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