1 /*
2 * Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. 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 sun.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 /**
462 * Disposes of a block of native memory, as obtained from {@link
463 * #allocateMemory} or {@link #reallocateMemory}. The address passed to
464 * this method may be null, in which case no action is taken.
465 *
466 * @see #allocateMemory
467 */
468 public native void freeMemory(long address);
469
470 /// random queries
471
472 /**
473 * This constant differs from all results that will ever be returned from
474 * {@link #staticFieldOffset}, {@link #objectFieldOffset},
475 * or {@link #arrayBaseOffset}.
476 */
477 public static final int INVALID_FIELD_OFFSET = -1;
478
479 /**
480 * Reports the location of a given field in the storage allocation of its
481 * class. Do not expect to perform any sort of arithmetic on this offset;
482 * it is just a cookie which is passed to the unsafe heap memory accessors.
483 *
484 * <p>Any given field will always have the same offset and base, and no
485 * two distinct fields of the same class will ever have the same offset
486 * and base.
487 *
488 * <p>As of 1.4.1, offsets for fields are represented as long values,
489 * although the Sun JVM does not use the most significant 32 bits.
490 * However, JVM implementations which store static fields at absolute
491 * addresses can use long offsets and null base pointers to express
492 * the field locations in a form usable by {@link #getInt(Object,long)}.
493 * Therefore, code which will be ported to such JVMs on 64-bit platforms
494 * must preserve all bits of static field offsets.
495 * @see #getInt(Object, long)
496 */
497 public native long objectFieldOffset(Field f);
498
499 /**
500 * Reports the location of a given static field, in conjunction with {@link
501 * #staticFieldBase}.
502 * <p>Do not expect to perform any sort of arithmetic on this offset;
503 * it is just a cookie which is passed to the unsafe heap memory accessors.
504 *
505 * <p>Any given field will always have the same offset, and no two distinct
506 * fields of the same class will ever have the same offset.
507 *
508 * <p>As of 1.4.1, offsets for fields are represented as long values,
509 * although the Sun JVM does not use the most significant 32 bits.
510 * It is hard to imagine a JVM technology which needs more than
511 * a few bits to encode an offset within a non-array object,
512 * However, for consistency with other methods in this class,
513 * this method reports its result as a long value.
514 * @see #getInt(Object, long)
515 */
516 public native long staticFieldOffset(Field f);
517
518 /**
519 * Reports the location of a given static field, in conjunction with {@link
520 * #staticFieldOffset}.
521 * <p>Fetch the base "Object", if any, with which static fields of the
522 * given class can be accessed via methods like {@link #getInt(Object,
523 * long)}. This value may be null. This value may refer to an object
524 * which is a "cookie", not guaranteed to be a real Object, and it should
525 * not be used in any way except as argument to the get and put routines in
526 * this class.
527 */
528 public native Object staticFieldBase(Field f);
529
530 /**
531 * Detects if the given class may need to be initialized. This is often
532 * needed in conjunction with obtaining the static field base of a
533 * class.
534 * @return false only if a call to {@code ensureClassInitialized} would have no effect
535 */
536 public native boolean shouldBeInitialized(Class<?> c);
537
538 /**
539 * Ensures the given class has been initialized. This is often
540 * needed in conjunction with obtaining the static field base of a
541 * class.
542 */
543 public native void ensureClassInitialized(Class<?> c);
544
545 /**
546 * Reports the offset of the first element in the storage allocation of a
547 * given array class. If {@link #arrayIndexScale} returns a non-zero value
548 * for the same class, you may use that scale factor, together with this
549 * base offset, to form new offsets to access elements of arrays of the
550 * given class.
551 *
552 * @see #getInt(Object, long)
553 * @see #putInt(Object, long, int)
554 */
555 public native int arrayBaseOffset(Class<?> arrayClass);
556
557 /** The value of {@code arrayBaseOffset(boolean[].class)} */
558 public static final int ARRAY_BOOLEAN_BASE_OFFSET
559 = theUnsafe.arrayBaseOffset(boolean[].class);
560
561 /** The value of {@code arrayBaseOffset(byte[].class)} */
562 public static final int ARRAY_BYTE_BASE_OFFSET
563 = theUnsafe.arrayBaseOffset(byte[].class);
564
565 /** The value of {@code arrayBaseOffset(short[].class)} */
566 public static final int ARRAY_SHORT_BASE_OFFSET
567 = theUnsafe.arrayBaseOffset(short[].class);
568
569 /** The value of {@code arrayBaseOffset(char[].class)} */
570 public static final int ARRAY_CHAR_BASE_OFFSET
571 = theUnsafe.arrayBaseOffset(char[].class);
572
573 /** The value of {@code arrayBaseOffset(int[].class)} */
574 public static final int ARRAY_INT_BASE_OFFSET
575 = theUnsafe.arrayBaseOffset(int[].class);
576
577 /** The value of {@code arrayBaseOffset(long[].class)} */
578 public static final int ARRAY_LONG_BASE_OFFSET
579 = theUnsafe.arrayBaseOffset(long[].class);
580
581 /** The value of {@code arrayBaseOffset(float[].class)} */
582 public static final int ARRAY_FLOAT_BASE_OFFSET
583 = theUnsafe.arrayBaseOffset(float[].class);
584
585 /** The value of {@code arrayBaseOffset(double[].class)} */
586 public static final int ARRAY_DOUBLE_BASE_OFFSET
587 = theUnsafe.arrayBaseOffset(double[].class);
588
589 /** The value of {@code arrayBaseOffset(Object[].class)} */
590 public static final int ARRAY_OBJECT_BASE_OFFSET
591 = theUnsafe.arrayBaseOffset(Object[].class);
592
593 /**
594 * Reports the scale factor for addressing elements in the storage
595 * allocation of a given array class. However, arrays of "narrow" types
596 * will generally not work properly with accessors like {@link
597 * #getByte(Object, long)}, so the scale factor for such classes is reported
598 * as zero.
599 *
600 * @see #arrayBaseOffset
601 * @see #getInt(Object, long)
602 * @see #putInt(Object, long, int)
603 */
604 public native int arrayIndexScale(Class<?> arrayClass);
605
606 /** The value of {@code arrayIndexScale(boolean[].class)} */
607 public static final int ARRAY_BOOLEAN_INDEX_SCALE
608 = theUnsafe.arrayIndexScale(boolean[].class);
609
610 /** The value of {@code arrayIndexScale(byte[].class)} */
611 public static final int ARRAY_BYTE_INDEX_SCALE
612 = theUnsafe.arrayIndexScale(byte[].class);
613
614 /** The value of {@code arrayIndexScale(short[].class)} */
615 public static final int ARRAY_SHORT_INDEX_SCALE
616 = theUnsafe.arrayIndexScale(short[].class);
617
618 /** The value of {@code arrayIndexScale(char[].class)} */
619 public static final int ARRAY_CHAR_INDEX_SCALE
620 = theUnsafe.arrayIndexScale(char[].class);
621
622 /** The value of {@code arrayIndexScale(int[].class)} */
623 public static final int ARRAY_INT_INDEX_SCALE
624 = theUnsafe.arrayIndexScale(int[].class);
625
626 /** The value of {@code arrayIndexScale(long[].class)} */
627 public static final int ARRAY_LONG_INDEX_SCALE
628 = theUnsafe.arrayIndexScale(long[].class);
629
630 /** The value of {@code arrayIndexScale(float[].class)} */
631 public static final int ARRAY_FLOAT_INDEX_SCALE
632 = theUnsafe.arrayIndexScale(float[].class);
633
634 /** The value of {@code arrayIndexScale(double[].class)} */
635 public static final int ARRAY_DOUBLE_INDEX_SCALE
636 = theUnsafe.arrayIndexScale(double[].class);
637
638 /** The value of {@code arrayIndexScale(Object[].class)} */
639 public static final int ARRAY_OBJECT_INDEX_SCALE
640 = theUnsafe.arrayIndexScale(Object[].class);
641
642 /**
643 * Reports the size in bytes of a native pointer, as stored via {@link
644 * #putAddress}. This value will be either 4 or 8. Note that the sizes of
645 * other primitive types (as stored in native memory blocks) is determined
646 * fully by their information content.
647 */
648 public native int addressSize();
649
650 /** The value of {@code addressSize()} */
651 public static final int ADDRESS_SIZE = theUnsafe.addressSize();
652
653 /**
654 * Reports the size in bytes of a native memory page (whatever that is).
655 * This value will always be a power of two.
656 */
657 public native int pageSize();
658
659
660 /// random trusted operations from JNI:
661
662 /**
663 * Tells the VM to define a class, without security checks. By default, the
664 * class loader and protection domain come from the caller's class.
665 */
666 public native Class<?> defineClass(String name, byte[] b, int off, int len,
667 ClassLoader loader,
668 ProtectionDomain protectionDomain);
669
670 /**
671 * Defines a class but does not make it known to the class loader or system dictionary.
672 * <p>
673 * For each CP entry, the corresponding CP patch must either be null or have
674 * the a format that matches its tag:
675 * <ul>
676 * <li>Integer, Long, Float, Double: the corresponding wrapper object type from java.lang
677 * <li>Utf8: a string (must have suitable syntax if used as signature or name)
678 * <li>Class: any java.lang.Class object
679 * <li>String: any object (not just a java.lang.String)
680 * <li>InterfaceMethodRef: (NYI) a method handle to invoke on that call site's arguments
681 * </ul>
682 * @param hostClass context for linkage, access control, protection domain, and class loader
683 * @param data bytes of a class file
684 * @param cpPatches where non-null entries exist, they replace corresponding CP entries in data
685 */
686 public native Class<?> defineAnonymousClass(Class<?> hostClass, byte[] data, Object[] cpPatches);
687
688 /**
689 * Allocates an instance but does not run any constructor.
690 * Initializes the class if it has not yet been.
691 */
692 @HotSpotIntrinsicCandidate
693 public native Object allocateInstance(Class<?> cls)
694 throws InstantiationException;
695
696 /** Throws the exception without telling the verifier. */
697 public native void throwException(Throwable ee);
698
699 /**
700 * Atomically updates Java variable to {@code x} if it is currently
701 * holding {@code expected}.
702 *
703 * <p>This operation has memory semantics of a {@code volatile} read
704 * and write. Corresponds to C11 atomic_compare_exchange_strong.
705 *
706 * @return {@code true} if successful
707 */
708 @HotSpotIntrinsicCandidate
709 public final native boolean compareAndSwapObject(Object o, long offset,
710 Object expected,
711 Object x);
712
713 /**
714 * Atomically updates Java variable to {@code x} if it is currently
715 * holding {@code expected}.
716 *
717 * <p>This operation has memory semantics of a {@code volatile} read
718 * and write. Corresponds to C11 atomic_compare_exchange_strong.
719 *
720 * @return {@code true} if successful
721 */
722 @HotSpotIntrinsicCandidate
723 public final native boolean compareAndSwapInt(Object o, long offset,
724 int expected,
725 int x);
726
727 /**
728 * Atomically updates Java variable to {@code x} if it is currently
729 * holding {@code expected}.
730 *
731 * <p>This operation has memory semantics of a {@code volatile} read
732 * and write. Corresponds to C11 atomic_compare_exchange_strong.
733 *
734 * @return {@code true} if successful
735 */
736 @HotSpotIntrinsicCandidate
737 public final native boolean compareAndSwapLong(Object o, long offset,
738 long expected,
739 long x);
740
741 /**
742 * Fetches a reference value from a given Java variable, with volatile
743 * load semantics. Otherwise identical to {@link #getObject(Object, long)}
744 */
745 @HotSpotIntrinsicCandidate
746 public native Object getObjectVolatile(Object o, long offset);
747
748 /**
749 * Stores a reference value into a given Java variable, with
750 * volatile store semantics. Otherwise identical to {@link #putObject(Object, long, Object)}
751 */
752 @HotSpotIntrinsicCandidate
753 public native void putObjectVolatile(Object o, long offset, Object x);
754
755 /** Volatile version of {@link #getInt(Object, long)} */
756 @HotSpotIntrinsicCandidate
757 public native int getIntVolatile(Object o, long offset);
758
759 /** Volatile version of {@link #putInt(Object, long, int)} */
760 @HotSpotIntrinsicCandidate
761 public native void putIntVolatile(Object o, long offset, int x);
762
763 /** Volatile version of {@link #getBoolean(Object, long)} */
764 @HotSpotIntrinsicCandidate
765 public native boolean getBooleanVolatile(Object o, long offset);
766
767 /** Volatile version of {@link #putBoolean(Object, long, boolean)} */
768 @HotSpotIntrinsicCandidate
769 public native void putBooleanVolatile(Object o, long offset, boolean x);
770
771 /** Volatile version of {@link #getByte(Object, long)} */
772 @HotSpotIntrinsicCandidate
773 public native byte getByteVolatile(Object o, long offset);
774
775 /** Volatile version of {@link #putByte(Object, long, byte)} */
776 @HotSpotIntrinsicCandidate
777 public native void putByteVolatile(Object o, long offset, byte x);
778
779 /** Volatile version of {@link #getShort(Object, long)} */
780 @HotSpotIntrinsicCandidate
781 public native short getShortVolatile(Object o, long offset);
782
783 /** Volatile version of {@link #putShort(Object, long, short)} */
784 @HotSpotIntrinsicCandidate
785 public native void putShortVolatile(Object o, long offset, short x);
786
787 /** Volatile version of {@link #getChar(Object, long)} */
788 @HotSpotIntrinsicCandidate
789 public native char getCharVolatile(Object o, long offset);
790
791 /** Volatile version of {@link #putChar(Object, long, char)} */
792 @HotSpotIntrinsicCandidate
793 public native void putCharVolatile(Object o, long offset, char x);
794
795 /** Volatile version of {@link #getLong(Object, long)} */
796 @HotSpotIntrinsicCandidate
797 public native long getLongVolatile(Object o, long offset);
798
799 /** Volatile version of {@link #putLong(Object, long, long)} */
800 @HotSpotIntrinsicCandidate
801 public native void putLongVolatile(Object o, long offset, long x);
802
803 /** Volatile version of {@link #getFloat(Object, long)} */
804 @HotSpotIntrinsicCandidate
805 public native float getFloatVolatile(Object o, long offset);
806
807 /** Volatile version of {@link #putFloat(Object, long, float)} */
808 @HotSpotIntrinsicCandidate
809 public native void putFloatVolatile(Object o, long offset, float x);
810
811 /** Volatile version of {@link #getDouble(Object, long)} */
812 @HotSpotIntrinsicCandidate
813 public native double getDoubleVolatile(Object o, long offset);
814
815 /** Volatile version of {@link #putDouble(Object, long, double)} */
816 @HotSpotIntrinsicCandidate
817 public native void putDoubleVolatile(Object o, long offset, double x);
818
819 /**
820 * Version of {@link #putObjectVolatile(Object, long, Object)}
821 * that does not guarantee immediate visibility of the store to
822 * other threads. This method is generally only useful if the
823 * underlying field is a Java volatile (or if an array cell, one
824 * that is otherwise only accessed using volatile accesses).
825 *
826 * Corresponds to C11 atomic_store_explicit(..., memory_order_release).
827 */
828 @HotSpotIntrinsicCandidate
829 public native void putOrderedObject(Object o, long offset, Object x);
830
831 /** Ordered/Lazy version of {@link #putIntVolatile(Object, long, int)} */
832 @HotSpotIntrinsicCandidate
833 public native void putOrderedInt(Object o, long offset, int x);
834
835 /** Ordered/Lazy version of {@link #putLongVolatile(Object, long, long)} */
836 @HotSpotIntrinsicCandidate
837 public native void putOrderedLong(Object o, long offset, long x);
838
839 /**
840 * Unblocks the given thread blocked on {@code park}, or, if it is
841 * not blocked, causes the subsequent call to {@code park} not to
842 * block. Note: this operation is "unsafe" solely because the
843 * caller must somehow ensure that the thread has not been
844 * destroyed. Nothing special is usually required to ensure this
845 * when called from Java (in which there will ordinarily be a live
846 * reference to the thread) but this is not nearly-automatically
847 * so when calling from native code.
848 *
849 * @param thread the thread to unpark.
850 */
851 @HotSpotIntrinsicCandidate
852 public native void unpark(Object thread);
853
854 /**
855 * Blocks current thread, returning when a balancing
856 * {@code unpark} occurs, or a balancing {@code unpark} has
857 * already occurred, or the thread is interrupted, or, if not
858 * absolute and time is not zero, the given time nanoseconds have
859 * elapsed, or if absolute, the given deadline in milliseconds
860 * since Epoch has passed, or spuriously (i.e., returning for no
861 * "reason"). Note: This operation is in the Unsafe class only
862 * because {@code unpark} is, so it would be strange to place it
863 * elsewhere.
864 */
865 @HotSpotIntrinsicCandidate
866 public native void park(boolean isAbsolute, long time);
867
868 /**
869 * Gets the load average in the system run queue assigned
870 * to the available processors averaged over various periods of time.
871 * This method retrieves the given {@code nelem} samples and
872 * assigns to the elements of the given {@code loadavg} array.
873 * The system imposes a maximum of 3 samples, representing
874 * averages over the last 1, 5, and 15 minutes, respectively.
875 *
876 * @param loadavg an array of double of size nelems
877 * @param nelems the number of samples to be retrieved and
878 * must be 1 to 3.
879 *
880 * @return the number of samples actually retrieved; or -1
881 * if the load average is unobtainable.
882 */
883 public native int getLoadAverage(double[] loadavg, int nelems);
884
885 // The following contain CAS-based Java implementations used on
886 // platforms not supporting native instructions
887
888 /**
889 * Atomically adds the given value to the current value of a field
890 * or array element within the given object {@code o}
891 * at the given {@code offset}.
892 *
893 * @param o object/array to update the field/element in
894 * @param offset field/element offset
895 * @param delta the value to add
896 * @return the previous value
897 * @since 1.8
898 */
899 @HotSpotIntrinsicCandidate
900 public final int getAndAddInt(Object o, long offset, int delta) {
901 int v;
902 do {
903 v = getIntVolatile(o, offset);
904 } while (!compareAndSwapInt(o, offset, v, v + delta));
905 return v;
906 }
907
908 /**
909 * Atomically adds the given value to the current value of a field
910 * or array element within the given object {@code o}
911 * at the given {@code offset}.
912 *
913 * @param o object/array to update the field/element in
914 * @param offset field/element offset
915 * @param delta the value to add
916 * @return the previous value
917 * @since 1.8
918 */
919 @HotSpotIntrinsicCandidate
920 public final long getAndAddLong(Object o, long offset, long delta) {
921 long v;
922 do {
923 v = getLongVolatile(o, offset);
924 } while (!compareAndSwapLong(o, offset, v, v + delta));
925 return v;
926 }
927
928 /**
929 * Atomically exchanges the given value with the current value of
930 * a field or array element within the given object {@code o}
931 * at the given {@code offset}.
932 *
933 * @param o object/array to update the field/element in
934 * @param offset field/element offset
935 * @param newValue new value
936 * @return the previous value
937 * @since 1.8
938 */
939 @HotSpotIntrinsicCandidate
940 public final int getAndSetInt(Object o, long offset, int newValue) {
941 int v;
942 do {
943 v = getIntVolatile(o, offset);
944 } while (!compareAndSwapInt(o, offset, v, newValue));
945 return v;
946 }
947
948 /**
949 * Atomically exchanges the given value with the current value of
950 * a field or array element within the given object {@code o}
951 * at the given {@code offset}.
952 *
953 * @param o object/array to update the field/element in
954 * @param offset field/element offset
955 * @param newValue new value
956 * @return the previous value
957 * @since 1.8
958 */
959 @HotSpotIntrinsicCandidate
960 public final long getAndSetLong(Object o, long offset, long newValue) {
961 long v;
962 do {
963 v = getLongVolatile(o, offset);
964 } while (!compareAndSwapLong(o, offset, v, newValue));
965 return v;
966 }
967
968 /**
969 * Atomically exchanges the given reference value with the current
970 * reference value of a field or array element within the given
971 * object {@code o} at the given {@code offset}.
972 *
973 * @param o object/array to update the field/element in
974 * @param offset field/element offset
975 * @param newValue new value
976 * @return the previous value
977 * @since 1.8
978 */
979 @HotSpotIntrinsicCandidate
980 public final Object getAndSetObject(Object o, long offset, Object newValue) {
981 Object v;
982 do {
983 v = getObjectVolatile(o, offset);
984 } while (!compareAndSwapObject(o, offset, v, newValue));
985 return v;
986 }
987
988
989 /**
990 * Ensures that loads before the fence will not be reordered with loads and
991 * stores after the fence; a "LoadLoad plus LoadStore barrier".
992 *
993 * Corresponds to C11 atomic_thread_fence(memory_order_acquire)
994 * (an "acquire fence").
995 *
996 * A pure LoadLoad fence is not provided, since the addition of LoadStore
997 * is almost always desired, and most current hardware instructions that
998 * provide a LoadLoad barrier also provide a LoadStore barrier for free.
999 * @since 1.8
1000 */
1001 @HotSpotIntrinsicCandidate
1002 public native void loadFence();
1003
1004 /**
1005 * Ensures that loads and stores before the fence will not be reordered with
1006 * stores after the fence; a "StoreStore plus LoadStore barrier".
1007 *
1008 * Corresponds to C11 atomic_thread_fence(memory_order_release)
1009 * (a "release fence").
1010 *
1011 * A pure StoreStore fence is not provided, since the addition of LoadStore
1012 * is almost always desired, and most current hardware instructions that
1013 * provide a StoreStore barrier also provide a LoadStore barrier for free.
1014 * @since 1.8
1015 */
1016 @HotSpotIntrinsicCandidate
1017 public native void storeFence();
1018
1019 /**
1020 * Ensures that loads and stores before the fence will not be reordered
1021 * with loads and stores after the fence. Implies the effects of both
1022 * loadFence() and storeFence(), and in addition, the effect of a StoreLoad
1023 * barrier.
1024 *
1025 * Corresponds to C11 atomic_thread_fence(memory_order_seq_cst).
1026 * @since 1.8
1027 */
1028 @HotSpotIntrinsicCandidate
1029 public native void fullFence();
1030
1031 /**
1032 * Throws IllegalAccessError; for use by the VM for access control
1033 * error support.
1034 * @since 1.8
1035 */
1036 private static void throwIllegalAccessError() {
1037 throw new IllegalAccessError();
1038 }
1039
1040 /**
1041 * @return Returns true if the native byte ordering of this
1042 * platform is big-endian, false if it is little-endian.
1043 */
1044 public final boolean isBigEndian() { return BE; }
1045
1046 /**
1047 * @return Returns true if this platform is capable of performing
1048 * accesses at addresses which are not aligned for the type of the
1049 * primitive type being accessed, false otherwise.
1050 */
1051 public final boolean unalignedAccess() { return unalignedAccess; }
1052
1053 /**
1054 * Fetches a value at some byte offset into a given Java object.
1055 * More specifically, fetches a value within the given object
1056 * <code>o</code> at the given offset, or (if <code>o</code> is
1057 * null) from the memory address whose numerical value is the
1058 * given offset. <p>
1059 *
1060 * The specification of this method is the same as {@link
1061 * #getLong(Object, long)} except that the offset does not need to
1062 * have been obtained from {@link #objectFieldOffset} on the
1063 * {@link java.lang.reflect.Field} of some Java field. The value
1064 * in memory is raw data, and need not correspond to any Java
1065 * variable. Unless <code>o</code> is null, the value accessed
1066 * must be entirely within the allocated object. The endianness
1067 * of the value in memory is the endianness of the native platform.
1068 *
1069 * <p> The read will be atomic with respect to the largest power
1070 * of two that divides the GCD of the offset and the storage size.
1071 * For example, getLongUnaligned will make atomic reads of 2-, 4-,
1072 * or 8-byte storage units if the offset is zero mod 2, 4, or 8,
1073 * respectively. There are no other guarantees of atomicity.
1074 * <p>
1075 * 8-byte atomicity is only guaranteed on platforms on which
1076 * support atomic accesses to longs.
1077 *
1078 * @param o Java heap object in which the value resides, if any, else
1079 * null
1080 * @param offset The offset in bytes from the start of the object
1081 * @return the value fetched from the indicated object
1082 * @throws RuntimeException No defined exceptions are thrown, not even
1083 * {@link NullPointerException}
1084 * @since 9
1085 */
1086 @HotSpotIntrinsicCandidate
1087 public final long getLongUnaligned(Object o, long offset) {
1088 if ((offset & 7) == 0) {
1089 return getLong(o, offset);
1090 } else if ((offset & 3) == 0) {
1091 return makeLong(getInt(o, offset),
1092 getInt(o, offset + 4));
1093 } else if ((offset & 1) == 0) {
1094 return makeLong(getShort(o, offset),
1095 getShort(o, offset + 2),
1096 getShort(o, offset + 4),
1097 getShort(o, offset + 6));
1098 } else {
1099 return makeLong(getByte(o, offset),
1100 getByte(o, offset + 1),
1101 getByte(o, offset + 2),
1102 getByte(o, offset + 3),
1103 getByte(o, offset + 4),
1104 getByte(o, offset + 5),
1105 getByte(o, offset + 6),
1106 getByte(o, offset + 7));
1107 }
1108 }
1109 /**
1110 * As {@link #getLongUnaligned(Object, long)} but with an
1111 * additional argument which specifies the endianness of the value
1112 * as stored in memory.
1113 *
1114 * @param o Java heap object in which the variable resides
1115 * @param offset The offset in bytes from the start of the object
1116 * @param bigEndian The endianness of the value
1117 * @return the value fetched from the indicated object
1118 * @since 9
1119 */
1120 public final long getLongUnaligned(Object o, long offset, boolean bigEndian) {
1121 return convEndian(bigEndian, getLongUnaligned(o, offset));
1122 }
1123
1124 /** @see #getLongUnaligned(Object, long) */
1125 @HotSpotIntrinsicCandidate
1126 public final int getIntUnaligned(Object o, long offset) {
1127 if ((offset & 3) == 0) {
1128 return getInt(o, offset);
1129 } else if ((offset & 1) == 0) {
1130 return makeInt(getShort(o, offset),
1131 getShort(o, offset + 2));
1132 } else {
1133 return makeInt(getByte(o, offset),
1134 getByte(o, offset + 1),
1135 getByte(o, offset + 2),
1136 getByte(o, offset + 3));
1137 }
1138 }
1139 /** @see #getLongUnaligned(Object, long, boolean) */
1140 public final int getIntUnaligned(Object o, long offset, boolean bigEndian) {
1141 return convEndian(bigEndian, getIntUnaligned(o, offset));
1142 }
1143
1144 /** @see #getLongUnaligned(Object, long) */
1145 @HotSpotIntrinsicCandidate
1146 public final short getShortUnaligned(Object o, long offset) {
1147 if ((offset & 1) == 0) {
1148 return getShort(o, offset);
1149 } else {
1150 return makeShort(getByte(o, offset),
1151 getByte(o, offset + 1));
1152 }
1153 }
1154 /** @see #getLongUnaligned(Object, long, boolean) */
1155 public final short getShortUnaligned(Object o, long offset, boolean bigEndian) {
1156 return convEndian(bigEndian, getShortUnaligned(o, offset));
1157 }
1158
1159 /** @see #getLongUnaligned(Object, long) */
1160 @HotSpotIntrinsicCandidate
1161 public final char getCharUnaligned(Object o, long offset) {
1162 return (char)getShortUnaligned(o, offset);
1163 }
1164
1165 /** @see #getLongUnaligned(Object, long, boolean) */
1166 public final char getCharUnaligned(Object o, long offset, boolean bigEndian) {
1167 return convEndian(bigEndian, getCharUnaligned(o, offset));
1168 }
1169
1170 /**
1171 * Stores a value at some byte offset into a given Java object.
1172 * <p>
1173 * The specification of this method is the same as {@link
1174 * #getLong(Object, long)} except that the offset does not need to
1175 * have been obtained from {@link #objectFieldOffset} on the
1176 * {@link java.lang.reflect.Field} of some Java field. The value
1177 * in memory is raw data, and need not correspond to any Java
1178 * variable. The endianness of the value in memory is the
1179 * endianness of the native platform.
1180 * <p>
1181 * The write will be atomic with respect to the largest power of
1182 * two that divides the GCD of the offset and the storage size.
1183 * For example, putLongUnaligned will make atomic writes of 2-, 4-,
1184 * or 8-byte storage units if the offset is zero mod 2, 4, or 8,
1185 * respectively. There are no other guarantees of atomicity.
1186 * <p>
1187 * 8-byte atomicity is only guaranteed on platforms on which
1188 * support atomic accesses to longs.
1189 *
1190 * @param o Java heap object in which the value resides, if any, else
1191 * null
1192 * @param offset The offset in bytes from the start of the object
1193 * @param x the value to store
1194 * @throws RuntimeException No defined exceptions are thrown, not even
1195 * {@link NullPointerException}
1196 * @since 9
1197 */
1198 @HotSpotIntrinsicCandidate
1199 public final void putLongUnaligned(Object o, long offset, long x) {
1200 if ((offset & 7) == 0) {
1201 putLong(o, offset, x);
1202 } else if ((offset & 3) == 0) {
1203 putLongParts(o, offset,
1204 (int)(x >> 0),
1205 (int)(x >>> 32));
1206 } else if ((offset & 1) == 0) {
1207 putLongParts(o, offset,
1208 (short)(x >>> 0),
1209 (short)(x >>> 16),
1210 (short)(x >>> 32),
1211 (short)(x >>> 48));
1212 } else {
1213 putLongParts(o, offset,
1214 (byte)(x >>> 0),
1215 (byte)(x >>> 8),
1216 (byte)(x >>> 16),
1217 (byte)(x >>> 24),
1218 (byte)(x >>> 32),
1219 (byte)(x >>> 40),
1220 (byte)(x >>> 48),
1221 (byte)(x >>> 56));
1222 }
1223 }
1224
1225 /**
1226 * As {@link #putLongUnaligned(Object, long, long)} but with an additional
1227 * argument which specifies the endianness of the value as stored in memory.
1228 * @param o Java heap object in which the value resides
1229 * @param offset The offset in bytes from the start of the object
1230 * @param x the value to store
1231 * @param bigEndian The endianness of the value
1232 * @throws RuntimeException No defined exceptions are thrown, not even
1233 * {@link NullPointerException}
1234 * @since 9
1235 */
1236 public final void putLongUnaligned(Object o, long offset, long x, boolean bigEndian) {
1237 putLongUnaligned(o, offset, convEndian(bigEndian, x));
1238 }
1239
1240 /** @see #putLongUnaligned(Object, long, long) */
1241 @HotSpotIntrinsicCandidate
1242 public final void putIntUnaligned(Object o, long offset, int x) {
1243 if ((offset & 3) == 0) {
1244 putInt(o, offset, x);
1245 } else if ((offset & 1) == 0) {
1246 putIntParts(o, offset,
1247 (short)(x >> 0),
1248 (short)(x >>> 16));
1249 } else {
1250 putIntParts(o, offset,
1251 (byte)(x >>> 0),
1252 (byte)(x >>> 8),
1253 (byte)(x >>> 16),
1254 (byte)(x >>> 24));
1255 }
1256 }
1257 /** @see #putLongUnaligned(Object, long, long, boolean) */
1258 public final void putIntUnaligned(Object o, long offset, int x, boolean bigEndian) {
1259 putIntUnaligned(o, offset, convEndian(bigEndian, x));
1260 }
1261
1262 /** @see #putLongUnaligned(Object, long, long) */
1263 @HotSpotIntrinsicCandidate
1264 public final void putShortUnaligned(Object o, long offset, short x) {
1265 if ((offset & 1) == 0) {
1266 putShort(o, offset, x);
1267 } else {
1268 putShortParts(o, offset,
1269 (byte)(x >>> 0),
1270 (byte)(x >>> 8));
1271 }
1272 }
1273 /** @see #putLongUnaligned(Object, long, long, boolean) */
1274 public final void putShortUnaligned(Object o, long offset, short x, boolean bigEndian) {
1275 putShortUnaligned(o, offset, convEndian(bigEndian, x));
1276 }
1277
1278 /** @see #putLongUnaligned(Object, long, long) */
1279 @HotSpotIntrinsicCandidate
1280 public final void putCharUnaligned(Object o, long offset, char x) {
1281 putShortUnaligned(o, offset, (short)x);
1282 }
1283 /** @see #putLongUnaligned(Object, long, long, boolean) */
1284 public final void putCharUnaligned(Object o, long offset, char x, boolean bigEndian) {
1285 putCharUnaligned(o, offset, convEndian(bigEndian, x));
1286 }
1287
1288 // JVM interface methods
1289 private native boolean unalignedAccess0();
1290 private native boolean isBigEndian0();
1291
1292 // BE is true iff the native endianness of this platform is big.
1293 private static final boolean BE = theUnsafe.isBigEndian0();
1294
1295 // unalignedAccess is true iff this platform can perform unaligned accesses.
1296 private static final boolean unalignedAccess = theUnsafe.unalignedAccess0();
1297
1298 private static int pickPos(int top, int pos) { return BE ? top - pos : pos; }
1299
1300 // These methods construct integers from bytes. The byte ordering
1301 // is the native endianness of this platform.
1302 private static long makeLong(byte i0, byte i1, byte i2, byte i3, byte i4, byte i5, byte i6, byte i7) {
1303 return ((toUnsignedLong(i0) << pickPos(56, 0))
1304 | (toUnsignedLong(i1) << pickPos(56, 8))
1305 | (toUnsignedLong(i2) << pickPos(56, 16))
1306 | (toUnsignedLong(i3) << pickPos(56, 24))
1307 | (toUnsignedLong(i4) << pickPos(56, 32))
1308 | (toUnsignedLong(i5) << pickPos(56, 40))
1309 | (toUnsignedLong(i6) << pickPos(56, 48))
1310 | (toUnsignedLong(i7) << pickPos(56, 56)));
1311 }
1312 private static long makeLong(short i0, short i1, short i2, short i3) {
1313 return ((toUnsignedLong(i0) << pickPos(48, 0))
1314 | (toUnsignedLong(i1) << pickPos(48, 16))
1315 | (toUnsignedLong(i2) << pickPos(48, 32))
1316 | (toUnsignedLong(i3) << pickPos(48, 48)));
1317 }
1318 private static long makeLong(int i0, int i1) {
1319 return (toUnsignedLong(i0) << pickPos(32, 0))
1320 | (toUnsignedLong(i1) << pickPos(32, 32));
1321 }
1322 private static int makeInt(short i0, short i1) {
1323 return (toUnsignedInt(i0) << pickPos(16, 0))
1324 | (toUnsignedInt(i1) << pickPos(16, 16));
1325 }
1326 private static int makeInt(byte i0, byte i1, byte i2, byte i3) {
1327 return ((toUnsignedInt(i0) << pickPos(24, 0))
1328 | (toUnsignedInt(i1) << pickPos(24, 8))
1329 | (toUnsignedInt(i2) << pickPos(24, 16))
1330 | (toUnsignedInt(i3) << pickPos(24, 24)));
1331 }
1332 private static short makeShort(byte i0, byte i1) {
1333 return (short)((toUnsignedInt(i0) << pickPos(8, 0))
1334 | (toUnsignedInt(i1) << pickPos(8, 8)));
1335 }
1336
1337 private static byte pick(byte le, byte be) { return BE ? be : le; }
1338 private static short pick(short le, short be) { return BE ? be : le; }
1339 private static int pick(int le, int be) { return BE ? be : le; }
1340
1341 // These methods write integers to memory from smaller parts
1342 // provided by their caller. The ordering in which these parts
1343 // are written is the native endianness of this platform.
1344 private void putLongParts(Object o, long offset, byte i0, byte i1, byte i2, byte i3, byte i4, byte i5, byte i6, byte i7) {
1345 putByte(o, offset + 0, pick(i0, i7));
1346 putByte(o, offset + 1, pick(i1, i6));
1347 putByte(o, offset + 2, pick(i2, i5));
1348 putByte(o, offset + 3, pick(i3, i4));
1349 putByte(o, offset + 4, pick(i4, i3));
1350 putByte(o, offset + 5, pick(i5, i2));
1351 putByte(o, offset + 6, pick(i6, i1));
1352 putByte(o, offset + 7, pick(i7, i0));
1353 }
1354 private void putLongParts(Object o, long offset, short i0, short i1, short i2, short i3) {
1355 putShort(o, offset + 0, pick(i0, i3));
1356 putShort(o, offset + 2, pick(i1, i2));
1357 putShort(o, offset + 4, pick(i2, i1));
1358 putShort(o, offset + 6, pick(i3, i0));
1359 }
1360 private void putLongParts(Object o, long offset, int i0, int i1) {
1361 putInt(o, offset + 0, pick(i0, i1));
1362 putInt(o, offset + 4, pick(i1, i0));
1363 }
1364 private void putIntParts(Object o, long offset, short i0, short i1) {
1365 putShort(o, offset + 0, pick(i0, i1));
1366 putShort(o, offset + 2, pick(i1, i0));
1367 }
1368 private void putIntParts(Object o, long offset, byte i0, byte i1, byte i2, byte i3) {
1369 putByte(o, offset + 0, pick(i0, i3));
1370 putByte(o, offset + 1, pick(i1, i2));
1371 putByte(o, offset + 2, pick(i2, i1));
1372 putByte(o, offset + 3, pick(i3, i0));
1373 }
1374 private void putShortParts(Object o, long offset, byte i0, byte i1) {
1375 putByte(o, offset + 0, pick(i0, i1));
1376 putByte(o, offset + 1, pick(i1, i0));
1377 }
1378
1379 // Zero-extend an integer
1380 private static int toUnsignedInt(byte n) { return n & 0xff; }
1381 private static int toUnsignedInt(short n) { return n & 0xffff; }
1382 private static long toUnsignedLong(byte n) { return n & 0xffl; }
1383 private static long toUnsignedLong(short n) { return n & 0xffffl; }
1384 private static long toUnsignedLong(int n) { return n & 0xffffffffl; }
1385
1386 // Maybe byte-reverse an integer
1387 private static char convEndian(boolean big, char n) { return big == BE ? n : Character.reverseBytes(n); }
1388 private static short convEndian(boolean big, short n) { return big == BE ? n : Short.reverseBytes(n) ; }
1389 private static int convEndian(boolean big, int n) { return big == BE ? n : Integer.reverseBytes(n) ; }
1390 private static long convEndian(boolean big, long n) { return big == BE ? n : Long.reverseBytes(n) ; }
1391 }