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