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 java.lang.reflect.Field;
29 import java.security.ProtectionDomain;
30
31 import sun.reflect.CallerSensitive;
32 import sun.reflect.Reflection;
33 import jdk.internal.misc.VM;
34
35 import jdk.internal.HotSpotIntrinsicCandidate;
36
37
38 /**
39 * A collection of methods for performing low-level, unsafe operations.
40 * Although the class and all methods are public, use of this class is
41 * limited because only trusted code can obtain instances of it.
42 *
43 * @author John R. Rose
44 * @see #getUnsafe
45 */
46
47 public final class Unsafe {
48
49 private static native void registerNatives();
50 static {
51 registerNatives();
52 sun.reflect.Reflection.registerMethodsToFilter(Unsafe.class, "getUnsafe");
53 }
54
55 private Unsafe() {}
56
57 private static final Unsafe theUnsafe = new Unsafe();
58
59 /**
60 * Provides the caller with the capability of performing unsafe
61 * operations.
62 *
63 * <p>The returned {@code Unsafe} object should be carefully guarded
64 * by the caller, since it can be used to read and write data at arbitrary
65 * memory addresses. It must never be passed to untrusted code.
66 *
67 * <p>Most methods in this class are very low-level, and correspond to a
68 * small number of hardware instructions (on typical machines). Compilers
69 * are encouraged to optimize these methods accordingly.
70 *
71 * <p>Here is a suggested idiom for using unsafe operations:
72 *
73 * <pre> {@code
74 * class MyTrustedClass {
75 * private static final Unsafe unsafe = Unsafe.getUnsafe();
76 * ...
77 * private long myCountAddress = ...;
78 * public int getCount() { return unsafe.getByte(myCountAddress); }
79 * }}</pre>
80 *
81 * (It may assist compilers to make the local variable {@code final}.)
82 *
83 * @throws SecurityException if a security manager exists and its
84 * {@code checkPropertiesAccess} method doesn't allow
85 * access to the system properties.
86 */
87 @CallerSensitive
88 public static Unsafe getUnsafe() {
89 Class<?> caller = Reflection.getCallerClass();
90 if (!VM.isSystemDomainLoader(caller.getClassLoader()))
91 throw new SecurityException("Unsafe");
92 return theUnsafe;
93 }
94
95 /// peek and poke operations
96 /// (compilers should optimize these to memory ops)
97
98 // These work on object fields in the Java heap.
99 // They will not work on elements of packed arrays.
100
101 /**
102 * Fetches a value from a given Java variable.
103 * More specifically, fetches a field or array element within the given
104 * object {@code o} at the given offset, or (if {@code o} is null)
105 * from the memory address whose numerical value is the given offset.
106 * <p>
107 * The results are undefined unless one of the following cases is true:
108 * <ul>
109 * <li>The offset was obtained from {@link #objectFieldOffset} on
110 * the {@link java.lang.reflect.Field} of some Java field and the object
111 * referred to by {@code o} is of a class compatible with that
112 * field's class.
113 *
114 * <li>The offset and object reference {@code o} (either null or
115 * non-null) were both obtained via {@link #staticFieldOffset}
116 * and {@link #staticFieldBase} (respectively) from the
117 * reflective {@link Field} representation of some Java field.
118 *
119 * <li>The object referred to by {@code o} is an array, and the offset
120 * is an integer of the form {@code B+N*S}, where {@code N} is
121 * a valid index into the array, and {@code B} and {@code S} are
122 * the values obtained by {@link #arrayBaseOffset} and {@link
123 * #arrayIndexScale} (respectively) from the array's class. The value
124 * referred to is the {@code N}<em>th</em> element of the array.
125 *
126 * </ul>
127 * <p>
128 * If one of the above cases is true, the call references a specific Java
129 * variable (field or array element). However, the results are undefined
130 * if that variable is not in fact of the type returned by this method.
131 * <p>
132 * This method refers to a variable by means of two parameters, and so
133 * it provides (in effect) a <em>double-register</em> addressing mode
134 * for Java variables. When the object reference is null, this method
135 * uses its offset as an absolute address. This is similar in operation
136 * to methods such as {@link #getInt(long)}, which provide (in effect) a
137 * <em>single-register</em> addressing mode for non-Java variables.
138 * However, because Java variables may have a different layout in memory
139 * from non-Java variables, programmers should not assume that these
140 * two addressing modes are ever equivalent. Also, programmers should
141 * remember that offsets from the double-register addressing mode cannot
142 * be portably confused with longs used in the single-register addressing
143 * mode.
144 *
145 * @param o Java heap object in which the variable resides, if any, else
146 * null
147 * @param offset indication of where the variable resides in a Java heap
148 * object, if any, else a memory address locating the variable
149 * statically
150 * @return the value fetched from the indicated Java variable
151 * @throws RuntimeException No defined exceptions are thrown, not even
152 * {@link NullPointerException}
153 */
154 @HotSpotIntrinsicCandidate
155 public native int getInt(Object o, long offset);
156
157 /**
158 * Stores a value into a given Java variable.
159 * <p>
160 * The first two parameters are interpreted exactly as with
161 * {@link #getInt(Object, long)} to refer to a specific
162 * Java variable (field or array element). The given value
163 * is stored into that variable.
164 * <p>
165 * The variable must be of the same type as the method
166 * parameter {@code x}.
167 *
168 * @param o Java heap object in which the variable resides, if any, else
169 * null
170 * @param offset indication of where the variable resides in a Java heap
171 * object, if any, else a memory address locating the variable
172 * statically
173 * @param x the value to store into the indicated Java variable
174 * @throws RuntimeException No defined exceptions are thrown, not even
175 * {@link NullPointerException}
176 */
177 @HotSpotIntrinsicCandidate
178 public native void putInt(Object o, long offset, int x);
179
180 /**
181 * Fetches a reference value from a given Java variable.
182 * @see #getInt(Object, long)
183 */
184 @HotSpotIntrinsicCandidate
185 public native Object getObject(Object o, long offset);
186
187 /**
188 * Stores a reference value into a given Java variable.
189 * <p>
190 * Unless the reference {@code x} being stored is either null
191 * or matches the field type, the results are undefined.
192 * If the reference {@code o} is non-null, card marks or
193 * other store barriers for that object (if the VM requires them)
194 * are updated.
195 * @see #putInt(Object, long, int)
196 */
197 @HotSpotIntrinsicCandidate
198 public native void putObject(Object o, long offset, Object x);
199
200 /** @see #getInt(Object, long) */
201 @HotSpotIntrinsicCandidate
202 public native boolean getBoolean(Object o, long offset);
203 /** @see #putInt(Object, long, int) */
204 @HotSpotIntrinsicCandidate
205 public native void putBoolean(Object o, long offset, boolean x);
206 /** @see #getInt(Object, long) */
207 @HotSpotIntrinsicCandidate
208 public native byte getByte(Object o, long offset);
209 /** @see #putInt(Object, long, int) */
210 @HotSpotIntrinsicCandidate
211 public native void putByte(Object o, long offset, byte x);
212 /** @see #getInt(Object, long) */
213 @HotSpotIntrinsicCandidate
214 public native short getShort(Object o, long offset);
215 /** @see #putInt(Object, long, int) */
216 @HotSpotIntrinsicCandidate
217 public native void putShort(Object o, long offset, short x);
218 /** @see #getInt(Object, long) */
219 @HotSpotIntrinsicCandidate
220 public native char getChar(Object o, long offset);
221 /** @see #putInt(Object, long, int) */
222 @HotSpotIntrinsicCandidate
223 public native void putChar(Object o, long offset, char x);
224 /** @see #getInt(Object, long) */
225 @HotSpotIntrinsicCandidate
226 public native long getLong(Object o, long offset);
227 /** @see #putInt(Object, long, int) */
228 @HotSpotIntrinsicCandidate
229 public native void putLong(Object o, long offset, long x);
230 /** @see #getInt(Object, long) */
231 @HotSpotIntrinsicCandidate
232 public native float getFloat(Object o, long offset);
233 /** @see #putInt(Object, long, int) */
234 @HotSpotIntrinsicCandidate
235 public native void putFloat(Object o, long offset, float x);
236 /** @see #getInt(Object, long) */
237 @HotSpotIntrinsicCandidate
238 public native double getDouble(Object o, long offset);
239 /** @see #putInt(Object, long, int) */
240 @HotSpotIntrinsicCandidate
241 public native void putDouble(Object o, long offset, double x);
242
243 // These read VM internal data.
244
245 /**
246 * Fetches an uncompressed reference value from a given native variable
247 * ignoring the VM's compressed references mode.
248 *
249 * @param address a memory address locating the variable
250 * @return the value fetched from the indicated native variable
251 */
252 public native Object getUncompressedObject(long address);
253
254 /**
255 * Fetches the {@link java.lang.Class} Java mirror for the given native
256 * metaspace {@code Klass} pointer.
257 *
258 * @param metaspaceKlass a native metaspace {@code Klass} pointer
259 * @return the {@link java.lang.Class} Java mirror
260 */
261 public native Class<?> getJavaMirror(long metaspaceKlass);
262
263 /**
264 * Fetches a native metaspace {@code Klass} pointer for the given Java
265 * object.
266 *
267 * @param o Java heap object for which to fetch the class pointer
268 * @return a native metaspace {@code Klass} pointer
269 */
270 public native long getKlassPointer(Object o);
271
272 // These work on values in the C heap.
273
274 /**
275 * Fetches a value from a given memory address. If the address is zero, or
276 * does not point into a block obtained from {@link #allocateMemory}, the
277 * results are undefined.
278 *
279 * @see #allocateMemory
280 */
281 @HotSpotIntrinsicCandidate
282 public native byte getByte(long address);
283
284 /**
285 * Stores a value into a given memory address. If the address is zero, or
286 * does not point into a block obtained from {@link #allocateMemory}, the
287 * results are undefined.
288 *
289 * @see #getByte(long)
290 */
291 @HotSpotIntrinsicCandidate
292 public native void putByte(long address, byte x);
293
294 /** @see #getByte(long) */
295 @HotSpotIntrinsicCandidate
296 public native short getShort(long address);
297 /** @see #putByte(long, byte) */
298 @HotSpotIntrinsicCandidate
299 public native void putShort(long address, short x);
300 /** @see #getByte(long) */
301 @HotSpotIntrinsicCandidate
302 public native char getChar(long address);
303 /** @see #putByte(long, byte) */
304 @HotSpotIntrinsicCandidate
305 public native void putChar(long address, char x);
306 /** @see #getByte(long) */
307 @HotSpotIntrinsicCandidate
308 public native int getInt(long address);
309 /** @see #putByte(long, byte) */
310 @HotSpotIntrinsicCandidate
311 public native void putInt(long address, int x);
312 /** @see #getByte(long) */
313 @HotSpotIntrinsicCandidate
314 public native long getLong(long address);
315 /** @see #putByte(long, byte) */
316 @HotSpotIntrinsicCandidate
317 public native void putLong(long address, long x);
318 /** @see #getByte(long) */
319 @HotSpotIntrinsicCandidate
320 public native float getFloat(long address);
321 /** @see #putByte(long, byte) */
322 @HotSpotIntrinsicCandidate
323 public native void putFloat(long address, float x);
324 /** @see #getByte(long) */
325 @HotSpotIntrinsicCandidate
326 public native double getDouble(long address);
327 /** @see #putByte(long, byte) */
328 @HotSpotIntrinsicCandidate
329 public native void putDouble(long address, double x);
330
331 /**
332 * Fetches a native pointer from a given memory address. If the address is
333 * zero, or does not point into a block obtained from {@link
334 * #allocateMemory}, the results are undefined.
335 *
336 * <p>If the native pointer is less than 64 bits wide, it is extended as
337 * an unsigned number to a Java long. The pointer may be indexed by any
338 * given byte offset, simply by adding that offset (as a simple integer) to
339 * the long representing the pointer. The number of bytes actually read
340 * from the target address may be determined by consulting {@link
341 * #addressSize}.
342 *
343 * @see #allocateMemory
344 */
345 @HotSpotIntrinsicCandidate
346 public native long getAddress(long address);
347
348 /**
349 * Stores a native pointer into a given memory address. If the address is
350 * zero, or does not point into a block obtained from {@link
351 * #allocateMemory}, the results are undefined.
352 *
353 * <p>The number of bytes actually written at the target address may be
354 * determined by consulting {@link #addressSize}.
355 *
356 * @see #getAddress(long)
357 */
358 @HotSpotIntrinsicCandidate
359 public native void putAddress(long address, long x);
360
361 /// wrappers for malloc, realloc, free:
362
363 /**
364 * Allocates a new block of native memory, of the given size in bytes. The
365 * contents of the memory are uninitialized; they will generally be
366 * garbage. The resulting native pointer will never be zero, and will be
367 * aligned for all value types. Dispose of this memory by calling {@link
368 * #freeMemory}, or resize it with {@link #reallocateMemory}.
369 *
370 * @throws IllegalArgumentException if the size is negative or too large
371 * for the native size_t type
372 *
373 * @throws OutOfMemoryError if the allocation is refused by the system
374 *
375 * @see #getByte(long)
376 * @see #putByte(long, byte)
377 */
378 public native long allocateMemory(long bytes);
379
380 /**
381 * Resizes a new block of native memory, to the given size in bytes. The
382 * contents of the new block past the size of the old block are
383 * uninitialized; they will generally be garbage. The resulting native
384 * pointer will be zero if and only if the requested size is zero. The
385 * resulting native pointer will be aligned for all value types. Dispose
386 * of this memory by calling {@link #freeMemory}, or resize it with {@link
387 * #reallocateMemory}. The address passed to this method may be null, in
388 * which case an allocation will be performed.
389 *
390 * @throws IllegalArgumentException if the size is negative or too large
391 * for the native size_t type
392 *
393 * @throws OutOfMemoryError if the allocation is refused by the system
394 *
395 * @see #allocateMemory
396 */
397 public native long reallocateMemory(long address, long bytes);
398
399 /**
400 * Sets all bytes in a given block of memory to a fixed value
401 * (usually zero).
402 *
403 * <p>This method determines a block's base address by means of two parameters,
404 * and so it provides (in effect) a <em>double-register</em> addressing mode,
405 * as discussed in {@link #getInt(Object,long)}. When the object reference is null,
406 * the offset supplies an absolute base address.
407 *
408 * <p>The stores are in coherent (atomic) units of a size determined
409 * by the address and length parameters. If the effective address and
410 * length are all even modulo 8, the stores take place in 'long' units.
411 * If the effective address and length are (resp.) even modulo 4 or 2,
412 * the stores take place in units of 'int' or 'short'.
413 *
414 * @since 1.7
415 */
416 public native void setMemory(Object o, long offset, long bytes, byte value);
417
418 /**
419 * Sets all bytes in a given block of memory to a fixed value
420 * (usually zero). This provides a <em>single-register</em> addressing mode,
421 * as discussed in {@link #getInt(Object,long)}.
422 *
423 * <p>Equivalent to {@code setMemory(null, address, bytes, value)}.
424 */
425 public void setMemory(long address, long bytes, byte value) {
426 setMemory(null, address, bytes, value);
427 }
428
429 /**
430 * Sets all bytes in a given block of memory to a copy of another
431 * block.
432 *
433 * <p>This method determines each block's base address by means of two parameters,
434 * and so it provides (in effect) a <em>double-register</em> addressing mode,
435 * as discussed in {@link #getInt(Object,long)}. When the object reference is null,
436 * the offset supplies an absolute base address.
437 *
438 * <p>The transfers are in coherent (atomic) units of a size determined
439 * by the address and length parameters. If the effective addresses and
440 * length are all even modulo 8, the transfer takes place in 'long' units.
441 * If the effective addresses and length are (resp.) even modulo 4 or 2,
442 * the transfer takes place in units of 'int' or 'short'.
443 *
444 * @since 1.7
445 */
446 @HotSpotIntrinsicCandidate
447 public native void copyMemory(Object srcBase, long srcOffset,
448 Object destBase, long destOffset,
449 long bytes);
450 /**
451 * Sets all bytes in a given block of memory to a copy of another
452 * block. This provides a <em>single-register</em> addressing mode,
453 * as discussed in {@link #getInt(Object,long)}.
454 *
455 * Equivalent to {@code copyMemory(null, srcAddress, null, destAddress, bytes)}.
456 */
457 public void copyMemory(long srcAddress, long destAddress, long bytes) {
458 copyMemory(null, srcAddress, null, destAddress, bytes);
459 }
460
461 private boolean isPrimitiveArray(Class<?> c) {
462 Class<?> componentType = c.getComponentType();
463 return componentType != null && componentType.isPrimitive();
464 }
465
466 private native void copySwapMemory0(Object srcBase, long srcOffset,
467 Object destBase, long destOffset,
468 long bytes, long elemSize);
469
470 /**
471 * Copies all elements from one block of memory to another block,
472 * *unconditionally* byte swapping the elements on the fly.
473 *
474 * <p>This method determines each block's base address by means of two parameters,
475 * and so it provides (in effect) a <em>double-register</em> addressing mode,
476 * as discussed in {@link #getInt(Object,long)}. When the object reference is null,
477 * the offset supplies an absolute base address.
478 *
479 * @since 9
480 */
481 public void copySwapMemory(Object srcBase, long srcOffset,
482 Object destBase, long destOffset,
483 long bytes, long elemSize) {
484 if (bytes < 0) {
485 throw new IllegalArgumentException();
486 }
487 if (elemSize != 2 && elemSize != 4 && elemSize != 8) {
488 throw new IllegalArgumentException();
489 }
490 if (bytes % elemSize != 0) {
491 throw new IllegalArgumentException();
492 }
493 if ((srcBase == null && srcOffset == 0) ||
494 (destBase == null && destOffset == 0)) {
495 throw new NullPointerException();
496 }
497
498 // Must be off-heap, or primitive heap arrays
499 if (srcBase != null && (srcOffset < 0 || !isPrimitiveArray(srcBase.getClass()))) {
500 throw new IllegalArgumentException();
501 }
502 if (destBase != null && (destOffset < 0 || !isPrimitiveArray(destBase.getClass()))) {
503 throw new IllegalArgumentException();
504 }
505
506 // Sanity check size and offsets on 32-bit platforms. Most
507 // significant 32 bits must be zero.
508 if (ADDRESS_SIZE == 4 &&
509 (bytes >>> 32 != 0 || srcOffset >>> 32 != 0 || destOffset >>> 32 != 0)) {
510 throw new IllegalArgumentException();
511 }
512
513 if (bytes == 0) {
514 return;
515 }
516
517 copySwapMemory0(srcBase, srcOffset, destBase, destOffset, bytes, elemSize);
518 }
519
520 /**
521 * Copies all elements from one block of memory to another block, byte swapping the
522 * elements on the fly.
523 *
524 * This provides a <em>single-register</em> addressing mode, as
525 * discussed in {@link #getInt(Object,long)}.
526 *
527 * Equivalent to {@code copySwapMemory(null, srcAddress, null, destAddress, bytes, elemSize)}.
528 */
529 public void copySwapMemory(long srcAddress, long destAddress, long bytes, long elemSize) {
530 copySwapMemory(null, srcAddress, null, destAddress, bytes, elemSize);
531 }
532
533 /**
534 * Disposes of a block of native memory, as obtained from {@link
535 * #allocateMemory} or {@link #reallocateMemory}. The address passed to
536 * this method may be null, in which case no action is taken.
537 *
538 * @see #allocateMemory
539 */
540 public native void freeMemory(long address);
541
542 /// random queries
543
544 /**
545 * This constant differs from all results that will ever be returned from
546 * {@link #staticFieldOffset}, {@link #objectFieldOffset},
547 * or {@link #arrayBaseOffset}.
548 */
549 public static final int INVALID_FIELD_OFFSET = -1;
550
551 /**
552 * Reports the location of a given field in the storage allocation of its
553 * class. Do not expect to perform any sort of arithmetic on this offset;
554 * it is just a cookie which is passed to the unsafe heap memory accessors.
555 *
556 * <p>Any given field will always have the same offset and base, and no
557 * two distinct fields of the same class will ever have the same offset
558 * and base.
559 *
560 * <p>As of 1.4.1, offsets for fields are represented as long values,
561 * although the Sun JVM does not use the most significant 32 bits.
562 * However, JVM implementations which store static fields at absolute
563 * addresses can use long offsets and null base pointers to express
564 * the field locations in a form usable by {@link #getInt(Object,long)}.
565 * Therefore, code which will be ported to such JVMs on 64-bit platforms
566 * must preserve all bits of static field offsets.
567 * @see #getInt(Object, long)
568 */
569 public native long objectFieldOffset(Field f);
570
571 /**
572 * Reports the location of a given static field, in conjunction with {@link
573 * #staticFieldBase}.
574 * <p>Do not expect to perform any sort of arithmetic on this offset;
575 * it is just a cookie which is passed to the unsafe heap memory accessors.
576 *
577 * <p>Any given field will always have the same offset, and no two distinct
578 * fields of the same class will ever have the same offset.
579 *
580 * <p>As of 1.4.1, offsets for fields are represented as long values,
581 * although the Sun JVM does not use the most significant 32 bits.
582 * It is hard to imagine a JVM technology which needs more than
583 * a few bits to encode an offset within a non-array object,
584 * However, for consistency with other methods in this class,
585 * this method reports its result as a long value.
586 * @see #getInt(Object, long)
587 */
588 public native long staticFieldOffset(Field f);
589
590 /**
591 * Reports the location of a given static field, in conjunction with {@link
592 * #staticFieldOffset}.
593 * <p>Fetch the base "Object", if any, with which static fields of the
594 * given class can be accessed via methods like {@link #getInt(Object,
595 * long)}. This value may be null. This value may refer to an object
596 * which is a "cookie", not guaranteed to be a real Object, and it should
597 * not be used in any way except as argument to the get and put routines in
598 * this class.
599 */
600 public native Object staticFieldBase(Field f);
601
602 /**
603 * Detects if the given class may need to be initialized. This is often
604 * needed in conjunction with obtaining the static field base of a
605 * class.
606 * @return false only if a call to {@code ensureClassInitialized} would have no effect
607 */
608 public native boolean shouldBeInitialized(Class<?> c);
609
610 /**
611 * Ensures the given class has been initialized. This is often
612 * needed in conjunction with obtaining the static field base of a
613 * class.
614 */
615 public native void ensureClassInitialized(Class<?> c);
616
617 /**
618 * Reports the offset of the first element in the storage allocation of a
619 * given array class. If {@link #arrayIndexScale} returns a non-zero value
620 * for the same class, you may use that scale factor, together with this
621 * base offset, to form new offsets to access elements of arrays of the
622 * given class.
623 *
624 * @see #getInt(Object, long)
625 * @see #putInt(Object, long, int)
626 */
627 public native int arrayBaseOffset(Class<?> arrayClass);
628
629 /** The value of {@code arrayBaseOffset(boolean[].class)} */
630 public static final int ARRAY_BOOLEAN_BASE_OFFSET
631 = theUnsafe.arrayBaseOffset(boolean[].class);
632
633 /** The value of {@code arrayBaseOffset(byte[].class)} */
634 public static final int ARRAY_BYTE_BASE_OFFSET
635 = theUnsafe.arrayBaseOffset(byte[].class);
636
637 /** The value of {@code arrayBaseOffset(short[].class)} */
638 public static final int ARRAY_SHORT_BASE_OFFSET
639 = theUnsafe.arrayBaseOffset(short[].class);
640
641 /** The value of {@code arrayBaseOffset(char[].class)} */
642 public static final int ARRAY_CHAR_BASE_OFFSET
643 = theUnsafe.arrayBaseOffset(char[].class);
644
645 /** The value of {@code arrayBaseOffset(int[].class)} */
646 public static final int ARRAY_INT_BASE_OFFSET
647 = theUnsafe.arrayBaseOffset(int[].class);
648
649 /** The value of {@code arrayBaseOffset(long[].class)} */
650 public static final int ARRAY_LONG_BASE_OFFSET
651 = theUnsafe.arrayBaseOffset(long[].class);
652
653 /** The value of {@code arrayBaseOffset(float[].class)} */
654 public static final int ARRAY_FLOAT_BASE_OFFSET
655 = theUnsafe.arrayBaseOffset(float[].class);
656
657 /** The value of {@code arrayBaseOffset(double[].class)} */
658 public static final int ARRAY_DOUBLE_BASE_OFFSET
659 = theUnsafe.arrayBaseOffset(double[].class);
660
661 /** The value of {@code arrayBaseOffset(Object[].class)} */
662 public static final int ARRAY_OBJECT_BASE_OFFSET
663 = theUnsafe.arrayBaseOffset(Object[].class);
664
665 /**
666 * Reports the scale factor for addressing elements in the storage
667 * allocation of a given array class. However, arrays of "narrow" types
668 * will generally not work properly with accessors like {@link
669 * #getByte(Object, long)}, so the scale factor for such classes is reported
670 * as zero.
671 *
672 * @see #arrayBaseOffset
673 * @see #getInt(Object, long)
674 * @see #putInt(Object, long, int)
675 */
676 public native int arrayIndexScale(Class<?> arrayClass);
677
678 /** The value of {@code arrayIndexScale(boolean[].class)} */
679 public static final int ARRAY_BOOLEAN_INDEX_SCALE
680 = theUnsafe.arrayIndexScale(boolean[].class);
681
682 /** The value of {@code arrayIndexScale(byte[].class)} */
683 public static final int ARRAY_BYTE_INDEX_SCALE
684 = theUnsafe.arrayIndexScale(byte[].class);
685
686 /** The value of {@code arrayIndexScale(short[].class)} */
687 public static final int ARRAY_SHORT_INDEX_SCALE
688 = theUnsafe.arrayIndexScale(short[].class);
689
690 /** The value of {@code arrayIndexScale(char[].class)} */
691 public static final int ARRAY_CHAR_INDEX_SCALE
692 = theUnsafe.arrayIndexScale(char[].class);
693
694 /** The value of {@code arrayIndexScale(int[].class)} */
695 public static final int ARRAY_INT_INDEX_SCALE
696 = theUnsafe.arrayIndexScale(int[].class);
697
698 /** The value of {@code arrayIndexScale(long[].class)} */
699 public static final int ARRAY_LONG_INDEX_SCALE
700 = theUnsafe.arrayIndexScale(long[].class);
701
702 /** The value of {@code arrayIndexScale(float[].class)} */
703 public static final int ARRAY_FLOAT_INDEX_SCALE
704 = theUnsafe.arrayIndexScale(float[].class);
705
706 /** The value of {@code arrayIndexScale(double[].class)} */
707 public static final int ARRAY_DOUBLE_INDEX_SCALE
708 = theUnsafe.arrayIndexScale(double[].class);
709
710 /** The value of {@code arrayIndexScale(Object[].class)} */
711 public static final int ARRAY_OBJECT_INDEX_SCALE
712 = theUnsafe.arrayIndexScale(Object[].class);
713
714 /**
715 * Reports the size in bytes of a native pointer, as stored via {@link
716 * #putAddress}. This value will be either 4 or 8. Note that the sizes of
717 * other primitive types (as stored in native memory blocks) is determined
718 * fully by their information content.
719 */
720 public native int addressSize();
721
722 /** The value of {@code addressSize()} */
723 public static final int ADDRESS_SIZE = theUnsafe.addressSize();
724
725 /**
726 * Reports the size in bytes of a native memory page (whatever that is).
727 * This value will always be a power of two.
728 */
729 public native int pageSize();
730
731
732 /// random trusted operations from JNI:
733
734 /**
735 * Tells the VM to define a class, without security checks. By default, the
736 * class loader and protection domain come from the caller's class.
737 */
738 public native Class<?> defineClass(String name, byte[] b, int off, int len,
739 ClassLoader loader,
740 ProtectionDomain protectionDomain);
741
742 /**
743 * Defines a class but does not make it known to the class loader or system dictionary.
744 * <p>
745 * For each CP entry, the corresponding CP patch must either be null or have
746 * the a format that matches its tag:
747 * <ul>
748 * <li>Integer, Long, Float, Double: the corresponding wrapper object type from java.lang
749 * <li>Utf8: a string (must have suitable syntax if used as signature or name)
750 * <li>Class: any java.lang.Class object
751 * <li>String: any object (not just a java.lang.String)
752 * <li>InterfaceMethodRef: (NYI) a method handle to invoke on that call site's arguments
753 * </ul>
754 * @param hostClass context for linkage, access control, protection domain, and class loader
755 * @param data bytes of a class file
756 * @param cpPatches where non-null entries exist, they replace corresponding CP entries in data
757 */
758 public native Class<?> defineAnonymousClass(Class<?> hostClass, byte[] data, Object[] cpPatches);
759
760 /**
761 * Allocates an instance but does not run any constructor.
762 * Initializes the class if it has not yet been.
763 */
764 @HotSpotIntrinsicCandidate
765 public native Object allocateInstance(Class<?> cls)
766 throws InstantiationException;
767
768 /** Throws the exception without telling the verifier. */
769 public native void throwException(Throwable ee);
770
771 /**
772 * Atomically updates Java variable to {@code x} if it is currently
773 * holding {@code expected}.
774 *
775 * <p>This operation has memory semantics of a {@code volatile} read
776 * and write. Corresponds to C11 atomic_compare_exchange_strong.
777 *
778 * @return {@code true} if successful
779 */
780 @HotSpotIntrinsicCandidate
781 public final native boolean compareAndSwapObject(Object o, long offset,
782 Object expected,
783 Object x);
784
785 @HotSpotIntrinsicCandidate
786 public final native Object compareAndExchangeObjectVolatile(Object o, long offset,
787 Object expected,
788 Object x);
789
790 @HotSpotIntrinsicCandidate
791 public final Object compareAndExchangeObjectAcquire(Object o, long offset,
792 Object expected,
793 Object x) {
794 return compareAndExchangeObjectVolatile(o, offset, expected, x);
795 }
796
797 @HotSpotIntrinsicCandidate
798 public final Object compareAndExchangeObjectRelease(Object o, long offset,
799 Object expected,
800 Object x) {
801 return compareAndExchangeObjectVolatile(o, offset, expected, x);
802 }
803
804 @HotSpotIntrinsicCandidate
805 public final boolean weakCompareAndSwapObject(Object o, long offset,
806 Object expected,
807 Object x) {
808 return compareAndSwapObject(o, offset, expected, x);
809 }
810
811 @HotSpotIntrinsicCandidate
812 public final boolean weakCompareAndSwapObjectAcquire(Object o, long offset,
813 Object expected,
814 Object x) {
815 return compareAndSwapObject(o, offset, expected, x);
816 }
817
818 @HotSpotIntrinsicCandidate
819 public final boolean weakCompareAndSwapObjectRelease(Object o, long offset,
820 Object expected,
821 Object x) {
822 return compareAndSwapObject(o, offset, expected, x);
823 }
824
825 /**
826 * Atomically updates Java variable to {@code x} if it is currently
827 * holding {@code expected}.
828 *
829 * <p>This operation has memory semantics of a {@code volatile} read
830 * and write. Corresponds to C11 atomic_compare_exchange_strong.
831 *
832 * @return {@code true} if successful
833 */
834 @HotSpotIntrinsicCandidate
835 public final native boolean compareAndSwapInt(Object o, long offset,
836 int expected,
837 int x);
838
839 @HotSpotIntrinsicCandidate
840 public final native int compareAndExchangeIntVolatile(Object o, long offset,
841 int expected,
842 int x);
843
844 @HotSpotIntrinsicCandidate
845 public final int compareAndExchangeIntAcquire(Object o, long offset,
846 int expected,
847 int x) {
848 return compareAndExchangeIntVolatile(o, offset, expected, x);
849 }
850
851 @HotSpotIntrinsicCandidate
852 public final int compareAndExchangeIntRelease(Object o, long offset,
853 int expected,
854 int x) {
855 return compareAndExchangeIntVolatile(o, offset, expected, x);
856 }
857
858 @HotSpotIntrinsicCandidate
859 public final boolean weakCompareAndSwapInt(Object o, long offset,
860 int expected,
861 int x) {
862 return compareAndSwapInt(o, offset, expected, x);
863 }
864
865 @HotSpotIntrinsicCandidate
866 public final boolean weakCompareAndSwapIntAcquire(Object o, long offset,
867 int expected,
868 int x) {
869 return compareAndSwapInt(o, offset, expected, x);
870 }
871
872 @HotSpotIntrinsicCandidate
873 public final boolean weakCompareAndSwapIntRelease(Object o, long offset,
874 int expected,
875 int x) {
876 return compareAndSwapInt(o, offset, expected, x);
877 }
878
879 /**
880 * Atomically updates Java variable to {@code x} if it is currently
881 * holding {@code expected}.
882 *
883 * <p>This operation has memory semantics of a {@code volatile} read
884 * and write. Corresponds to C11 atomic_compare_exchange_strong.
885 *
886 * @return {@code true} if successful
887 */
888 @HotSpotIntrinsicCandidate
889 public final native boolean compareAndSwapLong(Object o, long offset,
890 long expected,
891 long x);
892
893 @HotSpotIntrinsicCandidate
894 public final native long compareAndExchangeLongVolatile(Object o, long offset,
895 long expected,
896 long x);
897
898 @HotSpotIntrinsicCandidate
899 public final long compareAndExchangeLongAcquire(Object o, long offset,
900 long expected,
901 long x) {
902 return compareAndExchangeLongVolatile(o, offset, expected, x);
903 }
904
905 @HotSpotIntrinsicCandidate
906 public final long compareAndExchangeLongRelease(Object o, long offset,
907 long expected,
908 long x) {
909 return compareAndExchangeLongVolatile(o, offset, expected, x);
910 }
911
912 @HotSpotIntrinsicCandidate
913 public final boolean weakCompareAndSwapLong(Object o, long offset,
914 long expected,
915 long x) {
916 return compareAndSwapLong(o, offset, expected, x);
917 }
918
919 @HotSpotIntrinsicCandidate
920 public final boolean weakCompareAndSwapLongAcquire(Object o, long offset,
921 long expected,
922 long x) {
923 return compareAndSwapLong(o, offset, expected, x);
924 }
925
926 @HotSpotIntrinsicCandidate
927 public final boolean weakCompareAndSwapLongRelease(Object o, long offset,
928 long expected,
929 long x) {
930 return compareAndSwapLong(o, offset, expected, x);
931 }
932
933 /**
934 * Fetches a reference value from a given Java variable, with volatile
935 * load semantics. Otherwise identical to {@link #getObject(Object, long)}
936 */
937 @HotSpotIntrinsicCandidate
938 public native Object getObjectVolatile(Object o, long offset);
939
940 /**
941 * Stores a reference value into a given Java variable, with
942 * volatile store semantics. Otherwise identical to {@link #putObject(Object, long, Object)}
943 */
944 @HotSpotIntrinsicCandidate
945 public native void putObjectVolatile(Object o, long offset, Object x);
946
947 /** Volatile version of {@link #getInt(Object, long)} */
948 @HotSpotIntrinsicCandidate
949 public native int getIntVolatile(Object o, long offset);
950
951 /** Volatile version of {@link #putInt(Object, long, int)} */
952 @HotSpotIntrinsicCandidate
953 public native void putIntVolatile(Object o, long offset, int x);
954
955 /** Volatile version of {@link #getBoolean(Object, long)} */
956 @HotSpotIntrinsicCandidate
957 public native boolean getBooleanVolatile(Object o, long offset);
958
959 /** Volatile version of {@link #putBoolean(Object, long, boolean)} */
960 @HotSpotIntrinsicCandidate
961 public native void putBooleanVolatile(Object o, long offset, boolean x);
962
963 /** Volatile version of {@link #getByte(Object, long)} */
964 @HotSpotIntrinsicCandidate
965 public native byte getByteVolatile(Object o, long offset);
966
967 /** Volatile version of {@link #putByte(Object, long, byte)} */
968 @HotSpotIntrinsicCandidate
969 public native void putByteVolatile(Object o, long offset, byte x);
970
971 /** Volatile version of {@link #getShort(Object, long)} */
972 @HotSpotIntrinsicCandidate
973 public native short getShortVolatile(Object o, long offset);
974
975 /** Volatile version of {@link #putShort(Object, long, short)} */
976 @HotSpotIntrinsicCandidate
977 public native void putShortVolatile(Object o, long offset, short x);
978
979 /** Volatile version of {@link #getChar(Object, long)} */
980 @HotSpotIntrinsicCandidate
981 public native char getCharVolatile(Object o, long offset);
982
983 /** Volatile version of {@link #putChar(Object, long, char)} */
984 @HotSpotIntrinsicCandidate
985 public native void putCharVolatile(Object o, long offset, char x);
986
987 /** Volatile version of {@link #getLong(Object, long)} */
988 @HotSpotIntrinsicCandidate
989 public native long getLongVolatile(Object o, long offset);
990
991 /** Volatile version of {@link #putLong(Object, long, long)} */
992 @HotSpotIntrinsicCandidate
993 public native void putLongVolatile(Object o, long offset, long x);
994
995 /** Volatile version of {@link #getFloat(Object, long)} */
996 @HotSpotIntrinsicCandidate
997 public native float getFloatVolatile(Object o, long offset);
998
999 /** Volatile version of {@link #putFloat(Object, long, float)} */
1000 @HotSpotIntrinsicCandidate
1001 public native void putFloatVolatile(Object o, long offset, float x);
1002
1003 /** Volatile version of {@link #getDouble(Object, long)} */
1004 @HotSpotIntrinsicCandidate
1005 public native double getDoubleVolatile(Object o, long offset);
1006
1007 /** Volatile version of {@link #putDouble(Object, long, double)} */
1008 @HotSpotIntrinsicCandidate
1009 public native void putDoubleVolatile(Object o, long offset, double x);
1010
1011 /**
1012 * Version of {@link #putObjectVolatile(Object, long, Object)}
1013 * that does not guarantee immediate visibility of the store to
1014 * other threads. This method is generally only useful if the
1015 * underlying field is a Java volatile (or if an array cell, one
1016 * that is otherwise only accessed using volatile accesses).
1017 *
1018 * Corresponds to C11 atomic_store_explicit(..., memory_order_release).
1019 */
1020 @HotSpotIntrinsicCandidate
1021 public native void putOrderedObject(Object o, long offset, Object x);
1022
1023 /** Ordered/Lazy version of {@link #putIntVolatile(Object, long, int)} */
1024 @HotSpotIntrinsicCandidate
1025 public native void putOrderedInt(Object o, long offset, int x);
1026
1027 /** Ordered/Lazy version of {@link #putLongVolatile(Object, long, long)} */
1028 @HotSpotIntrinsicCandidate
1029 public native void putOrderedLong(Object o, long offset, long x);
1030
1031 /** Acquire version of {@link #getObjectVolatile(Object, long)} */
1032 @HotSpotIntrinsicCandidate
1033 public final Object getObjectAcquire(Object o, long offset) {
1034 return getObjectVolatile(o, offset);
1035 }
1036
1037 /** Acquire version of {@link #getBooleanVolatile(Object, long)} */
1038 @HotSpotIntrinsicCandidate
1039 public final boolean getBooleanAcquire(Object o, long offset) {
1040 return getBooleanVolatile(o, offset);
1041 }
1042
1043 /** Acquire version of {@link #getByteVolatile(Object, long)} */
1044 @HotSpotIntrinsicCandidate
1045 public final byte getByteAcquire(Object o, long offset) {
1046 return getByteVolatile(o, offset);
1047 }
1048
1049 /** Acquire version of {@link #getShortVolatile(Object, long)} */
1050 @HotSpotIntrinsicCandidate
1051 public final short getShortAcquire(Object o, long offset) {
1052 return getShortVolatile(o, offset);
1053 }
1054
1055 /** Acquire version of {@link #getCharVolatile(Object, long)} */
1056 @HotSpotIntrinsicCandidate
1057 public final char getCharAcquire(Object o, long offset) {
1058 return getCharVolatile(o, offset);
1059 }
1060
1061 /** Acquire version of {@link #getIntVolatile(Object, long)} */
1062 @HotSpotIntrinsicCandidate
1063 public final int getIntAcquire(Object o, long offset) {
1064 return getIntVolatile(o, offset);
1065 }
1066
1067 /** Acquire version of {@link #getFloatVolatile(Object, long)} */
1068 @HotSpotIntrinsicCandidate
1069 public final float getFloatAcquire(Object o, long offset) {
1070 return getFloatVolatile(o, offset);
1071 }
1072
1073 /** Acquire version of {@link #getLongVolatile(Object, long)} */
1074 @HotSpotIntrinsicCandidate
1075 public final long getLongAcquire(Object o, long offset) {
1076 return getLongVolatile(o, offset);
1077 }
1078
1079 /** Acquire version of {@link #getDoubleVolatile(Object, long)} */
1080 @HotSpotIntrinsicCandidate
1081 public final double getDoubleAcquire(Object o, long offset) {
1082 return getDoubleVolatile(o, offset);
1083 }
1084
1085 /** Release version of {@link #putObjectVolatile(Object, long, Object)} */
1086 @HotSpotIntrinsicCandidate
1087 public final void putObjectRelease(Object o, long offset, Object x) {
1088 putObjectVolatile(o, offset, x);
1089 }
1090
1091 /** Release version of {@link #putBooleanVolatile(Object, long, boolean)} */
1092 @HotSpotIntrinsicCandidate
1093 public final void putBooleanRelease(Object o, long offset, boolean x) {
1094 putBooleanVolatile(o, offset, x);
1095 }
1096
1097 /** Release version of {@link #putByteVolatile(Object, long, byte)} */
1098 @HotSpotIntrinsicCandidate
1099 public final void putByteRelease(Object o, long offset, byte x) {
1100 putByteVolatile(o, offset, x);
1101 }
1102
1103 /** Release version of {@link #putShortVolatile(Object, long, short)} */
1104 @HotSpotIntrinsicCandidate
1105 public final void putShortRelease(Object o, long offset, short x) {
1106 putShortVolatile(o, offset, x);
1107 }
1108
1109 /** Release version of {@link #putCharVolatile(Object, long, char)} */
1110 @HotSpotIntrinsicCandidate
1111 public final void putCharRelease(Object o, long offset, char x) {
1112 putCharVolatile(o, offset, x);
1113 }
1114
1115 /** Release version of {@link #putIntVolatile(Object, long, int)} */
1116 @HotSpotIntrinsicCandidate
1117 public final void putIntRelease(Object o, long offset, int x) {
1118 putIntVolatile(o, offset, x);
1119 }
1120
1121 /** Release version of {@link #putFloatVolatile(Object, long, float)} */
1122 @HotSpotIntrinsicCandidate
1123 public final void putFloatRelease(Object o, long offset, float x) {
1124 putFloatVolatile(o, offset, x);
1125 }
1126
1127 /** Release version of {@link #putLongVolatile(Object, long, long)} */
1128 @HotSpotIntrinsicCandidate
1129 public final void putLongRelease(Object o, long offset, long x) {
1130 putLongVolatile(o, offset, x);
1131 }
1132
1133 /** Release version of {@link #putDoubleVolatile(Object, long, double)} */
1134 @HotSpotIntrinsicCandidate
1135 public final void putDoubleRelease(Object o, long offset, double x) {
1136 putDoubleVolatile(o, offset, x);
1137 }
1138
1139 // ------------------------------ Opaque --------------------------------------
1140
1141 /** Opaque version of {@link #getObjectVolatile(Object, long)} */
1142 @HotSpotIntrinsicCandidate
1143 public final Object getObjectOpaque(Object o, long offset) {
1144 return getObjectVolatile(o, offset);
1145 }
1146
1147 /** Opaque version of {@link #getBooleanVolatile(Object, long)} */
1148 @HotSpotIntrinsicCandidate
1149 public final boolean getBooleanOpaque(Object o, long offset) {
1150 return getBooleanVolatile(o, offset);
1151 }
1152
1153 /** Opaque version of {@link #getByteVolatile(Object, long)} */
1154 @HotSpotIntrinsicCandidate
1155 public final byte getByteOpaque(Object o, long offset) {
1156 return getByteVolatile(o, offset);
1157 }
1158
1159 /** Opaque version of {@link #getShortVolatile(Object, long)} */
1160 @HotSpotIntrinsicCandidate
1161 public final short getShortOpaque(Object o, long offset) {
1162 return getShortVolatile(o, offset);
1163 }
1164
1165 /** Opaque version of {@link #getCharVolatile(Object, long)} */
1166 @HotSpotIntrinsicCandidate
1167 public final char getCharOpaque(Object o, long offset) {
1168 return getCharVolatile(o, offset);
1169 }
1170
1171 /** Opaque version of {@link #getIntVolatile(Object, long)} */
1172 @HotSpotIntrinsicCandidate
1173 public final int getIntOpaque(Object o, long offset) {
1174 return getIntVolatile(o, offset);
1175 }
1176
1177 /** Opaque version of {@link #getFloatVolatile(Object, long)} */
1178 @HotSpotIntrinsicCandidate
1179 public final float getFloatOpaque(Object o, long offset) {
1180 return getFloatVolatile(o, offset);
1181 }
1182
1183 /** Opaque version of {@link #getLongVolatile(Object, long)} */
1184 @HotSpotIntrinsicCandidate
1185 public final long getLongOpaque(Object o, long offset) {
1186 return getLongVolatile(o, offset);
1187 }
1188
1189 /** Opaque version of {@link #getDoubleVolatile(Object, long)} */
1190 @HotSpotIntrinsicCandidate
1191 public final double getDoubleOpaque(Object o, long offset) {
1192 return getDoubleVolatile(o, offset);
1193 }
1194
1195 /** Opaque version of {@link #putObjectVolatile(Object, long, Object)} */
1196 @HotSpotIntrinsicCandidate
1197 public final void putObjectOpaque(Object o, long offset, Object x) {
1198 putObjectVolatile(o, offset, x);
1199 }
1200
1201 /** Opaque version of {@link #putBooleanVolatile(Object, long, boolean)} */
1202 @HotSpotIntrinsicCandidate
1203 public final void putBooleanOpaque(Object o, long offset, boolean x) {
1204 putBooleanVolatile(o, offset, x);
1205 }
1206
1207 /** Opaque version of {@link #putByteVolatile(Object, long, byte)} */
1208 @HotSpotIntrinsicCandidate
1209 public final void putByteOpaque(Object o, long offset, byte x) {
1210 putByteVolatile(o, offset, x);
1211 }
1212
1213 /** Opaque version of {@link #putShortVolatile(Object, long, short)} */
1214 @HotSpotIntrinsicCandidate
1215 public final void putShortOpaque(Object o, long offset, short x) {
1216 putShortVolatile(o, offset, x);
1217 }
1218
1219 /** Opaque version of {@link #putCharVolatile(Object, long, char)} */
1220 @HotSpotIntrinsicCandidate
1221 public final void putCharOpaque(Object o, long offset, char x) {
1222 putCharVolatile(o, offset, x);
1223 }
1224
1225 /** Opaque version of {@link #putIntVolatile(Object, long, int)} */
1226 @HotSpotIntrinsicCandidate
1227 public final void putIntOpaque(Object o, long offset, int x) {
1228 putIntVolatile(o, offset, x);
1229 }
1230
1231 /** Opaque version of {@link #putFloatVolatile(Object, long, float)} */
1232 @HotSpotIntrinsicCandidate
1233 public final void putFloatOpaque(Object o, long offset, float x) {
1234 putFloatVolatile(o, offset, x);
1235 }
1236
1237 /** Opaque version of {@link #putLongVolatile(Object, long, long)} */
1238 @HotSpotIntrinsicCandidate
1239 public final void putLongOpaque(Object o, long offset, long x) {
1240 putLongVolatile(o, offset, x);
1241 }
1242
1243 /** Opaque version of {@link #putDoubleVolatile(Object, long, double)} */
1244 @HotSpotIntrinsicCandidate
1245 public final void putDoubleOpaque(Object o, long offset, double x) {
1246 putDoubleVolatile(o, offset, x);
1247 }
1248
1249 /**
1250 * Unblocks the given thread blocked on {@code park}, or, if it is
1251 * not blocked, causes the subsequent call to {@code park} not to
1252 * block. Note: this operation is "unsafe" solely because the
1253 * caller must somehow ensure that the thread has not been
1254 * destroyed. Nothing special is usually required to ensure this
1255 * when called from Java (in which there will ordinarily be a live
1256 * reference to the thread) but this is not nearly-automatically
1257 * so when calling from native code.
1258 *
1259 * @param thread the thread to unpark.
1260 */
1261 @HotSpotIntrinsicCandidate
1262 public native void unpark(Object thread);
1263
1264 /**
1265 * Blocks current thread, returning when a balancing
1266 * {@code unpark} occurs, or a balancing {@code unpark} has
1267 * already occurred, or the thread is interrupted, or, if not
1268 * absolute and time is not zero, the given time nanoseconds have
1269 * elapsed, or if absolute, the given deadline in milliseconds
1270 * since Epoch has passed, or spuriously (i.e., returning for no
1271 * "reason"). Note: This operation is in the Unsafe class only
1272 * because {@code unpark} is, so it would be strange to place it
1273 * elsewhere.
1274 */
1275 @HotSpotIntrinsicCandidate
1276 public native void park(boolean isAbsolute, long time);
1277
1278 /**
1279 * Gets the load average in the system run queue assigned
1280 * to the available processors averaged over various periods of time.
1281 * This method retrieves the given {@code nelem} samples and
1282 * assigns to the elements of the given {@code loadavg} array.
1283 * The system imposes a maximum of 3 samples, representing
1284 * averages over the last 1, 5, and 15 minutes, respectively.
1285 *
1286 * @param loadavg an array of double of size nelems
1287 * @param nelems the number of samples to be retrieved and
1288 * must be 1 to 3.
1289 *
1290 * @return the number of samples actually retrieved; or -1
1291 * if the load average is unobtainable.
1292 */
1293 public native int getLoadAverage(double[] loadavg, int nelems);
1294
1295 // The following contain CAS-based Java implementations used on
1296 // platforms not supporting native instructions
1297
1298 /**
1299 * Atomically adds the given value to the current value of a field
1300 * or array element within the given object {@code o}
1301 * at the given {@code offset}.
1302 *
1303 * @param o object/array to update the field/element in
1304 * @param offset field/element offset
1305 * @param delta the value to add
1306 * @return the previous value
1307 * @since 1.8
1308 */
1309 @HotSpotIntrinsicCandidate
1310 public final int getAndAddInt(Object o, long offset, int delta) {
1311 int v;
1312 do {
1313 v = getIntVolatile(o, offset);
1314 } while (!compareAndSwapInt(o, offset, v, v + delta));
1315 return v;
1316 }
1317
1318 /**
1319 * Atomically adds the given value to the current value of a field
1320 * or array element within the given object {@code o}
1321 * at the given {@code offset}.
1322 *
1323 * @param o object/array to update the field/element in
1324 * @param offset field/element offset
1325 * @param delta the value to add
1326 * @return the previous value
1327 * @since 1.8
1328 */
1329 @HotSpotIntrinsicCandidate
1330 public final long getAndAddLong(Object o, long offset, long delta) {
1331 long v;
1332 do {
1333 v = getLongVolatile(o, offset);
1334 } while (!compareAndSwapLong(o, offset, v, v + delta));
1335 return v;
1336 }
1337
1338 /**
1339 * Atomically exchanges the given value with the current value of
1340 * a field or array element within the given object {@code o}
1341 * at the given {@code offset}.
1342 *
1343 * @param o object/array to update the field/element in
1344 * @param offset field/element offset
1345 * @param newValue new value
1346 * @return the previous value
1347 * @since 1.8
1348 */
1349 @HotSpotIntrinsicCandidate
1350 public final int getAndSetInt(Object o, long offset, int newValue) {
1351 int v;
1352 do {
1353 v = getIntVolatile(o, offset);
1354 } while (!compareAndSwapInt(o, offset, v, newValue));
1355 return v;
1356 }
1357
1358 /**
1359 * Atomically exchanges the given value with the current value of
1360 * a field or array element within the given object {@code o}
1361 * at the given {@code offset}.
1362 *
1363 * @param o object/array to update the field/element in
1364 * @param offset field/element offset
1365 * @param newValue new value
1366 * @return the previous value
1367 * @since 1.8
1368 */
1369 @HotSpotIntrinsicCandidate
1370 public final long getAndSetLong(Object o, long offset, long newValue) {
1371 long v;
1372 do {
1373 v = getLongVolatile(o, offset);
1374 } while (!compareAndSwapLong(o, offset, v, newValue));
1375 return v;
1376 }
1377
1378 /**
1379 * Atomically exchanges the given reference value with the current
1380 * reference value of a field or array element within the given
1381 * object {@code o} at the given {@code offset}.
1382 *
1383 * @param o object/array to update the field/element in
1384 * @param offset field/element offset
1385 * @param newValue new value
1386 * @return the previous value
1387 * @since 1.8
1388 */
1389 @HotSpotIntrinsicCandidate
1390 public final Object getAndSetObject(Object o, long offset, Object newValue) {
1391 Object v;
1392 do {
1393 v = getObjectVolatile(o, offset);
1394 } while (!compareAndSwapObject(o, offset, v, newValue));
1395 return v;
1396 }
1397
1398
1399 /**
1400 * Ensures that loads before the fence will not be reordered with loads and
1401 * stores after the fence; a "LoadLoad plus LoadStore barrier".
1402 *
1403 * Corresponds to C11 atomic_thread_fence(memory_order_acquire)
1404 * (an "acquire fence").
1405 *
1406 * A pure LoadLoad fence is not provided, since the addition of LoadStore
1407 * is almost always desired, and most current hardware instructions that
1408 * provide a LoadLoad barrier also provide a LoadStore barrier for free.
1409 * @since 1.8
1410 */
1411 @HotSpotIntrinsicCandidate
1412 public native void loadFence();
1413
1414 /**
1415 * Ensures that loads and stores before the fence will not be reordered with
1416 * stores after the fence; a "StoreStore plus LoadStore barrier".
1417 *
1418 * Corresponds to C11 atomic_thread_fence(memory_order_release)
1419 * (a "release fence").
1420 *
1421 * A pure StoreStore fence is not provided, since the addition of LoadStore
1422 * is almost always desired, and most current hardware instructions that
1423 * provide a StoreStore barrier also provide a LoadStore barrier for free.
1424 * @since 1.8
1425 */
1426 @HotSpotIntrinsicCandidate
1427 public native void storeFence();
1428
1429 /**
1430 * Ensures that loads and stores before the fence will not be reordered
1431 * with loads and stores after the fence. Implies the effects of both
1432 * loadFence() and storeFence(), and in addition, the effect of a StoreLoad
1433 * barrier.
1434 *
1435 * Corresponds to C11 atomic_thread_fence(memory_order_seq_cst).
1436 * @since 1.8
1437 */
1438 @HotSpotIntrinsicCandidate
1439 public native void fullFence();
1440
1441 /**
1442 * Ensures that loads before the fence will not be reordered with
1443 * loads after the fence.
1444 */
1445 public final void loadLoadFence() {
1446 loadFence();
1447 }
1448
1449 /**
1450 * Ensures that stores before the fence will not be reordered with
1451 * stores after the fence.
1452 */
1453 public final void storeStoreFence() {
1454 storeFence();
1455 }
1456
1457
1458 /**
1459 * Throws IllegalAccessError; for use by the VM for access control
1460 * error support.
1461 * @since 1.8
1462 */
1463 private static void throwIllegalAccessError() {
1464 throw new IllegalAccessError();
1465 }
1466
1467 /**
1468 * @return Returns true if the native byte ordering of this
1469 * platform is big-endian, false if it is little-endian.
1470 */
1471 public final boolean isBigEndian() { return BE; }
1472
1473 /**
1474 * @return Returns true if this platform is capable of performing
1475 * accesses at addresses which are not aligned for the type of the
1476 * primitive type being accessed, false otherwise.
1477 */
1478 public final boolean unalignedAccess() { return unalignedAccess; }
1479
1480 /**
1481 * Fetches a value at some byte offset into a given Java object.
1482 * More specifically, fetches a value within the given object
1483 * <code>o</code> at the given offset, or (if <code>o</code> is
1484 * null) from the memory address whose numerical value is the
1485 * given offset. <p>
1486 *
1487 * The specification of this method is the same as {@link
1488 * #getLong(Object, long)} except that the offset does not need to
1489 * have been obtained from {@link #objectFieldOffset} on the
1490 * {@link java.lang.reflect.Field} of some Java field. The value
1491 * in memory is raw data, and need not correspond to any Java
1492 * variable. Unless <code>o</code> is null, the value accessed
1493 * must be entirely within the allocated object. The endianness
1494 * of the value in memory is the endianness of the native platform.
1495 *
1496 * <p> The read will be atomic with respect to the largest power
1497 * of two that divides the GCD of the offset and the storage size.
1498 * For example, getLongUnaligned will make atomic reads of 2-, 4-,
1499 * or 8-byte storage units if the offset is zero mod 2, 4, or 8,
1500 * respectively. There are no other guarantees of atomicity.
1501 * <p>
1502 * 8-byte atomicity is only guaranteed on platforms on which
1503 * support atomic accesses to longs.
1504 *
1505 * @param o Java heap object in which the value resides, if any, else
1506 * null
1507 * @param offset The offset in bytes from the start of the object
1508 * @return the value fetched from the indicated object
1509 * @throws RuntimeException No defined exceptions are thrown, not even
1510 * {@link NullPointerException}
1511 * @since 9
1512 */
1513 @HotSpotIntrinsicCandidate
1514 public final long getLongUnaligned(Object o, long offset) {
1515 if ((offset & 7) == 0) {
1516 return getLong(o, offset);
1517 } else if ((offset & 3) == 0) {
1518 return makeLong(getInt(o, offset),
1519 getInt(o, offset + 4));
1520 } else if ((offset & 1) == 0) {
1521 return makeLong(getShort(o, offset),
1522 getShort(o, offset + 2),
1523 getShort(o, offset + 4),
1524 getShort(o, offset + 6));
1525 } else {
1526 return makeLong(getByte(o, offset),
1527 getByte(o, offset + 1),
1528 getByte(o, offset + 2),
1529 getByte(o, offset + 3),
1530 getByte(o, offset + 4),
1531 getByte(o, offset + 5),
1532 getByte(o, offset + 6),
1533 getByte(o, offset + 7));
1534 }
1535 }
1536 /**
1537 * As {@link #getLongUnaligned(Object, long)} but with an
1538 * additional argument which specifies the endianness of the value
1539 * as stored in memory.
1540 *
1541 * @param o Java heap object in which the variable resides
1542 * @param offset The offset in bytes from the start of the object
1543 * @param bigEndian The endianness of the value
1544 * @return the value fetched from the indicated object
1545 * @since 9
1546 */
1547 public final long getLongUnaligned(Object o, long offset, boolean bigEndian) {
1548 return convEndian(bigEndian, getLongUnaligned(o, offset));
1549 }
1550
1551 /** @see #getLongUnaligned(Object, long) */
1552 @HotSpotIntrinsicCandidate
1553 public final int getIntUnaligned(Object o, long offset) {
1554 if ((offset & 3) == 0) {
1555 return getInt(o, offset);
1556 } else if ((offset & 1) == 0) {
1557 return makeInt(getShort(o, offset),
1558 getShort(o, offset + 2));
1559 } else {
1560 return makeInt(getByte(o, offset),
1561 getByte(o, offset + 1),
1562 getByte(o, offset + 2),
1563 getByte(o, offset + 3));
1564 }
1565 }
1566 /** @see #getLongUnaligned(Object, long, boolean) */
1567 public final int getIntUnaligned(Object o, long offset, boolean bigEndian) {
1568 return convEndian(bigEndian, getIntUnaligned(o, offset));
1569 }
1570
1571 /** @see #getLongUnaligned(Object, long) */
1572 @HotSpotIntrinsicCandidate
1573 public final short getShortUnaligned(Object o, long offset) {
1574 if ((offset & 1) == 0) {
1575 return getShort(o, offset);
1576 } else {
1577 return makeShort(getByte(o, offset),
1578 getByte(o, offset + 1));
1579 }
1580 }
1581 /** @see #getLongUnaligned(Object, long, boolean) */
1582 public final short getShortUnaligned(Object o, long offset, boolean bigEndian) {
1583 return convEndian(bigEndian, getShortUnaligned(o, offset));
1584 }
1585
1586 /** @see #getLongUnaligned(Object, long) */
1587 @HotSpotIntrinsicCandidate
1588 public final char getCharUnaligned(Object o, long offset) {
1589 if ((offset & 1) == 0) {
1590 return getChar(o, offset);
1591 } else {
1592 return (char)makeShort(getByte(o, offset),
1593 getByte(o, offset + 1));
1594 }
1595 }
1596
1597 /** @see #getLongUnaligned(Object, long, boolean) */
1598 public final char getCharUnaligned(Object o, long offset, boolean bigEndian) {
1599 return convEndian(bigEndian, getCharUnaligned(o, offset));
1600 }
1601
1602 /**
1603 * Stores a value at some byte offset into a given Java object.
1604 * <p>
1605 * The specification of this method is the same as {@link
1606 * #getLong(Object, long)} except that the offset does not need to
1607 * have been obtained from {@link #objectFieldOffset} on the
1608 * {@link java.lang.reflect.Field} of some Java field. The value
1609 * in memory is raw data, and need not correspond to any Java
1610 * variable. The endianness of the value in memory is the
1611 * endianness of the native platform.
1612 * <p>
1613 * The write will be atomic with respect to the largest power of
1614 * two that divides the GCD of the offset and the storage size.
1615 * For example, putLongUnaligned will make atomic writes of 2-, 4-,
1616 * or 8-byte storage units if the offset is zero mod 2, 4, or 8,
1617 * respectively. There are no other guarantees of atomicity.
1618 * <p>
1619 * 8-byte atomicity is only guaranteed on platforms on which
1620 * support atomic accesses to longs.
1621 *
1622 * @param o Java heap object in which the value resides, if any, else
1623 * null
1624 * @param offset The offset in bytes from the start of the object
1625 * @param x the value to store
1626 * @throws RuntimeException No defined exceptions are thrown, not even
1627 * {@link NullPointerException}
1628 * @since 9
1629 */
1630 @HotSpotIntrinsicCandidate
1631 public final void putLongUnaligned(Object o, long offset, long x) {
1632 if ((offset & 7) == 0) {
1633 putLong(o, offset, x);
1634 } else if ((offset & 3) == 0) {
1635 putLongParts(o, offset,
1636 (int)(x >> 0),
1637 (int)(x >>> 32));
1638 } else if ((offset & 1) == 0) {
1639 putLongParts(o, offset,
1640 (short)(x >>> 0),
1641 (short)(x >>> 16),
1642 (short)(x >>> 32),
1643 (short)(x >>> 48));
1644 } else {
1645 putLongParts(o, offset,
1646 (byte)(x >>> 0),
1647 (byte)(x >>> 8),
1648 (byte)(x >>> 16),
1649 (byte)(x >>> 24),
1650 (byte)(x >>> 32),
1651 (byte)(x >>> 40),
1652 (byte)(x >>> 48),
1653 (byte)(x >>> 56));
1654 }
1655 }
1656
1657 /**
1658 * As {@link #putLongUnaligned(Object, long, long)} but with an additional
1659 * argument which specifies the endianness of the value as stored in memory.
1660 * @param o Java heap object in which the value resides
1661 * @param offset The offset in bytes from the start of the object
1662 * @param x the value to store
1663 * @param bigEndian The endianness of the value
1664 * @throws RuntimeException No defined exceptions are thrown, not even
1665 * {@link NullPointerException}
1666 * @since 9
1667 */
1668 public final void putLongUnaligned(Object o, long offset, long x, boolean bigEndian) {
1669 putLongUnaligned(o, offset, convEndian(bigEndian, x));
1670 }
1671
1672 /** @see #putLongUnaligned(Object, long, long) */
1673 @HotSpotIntrinsicCandidate
1674 public final void putIntUnaligned(Object o, long offset, int x) {
1675 if ((offset & 3) == 0) {
1676 putInt(o, offset, x);
1677 } else if ((offset & 1) == 0) {
1678 putIntParts(o, offset,
1679 (short)(x >> 0),
1680 (short)(x >>> 16));
1681 } else {
1682 putIntParts(o, offset,
1683 (byte)(x >>> 0),
1684 (byte)(x >>> 8),
1685 (byte)(x >>> 16),
1686 (byte)(x >>> 24));
1687 }
1688 }
1689 /** @see #putLongUnaligned(Object, long, long, boolean) */
1690 public final void putIntUnaligned(Object o, long offset, int x, boolean bigEndian) {
1691 putIntUnaligned(o, offset, convEndian(bigEndian, x));
1692 }
1693
1694 /** @see #putLongUnaligned(Object, long, long) */
1695 @HotSpotIntrinsicCandidate
1696 public final void putShortUnaligned(Object o, long offset, short x) {
1697 if ((offset & 1) == 0) {
1698 putShort(o, offset, x);
1699 } else {
1700 putShortParts(o, offset,
1701 (byte)(x >>> 0),
1702 (byte)(x >>> 8));
1703 }
1704 }
1705 /** @see #putLongUnaligned(Object, long, long, boolean) */
1706 public final void putShortUnaligned(Object o, long offset, short x, boolean bigEndian) {
1707 putShortUnaligned(o, offset, convEndian(bigEndian, x));
1708 }
1709
1710 /** @see #putLongUnaligned(Object, long, long) */
1711 @HotSpotIntrinsicCandidate
1712 public final void putCharUnaligned(Object o, long offset, char x) {
1713 putShortUnaligned(o, offset, (short)x);
1714 }
1715 /** @see #putLongUnaligned(Object, long, long, boolean) */
1716 public final void putCharUnaligned(Object o, long offset, char x, boolean bigEndian) {
1717 putCharUnaligned(o, offset, convEndian(bigEndian, x));
1718 }
1719
1720 // JVM interface methods
1721 private native boolean unalignedAccess0();
1722 private native boolean isBigEndian0();
1723
1724 // BE is true iff the native endianness of this platform is big.
1725 private static final boolean BE = theUnsafe.isBigEndian0();
1726
1727 // unalignedAccess is true iff this platform can perform unaligned accesses.
1728 private static final boolean unalignedAccess = theUnsafe.unalignedAccess0();
1729
1730 private static int pickPos(int top, int pos) { return BE ? top - pos : pos; }
1731
1732 // These methods construct integers from bytes. The byte ordering
1733 // is the native endianness of this platform.
1734 private static long makeLong(byte i0, byte i1, byte i2, byte i3, byte i4, byte i5, byte i6, byte i7) {
1735 return ((toUnsignedLong(i0) << pickPos(56, 0))
1736 | (toUnsignedLong(i1) << pickPos(56, 8))
1737 | (toUnsignedLong(i2) << pickPos(56, 16))
1738 | (toUnsignedLong(i3) << pickPos(56, 24))
1739 | (toUnsignedLong(i4) << pickPos(56, 32))
1740 | (toUnsignedLong(i5) << pickPos(56, 40))
1741 | (toUnsignedLong(i6) << pickPos(56, 48))
1742 | (toUnsignedLong(i7) << pickPos(56, 56)));
1743 }
1744 private static long makeLong(short i0, short i1, short i2, short i3) {
1745 return ((toUnsignedLong(i0) << pickPos(48, 0))
1746 | (toUnsignedLong(i1) << pickPos(48, 16))
1747 | (toUnsignedLong(i2) << pickPos(48, 32))
1748 | (toUnsignedLong(i3) << pickPos(48, 48)));
1749 }
1750 private static long makeLong(int i0, int i1) {
1751 return (toUnsignedLong(i0) << pickPos(32, 0))
1752 | (toUnsignedLong(i1) << pickPos(32, 32));
1753 }
1754 private static int makeInt(short i0, short i1) {
1755 return (toUnsignedInt(i0) << pickPos(16, 0))
1756 | (toUnsignedInt(i1) << pickPos(16, 16));
1757 }
1758 private static int makeInt(byte i0, byte i1, byte i2, byte i3) {
1759 return ((toUnsignedInt(i0) << pickPos(24, 0))
1760 | (toUnsignedInt(i1) << pickPos(24, 8))
1761 | (toUnsignedInt(i2) << pickPos(24, 16))
1762 | (toUnsignedInt(i3) << pickPos(24, 24)));
1763 }
1764 private static short makeShort(byte i0, byte i1) {
1765 return (short)((toUnsignedInt(i0) << pickPos(8, 0))
1766 | (toUnsignedInt(i1) << pickPos(8, 8)));
1767 }
1768
1769 private static byte pick(byte le, byte be) { return BE ? be : le; }
1770 private static short pick(short le, short be) { return BE ? be : le; }
1771 private static int pick(int le, int be) { return BE ? be : le; }
1772
1773 // These methods write integers to memory from smaller parts
1774 // provided by their caller. The ordering in which these parts
1775 // are written is the native endianness of this platform.
1776 private void putLongParts(Object o, long offset, byte i0, byte i1, byte i2, byte i3, byte i4, byte i5, byte i6, byte i7) {
1777 putByte(o, offset + 0, pick(i0, i7));
1778 putByte(o, offset + 1, pick(i1, i6));
1779 putByte(o, offset + 2, pick(i2, i5));
1780 putByte(o, offset + 3, pick(i3, i4));
1781 putByte(o, offset + 4, pick(i4, i3));
1782 putByte(o, offset + 5, pick(i5, i2));
1783 putByte(o, offset + 6, pick(i6, i1));
1784 putByte(o, offset + 7, pick(i7, i0));
1785 }
1786 private void putLongParts(Object o, long offset, short i0, short i1, short i2, short i3) {
1787 putShort(o, offset + 0, pick(i0, i3));
1788 putShort(o, offset + 2, pick(i1, i2));
1789 putShort(o, offset + 4, pick(i2, i1));
1790 putShort(o, offset + 6, pick(i3, i0));
1791 }
1792 private void putLongParts(Object o, long offset, int i0, int i1) {
1793 putInt(o, offset + 0, pick(i0, i1));
1794 putInt(o, offset + 4, pick(i1, i0));
1795 }
1796 private void putIntParts(Object o, long offset, short i0, short i1) {
1797 putShort(o, offset + 0, pick(i0, i1));
1798 putShort(o, offset + 2, pick(i1, i0));
1799 }
1800 private void putIntParts(Object o, long offset, byte i0, byte i1, byte i2, byte i3) {
1801 putByte(o, offset + 0, pick(i0, i3));
1802 putByte(o, offset + 1, pick(i1, i2));
1803 putByte(o, offset + 2, pick(i2, i1));
1804 putByte(o, offset + 3, pick(i3, i0));
1805 }
1806 private void putShortParts(Object o, long offset, byte i0, byte i1) {
1807 putByte(o, offset + 0, pick(i0, i1));
1808 putByte(o, offset + 1, pick(i1, i0));
1809 }
1810
1811 // Zero-extend an integer
1812 private static int toUnsignedInt(byte n) { return n & 0xff; }
1813 private static int toUnsignedInt(short n) { return n & 0xffff; }
1814 private static long toUnsignedLong(byte n) { return n & 0xffl; }
1815 private static long toUnsignedLong(short n) { return n & 0xffffl; }
1816 private static long toUnsignedLong(int n) { return n & 0xffffffffl; }
1817
1818 // Maybe byte-reverse an integer
1819 private static char convEndian(boolean big, char n) { return big == BE ? n : Character.reverseBytes(n); }
1820 private static short convEndian(boolean big, short n) { return big == BE ? n : Short.reverseBytes(n) ; }
1821 private static int convEndian(boolean big, int n) { return big == BE ? n : Integer.reverseBytes(n) ; }
1822 private static long convEndian(boolean big, long n) { return big == BE ? n : Long.reverseBytes(n) ; }
1823 }