@code ensureClassInitialized} would have no effect
1004 */
1005 public boolean shouldBeInitialized(Class<?> c) {
1006 if (c == null) {
1007 throw new NullPointerException();
1008 }
1009
1010 return shouldBeInitialized0(c);
1011 }
1012
1013 /**
1014 * Ensures the given class has been initialized. This is often
1015 * needed in conjunction with obtaining the static field base of a
1016 * class.
1017 */
1018 public void ensureClassInitialized(Class<?> c) {
1019 if (c == null) {
1020 throw new NullPointerException();
1021 }
1022
1023 ensureClassInitialized0(c);
1024 }
1025
1026 /**
1027 * Reports the offset of the first element in the storage allocation of a
1028 * given array class. If {@link #arrayIndexScale} returns a non-zero value
1029 * for the same class, you may use that scale factor, together with this
1030 * base offset, to form new offsets to access elements of arrays of the
1031 * given class.
1032 *
1033 * @see #getInt(Object, long)
1034 * @see #putInt(Object, long, int)
1035 */
1036 public int arrayBaseOffset(Class<?> arrayClass) {
1037 if (arrayClass == null) {
1038 throw new NullPointerException();
1039 }
1040
1041 return arrayBaseOffset0(arrayClass);
1042 }
1043
1044
1045 /** The value of {@code arrayBaseOffset(boolean[].class)} */
1046 public static final int ARRAY_BOOLEAN_BASE_OFFSET
1047 = theUnsafe.arrayBaseOffset(boolean[].class);
1048
1049 /** The value of {@code arrayBaseOffset(byte[].class)} */
1050 public static final int ARRAY_BYTE_BASE_OFFSET
1051 = theUnsafe.arrayBaseOffset(byte[].class);
1052
1053 /** The value of {@code arrayBaseOffset(short[].class)} */
1054 public static final int ARRAY_SHORT_BASE_OFFSET
1055 = theUnsafe.arrayBaseOffset(short[].class);
1056
1057 /** The value of {@code arrayBaseOffset(char[].class)} */
1058 public static final int ARRAY_CHAR_BASE_OFFSET
1059 = theUnsafe.arrayBaseOffset(char[].class);
1060
1061 /** The value of {@code arrayBaseOffset(int[].class)} */
1062 public static final int ARRAY_INT_BASE_OFFSET
1063 = theUnsafe.arrayBaseOffset(int[].class);
1064
1065 /** The value of {@code arrayBaseOffset(long[].class)} */
1066 public static final int ARRAY_LONG_BASE_OFFSET
1067 = theUnsafe.arrayBaseOffset(long[].class);
1068
1069 /** The value of {@code arrayBaseOffset(float[].class)} */
1070 public static final int ARRAY_FLOAT_BASE_OFFSET
1071 = theUnsafe.arrayBaseOffset(float[].class);
1072
1073 /** The value of {@code arrayBaseOffset(double[].class)} */
1074 public static final int ARRAY_DOUBLE_BASE_OFFSET
1075 = theUnsafe.arrayBaseOffset(double[].class);
1076
1077 /** The value of {@code arrayBaseOffset(Object[].class)} */
1078 public static final int ARRAY_OBJECT_BASE_OFFSET
1079 = theUnsafe.arrayBaseOffset(Object[].class);
1080
1081 /**
1082 * Reports the scale factor for addressing elements in the storage
1083 * allocation of a given array class. However, arrays of "narrow" types
1084 * will generally not work properly with accessors like {@link
1085 * #getByte(Object, long)}, so the scale factor for such classes is reported
1086 * as zero.
1087 *
1088 * @see #arrayBaseOffset
1089 * @see #getInt(Object, long)
1090 * @see #putInt(Object, long, int)
1091 */
1092 public int arrayIndexScale(Class<?> arrayClass) {
1093 if (arrayClass == null) {
1094 throw new NullPointerException();
1095 }
1096
1097 return arrayIndexScale0(arrayClass);
1098 }
1099
1100
1101 /** The value of {@code arrayIndexScale(boolean[].class)} */
1102 public static final int ARRAY_BOOLEAN_INDEX_SCALE
1103 = theUnsafe.arrayIndexScale(boolean[].class);
1104
1105 /** The value of {@code arrayIndexScale(byte[].class)} */
1106 public static final int ARRAY_BYTE_INDEX_SCALE
1107 = theUnsafe.arrayIndexScale(byte[].class);
1108
1109 /** The value of {@code arrayIndexScale(short[].class)} */
1110 public static final int ARRAY_SHORT_INDEX_SCALE
1111 = theUnsafe.arrayIndexScale(short[].class);
1112
1113 /** The value of {@code arrayIndexScale(char[].class)} */
1114 public static final int ARRAY_CHAR_INDEX_SCALE
1115 = theUnsafe.arrayIndexScale(char[].class);
1116
1117 /** The value of {@code arrayIndexScale(int[].class)} */
1118 public static final int ARRAY_INT_INDEX_SCALE
1119 = theUnsafe.arrayIndexScale(int[].class);
1120
1121 /** The value of {@code arrayIndexScale(long[].class)} */
1122 public static final int ARRAY_LONG_INDEX_SCALE
1123 = theUnsafe.arrayIndexScale(long[].class);
1124
1125 /** The value of {@code arrayIndexScale(float[].class)} */
1126 public static final int ARRAY_FLOAT_INDEX_SCALE
1127 = theUnsafe.arrayIndexScale(float[].class);
1128
1129 /** The value of {@code arrayIndexScale(double[].class)} */
1130 public static final int ARRAY_DOUBLE_INDEX_SCALE
1131 = theUnsafe.arrayIndexScale(double[].class);
1132
1133 /** The value of {@code arrayIndexScale(Object[].class)} */
1134 public static final int ARRAY_OBJECT_INDEX_SCALE
1135 = theUnsafe.arrayIndexScale(Object[].class);
1136
1137 /**
1138 * Reports the size in bytes of a native pointer, as stored via {@link
1139 * #putAddress}. This value will be either 4 or 8. Note that the sizes of
1140 * other primitive types (as stored in native memory blocks) is determined
1141 * fully by their information content.
1142 */
1143 public int addressSize() {
1144 return ADDRESS_SIZE;
1145 }
1146
1147 /** The value of {@code addressSize()} */
1148 public static final int ADDRESS_SIZE = theUnsafe.addressSize0();
1149
1150 /**
1151 * Reports the size in bytes of a native memory page (whatever that is).
1152 * This value will always be a power of two.
1153 */
1154 public native int pageSize();
1155
1156
1157 /// random trusted operations from JNI:
1158
1159 /**
1160 * Tells the VM to define a class, without security checks. By default, the
1161 * class loader and protection domain come from the caller's class.
1162 */
1163 public Class<?> defineClass(String name, byte[] b, int off, int len,
1164 ClassLoader loader,
1165 ProtectionDomain protectionDomain) {
1166 if (b == null) {
1167 throw new NullPointerException();
1168 }
1169 if (len < 0) {
1170 throw new ArrayIndexOutOfBoundsException();
1171 }
1172
1173 return defineClass0(name, b, off, len, loader, protectionDomain);
1174 }
1175
1176 public native Class<?> defineClass0(String name, byte[] b, int off, int len,
1177 ClassLoader loader,
1178 ProtectionDomain protectionDomain);
1179
1180 /**
1181 * Defines a class but does not make it known to the class loader or system dictionary.
1182 * <p>
1183 * For each CP entry, the corresponding CP patch must either be null or have
1184 * the a format that matches its tag:
1185 * <ul>
1186 * <li>Integer, Long, Float, Double: the corresponding wrapper object type from java.lang
1187 * <li>Utf8: a string (must have suitable syntax if used as signature or name)
1188 * <li>Class: any java.lang.Class object
1189 * <li>String: any object (not just a java.lang.String)
1190 * <li>InterfaceMethodRef: (NYI) a method handle to invoke on that call site's arguments
1191 * </ul>
1192 * @param hostClass context for linkage, access control, protection domain, and class loader
1193 * @param data bytes of a class file
1194 * @param cpPatches where non-null entries exist, they replace corresponding CP entries in data
1195 */
1196 public Class<?> defineAnonymousClass(Class<?> hostClass, byte[] data, Object[] cpPatches) {
1197 if (hostClass == null || data == null) {
1198 throw new NullPointerException();
1199 }
1200
1201 return defineAnonymousClass0(hostClass, data, cpPatches);
1202 }
1203
1204 /**
1205 * Allocates an instance but does not run any constructor.
1206 * Initializes the class if it has not yet been.
1207 */
1208 @HotSpotIntrinsicCandidate
1209 public native Object allocateInstance(Class<?> cls)
1210 throws InstantiationException;
1211
1212 /**
1213 * Allocates an array of a given type, but does not do zeroing.
1214 * <p>
1215 * This method should only be used in the very rare cases where a high-performance code
1216 * overwrites the destination array completely, and compilers cannot assist in zeroing elimination.
1217 * In an overwhelming majority of cases, a normal Java allocation should be used instead.
1218 * <p>
1219 * Users of this method are <b>required</b> to overwrite the initial (garbage) array contents
1220 * before allowing untrusted code, or code in other threads, to observe the reference
1221 * to the newly allocated array. In addition, the publication of the array reference must be
1222 * safe according to the Java Memory Model requirements.
1223 * <p>
1224 * The safest approach to deal with an uninitialized array is to keep the reference to it in local
1225 * variable at least until the initialization is complete, and then publish it <b>once</b>, either
1226 * by writing it to a <em>volatile</em> field, or storing it into a <em>final</em> field in constructor,
1227 * or issuing a {@link #storeFence} before publishing the reference.
1228 * <p>
1229 * @implnote This method can only allocate primitive arrays, to avoid garbage reference
1230 * elements that could break heap integrity.
1231 *
1232 * @param componentType array component type to allocate
1233 * @param length array size to allocate
1234 * @throws IllegalArgumentException if component type is null, or not a primitive class;
1235 * or the length is negative
1236 */
1237 public Object allocateUninitializedArray(Class<?> componentType, int length) {
1238 if (componentType == null) {
1239 throw new IllegalArgumentException("Component type is null");
1240 }
1241 if (!componentType.isPrimitive()) {
1242 throw new IllegalArgumentException("Component type is not primitive");
1243 }
1244 if (length < 0) {
1245 throw new IllegalArgumentException("Negative length");
1246 }
1247 return allocateUninitializedArray0(componentType, length);
1248 }
1249
1250 @HotSpotIntrinsicCandidate
1251 private Object allocateUninitializedArray0(Class<?> componentType, int length) {
1252 // These fallbacks provide zeroed arrays, but intrinsic is not required to
1253 // return the zeroed arrays.
1254 if (componentType == byte.class) return new byte[length];
1255 if (componentType == boolean.class) return new boolean[length];
1256 if (componentType == short.class) return new short[length];
1257 if (componentType == char.class) return new char[length];
1258 if (componentType == int.class) return new int[length];
1259 if (componentType == float.class) return new float[length];
1260 if (componentType == long.class) return new long[length];
1261 if (componentType == double.class) return new double[length];
1262 return null;
1263 }
1264
1265 /** Throws the exception without telling the verifier. */
1266 public native void throwException(Throwable ee);
1267
1268 /**
1269 * Atomically updates Java variable to {@code x} if it is currently
1270 * holding {@code expected}.
1271 *
1272 * <p>This operation has memory semantics of a {@code volatile} read
1273 * and write. Corresponds to C11 atomic_compare_exchange_strong.
1274 *
1275 * @return {@code true} if successful
1276 */
1277 @HotSpotIntrinsicCandidate
1278 public final native boolean compareAndSwapObject(Object o, long offset,
1279 Object expected,
1280 Object x);
1281
1282 @HotSpotIntrinsicCandidate
1283 public final native Object compareAndExchangeObjectVolatile(Object o, long offset,
1284 Object expected,
1285 Object x);
1286
1287 @HotSpotIntrinsicCandidate
1288 public final Object compareAndExchangeObjectAcquire(Object o, long offset,
1289 Object expected,
1290 Object x) {
1291 return compareAndExchangeObjectVolatile(o, offset, expected, x);
1292 }
1293
1294 @HotSpotIntrinsicCandidate
1295 public final Object compareAndExchangeObjectRelease(Object o, long offset,
1296 Object expected,
1297 Object x) {
1298 return compareAndExchangeObjectVolatile(o, offset, expected, x);
1299 }
1300
1301 @HotSpotIntrinsicCandidate
1302 public final boolean weakCompareAndSwapObject(Object o, long offset,
1303 Object expected,
1304 Object x) {
1305 return compareAndSwapObject(o, offset, expected, x);
1306 }
1307
1308 @HotSpotIntrinsicCandidate
1309 public final boolean weakCompareAndSwapObjectAcquire(Object o, long offset,
1310 Object expected,
1311 Object x) {
1312 return compareAndSwapObject(o, offset, expected, x);
1313 }
1314
1315 @HotSpotIntrinsicCandidate
1316 public final boolean weakCompareAndSwapObjectRelease(Object o, long offset,
1317 Object expected,
1318 Object x) {
1319 return compareAndSwapObject(o, offset, expected, x);
1320 }
1321
1322 @HotSpotIntrinsicCandidate
1323 public final boolean weakCompareAndSwapObjectVolatile(Object o, long offset,
1324 Object expected,
1325 Object x) {
1326 return compareAndSwapObject(o, offset, expected, x);
1327 }
1328
1329 /**
1330 * Atomically updates Java variable to {@code x} if it is currently
1331 * holding {@code expected}.
1332 *
1333 * <p>This operation has memory semantics of a {@code volatile} read
1334 * and write. Corresponds to C11 atomic_compare_exchange_strong.
1335 *
1336 * @return {@code true} if successful
1337 */
1338 @HotSpotIntrinsicCandidate
1339 public final native boolean compareAndSwapInt(Object o, long offset,
1340 int expected,
1341 int x);
1342
1343 @HotSpotIntrinsicCandidate
1344 public final native int compareAndExchangeIntVolatile(Object o, long offset,
1345 int expected,
1346 int x);
1347
1348 @HotSpotIntrinsicCandidate
1349 public final int compareAndExchangeIntAcquire(Object o, long offset,
1350 int expected,
1351 int x) {
1352 return compareAndExchangeIntVolatile(o, offset, expected, x);
1353 }
1354
1355 @HotSpotIntrinsicCandidate
1356 public final int compareAndExchangeIntRelease(Object o, long offset,
1357 int expected,
1358 int x) {
1359 return compareAndExchangeIntVolatile(o, offset, expected, x);
1360 }
1361
1362 @HotSpotIntrinsicCandidate
1363 public final boolean weakCompareAndSwapInt(Object o, long offset,
1364 int expected,
1365 int x) {
1366 return compareAndSwapInt(o, offset, expected, x);
1367 }
1368
1369 @HotSpotIntrinsicCandidate
1370 public final boolean weakCompareAndSwapIntAcquire(Object o, long offset,
1371 int expected,
1372 int x) {
1373 return compareAndSwapInt(o, offset, expected, x);
1374 }
1375
1376 @HotSpotIntrinsicCandidate
1377 public final boolean weakCompareAndSwapIntRelease(Object o, long offset,
1378 int expected,
1379 int x) {
1380 return compareAndSwapInt(o, offset, expected, x);
1381 }
1382
1383 @HotSpotIntrinsicCandidate
1384 public final boolean weakCompareAndSwapIntVolatile(Object o, long offset,
1385 int expected,
1386 int x) {
1387 return compareAndSwapInt(o, offset, expected, x);
1388 }
1389
1390 @HotSpotIntrinsicCandidate
1391 public final byte compareAndExchangeByteVolatile(Object o, long offset,
1392 byte expected,
1393 byte x) {
1394 long wordOffset = offset & ~3;
1395 int shift = (int) (offset & 3) << 3;
1396 if (BE) {
1397 shift = 24 - shift;
1398 }
1399 int mask = 0xFF << shift;
1400 int maskedExpected = (expected & 0xFF) << shift;
1401 int maskedX = (x & 0xFF) << shift;
1402 int fullWord;
1403 do {
1404 fullWord = getIntVolatile(o, wordOffset);
1405 if ((fullWord & mask) != maskedExpected)
1406 return (byte) ((fullWord & mask) >> shift);
1407 } while (!weakCompareAndSwapIntVolatile(o, wordOffset,
1408 fullWord, (fullWord & ~mask) | maskedX));
1409 return expected;
1410 }
1411
1412 @HotSpotIntrinsicCandidate
1413 public final boolean compareAndSwapByte(Object o, long offset,
1414 byte expected,
1415 byte x) {
1416 return compareAndExchangeByteVolatile(o, offset, expected, x) == expected;
1417 }
1418
1419 @HotSpotIntrinsicCandidate
1420 public final boolean weakCompareAndSwapByteVolatile(Object o, long offset,
1421 byte expected,
1422 byte x) {
1423 return compareAndSwapByte(o, offset, expected, x);
1424 }
1425
1426 @HotSpotIntrinsicCandidate
1427 public final boolean weakCompareAndSwapByteAcquire(Object o, long offset,
1428 byte expected,
1429 byte x) {
1430 return weakCompareAndSwapByteVolatile(o, offset, expected, x);
1431 }
1432
1433 @HotSpotIntrinsicCandidate
1434 public final boolean weakCompareAndSwapByteRelease(Object o, long offset,
1435 byte expected,
1436 byte x) {
1437 return weakCompareAndSwapByteVolatile(o, offset, expected, x);
1438 }
1439
1440 @HotSpotIntrinsicCandidate
1441 public final boolean weakCompareAndSwapByte(Object o, long offset,
1442 byte expected,
1443 byte x) {
1444 return weakCompareAndSwapByteVolatile(o, offset, expected, x);
1445 }
1446
1447 @HotSpotIntrinsicCandidate
1448 public final byte compareAndExchangeByteAcquire(Object o, long offset,
1449 byte expected,
1450 byte x) {
1451 return compareAndExchangeByteVolatile(o, offset, expected, x);
1452 }
1453
1454 @HotSpotIntrinsicCandidate
1455 public final byte compareAndExchangeByteRelease(Object o, long offset,
1456 byte expected,
1457 byte x) {
1458 return compareAndExchangeByteVolatile(o, offset, expected, x);
1459 }
1460
1461 @HotSpotIntrinsicCandidate
1462 public final short compareAndExchangeShortVolatile(Object o, long offset,
1463 short expected,
1464 short x) {
1465 if ((offset & 3) == 3) {
1466 throw new IllegalArgumentException("Update spans the word, not supported");
1467 }
1468 long wordOffset = offset & ~3;
1469 int shift = (int) (offset & 3) << 3;
1470 if (BE) {
1471 shift = 16 - shift;
1472 }
1473 int mask = 0xFFFF << shift;
1474 int maskedExpected = (expected & 0xFFFF) << shift;
1475 int maskedX = (x & 0xFFFF) << shift;
1476 int fullWord;
1477 do {
1478 fullWord = getIntVolatile(o, wordOffset);
1479 if ((fullWord & mask) != maskedExpected) {
1480 return (short) ((fullWord & mask) >> shift);
1481 }
1482 } while (!weakCompareAndSwapIntVolatile(o, wordOffset,
1483 fullWord, (fullWord & ~mask) | maskedX));
1484 return expected;
1485 }
1486
1487 @HotSpotIntrinsicCandidate
1488 public final boolean compareAndSwapShort(Object o, long offset,
1489 short expected,
1490 short x) {
1491 return compareAndExchangeShortVolatile(o, offset, expected, x) == expected;
1492 }
1493
1494 @HotSpotIntrinsicCandidate
1495 public final boolean weakCompareAndSwapShortVolatile(Object o, long offset,
1496 short expected,
1497 short x) {
1498 return compareAndSwapShort(o, offset, expected, x);
1499 }
1500
1501 @HotSpotIntrinsicCandidate
1502 public final boolean weakCompareAndSwapShortAcquire(Object o, long offset,
1503 short expected,
1504 short x) {
1505 return weakCompareAndSwapShortVolatile(o, offset, expected, x);
1506 }
1507
1508 @HotSpotIntrinsicCandidate
1509 public final boolean weakCompareAndSwapShortRelease(Object o, long offset,
1510 short expected,
1511 short x) {
1512 return weakCompareAndSwapShortVolatile(o, offset, expected, x);
1513 }
1514
1515 @HotSpotIntrinsicCandidate
1516 public final boolean weakCompareAndSwapShort(Object o, long offset,
1517 short expected,
1518 short x) {
1519 return weakCompareAndSwapShortVolatile(o, offset, expected, x);
1520 }
1521
1522
1523 @HotSpotIntrinsicCandidate
1524 public final short compareAndExchangeShortAcquire(Object o, long offset,
1525 short expected,
1526 short x) {
1527 return compareAndExchangeShortVolatile(o, offset, expected, x);
1528 }
1529
1530 @HotSpotIntrinsicCandidate
1531 public final short compareAndExchangeShortRelease(Object o, long offset,
1532 short expected,
1533 short x) {
1534 return compareAndExchangeShortVolatile(o, offset, expected, x);
1535 }
1536
1537 @ForceInline
1538 private char s2c(short s) {
1539 return (char) s;
1540 }
1541
1542 @ForceInline
1543 private short c2s(char s) {
1544 return (short) s;
1545 }
1546
1547 @ForceInline
1548 public final boolean compareAndSwapChar(Object o, long offset,
1549 char expected,
1550 char x) {
1551 return compareAndSwapShort(o, offset, c2s(expected), c2s(x));
1552 }
1553
1554 @ForceInline
1555 public final char compareAndExchangeCharVolatile(Object o, long offset,
1556 char expected,
1557 char x) {
1558 return s2c(compareAndExchangeShortVolatile(o, offset, c2s(expected), c2s(x)));
1559 }
1560
1561 @ForceInline
1562 public final char compareAndExchangeCharAcquire(Object o, long offset,
1563 char expected,
1564 char x) {
1565 return s2c(compareAndExchangeShortAcquire(o, offset, c2s(expected), c2s(x)));
1566 }
1567
1568 @ForceInline
1569 public final char compareAndExchangeCharRelease(Object o, long offset,
1570 char expected,
1571 char x) {
1572 return s2c(compareAndExchangeShortRelease(o, offset, c2s(expected), c2s(x)));
1573 }
1574
1575 @ForceInline
1576 public final boolean weakCompareAndSwapCharVolatile(Object o, long offset,
1577 char expected,
1578 char x) {
1579 return weakCompareAndSwapShortVolatile(o, offset, c2s(expected), c2s(x));
1580 }
1581
1582 @ForceInline
1583 public final boolean weakCompareAndSwapCharAcquire(Object o, long offset,
1584 char expected,
1585 char x) {
1586 return weakCompareAndSwapShortAcquire(o, offset, c2s(expected), c2s(x));
1587 }
1588
1589 @ForceInline
1590 public final boolean weakCompareAndSwapCharRelease(Object o, long offset,
1591 char expected,
1592 char x) {
1593 return weakCompareAndSwapShortRelease(o, offset, c2s(expected), c2s(x));
1594 }
1595
1596 @ForceInline
1597 public final boolean weakCompareAndSwapChar(Object o, long offset,
1598 char expected,
1599 char x) {
1600 return weakCompareAndSwapShort(o, offset, c2s(expected), c2s(x));
1601 }
1602
1603 /**
1604 * The JVM converts ints to booleans using two different
1605 * conventions, byte testing against zero and truncation to
1606 * least-significant bit.
1607 *
1608 * <p>The JNI documents specify that, at least for returning
1609 * values from native methods, a Java boolean value is converted
1610 * to the value-set 0..1 by first truncating to a byte (0..255 or
1611 * maybe -128..127) and then testing against zero. Thus, Java
1612 * booleans in non-Java data structures are by convention
1613 * represented as 8-bit containers containing either zero (for
1614 * false) or any non-zero value (for true).
1615 *
1616 * <p>Java booleans in the heap are also stored in bytes, but are
1617 * strongly normalized to the value-set 0..1 (i.e., they are
1618 * truncated to the least-significant bit).
1619 *
1620 * <p>The main reason for having different conventions for
1621 * conversion is performance: Truncation to the least-significant
1622 * bit can be usually implemented with fewer (machine)
1623 * instructions than byte testing against zero.
1624 *
1625 * <p>A number of Unsafe methods load boolean values from the heap
1626 * as bytes. Unsafe converts those values according to the JNI
1627 * rules (i.e, using the "testing against zero" convention). The
1628 * method {@code byte2bool} implements that conversion.
1629 *
1630 * @param b the byte to be converted to boolean
1631 * @return the result of the conversion
1632 */
1633 @ForceInline
1634 private boolean byte2bool(byte b) {
1635 return b != 0;
1636 }
1637
1638 /**
1639 * Convert a boolean value to a byte. The return value is strongly
1640 * normalized to the value-set 0..1 (i.e., the value is truncated
1641 * to the least-significant bit). See {@link #byte2bool(byte)} for
1642 * more details on conversion conventions.
1643 *
1644 * @param b the boolean to be converted to byte (and then normalized)
1645 * @return the result of the conversion
1646 */
1647 @ForceInline
1648 private byte bool2byte(boolean b) {
1649 return b ? (byte)1 : (byte)0;
1650 }
1651
1652 @ForceInline
1653 public final boolean compareAndSwapBoolean(Object o, long offset,
1654 boolean expected,
1655 boolean x) {
1656 return compareAndSwapByte(o, offset, bool2byte(expected), bool2byte(x));
1657 }
1658
1659 @ForceInline
1660 public final boolean compareAndExchangeBooleanVolatile(Object o, long offset,
1661 boolean expected,
1662 boolean x) {
1663 return byte2bool(compareAndExchangeByteVolatile(o, offset, bool2byte(expected), bool2byte(x)));
1664 }
1665
1666 @ForceInline
1667 public final boolean compareAndExchangeBooleanAcquire(Object o, long offset,
1668 boolean expected,
1669 boolean x) {
1670 return byte2bool(compareAndExchangeByteAcquire(o, offset, bool2byte(expected), bool2byte(x)));
1671 }
1672
1673 @ForceInline
1674 public final boolean compareAndExchangeBooleanRelease(Object o, long offset,
1675 boolean expected,
1676 boolean x) {
1677 return byte2bool(compareAndExchangeByteRelease(o, offset, bool2byte(expected), bool2byte(x)));
1678 }
1679
1680 @ForceInline
1681 public final boolean weakCompareAndSwapBooleanVolatile(Object o, long offset,
1682 boolean expected,
1683 boolean x) {
1684 return weakCompareAndSwapByteVolatile(o, offset, bool2byte(expected), bool2byte(x));
1685 }
1686
1687 @ForceInline
1688 public final boolean weakCompareAndSwapBooleanAcquire(Object o, long offset,
1689 boolean expected,
1690 boolean x) {
1691 return weakCompareAndSwapByteAcquire(o, offset, bool2byte(expected), bool2byte(x));
1692 }
1693
1694 @ForceInline
1695 public final boolean weakCompareAndSwapBooleanRelease(Object o, long offset,
1696 boolean expected,
1697 boolean x) {
1698 return weakCompareAndSwapByteRelease(o, offset, bool2byte(expected), bool2byte(x));
1699 }
1700
1701 @ForceInline
1702 public final boolean weakCompareAndSwapBoolean(Object o, long offset,
1703 boolean expected,
1704 boolean x) {
1705 return weakCompareAndSwapByte(o, offset, bool2byte(expected), bool2byte(x));
1706 }
1707
1708 /**
1709 * Atomically updates Java variable to {@code x} if it is currently
1710 * holding {@code expected}.
1711 *
1712 * <p>This operation has memory semantics of a {@code volatile} read
1713 * and write. Corresponds to C11 atomic_compare_exchange_strong.
1714 *
1715 * @return {@code true} if successful
1716 */
1717 @ForceInline
1718 public final boolean compareAndSwapFloat(Object o, long offset,
1719 float expected,
1720 float x) {
1721 return compareAndSwapInt(o, offset,
1722 Float.floatToRawIntBits(expected),
1723 Float.floatToRawIntBits(x));
1724 }
1725
1726 @ForceInline
1727 public final float compareAndExchangeFloatVolatile(Object o, long offset,
1728 float expected,
1729 float x) {
1730 int w = compareAndExchangeIntVolatile(o, offset,
1731 Float.floatToRawIntBits(expected),
1732 Float.floatToRawIntBits(x));
1733 return Float.intBitsToFloat(w);
1734 }
1735
1736 @ForceInline
1737 public final float compareAndExchangeFloatAcquire(Object o, long offset,
1738 float expected,
1739 float x) {
1740 int w = compareAndExchangeIntAcquire(o, offset,
1741 Float.floatToRawIntBits(expected),
1742 Float.floatToRawIntBits(x));
1743 return Float.intBitsToFloat(w);
1744 }
1745
1746 @ForceInline
1747 public final float compareAndExchangeFloatRelease(Object o, long offset,
1748 float expected,
1749 float x) {
1750 int w = compareAndExchangeIntRelease(o, offset,
1751 Float.floatToRawIntBits(expected),
1752 Float.floatToRawIntBits(x));
1753 return Float.intBitsToFloat(w);
1754 }
1755
1756 @ForceInline
1757 public final boolean weakCompareAndSwapFloat(Object o, long offset,
1758 float expected,
1759 float x) {
1760 return weakCompareAndSwapInt(o, offset,
1761 Float.floatToRawIntBits(expected),
1762 Float.floatToRawIntBits(x));
1763 }
1764
1765 @ForceInline
1766 public final boolean weakCompareAndSwapFloatAcquire(Object o, long offset,
1767 float expected,
1768 float x) {
1769 return weakCompareAndSwapIntAcquire(o, offset,
1770 Float.floatToRawIntBits(expected),
1771 Float.floatToRawIntBits(x));
1772 }
1773
1774 @ForceInline
1775 public final boolean weakCompareAndSwapFloatRelease(Object o, long offset,
1776 float expected,
1777 float x) {
1778 return weakCompareAndSwapIntRelease(o, offset,
1779 Float.floatToRawIntBits(expected),
1780 Float.floatToRawIntBits(x));
1781 }
1782
1783 @ForceInline
1784 public final boolean weakCompareAndSwapFloatVolatile(Object o, long offset,
1785 float expected,
1786 float x) {
1787 return weakCompareAndSwapIntVolatile(o, offset,
1788 Float.floatToRawIntBits(expected),
1789 Float.floatToRawIntBits(x));
1790 }
1791
1792 /**
1793 * Atomically updates Java variable to {@code x} if it is currently
1794 * holding {@code expected}.
1795 *
1796 * <p>This operation has memory semantics of a {@code volatile} read
1797 * and write. Corresponds to C11 atomic_compare_exchange_strong.
1798 *
1799 * @return {@code true} if successful
1800 */
1801 @ForceInline
1802 public final boolean compareAndSwapDouble(Object o, long offset,
1803 double expected,
1804 double x) {
1805 return compareAndSwapLong(o, offset,
1806 Double.doubleToRawLongBits(expected),
1807 Double.doubleToRawLongBits(x));
1808 }
1809
1810 @ForceInline
1811 public final double compareAndExchangeDoubleVolatile(Object o, long offset,
1812 double expected,
1813 double x) {
1814 long w = compareAndExchangeLongVolatile(o, offset,
1815 Double.doubleToRawLongBits(expected),
1816 Double.doubleToRawLongBits(x));
1817 return Double.longBitsToDouble(w);
1818 }
1819
1820 @ForceInline
1821 public final double compareAndExchangeDoubleAcquire(Object o, long offset,
1822 double expected,
1823 double x) {
1824 long w = compareAndExchangeLongAcquire(o, offset,
1825 Double.doubleToRawLongBits(expected),
1826 Double.doubleToRawLongBits(x));
1827 return Double.longBitsToDouble(w);
1828 }
1829
1830 @ForceInline
1831 public final double compareAndExchangeDoubleRelease(Object o, long offset,
1832 double expected,
1833 double x) {
1834 long w = compareAndExchangeLongRelease(o, offset,
1835 Double.doubleToRawLongBits(expected),
1836 Double.doubleToRawLongBits(x));
1837 return Double.longBitsToDouble(w);
1838 }
1839
1840 @ForceInline
1841 public final boolean weakCompareAndSwapDouble(Object o, long offset,
1842 double expected,
1843 double x) {
1844 return weakCompareAndSwapLong(o, offset,
1845 Double.doubleToRawLongBits(expected),
1846 Double.doubleToRawLongBits(x));
1847 }
1848
1849 @ForceInline
1850 public final boolean weakCompareAndSwapDoubleAcquire(Object o, long offset,
1851 double expected,
1852 double x) {
1853 return weakCompareAndSwapLongAcquire(o, offset,
1854 Double.doubleToRawLongBits(expected),
1855 Double.doubleToRawLongBits(x));
1856 }
1857
1858 @ForceInline
1859 public final boolean weakCompareAndSwapDoubleRelease(Object o, long offset,
1860 double expected,
1861 double x) {
1862 return weakCompareAndSwapLongRelease(o, offset,
1863 Double.doubleToRawLongBits(expected),
1864 Double.doubleToRawLongBits(x));
1865 }
1866
1867 @ForceInline
1868 public final boolean weakCompareAndSwapDoubleVolatile(Object o, long offset,
1869 double expected,
1870 double x) {
1871 return weakCompareAndSwapLongVolatile(o, offset,
1872 Double.doubleToRawLongBits(expected),
1873 Double.doubleToRawLongBits(x));
1874 }
1875
1876 /**
1877 * Atomically updates Java variable to {@code x} if it is currently
1878 * holding {@code expected}.
1879 *
1880 * <p>This operation has memory semantics of a {@code volatile} read
1881 * and write. Corresponds to C11 atomic_compare_exchange_strong.
1882 *
1883 * @return {@code true} if successful
1884 */
1885 @HotSpotIntrinsicCandidate
1886 public final native boolean compareAndSwapLong(Object o, long offset,
1887 long expected,
1888 long x);
1889
1890 @HotSpotIntrinsicCandidate
1891 public final native long compareAndExchangeLongVolatile(Object o, long offset,
1892 long expected,
1893 long x);
1894
1895 @HotSpotIntrinsicCandidate
1896 public final long compareAndExchangeLongAcquire(Object o, long offset,
1897 long expected,
1898 long x) {
1899 return compareAndExchangeLongVolatile(o, offset, expected, x);
1900 }
1901
1902 @HotSpotIntrinsicCandidate
1903 public final long compareAndExchangeLongRelease(Object o, long offset,
1904 long expected,
1905 long x) {
1906 return compareAndExchangeLongVolatile(o, offset, expected, x);
1907 }
1908
1909 @HotSpotIntrinsicCandidate
1910 public final boolean weakCompareAndSwapLong(Object o, long offset,
1911 long expected,
1912 long x) {
1913 return compareAndSwapLong(o, offset, expected, x);
1914 }
1915
1916 @HotSpotIntrinsicCandidate
1917 public final boolean weakCompareAndSwapLongAcquire(Object o, long offset,
1918 long expected,
1919 long x) {
1920 return compareAndSwapLong(o, offset, expected, x);
1921 }
1922
1923 @HotSpotIntrinsicCandidate
1924 public final boolean weakCompareAndSwapLongRelease(Object o, long offset,
1925 long expected,
1926 long x) {
1927 return compareAndSwapLong(o, offset, expected, x);
1928 }
1929
1930 @HotSpotIntrinsicCandidate
1931 public final boolean weakCompareAndSwapLongVolatile(Object o, long offset,
1932 long expected,
1933 long x) {
1934 return compareAndSwapLong(o, offset, expected, x);
1935 }
1936
1937 /**
1938 * Fetches a reference value from a given Java variable, with volatile
1939 * load semantics. Otherwise identical to {@link #getObject(Object, long)}
1940 */
1941 @HotSpotIntrinsicCandidate
1942 public native Object getObjectVolatile(Object o, long offset);
1943
1944 /**
1945 * Stores a reference value into a given Java variable, with
1946 * volatile store semantics. Otherwise identical to {@link #putObject(Object, long, Object)}
1947 */
1948 @HotSpotIntrinsicCandidate
1949 public native void putObjectVolatile(Object o, long offset, Object x);
1950
1951 /** Volatile version of {@link #getInt(Object, long)} */
1952 @HotSpotIntrinsicCandidate
1953 public native int getIntVolatile(Object o, long offset);
1954
1955 /** Volatile version of {@link #putInt(Object, long, int)} */
1956 @HotSpotIntrinsicCandidate
1957 public native void putIntVolatile(Object o, long offset, int x);
1958
1959 /** Volatile version of {@link #getBoolean(Object, long)} */
1960 @HotSpotIntrinsicCandidate
1961 public native boolean getBooleanVolatile(Object o, long offset);
1962
1963 /** Volatile version of {@link #putBoolean(Object, long, boolean)} */
1964 @HotSpotIntrinsicCandidate
1965 public native void putBooleanVolatile(Object o, long offset, boolean x);
1966
1967 /** Volatile version of {@link #getByte(Object, long)} */
1968 @HotSpotIntrinsicCandidate
1969 public native byte getByteVolatile(Object o, long offset);
1970
1971 /** Volatile version of {@link #putByte(Object, long, byte)} */
1972 @HotSpotIntrinsicCandidate
1973 public native void putByteVolatile(Object o, long offset, byte x);
1974
1975 /** Volatile version of {@link #getShort(Object, long)} */
1976 @HotSpotIntrinsicCandidate
1977 public native short getShortVolatile(Object o, long offset);
1978
1979 /** Volatile version of {@link #putShort(Object, long, short)} */
1980 @HotSpotIntrinsicCandidate
1981 public native void putShortVolatile(Object o, long offset, short x);
1982
1983 /** Volatile version of {@link #getChar(Object, long)} */
1984 @HotSpotIntrinsicCandidate
1985 public native char getCharVolatile(Object o, long offset);
1986
1987 /** Volatile version of {@link #putChar(Object, long, char)} */
1988 @HotSpotIntrinsicCandidate
1989 public native void putCharVolatile(Object o, long offset, char x);
1990
1991 /** Volatile version of {@link #getLong(Object, long)} */
1992 @HotSpotIntrinsicCandidate
1993 public native long getLongVolatile(Object o, long offset);
1994
1995 /** Volatile version of {@link #putLong(Object, long, long)} */
1996 @HotSpotIntrinsicCandidate
1997 public native void putLongVolatile(Object o, long offset, long x);
1998
1999 /** Volatile version of {@link #getFloat(Object, long)} */
2000 @HotSpotIntrinsicCandidate
2001 public native float getFloatVolatile(Object o, long offset);
2002
2003 /** Volatile version of {@link #putFloat(Object, long, float)} */
2004 @HotSpotIntrinsicCandidate
2005 public native void putFloatVolatile(Object o, long offset, float x);
2006
2007 /** Volatile version of {@link #getDouble(Object, long)} */
2008 @HotSpotIntrinsicCandidate
2009 public native double getDoubleVolatile(Object o, long offset);
2010
2011 /** Volatile version of {@link #putDouble(Object, long, double)} */
2012 @HotSpotIntrinsicCandidate
2013 public native void putDoubleVolatile(Object o, long offset, double x);
2014
2015
2016
2017 /** Acquire version of {@link #getObjectVolatile(Object, long)} */
2018 @HotSpotIntrinsicCandidate
2019 public final Object getObjectAcquire(Object o, long offset) {
2020 return getObjectVolatile(o, offset);
2021 }
2022
2023 /** Acquire version of {@link #getBooleanVolatile(Object, long)} */
2024 @HotSpotIntrinsicCandidate
2025 public final boolean getBooleanAcquire(Object o, long offset) {
2026 return getBooleanVolatile(o, offset);
2027 }
2028
2029 /** Acquire version of {@link #getByteVolatile(Object, long)} */
2030 @HotSpotIntrinsicCandidate
2031 public final byte getByteAcquire(Object o, long offset) {
2032 return getByteVolatile(o, offset);
2033 }
2034
2035 /** Acquire version of {@link #getShortVolatile(Object, long)} */
2036 @HotSpotIntrinsicCandidate
2037 public final short getShortAcquire(Object o, long offset) {
2038 return getShortVolatile(o, offset);
2039 }
2040
2041 /** Acquire version of {@link #getCharVolatile(Object, long)} */
2042 @HotSpotIntrinsicCandidate
2043 public final char getCharAcquire(Object o, long offset) {
2044 return getCharVolatile(o, offset);
2045 }
2046
2047 /** Acquire version of {@link #getIntVolatile(Object, long)} */
2048 @HotSpotIntrinsicCandidate
2049 public final int getIntAcquire(Object o, long offset) {
2050 return getIntVolatile(o, offset);
2051 }
2052
2053 /** Acquire version of {@link #getFloatVolatile(Object, long)} */
2054 @HotSpotIntrinsicCandidate
2055 public final float getFloatAcquire(Object o, long offset) {
2056 return getFloatVolatile(o, offset);
2057 }
2058
2059 /** Acquire version of {@link #getLongVolatile(Object, long)} */
2060 @HotSpotIntrinsicCandidate
2061 public final long getLongAcquire(Object o, long offset) {
2062 return getLongVolatile(o, offset);
2063 }
2064
2065 /** Acquire version of {@link #getDoubleVolatile(Object, long)} */
2066 @HotSpotIntrinsicCandidate
2067 public final double getDoubleAcquire(Object o, long offset) {
2068 return getDoubleVolatile(o, offset);
2069 }
2070
2071 /*
2072 * Versions of {@link #putObjectVolatile(Object, long, Object)}
2073 * that do not guarantee immediate visibility of the store to
2074 * other threads. This method is generally only useful if the
2075 * underlying field is a Java volatile (or if an array cell, one
2076 * that is otherwise only accessed using volatile accesses).
2077 *
2078 * Corresponds to C11 atomic_store_explicit(..., memory_order_release).
2079 */
2080
2081 /** Release version of {@link #putObjectVolatile(Object, long, Object)} */
2082 @HotSpotIntrinsicCandidate
2083 public final void putObjectRelease(Object o, long offset, Object x) {
2084 putObjectVolatile(o, offset, x);
2085 }
2086
2087 /** Release version of {@link #putBooleanVolatile(Object, long, boolean)} */
2088 @HotSpotIntrinsicCandidate
2089 public final void putBooleanRelease(Object o, long offset, boolean x) {
2090 putBooleanVolatile(o, offset, x);
2091 }
2092
2093 /** Release version of {@link #putByteVolatile(Object, long, byte)} */
2094 @HotSpotIntrinsicCandidate
2095 public final void putByteRelease(Object o, long offset, byte x) {
2096 putByteVolatile(o, offset, x);
2097 }
2098
2099 /** Release version of {@link #putShortVolatile(Object, long, short)} */
2100 @HotSpotIntrinsicCandidate
2101 public final void putShortRelease(Object o, long offset, short x) {
2102 putShortVolatile(o, offset, x);
2103 }
2104
2105 /** Release version of {@link #putCharVolatile(Object, long, char)} */
2106 @HotSpotIntrinsicCandidate
2107 public final void putCharRelease(Object o, long offset, char x) {
2108 putCharVolatile(o, offset, x);
2109 }
2110
2111 /** Release version of {@link #putIntVolatile(Object, long, int)} */
2112 @HotSpotIntrinsicCandidate
2113 public final void putIntRelease(Object o, long offset, int x) {
2114 putIntVolatile(o, offset, x);
2115 }
2116
2117 /** Release version of {@link #putFloatVolatile(Object, long, float)} */
2118 @HotSpotIntrinsicCandidate
2119 public final void putFloatRelease(Object o, long offset, float x) {
2120 putFloatVolatile(o, offset, x);
2121 }
2122
2123 /** Release version of {@link #putLongVolatile(Object, long, long)} */
2124 @HotSpotIntrinsicCandidate
2125 public final void putLongRelease(Object o, long offset, long x) {
2126 putLongVolatile(o, offset, x);
2127 }
2128
2129 /** Release version of {@link #putDoubleVolatile(Object, long, double)} */
2130 @HotSpotIntrinsicCandidate
2131 public final void putDoubleRelease(Object o, long offset, double x) {
2132 putDoubleVolatile(o, offset, x);
2133 }
2134
2135 // ------------------------------ Opaque --------------------------------------
2136
2137 /** Opaque version of {@link #getObjectVolatile(Object, long)} */
2138 @HotSpotIntrinsicCandidate
2139 public final Object getObjectOpaque(Object o, long offset) {
2140 return getObjectVolatile(o, offset);
2141 }
2142
2143 /** Opaque version of {@link #getBooleanVolatile(Object, long)} */
2144 @HotSpotIntrinsicCandidate
2145 public final boolean getBooleanOpaque(Object o, long offset) {
2146 return getBooleanVolatile(o, offset);
2147 }
2148
2149 /** Opaque version of {@link #getByteVolatile(Object, long)} */
2150 @HotSpotIntrinsicCandidate
2151 public final byte getByteOpaque(Object o, long offset) {
2152 return getByteVolatile(o, offset);
2153 }
2154
2155 /** Opaque version of {@link #getShortVolatile(Object, long)} */
2156 @HotSpotIntrinsicCandidate
2157 public final short getShortOpaque(Object o, long offset) {
2158 return getShortVolatile(o, offset);
2159 }
2160
2161 /** Opaque version of {@link #getCharVolatile(Object, long)} */
2162 @HotSpotIntrinsicCandidate
2163 public final char getCharOpaque(Object o, long offset) {
2164 return getCharVolatile(o, offset);
2165 }
2166
2167 /** Opaque version of {@link #getIntVolatile(Object, long)} */
2168 @HotSpotIntrinsicCandidate
2169 public final int getIntOpaque(Object o, long offset) {
2170 return getIntVolatile(o, offset);
2171 }
2172
2173 /** Opaque version of {@link #getFloatVolatile(Object, long)} */
2174 @HotSpotIntrinsicCandidate
2175 public final float getFloatOpaque(Object o, long offset) {
2176 return getFloatVolatile(o, offset);
2177 }
2178
2179 /** Opaque version of {@link #getLongVolatile(Object, long)} */
2180 @HotSpotIntrinsicCandidate
2181 public final long getLongOpaque(Object o, long offset) {
2182 return getLongVolatile(o, offset);
2183 }
2184
2185 /** Opaque version of {@link #getDoubleVolatile(Object, long)} */
2186 @HotSpotIntrinsicCandidate
2187 public final double getDoubleOpaque(Object o, long offset) {
2188 return getDoubleVolatile(o, offset);
2189 }
2190
2191 /** Opaque version of {@link #putObjectVolatile(Object, long, Object)} */
2192 @HotSpotIntrinsicCandidate
2193 public final void putObjectOpaque(Object o, long offset, Object x) {
2194 putObjectVolatile(o, offset, x);
2195 }
2196
2197 /** Opaque version of {@link #putBooleanVolatile(Object, long, boolean)} */
2198 @HotSpotIntrinsicCandidate
2199 public final void putBooleanOpaque(Object o, long offset, boolean x) {
2200 putBooleanVolatile(o, offset, x);
2201 }
2202
2203 /** Opaque version of {@link #putByteVolatile(Object, long, byte)} */
2204 @HotSpotIntrinsicCandidate
2205 public final void putByteOpaque(Object o, long offset, byte x) {
2206 putByteVolatile(o, offset, x);
2207 }
2208
2209 /** Opaque version of {@link #putShortVolatile(Object, long, short)} */
2210 @HotSpotIntrinsicCandidate
2211 public final void putShortOpaque(Object o, long offset, short x) {
2212 putShortVolatile(o, offset, x);
2213 }
2214
2215 /** Opaque version of {@link #putCharVolatile(Object, long, char)} */
2216 @HotSpotIntrinsicCandidate
2217 public final void putCharOpaque(Object o, long offset, char x) {
2218 putCharVolatile(o, offset, x);
2219 }
2220
2221 /** Opaque version of {@link #putIntVolatile(Object, long, int)} */
2222 @HotSpotIntrinsicCandidate
2223 public final void putIntOpaque(Object o, long offset, int x) {
2224 putIntVolatile(o, offset, x);
2225 }
2226
2227 /** Opaque version of {@link #putFloatVolatile(Object, long, float)} */
2228 @HotSpotIntrinsicCandidate
2229 public final void putFloatOpaque(Object o, long offset, float x) {
2230 putFloatVolatile(o, offset, x);
2231 }
2232
2233 /** Opaque version of {@link #putLongVolatile(Object, long, long)} */
2234 @HotSpotIntrinsicCandidate
2235 public final void putLongOpaque(Object o, long offset, long x) {
2236 putLongVolatile(o, offset, x);
2237 }
2238
2239 /** Opaque version of {@link #putDoubleVolatile(Object, long, double)} */
2240 @HotSpotIntrinsicCandidate
2241 public final void putDoubleOpaque(Object o, long offset, double x) {
2242 putDoubleVolatile(o, offset, x);
2243 }
2244
2245 /**
2246 * Unblocks the given thread blocked on {@code park}, or, if it is
2247 * not blocked, causes the subsequent call to {@code park} not to
2248 * block. Note: this operation is "unsafe" solely because the
2249 * caller must somehow ensure that the thread has not been
2250 * destroyed. Nothing special is usually required to ensure this
2251 * when called from Java (in which there will ordinarily be a live
2252 * reference to the thread) but this is not nearly-automatically
2253 * so when calling from native code.
2254 *
2255 * @param thread the thread to unpark.
2256 */
2257 @HotSpotIntrinsicCandidate
2258 public native void unpark(Object thread);
2259
2260 /**
2261 * Blocks current thread, returning when a balancing
2262 * {@code unpark} occurs, or a balancing {@code unpark} has
2263 * already occurred, or the thread is interrupted, or, if not
2264 * absolute and time is not zero, the given time nanoseconds have
2265 * elapsed, or if absolute, the given deadline in milliseconds
2266 * since Epoch has passed, or spuriously (i.e., returning for no
2267 * "reason"). Note: This operation is in the Unsafe class only
2268 * because {@code unpark} is, so it would be strange to place it
2269 * elsewhere.
2270 */
2271 @HotSpotIntrinsicCandidate
2272 public native void park(boolean isAbsolute, long time);
2273
2274 /**
2275 * Gets the load average in the system run queue assigned
2276 * to the available processors averaged over various periods of time.
2277 * This method retrieves the given {@code nelem} samples and
2278 * assigns to the elements of the given {@code loadavg} array.
2279 * The system imposes a maximum of 3 samples, representing
2280 * averages over the last 1, 5, and 15 minutes, respectively.
2281 *
2282 * @param loadavg an array of double of size nelems
2283 * @param nelems the number of samples to be retrieved and
2284 * must be 1 to 3.
2285 *
2286 * @return the number of samples actually retrieved; or -1
2287 * if the load average is unobtainable.
2288 */
2289 public int getLoadAverage(double[] loadavg, int nelems) {
2290 if (nelems < 0 || nelems > 3 || nelems > loadavg.length) {
2291 throw new ArrayIndexOutOfBoundsException();
2292 }
2293
2294 return getLoadAverage0(loadavg, nelems);
2295 }
2296
2297 // The following contain CAS-based Java implementations used on
2298 // platforms not supporting native instructions
2299
2300 /**
2301 * Atomically adds the given value to the current value of a field
2302 * or array element within the given object {@code o}
2303 * at the given {@code offset}.
2304 *
2305 * @param o object/array to update the field/element in
2306 * @param offset field/element offset
2307 * @param delta the value to add
2308 * @return the previous value
2309 * @since 1.8
2310 */
2311 @HotSpotIntrinsicCandidate
2312 public final int getAndAddInt(Object o, long offset, int delta) {
2313 int v;
2314 do {
2315 v = getIntVolatile(o, offset);
2316 } while (!weakCompareAndSwapIntVolatile(o, offset, v, v + delta));
2317 return v;
2318 }
2319
2320 /**
2321 * Atomically adds the given value to the current value of a field
2322 * or array element within the given object {@code o}
2323 * at the given {@code offset}.
2324 *
2325 * @param o object/array to update the field/element in
2326 * @param offset field/element offset
2327 * @param delta the value to add
2328 * @return the previous value
2329 * @since 1.8
2330 */
2331 @HotSpotIntrinsicCandidate
2332 public final long getAndAddLong(Object o, long offset, long delta) {
2333 long v;
2334 do {
2335 v = getLongVolatile(o, offset);
2336 } while (!weakCompareAndSwapLongVolatile(o, offset, v, v + delta));
2337 return v;
2338 }
2339
2340 @HotSpotIntrinsicCandidate
2341 public final byte getAndAddByte(Object o, long offset, byte delta) {
2342 byte v;
2343 do {
2344 v = getByteVolatile(o, offset);
2345 } while (!weakCompareAndSwapByteVolatile(o, offset, v, (byte) (v + delta)));
2346 return v;
2347 }
2348
2349 @HotSpotIntrinsicCandidate
2350 public final short getAndAddShort(Object o, long offset, short delta) {
2351 short v;
2352 do {
2353 v = getShortVolatile(o, offset);
2354 } while (!weakCompareAndSwapShortVolatile(o, offset, v, (short) (v + delta)));
2355 return v;
2356 }
2357
2358 @ForceInline
2359 public final char getAndAddChar(Object o, long offset, char delta) {
2360 return (char) getAndAddShort(o, offset, (short) delta);
2361 }
2362
2363 @ForceInline
2364 public final float getAndAddFloat(Object o, long offset, float delta) {
2365 int expectedBits;
2366 float v;
2367 do {
2368 // Load and CAS with the raw bits to avoid issues with NaNs and
2369 // possible bit conversion from signaling NaNs to quiet NaNs that
2370 // may result in the loop not terminating.
2371 expectedBits = getIntVolatile(o, offset);
2372 v = Float.intBitsToFloat(expectedBits);
2373 } while (!weakCompareAndSwapIntVolatile(o, offset,
2374 expectedBits, Float.floatToRawIntBits(v + delta)));
2375 return v;
2376 }
2377
2378 @ForceInline
2379 public final double getAndAddDouble(Object o, long offset, double delta) {
2380 long expectedBits;
2381 double v;
2382 do {
2383 // Load and CAS with the raw bits to avoid issues with NaNs and
2384 // possible bit conversion from signaling NaNs to quiet NaNs that
2385 // may result in the loop not terminating.
2386 expectedBits = getLongVolatile(o, offset);
2387 v = Double.longBitsToDouble(expectedBits);
2388 } while (!weakCompareAndSwapLongVolatile(o, offset,
2389 expectedBits, Double.doubleToRawLongBits(v + delta)));
2390 return v;
2391 }
2392
2393 /**
2394 * Atomically exchanges the given value with the current value of
2395 * a field or array element within the given object {@code o}
2396 * at the given {@code offset}.
2397 *
2398 * @param o object/array to update the field/element in
2399 * @param offset field/element offset
2400 * @param newValue new value
2401 * @return the previous value
2402 * @since 1.8
2403 */
2404 @HotSpotIntrinsicCandidate
2405 public final int getAndSetInt(Object o, long offset, int newValue) {
2406 int v;
2407 do {
2408 v = getIntVolatile(o, offset);
2409 } while (!weakCompareAndSwapIntVolatile(o, offset, v, newValue));
2410 return v;
2411 }
2412
2413 /**
2414 * Atomically exchanges the given value with the current value of
2415 * a field or array element within the given object {@code o}
2416 * at the given {@code offset}.
2417 *
2418 * @param o object/array to update the field/element in
2419 * @param offset field/element offset
2420 * @param newValue new value
2421 * @return the previous value
2422 * @since 1.8
2423 */
2424 @HotSpotIntrinsicCandidate
2425 public final long getAndSetLong(Object o, long offset, long newValue) {
2426 long v;
2427 do {
2428 v = getLongVolatile(o, offset);
2429 } while (!weakCompareAndSwapLongVolatile(o, offset, v, newValue));
2430 return v;
2431 }
2432
2433 /**
2434 * Atomically exchanges the given reference value with the current
2435 * reference value of a field or array element within the given
2436 * object {@code o} at the given {@code offset}.
2437 *
2438 * @param o object/array to update the field/element in
2439 * @param offset field/element offset
2440 * @param newValue new value
2441 * @return the previous value
2442 * @since 1.8
2443 */
2444 @HotSpotIntrinsicCandidate
2445 public final Object getAndSetObject(Object o, long offset, Object newValue) {
2446 Object v;
2447 do {
2448 v = getObjectVolatile(o, offset);
2449 } while (!weakCompareAndSwapObjectVolatile(o, offset, v, newValue));
2450 return v;
2451 }
2452
2453 @HotSpotIntrinsicCandidate
2454 public final byte getAndSetByte(Object o, long offset, byte newValue) {
2455 byte v;
2456 do {
2457 v = getByteVolatile(o, offset);
2458 } while (!weakCompareAndSwapByteVolatile(o, offset, v, newValue));
2459 return v;
2460 }
2461
2462 @ForceInline
2463 public final boolean getAndSetBoolean(Object o, long offset, boolean newValue) {
2464 return byte2bool(getAndSetByte(o, offset, bool2byte(newValue)));
2465 }
2466
2467 @HotSpotIntrinsicCandidate
2468 public final short getAndSetShort(Object o, long offset, short newValue) {
2469 short v;
2470 do {
2471 v = getShortVolatile(o, offset);
2472 } while (!weakCompareAndSwapShortVolatile(o, offset, v, newValue));
2473 return v;
2474 }
2475
2476 @ForceInline
2477 public final char getAndSetChar(Object o, long offset, char newValue) {
2478 return s2c(getAndSetShort(o, offset, c2s(newValue)));
2479 }
2480
2481 @ForceInline
2482 public final float getAndSetFloat(Object o, long offset, float newValue) {
2483 int v = getAndSetInt(o, offset, Float.floatToRawIntBits(newValue));
2484 return Float.intBitsToFloat(v);
2485 }
2486
2487 @ForceInline
2488 public final double getAndSetDouble(Object o, long offset, double newValue) {
2489 long v = getAndSetLong(o, offset, Double.doubleToRawLongBits(newValue));
2490 return Double.longBitsToDouble(v);
2491 }
2492
2493 /**
2494 * Ensures that loads before the fence will not be reordered with loads and
2495 * stores after the fence; a "LoadLoad plus LoadStore barrier".
2496 *
2497 * Corresponds to C11 atomic_thread_fence(memory_order_acquire)
2498 * (an "acquire fence").
2499 *
2500 * A pure LoadLoad fence is not provided, since the addition of LoadStore
2501 * is almost always desired, and most current hardware instructions that
2502 * provide a LoadLoad barrier also provide a LoadStore barrier for free.
2503 * @since 1.8
2504 */
2505 @HotSpotIntrinsicCandidate
2506 public native void loadFence();
2507
2508 /**
2509 * Ensures that loads and stores before the fence will not be reordered with
2510 * stores after the fence; a "StoreStore plus LoadStore barrier".
2511 *
2512 * Corresponds to C11 atomic_thread_fence(memory_order_release)
2513 * (a "release fence").
2514 *
2515 * A pure StoreStore fence is not provided, since the addition of LoadStore
2516 * is almost always desired, and most current hardware instructions that
2517 * provide a StoreStore barrier also provide a LoadStore barrier for free.
2518 * @since 1.8
2519 */
2520 @HotSpotIntrinsicCandidate
2521 public native void storeFence();
2522
2523 /**
2524 * Ensures that loads and stores before the fence will not be reordered
2525 * with loads and stores after the fence. Implies the effects of both
2526 * loadFence() and storeFence(), and in addition, the effect of a StoreLoad
2527 * barrier.
2528 *
2529 * Corresponds to C11 atomic_thread_fence(memory_order_seq_cst).
2530 * @since 1.8
2531 */
2532 @HotSpotIntrinsicCandidate
2533 public native void fullFence();
2534
2535 /**
2536 * Ensures that loads before the fence will not be reordered with
2537 * loads after the fence.
2538 */
2539 public final void loadLoadFence() {
2540 loadFence();
2541 }
2542
2543 /**
2544 * Ensures that stores before the fence will not be reordered with
2545 * stores after the fence.
2546 */
2547 public final void storeStoreFence() {
2548 storeFence();
2549 }
2550
2551
2552 /**
2553 * Throws IllegalAccessError; for use by the VM for access control
2554 * error support.
2555 * @since 1.8
2556 */
2557 private static void throwIllegalAccessError() {
2558 throw new IllegalAccessError();
2559 }
2560
2561 /**
2562 * @return Returns true if the native byte ordering of this
2563 * platform is big-endian, false if it is little-endian.
2564 */
2565 public final boolean isBigEndian() { return BE; }
2566
2567 /**
2568 * @return Returns true if this platform is capable of performing
2569 * accesses at addresses which are not aligned for the type of the
2570 * primitive type being accessed, false otherwise.
2571 */
2572 public final boolean unalignedAccess() { return unalignedAccess; }
2573
2574 /**
2575 * Fetches a value at some byte offset into a given Java object.
2576 * More specifically, fetches a value within the given object
2577 * <code>o</code> at the given offset, or (if <code>o</code> is
2578 * null) from the memory address whose numerical value is the
2579 * given offset. <p>
2580 *
2581 * The specification of this method is the same as {@link
2582 * #getLong(Object, long)} except that the offset does not need to
2583 * have been obtained from {@link #objectFieldOffset} on the
2584 * {@link java.lang.reflect.Field} of some Java field. The value
2585 * in memory is raw data, and need not correspond to any Java
2586 * variable. Unless <code>o</code> is null, the value accessed
2587 * must be entirely within the allocated object. The endianness
2588 * of the value in memory is the endianness of the native platform.
2589 *
2590 * <p> The read will be atomic with respect to the largest power
2591 * of two that divides the GCD of the offset and the storage size.
2592 * For example, getLongUnaligned will make atomic reads of 2-, 4-,
2593 * or 8-byte storage units if the offset is zero mod 2, 4, or 8,
2594 * respectively. There are no other guarantees of atomicity.
2595 * <p>
2596 * 8-byte atomicity is only guaranteed on platforms on which
2597 * support atomic accesses to longs.
2598 *
2599 * @param o Java heap object in which the value resides, if any, else
2600 * null
2601 * @param offset The offset in bytes from the start of the object
2602 * @return the value fetched from the indicated object
2603 * @throws RuntimeException No defined exceptions are thrown, not even
2604 * {@link NullPointerException}
2605 * @since 9
2606 */
2607 @HotSpotIntrinsicCandidate
2608 public final long getLongUnaligned(Object o, long offset) {
2609 if ((offset & 7) == 0) {
2610 return getLong(o, offset);
2611 } else if ((offset & 3) == 0) {
2612 return makeLong(getInt(o, offset),
2613 getInt(o, offset + 4));
2614 } else if ((offset & 1) == 0) {
2615 return makeLong(getShort(o, offset),
2616 getShort(o, offset + 2),
2617 getShort(o, offset + 4),
2618 getShort(o, offset + 6));
2619 } else {
2620 return makeLong(getByte(o, offset),
2621 getByte(o, offset + 1),
2622 getByte(o, offset + 2),
2623 getByte(o, offset + 3),
2624 getByte(o, offset + 4),
2625 getByte(o, offset + 5),
2626 getByte(o, offset + 6),
2627 getByte(o, offset + 7));
2628 }
2629 }
2630 /**
2631 * As {@link #getLongUnaligned(Object, long)} but with an
2632 * additional argument which specifies the endianness of the value
2633 * as stored in memory.
2634 *
2635 * @param o Java heap object in which the variable resides
2636 * @param offset The offset in bytes from the start of the object
2637 * @param bigEndian The endianness of the value
2638 * @return the value fetched from the indicated object
2639 * @since 9
2640 */
2641 public final long getLongUnaligned(Object o, long offset, boolean bigEndian) {
2642 return convEndian(bigEndian, getLongUnaligned(o, offset));
2643 }
2644
2645 /** @see #getLongUnaligned(Object, long) */
2646 @HotSpotIntrinsicCandidate
2647 public final int getIntUnaligned(Object o, long offset) {
2648 if ((offset & 3) == 0) {
2649 return getInt(o, offset);
2650 } else if ((offset & 1) == 0) {
2651 return makeInt(getShort(o, offset),
2652 getShort(o, offset + 2));
2653 } else {
2654 return makeInt(getByte(o, offset),
2655 getByte(o, offset + 1),
2656 getByte(o, offset + 2),
2657 getByte(o, offset + 3));
2658 }
2659 }
2660 /** @see #getLongUnaligned(Object, long, boolean) */
2661 public final int getIntUnaligned(Object o, long offset, boolean bigEndian) {
2662 return convEndian(bigEndian, getIntUnaligned(o, offset));
2663 }
2664
2665 /** @see #getLongUnaligned(Object, long) */
2666 @HotSpotIntrinsicCandidate
2667 public final short getShortUnaligned(Object o, long offset) {
2668 if ((offset & 1) == 0) {
2669 return getShort(o, offset);
2670 } else {
2671 return makeShort(getByte(o, offset),
2672 getByte(o, offset + 1));
2673 }
2674 }
2675 /** @see #getLongUnaligned(Object, long, boolean) */
2676 public final short getShortUnaligned(Object o, long offset, boolean bigEndian) {
2677 return convEndian(bigEndian, getShortUnaligned(o, offset));
2678 }
2679
2680 /** @see #getLongUnaligned(Object, long) */
2681 @HotSpotIntrinsicCandidate
2682 public final char getCharUnaligned(Object o, long offset) {
2683 if ((offset & 1) == 0) {
2684 return getChar(o, offset);
2685 } else {
2686 return (char)makeShort(getByte(o, offset),
2687 getByte(o, offset + 1));
2688 }
2689 }
2690
2691 /** @see #getLongUnaligned(Object, long, boolean) */
2692 public final char getCharUnaligned(Object o, long offset, boolean bigEndian) {
2693 return convEndian(bigEndian, getCharUnaligned(o, offset));
2694 }
2695
2696 /**
2697 * Stores a value at some byte offset into a given Java object.
2698 * <p>
2699 * The specification of this method is the same as {@link
2700 * #getLong(Object, long)} except that the offset does not need to
2701 * have been obtained from {@link #objectFieldOffset} on the
2702 * {@link java.lang.reflect.Field} of some Java field. The value
2703 * in memory is raw data, and need not correspond to any Java
2704 * variable. The endianness of the value in memory is the
2705 * endianness of the native platform.
2706 * <p>
2707 * The write will be atomic with respect to the largest power of
2708 * two that divides the GCD of the offset and the storage size.
2709 * For example, putLongUnaligned will make atomic writes of 2-, 4-,
2710 * or 8-byte storage units if the offset is zero mod 2, 4, or 8,
2711 * respectively. There are no other guarantees of atomicity.
2712 * <p>
2713 * 8-byte atomicity is only guaranteed on platforms on which
2714 * support atomic accesses to longs.
2715 *
2716 * @param o Java heap object in which the value resides, if any, else
2717 * null
2718 * @param offset The offset in bytes from the start of the object
2719 * @param x the value to store
2720 * @throws RuntimeException No defined exceptions are thrown, not even
2721 * {@link NullPointerException}
2722 * @since 9
2723 */
2724 @HotSpotIntrinsicCandidate
2725 public final void putLongUnaligned(Object o, long offset, long x) {
2726 if ((offset & 7) == 0) {
2727 putLong(o, offset, x);
2728 } else if ((offset & 3) == 0) {
2729 putLongParts(o, offset,
2730 (int)(x >> 0),
2731 (int)(x >>> 32));
2732 } else if ((offset & 1) == 0) {
2733 putLongParts(o, offset,
2734 (short)(x >>> 0),
2735 (short)(x >>> 16),
2736 (short)(x >>> 32),
2737 (short)(x >>> 48));
2738 } else {
2739 putLongParts(o, offset,
2740 (byte)(x >>> 0),
2741 (byte)(x >>> 8),
2742 (byte)(x >>> 16),
2743 (byte)(x >>> 24),
2744 (byte)(x >>> 32),
2745 (byte)(x >>> 40),
2746 (byte)(x >>> 48),
2747 (byte)(x >>> 56));
2748 }
2749 }
2750
2751 /**
2752 * As {@link #putLongUnaligned(Object, long, long)} but with an additional
2753 * argument which specifies the endianness of the value as stored in memory.
2754 * @param o Java heap object in which the value resides
2755 * @param offset The offset in bytes from the start of the object
2756 * @param x the value to store
2757 * @param bigEndian The endianness of the value
2758 * @throws RuntimeException No defined exceptions are thrown, not even
2759 * {@link NullPointerException}
2760 * @since 9
2761 */
2762 public final void putLongUnaligned(Object o, long offset, long x, boolean bigEndian) {
2763 putLongUnaligned(o, offset, convEndian(bigEndian, x));
2764 }
2765
2766 /** @see #putLongUnaligned(Object, long, long) */
2767 @HotSpotIntrinsicCandidate
2768 public final void putIntUnaligned(Object o, long offset, int x) {
2769 if ((offset & 3) == 0) {
2770 putInt(o, offset, x);
2771 } else if ((offset & 1) == 0) {
2772 putIntParts(o, offset,
2773 (short)(x >> 0),
2774 (short)(x >>> 16));
2775 } else {
2776 putIntParts(o, offset,
2777 (byte)(x >>> 0),
2778 (byte)(x >>> 8),
2779 (byte)(x >>> 16),
2780 (byte)(x >>> 24));
2781 }
2782 }
2783 /** @see #putLongUnaligned(Object, long, long, boolean) */
2784 public final void putIntUnaligned(Object o, long offset, int x, boolean bigEndian) {
2785 putIntUnaligned(o, offset, convEndian(bigEndian, x));
2786 }
2787
2788 /** @see #putLongUnaligned(Object, long, long) */
2789 @HotSpotIntrinsicCandidate
2790 public final void putShortUnaligned(Object o, long offset, short x) {
2791 if ((offset & 1) == 0) {
2792 putShort(o, offset, x);
2793 } else {
2794 putShortParts(o, offset,
2795 (byte)(x >>> 0),
2796 (byte)(x >>> 8));
2797 }
2798 }
2799 /** @see #putLongUnaligned(Object, long, long, boolean) */
2800 public final void putShortUnaligned(Object o, long offset, short x, boolean bigEndian) {
2801 putShortUnaligned(o, offset, convEndian(bigEndian, x));
2802 }
2803
2804 /** @see #putLongUnaligned(Object, long, long) */
2805 @HotSpotIntrinsicCandidate
2806 public final void putCharUnaligned(Object o, long offset, char x) {
2807 putShortUnaligned(o, offset, (short)x);
2808 }
2809 /** @see #putLongUnaligned(Object, long, long, boolean) */
2810 public final void putCharUnaligned(Object o, long offset, char x, boolean bigEndian) {
2811 putCharUnaligned(o, offset, convEndian(bigEndian, x));
2812 }
2813
2814 // JVM interface methods
2815 // BE is true iff the native endianness of this platform is big.
2816 private static final boolean BE = theUnsafe.isBigEndian0();
2817
2818 // unalignedAccess is true iff this platform can perform unaligned accesses.
2819 private static final boolean unalignedAccess = theUnsafe.unalignedAccess0();
2820
2821 private static int pickPos(int top, int pos) { return BE ? top - pos : pos; }
2822
2823 // These methods construct integers from bytes. The byte ordering
2824 // is the native endianness of this platform.
2825 private static long makeLong(byte i0, byte i1, byte i2, byte i3, byte i4, byte i5, byte i6, byte i7) {
2826 return ((toUnsignedLong(i0) << pickPos(56, 0))
2827 | (toUnsignedLong(i1) << pickPos(56, 8))
2828 | (toUnsignedLong(i2) << pickPos(56, 16))
2829 | (toUnsignedLong(i3) << pickPos(56, 24))
2830 | (toUnsignedLong(i4) << pickPos(56, 32))
2831 | (toUnsignedLong(i5) << pickPos(56, 40))
2832 | (toUnsignedLong(i6) << pickPos(56, 48))
2833 | (toUnsignedLong(i7) << pickPos(56, 56)));
2834 }
2835 private static long makeLong(short i0, short i1, short i2, short i3) {
2836 return ((toUnsignedLong(i0) << pickPos(48, 0))
2837 | (toUnsignedLong(i1) << pickPos(48, 16))
2838 | (toUnsignedLong(i2) << pickPos(48, 32))
2839 | (toUnsignedLong(i3) << pickPos(48, 48)));
2840 }
2841 private static long makeLong(int i0, int i1) {
2842 return (toUnsignedLong(i0) << pickPos(32, 0))
2843 | (toUnsignedLong(i1) << pickPos(32, 32));
2844 }
2845 private static int makeInt(short i0, short i1) {
2846 return (toUnsignedInt(i0) << pickPos(16, 0))
2847 | (toUnsignedInt(i1) << pickPos(16, 16));
2848 }
2849 private static int makeInt(byte i0, byte i1, byte i2, byte i3) {
2850 return ((toUnsignedInt(i0) << pickPos(24, 0))
2851 | (toUnsignedInt(i1) << pickPos(24, 8))
2852 | (toUnsignedInt(i2) << pickPos(24, 16))
2853 | (toUnsignedInt(i3) << pickPos(24, 24)));
2854 }
2855 private static short makeShort(byte i0, byte i1) {
2856 return (short)((toUnsignedInt(i0) << pickPos(8, 0))
2857 | (toUnsignedInt(i1) << pickPos(8, 8)));
2858 }
2859
2860 private static byte pick(byte le, byte be) { return BE ? be : le; }
2861 private static short pick(short le, short be) { return BE ? be : le; }
2862 private static int pick(int le, int be) { return BE ? be : le; }
2863
2864 // These methods write integers to memory from smaller parts
2865 // provided by their caller. The ordering in which these parts
2866 // are written is the native endianness of this platform.
2867 private void putLongParts(Object o, long offset, byte i0, byte i1, byte i2, byte i3, byte i4, byte i5, byte i6, byte i7) {
2868 putByte(o, offset + 0, pick(i0, i7));
2869 putByte(o, offset + 1, pick(i1, i6));
2870 putByte(o, offset + 2, pick(i2, i5));
2871 putByte(o, offset + 3, pick(i3, i4));
2872 putByte(o, offset + 4, pick(i4, i3));
2873 putByte(o, offset + 5, pick(i5, i2));
2874 putByte(o, offset + 6, pick(i6, i1));
2875 putByte(o, offset + 7, pick(i7, i0));
2876 }
2877 private void putLongParts(Object o, long offset, short i0, short i1, short i2, short i3) {
2878 putShort(o, offset + 0, pick(i0, i3));
2879 putShort(o, offset + 2, pick(i1, i2));
2880 putShort(o, offset + 4, pick(i2, i1));
2881 putShort(o, offset + 6, pick(i3, i0));
2882 }
2883 private void putLongParts(Object o, long offset, int i0, int i1) {
2884 putInt(o, offset + 0, pick(i0, i1));
2885 putInt(o, offset + 4, pick(i1, i0));
2886 }
2887 private void putIntParts(Object o, long offset, short i0, short i1) {
2888 putShort(o, offset + 0, pick(i0, i1));
2889 putShort(o, offset + 2, pick(i1, i0));
2890 }
2891 private void putIntParts(Object o, long offset, byte i0, byte i1, byte i2, byte i3) {
2892 putByte(o, offset + 0, pick(i0, i3));
2893 putByte(o, offset + 1, pick(i1, i2));
2894 putByte(o, offset + 2, pick(i2, i1));
2895 putByte(o, offset + 3, pick(i3, i0));
2896 }
2897 private void putShortParts(Object o, long offset, byte i0, byte i1) {
2898 putByte(o, offset + 0, pick(i0, i1));
2899 putByte(o, offset + 1, pick(i1, i0));
2900 }
2901
2902 // Zero-extend an integer
2903 private static int toUnsignedInt(byte n) { return n & 0xff; }
2904 private static int toUnsignedInt(short n) { return n & 0xffff; }
2905 private static long toUnsignedLong(byte n) { return n & 0xffl; }
2906 private static long toUnsignedLong(short n) { return n & 0xffffl; }
2907 private static long toUnsignedLong(int n) { return n & 0xffffffffl; }
2908
2909 // Maybe byte-reverse an integer
2910 private static char convEndian(boolean big, char n) { return big == BE ? n : Character.reverseBytes(n); }
2911 private static short convEndian(boolean big, short n) { return big == BE ? n : Short.reverseBytes(n) ; }
2912 private static int convEndian(boolean big, int n) { return big == BE ? n : Integer.reverseBytes(n) ; }
2913 private static long convEndian(boolean big, long n) { return big == BE ? n : Long.reverseBytes(n) ; }
2914
2915
2916
2917 private native long allocateMemory0(long bytes);
2918 private native long reallocateMemory0(long address, long bytes);
2919 private native void freeMemory0(long address);
2920 private native void setMemory0(Object o, long offset, long bytes, byte value);
2921 @HotSpotIntrinsicCandidate
2922 private native void copyMemory0(Object srcBase, long srcOffset, Object destBase, long destOffset, long bytes);
2923 private native void copySwapMemory0(Object srcBase, long srcOffset, Object destBase, long destOffset, long bytes, long elemSize);
2924 private native long objectFieldOffset0(Field f);
2925 private native long staticFieldOffset0(Field f);
2926 private native Object staticFieldBase0(Field f);
2927 private native boolean shouldBeInitialized0(Class<?> c);
2928 private native void ensureClassInitialized0(Class<?> c);
2929 private native int arrayBaseOffset0(Class<?> arrayClass);
2930 private native int arrayIndexScale0(Class<?> arrayClass);
2931 private native int addressSize0();
2932 private native Class<?> defineAnonymousClass0(Class<?> hostClass, byte[] data, Object[] cpPatches);
2933 private native int getLoadAverage0(double[] loadavg, int nelems);
2934 private native boolean unalignedAccess0();
2935 private native boolean isBigEndian0();
2936 }