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.vm.annotation.ForceInline; 32 import sun.reflect.CallerSensitive; 33 import sun.reflect.Reflection; 34 import jdk.internal.misc.VM; 35 36 import jdk.internal.HotSpotIntrinsicCandidate; 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 sun.reflect.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 /** @see #putInt(Object, long, int) */ 214 @HotSpotIntrinsicCandidate 215 public native void putBoolean(Object o, long offset, boolean x); 216 /** @see #getInt(Object, long) */ 217 @HotSpotIntrinsicCandidate 218 public native byte getByte(Object o, long offset); 219 /** @see #putInt(Object, long, int) */ 220 @HotSpotIntrinsicCandidate 221 public native void putByte(Object o, long offset, byte x); 222 /** @see #getInt(Object, long) */ 223 @HotSpotIntrinsicCandidate 224 public native short getShort(Object o, long offset); 225 /** @see #putInt(Object, long, int) */ 226 @HotSpotIntrinsicCandidate 227 public native void putShort(Object o, long offset, short x); 228 /** @see #getInt(Object, long) */ 229 @HotSpotIntrinsicCandidate 230 public native char getChar(Object o, long offset); 231 /** @see #putInt(Object, long, int) */ 232 @HotSpotIntrinsicCandidate 233 public native void putChar(Object o, long offset, char x); 234 /** @see #getInt(Object, long) */ 235 @HotSpotIntrinsicCandidate 236 public native long getLong(Object o, long offset); 237 /** @see #putInt(Object, long, int) */ 238 @HotSpotIntrinsicCandidate 239 public native void putLong(Object o, long offset, long x); 240 /** @see #getInt(Object, long) */ 241 @HotSpotIntrinsicCandidate 242 public native float getFloat(Object o, long offset); 243 /** @see #putInt(Object, long, int) */ 244 @HotSpotIntrinsicCandidate 245 public native void putFloat(Object o, long offset, float x); 246 /** @see #getInt(Object, long) */ 247 @HotSpotIntrinsicCandidate 248 public native double getDouble(Object o, long offset); 249 /** @see #putInt(Object, long, int) */ 250 @HotSpotIntrinsicCandidate 251 public native void putDouble(Object o, long offset, double x); 252 253 // These read VM internal data. 254 255 /** 256 * Fetches an uncompressed reference value from a given native variable 257 * ignoring the VM's compressed references mode. 258 * 259 * @param address a memory address locating the variable 260 * @return the value fetched from the indicated native variable 261 */ 262 public native Object getUncompressedObject(long address); 263 264 /** 265 * Fetches the {@link java.lang.Class} Java mirror for the given native 266 * metaspace {@code Klass} pointer. 267 * 268 * @param metaspaceKlass a native metaspace {@code Klass} pointer 269 * @return the {@link java.lang.Class} Java mirror 270 */ 271 public native Class<?> getJavaMirror(long metaspaceKlass); 272 273 /** 274 * Fetches a native metaspace {@code Klass} pointer for the given Java 275 * object. 276 * 277 * @param o Java heap object for which to fetch the class pointer 278 * @return a native metaspace {@code Klass} pointer 279 */ 280 public native long getKlassPointer(Object o); 281 282 // These work on values in the C heap. 283 284 /** 285 * Fetches a value from a given memory address. If the address is zero, or 286 * does not point into a block obtained from {@link #allocateMemory}, the 287 * results are undefined. 288 * 289 * @see #allocateMemory 290 */ 291 @HotSpotIntrinsicCandidate 292 public native byte getByte(long address); 293 294 /** 295 * Stores a value into a given memory address. If the address is zero, or 296 * does not point into a block obtained from {@link #allocateMemory}, the 297 * results are undefined. 298 * 299 * @see #getByte(long) 300 */ 301 @HotSpotIntrinsicCandidate 302 public native void putByte(long address, byte x); 303 304 /** @see #getByte(long) */ 305 @HotSpotIntrinsicCandidate 306 public native short getShort(long address); 307 /** @see #putByte(long, byte) */ 308 @HotSpotIntrinsicCandidate 309 public native void putShort(long address, short x); 310 /** @see #getByte(long) */ 311 @HotSpotIntrinsicCandidate 312 public native char getChar(long address); 313 /** @see #putByte(long, byte) */ 314 @HotSpotIntrinsicCandidate 315 public native void putChar(long address, char x); 316 /** @see #getByte(long) */ 317 @HotSpotIntrinsicCandidate 318 public native int getInt(long address); 319 /** @see #putByte(long, byte) */ 320 @HotSpotIntrinsicCandidate 321 public native void putInt(long address, int x); 322 /** @see #getByte(long) */ 323 @HotSpotIntrinsicCandidate 324 public native long getLong(long address); 325 /** @see #putByte(long, byte) */ 326 @HotSpotIntrinsicCandidate 327 public native void putLong(long address, long x); 328 /** @see #getByte(long) */ 329 @HotSpotIntrinsicCandidate 330 public native float getFloat(long address); 331 /** @see #putByte(long, byte) */ 332 @HotSpotIntrinsicCandidate 333 public native void putFloat(long address, float x); 334 /** @see #getByte(long) */ 335 @HotSpotIntrinsicCandidate 336 public native double getDouble(long address); 337 /** @see #putByte(long, byte) */ 338 @HotSpotIntrinsicCandidate 339 public native void putDouble(long address, double x); 340 341 /** 342 * Fetches a native pointer from a given memory address. If the address is 343 * zero, or does not point into a block obtained from {@link 344 * #allocateMemory}, the results are undefined. 345 * 346 * <p>If the native pointer is less than 64 bits wide, it is extended as 347 * an unsigned number to a Java long. The pointer may be indexed by any 348 * given byte offset, simply by adding that offset (as a simple integer) to 349 * the long representing the pointer. The number of bytes actually read 350 * from the target address may be determined by consulting {@link 351 * #addressSize}. 352 * 353 * @see #allocateMemory 354 */ 355 @HotSpotIntrinsicCandidate 356 public native long getAddress(long address); 357 358 /** 359 * Stores a native pointer into a given memory address. If the address is 360 * zero, or does not point into a block obtained from {@link 361 * #allocateMemory}, the results are undefined. 362 * 363 * <p>The number of bytes actually written at the target address may be 364 * determined by consulting {@link #addressSize}. 365 * 366 * @see #getAddress(long) 367 */ 368 @HotSpotIntrinsicCandidate 369 public native void putAddress(long address, long x); 370 371 372 373 /// helper methods for validating various types of objects/values 374 375 /** 376 * Create an exception reflecting that some of the input was invalid 377 * 378 * <em>Note:</em> It is the resposibility of the caller to make 379 * sure arguments are checked before the methods are called. While 380 * some rudimentary checks are performed on the input, the checks 381 * are best effort and when performance is an overriding priority, 382 * as when methods of this class are optimized by the runtime 383 * compiler, some or all checks (if any) may be elided. Hence, the 384 * caller must not rely on the checks and corresponding 385 * exceptions! 386 * 387 * @return an exception object 388 */ 389 private RuntimeException invalidInput() { 390 return new IllegalArgumentException(); 391 } 392 393 /** 394 * Check if a value is 32-bit clean (32 MSB are all zero) 395 * 396 * @param value the 64-bit value to check 397 * 398 * @return true if the value is 32-bit clean 399 */ 400 private boolean is32BitClean(long value) { 401 return value >>> 32 == 0; 402 } 403 404 /** 405 * Check the validity of a size (the equivalent of a size_t) 406 * 407 * @throws RuntimeException if the size is invalid 408 * (<em>Note:</em> after optimization, invalid inputs may 409 * go undetected, which will lead to unpredictable 410 * behavior) 411 */ 412 private void checkSize(long size) { 413 if (ADDRESS_SIZE == 4) { 414 // Note: this will also check for negative sizes 415 if (!is32BitClean(size)) { 416 throw invalidInput(); 417 } 418 } else if (size < 0) { 419 throw invalidInput(); 420 } 421 } 422 423 /** 424 * Check the validity of a native address (the equivalent of void*) 425 * 426 * @throws RuntimeException if the address is invalid 427 * (<em>Note:</em> after optimization, invalid inputs may 428 * go undetected, which will lead to unpredictable 429 * behavior) 430 */ 431 private void checkNativeAddress(long address) { 432 if (ADDRESS_SIZE == 4) { 433 // Accept both zero and sign extended pointers. A valid 434 // pointer will, after the +1 below, either have produced 435 // the value 0x0 or 0x1. Masking off the low bit allows 436 // for testing against 0. 437 if ((((address >> 32) + 1) & ~1) != 0) { 438 throw invalidInput(); 439 } 440 } 441 } 442 443 /** 444 * Check the validity of an offset, relative to a base object 445 * 446 * @param o the base object 447 * @param offset the offset to check 448 * 449 * @throws RuntimeException if the size is invalid 450 * (<em>Note:</em> after optimization, invalid inputs may 451 * go undetected, which will lead to unpredictable 452 * behavior) 453 */ 454 private void checkOffset(Object o, long offset) { 455 if (ADDRESS_SIZE == 4) { 456 // Note: this will also check for negative offsets 457 if (!is32BitClean(offset)) { 458 throw invalidInput(); 459 } 460 } else if (offset < 0) { 461 throw invalidInput(); 462 } 463 } 464 465 /** 466 * Check the validity of a double-register pointer 467 * 468 * Note: This code deliberately does *not* check for NPE for (at 469 * least) three reasons: 470 * 471 * 1) NPE is not just NULL/0 - there is a range of values all 472 * resulting in an NPE, which is not trivial to check for 473 * 474 * 2) It is the responsibility of the callers of Unsafe methods 475 * to verify the input, so throwing an exception here is not really 476 * useful - passing in a NULL pointer is a critical error and the 477 * must not expect an exception to be thrown anyway. 478 * 479 * 3) the actual operations will detect NULL pointers anyway by 480 * means of traps and signals (like SIGSEGV). 481 * 482 * @param o Java heap object, or null 483 * @param offset indication of where the variable resides in a Java heap 484 * object, if any, else a memory address locating the variable 485 * statically 486 * 487 * @throws RuntimeException if the pointer is invalid 488 * (<em>Note:</em> after optimization, invalid inputs may 489 * go undetected, which will lead to unpredictable 490 * behavior) 491 */ 492 private void checkPointer(Object o, long offset) { 493 if (o == null) { 494 checkNativeAddress(offset); 495 } else { 496 checkOffset(o, offset); 497 } 498 } 499 500 /** 501 * Check if a type is a primitive array type 502 * 503 * @param c the type to check 504 * 505 * @return true if the type is a primitive array type 506 */ 507 private void checkPrimitiveArray(Class<?> c) { 508 Class<?> componentType = c.getComponentType(); 509 if (componentType == null || !componentType.isPrimitive()) { 510 throw invalidInput(); 511 } 512 } 513 514 /** 515 * Check that a pointer is a valid primitive array type pointer 516 * 517 * Note: pointers off-heap are considered to be primitive arrays 518 * 519 * @throws RuntimeException if the pointer is invalid 520 * (<em>Note:</em> after optimization, invalid inputs may 521 * go undetected, which will lead to unpredictable 522 * behavior) 523 */ 524 private void checkPrimitivePointer(Object o, long offset) { 525 checkPointer(o, offset); 526 527 if (o != null) { 528 // If on heap, it it must be a primitive array 529 checkPrimitiveArray(o.getClass()); 530 } 531 } 532 533 534 /// wrappers for malloc, realloc, free: 535 536 /** 537 * Allocates a new block of native memory, of the given size in bytes. The 538 * contents of the memory are uninitialized; they will generally be 539 * garbage. The resulting native pointer will never be zero, and will be 540 * aligned for all value types. Dispose of this memory by calling {@link 541 * #freeMemory}, or resize it with {@link #reallocateMemory}. 542 * 543 * <em>Note:</em> It is the resposibility of the caller to make 544 * sure arguments are checked before the methods are called. While 545 * some rudimentary checks are performed on the input, the checks 546 * are best effort and when performance is an overriding priority, 547 * as when methods of this class are optimized by the runtime 548 * compiler, some or all checks (if any) may be elided. Hence, the 549 * caller must not rely on the checks and corresponding 550 * exceptions! 551 * 552 * @throws RuntimeException if the size is negative or too large 553 * for the native size_t type 554 * 555 * @throws OutOfMemoryError if the allocation is refused by the system 556 * 557 * @see #getByte(long) 558 * @see #putByte(long, byte) 559 */ 560 public long allocateMemory(long bytes) { 561 allocateMemoryChecks(bytes); 562 563 if (bytes == 0) { 564 return 0; 565 } 566 567 long p = allocateMemory0(bytes); 568 if (p == 0) { 569 throw new OutOfMemoryError(); 570 } 571 572 return p; 573 } 574 575 /** 576 * Validate the arguments to allocateMemory 577 * 578 * @throws RuntimeException if the arguments are invalid 579 * (<em>Note:</em> after optimization, invalid inputs may 580 * go undetected, which will lead to unpredictable 581 * behavior) 582 */ 583 private void allocateMemoryChecks(long bytes) { 584 checkSize(bytes); 585 } 586 587 /** 588 * Resizes a new block of native memory, to the given size in bytes. The 589 * contents of the new block past the size of the old block are 590 * uninitialized; they will generally be garbage. The resulting native 591 * pointer will be zero if and only if the requested size is zero. The 592 * resulting native pointer will be aligned for all value types. Dispose 593 * of this memory by calling {@link #freeMemory}, or resize it with {@link 594 * #reallocateMemory}. The address passed to this method may be null, in 595 * which case an allocation will be performed. 596 * 597 * <em>Note:</em> It is the resposibility of the caller to make 598 * sure arguments are checked before the methods are called. While 599 * some rudimentary checks are performed on the input, the checks 600 * are best effort and when performance is an overriding priority, 601 * as when methods of this class are optimized by the runtime 602 * compiler, some or all checks (if any) may be elided. Hence, the 603 * caller must not rely on the checks and corresponding 604 * exceptions! 605 * 606 * @throws RuntimeException if the size is negative or too large 607 * for the native size_t type 608 * 609 * @throws OutOfMemoryError if the allocation is refused by the system 610 * 611 * @see #allocateMemory 612 */ 613 public long reallocateMemory(long address, long bytes) { 614 reallocateMemoryChecks(address, bytes); 615 616 if (bytes == 0) { 617 freeMemory(address); 618 return 0; 619 } 620 621 long p = (address == 0) ? allocateMemory0(bytes) : reallocateMemory0(address, bytes); 622 if (p == 0) { 623 throw new OutOfMemoryError(); 624 } 625 626 return p; 627 } 628 629 /** 630 * Validate the arguments to reallocateMemory 631 * 632 * @throws RuntimeException if the arguments are invalid 633 * (<em>Note:</em> after optimization, invalid inputs may 634 * go undetected, which will lead to unpredictable 635 * behavior) 636 */ 637 private void reallocateMemoryChecks(long address, long bytes) { 638 checkPointer(null, address); 639 checkSize(bytes); 640 } 641 642 /** 643 * Sets all bytes in a given block of memory to a fixed value 644 * (usually zero). 645 * 646 * <p>This method determines a block's base address by means of two parameters, 647 * and so it provides (in effect) a <em>double-register</em> addressing mode, 648 * as discussed in {@link #getInt(Object,long)}. When the object reference is null, 649 * the offset supplies an absolute base address. 650 * 651 * <p>The stores are in coherent (atomic) units of a size determined 652 * by the address and length parameters. If the effective address and 653 * length are all even modulo 8, the stores take place in 'long' units. 654 * If the effective address and length are (resp.) even modulo 4 or 2, 655 * the stores take place in units of 'int' or 'short'. 656 * 657 * <em>Note:</em> It is the resposibility of the caller to make 658 * sure arguments are checked before the methods are called. While 659 * some rudimentary checks are performed on the input, the checks 660 * are best effort and when performance is an overriding priority, 661 * as when methods of this class are optimized by the runtime 662 * compiler, some or all checks (if any) may be elided. Hence, the 663 * caller must not rely on the checks and corresponding 664 * exceptions! 665 * 666 * @throws RuntimeException if any of the arguments is invalid 667 * 668 * @since 1.7 669 */ 670 public void setMemory(Object o, long offset, long bytes, byte value) { 671 setMemoryChecks(o, offset, bytes, value); 672 673 if (bytes == 0) { 674 return; 675 } 676 677 setMemory0(o, offset, bytes, value); 678 } 679 680 /** 681 * Sets all bytes in a given block of memory to a fixed value 682 * (usually zero). This provides a <em>single-register</em> addressing mode, 683 * as discussed in {@link #getInt(Object,long)}. 684 * 685 * <p>Equivalent to {@code setMemory(null, address, bytes, value)}. 686 */ 687 public void setMemory(long address, long bytes, byte value) { 688 setMemory(null, address, bytes, value); 689 } 690 691 /** 692 * Validate the arguments to setMemory 693 * 694 * @throws RuntimeException if the arguments are invalid 695 * (<em>Note:</em> after optimization, invalid inputs may 696 * go undetected, which will lead to unpredictable 697 * behavior) 698 */ 699 private void setMemoryChecks(Object o, long offset, long bytes, byte value) { 700 checkPrimitivePointer(o, offset); 701 checkSize(bytes); 702 } 703 704 /** 705 * Sets all bytes in a given block of memory to a copy of another 706 * block. 707 * 708 * <p>This method determines each block's base address by means of two parameters, 709 * and so it provides (in effect) a <em>double-register</em> addressing mode, 710 * as discussed in {@link #getInt(Object,long)}. When the object reference is null, 711 * the offset supplies an absolute base address. 712 * 713 * <p>The transfers are in coherent (atomic) units of a size determined 714 * by the address and length parameters. If the effective addresses and 715 * length are all even modulo 8, the transfer takes place in 'long' units. 716 * If the effective addresses and length are (resp.) even modulo 4 or 2, 717 * the transfer takes place in units of 'int' or 'short'. 718 * 719 * <em>Note:</em> It is the resposibility of the caller to make 720 * sure arguments are checked before the methods are called. While 721 * some rudimentary checks are performed on the input, the checks 722 * are best effort and when performance is an overriding priority, 723 * as when methods of this class are optimized by the runtime 724 * compiler, some or all checks (if any) may be elided. Hence, the 725 * caller must not rely on the checks and corresponding 726 * exceptions! 727 * 728 * @throws RuntimeException if any of the arguments is invalid 729 * 730 * @since 1.7 731 */ 732 public void copyMemory(Object srcBase, long srcOffset, 733 Object destBase, long destOffset, 734 long bytes) { 735 copyMemoryChecks(srcBase, srcOffset, destBase, destOffset, bytes); 736 737 if (bytes == 0) { 738 return; 739 } 740 741 copyMemory0(srcBase, srcOffset, destBase, destOffset, bytes); 742 } 743 744 /** 745 * Sets all bytes in a given block of memory to a copy of another 746 * block. This provides a <em>single-register</em> addressing mode, 747 * as discussed in {@link #getInt(Object,long)}. 748 * 749 * Equivalent to {@code copyMemory(null, srcAddress, null, destAddress, bytes)}. 750 */ 751 public void copyMemory(long srcAddress, long destAddress, long bytes) { 752 copyMemory(null, srcAddress, null, destAddress, bytes); 753 } 754 755 /** 756 * Validate the arguments to copyMemory 757 * 758 * @throws RuntimeException if any of the arguments is invalid 759 * (<em>Note:</em> after optimization, invalid inputs may 760 * go undetected, which will lead to unpredictable 761 * behavior) 762 */ 763 private void copyMemoryChecks(Object srcBase, long srcOffset, 764 Object destBase, long destOffset, 765 long bytes) { 766 checkSize(bytes); 767 checkPrimitivePointer(srcBase, srcOffset); 768 checkPrimitivePointer(destBase, destOffset); 769 } 770 771 /** 772 * Copies all elements from one block of memory to another block, 773 * *unconditionally* byte swapping the elements on the fly. 774 * 775 * <p>This method determines each block's base address by means of two parameters, 776 * and so it provides (in effect) a <em>double-register</em> addressing mode, 777 * as discussed in {@link #getInt(Object,long)}. When the object reference is null, 778 * the offset supplies an absolute base address. 779 * 780 * <em>Note:</em> It is the resposibility of the caller to make 781 * sure arguments are checked before the methods are called. While 782 * some rudimentary checks are performed on the input, the checks 783 * are best effort and when performance is an overriding priority, 784 * as when methods of this class are optimized by the runtime 785 * compiler, some or all checks (if any) may be elided. Hence, the 786 * caller must not rely on the checks and corresponding 787 * exceptions! 788 * 789 * @throws RuntimeException if any of the arguments is invalid 790 * 791 * @since 9 792 */ 793 public void copySwapMemory(Object srcBase, long srcOffset, 794 Object destBase, long destOffset, 795 long bytes, long elemSize) { 796 copySwapMemoryChecks(srcBase, srcOffset, destBase, destOffset, bytes, elemSize); 797 798 if (bytes == 0) { 799 return; 800 } 801 802 copySwapMemory0(srcBase, srcOffset, destBase, destOffset, bytes, elemSize); 803 } 804 805 private void copySwapMemoryChecks(Object srcBase, long srcOffset, 806 Object destBase, long destOffset, 807 long bytes, long elemSize) { 808 checkSize(bytes); 809 810 if (elemSize != 2 && elemSize != 4 && elemSize != 8) { 811 throw invalidInput(); 812 } 813 if (bytes % elemSize != 0) { 814 throw invalidInput(); 815 } 816 817 checkPrimitivePointer(srcBase, srcOffset); 818 checkPrimitivePointer(destBase, destOffset); 819 } 820 821 /** 822 * Copies all elements from one block of memory to another block, byte swapping the 823 * elements on the fly. 824 * 825 * This provides a <em>single-register</em> addressing mode, as 826 * discussed in {@link #getInt(Object,long)}. 827 * 828 * Equivalent to {@code copySwapMemory(null, srcAddress, null, destAddress, bytes, elemSize)}. 829 */ 830 public void copySwapMemory(long srcAddress, long destAddress, long bytes, long elemSize) { 831 copySwapMemory(null, srcAddress, null, destAddress, bytes, elemSize); 832 } 833 834 /** 835 * Disposes of a block of native memory, as obtained from {@link 836 * #allocateMemory} or {@link #reallocateMemory}. The address passed to 837 * this method may be null, in which case no action is taken. 838 * 839 * <em>Note:</em> It is the resposibility of the caller to make 840 * sure arguments are checked before the methods are called. While 841 * some rudimentary checks are performed on the input, the checks 842 * are best effort and when performance is an overriding priority, 843 * as when methods of this class are optimized by the runtime 844 * compiler, some or all checks (if any) may be elided. Hence, the 845 * caller must not rely on the checks and corresponding 846 * exceptions! 847 * 848 * @throws RuntimeException if any of the arguments is invalid 849 * 850 * @see #allocateMemory 851 */ 852 public void freeMemory(long address) { 853 freeMemoryChecks(address); 854 855 if (address == 0) { 856 return; 857 } 858 859 freeMemory0(address); 860 } 861 862 /** 863 * Validate the arguments to freeMemory 864 * 865 * @throws RuntimeException if the arguments are invalid 866 * (<em>Note:</em> after optimization, invalid inputs may 867 * go undetected, which will lead to unpredictable 868 * behavior) 869 */ 870 private void freeMemoryChecks(long address) { 871 checkPointer(null, address); 872 } 873 874 /// random queries 875 876 /** 877 * This constant differs from all results that will ever be returned from 878 * {@link #staticFieldOffset}, {@link #objectFieldOffset}, 879 * or {@link #arrayBaseOffset}. 880 */ 881 public static final int INVALID_FIELD_OFFSET = -1; 882 883 /** 884 * Reports the location of a given field in the storage allocation of its 885 * class. Do not expect to perform any sort of arithmetic on this offset; 886 * it is just a cookie which is passed to the unsafe heap memory accessors. 887 * 888 * <p>Any given field will always have the same offset and base, and no 889 * two distinct fields of the same class will ever have the same offset 890 * and base. 891 * 892 * <p>As of 1.4.1, offsets for fields are represented as long values, 893 * although the Sun JVM does not use the most significant 32 bits. 894 * However, JVM implementations which store static fields at absolute 895 * addresses can use long offsets and null base pointers to express 896 * the field locations in a form usable by {@link #getInt(Object,long)}. 897 * Therefore, code which will be ported to such JVMs on 64-bit platforms 898 * must preserve all bits of static field offsets. 899 * @see #getInt(Object, long) 900 */ 901 public long objectFieldOffset(Field f) { 902 if (f == null) { 903 throw new NullPointerException(); 904 } 905 906 return objectFieldOffset0(f); 907 } 908 909 /** 910 * Reports the location of a given static field, in conjunction with {@link 911 * #staticFieldBase}. 912 * <p>Do not expect to perform any sort of arithmetic on this offset; 913 * it is just a cookie which is passed to the unsafe heap memory accessors. 914 * 915 * <p>Any given field will always have the same offset, and no two distinct 916 * fields of the same class will ever have the same offset. 917 * 918 * <p>As of 1.4.1, offsets for fields are represented as long values, 919 * although the Sun JVM does not use the most significant 32 bits. 920 * It is hard to imagine a JVM technology which needs more than 921 * a few bits to encode an offset within a non-array object, 922 * However, for consistency with other methods in this class, 923 * this method reports its result as a long value. 924 * @see #getInt(Object, long) 925 */ 926 public long staticFieldOffset(Field f) { 927 if (f == null) { 928 throw new NullPointerException(); 929 } 930 931 return staticFieldOffset0(f); 932 } 933 934 /** 935 * Reports the location of a given static field, in conjunction with {@link 936 * #staticFieldOffset}. 937 * <p>Fetch the base "Object", if any, with which static fields of the 938 * given class can be accessed via methods like {@link #getInt(Object, 939 * long)}. This value may be null. This value may refer to an object 940 * which is a "cookie", not guaranteed to be a real Object, and it should 941 * not be used in any way except as argument to the get and put routines in 942 * this class. 943 */ 944 public Object staticFieldBase(Field f) { 945 if (f == null) { 946 throw new NullPointerException(); 947 } 948 949 return staticFieldBase0(f); 950 } 951 952 /** 953 * Detects if the given class may need to be initialized. This is often 954 * needed in conjunction with obtaining the static field base of a 955 * class. 956 * @return false only if a call to {@code ensureClassInitialized} would have no effect 957 */ 958 public boolean shouldBeInitialized(Class<?> c) { 959 if (c == null) { 960 throw new NullPointerException(); 961 } 962 963 return shouldBeInitialized0(c); 964 } 965 966 /** 967 * Ensures the given class has been initialized. This is often 968 * needed in conjunction with obtaining the static field base of a 969 * class. 970 */ 971 public void ensureClassInitialized(Class<?> c) { 972 if (c == null) { 973 throw new NullPointerException(); 974 } 975 976 ensureClassInitialized0(c); 977 } 978 979 /** 980 * Reports the offset of the first element in the storage allocation of a 981 * given array class. If {@link #arrayIndexScale} returns a non-zero value 982 * for the same class, you may use that scale factor, together with this 983 * base offset, to form new offsets to access elements of arrays of the 984 * given class. 985 * 986 * @see #getInt(Object, long) 987 * @see #putInt(Object, long, int) 988 */ 989 public int arrayBaseOffset(Class<?> arrayClass) { 990 if (arrayClass == null) { 991 throw new NullPointerException(); 992 } 993 994 return arrayBaseOffset0(arrayClass); 995 } 996 997 998 /** The value of {@code arrayBaseOffset(boolean[].class)} */ 999 public static final int ARRAY_BOOLEAN_BASE_OFFSET 1000 = theUnsafe.arrayBaseOffset(boolean[].class); 1001 1002 /** The value of {@code arrayBaseOffset(byte[].class)} */ 1003 public static final int ARRAY_BYTE_BASE_OFFSET 1004 = theUnsafe.arrayBaseOffset(byte[].class); 1005 1006 /** The value of {@code arrayBaseOffset(short[].class)} */ 1007 public static final int ARRAY_SHORT_BASE_OFFSET 1008 = theUnsafe.arrayBaseOffset(short[].class); 1009 1010 /** The value of {@code arrayBaseOffset(char[].class)} */ 1011 public static final int ARRAY_CHAR_BASE_OFFSET 1012 = theUnsafe.arrayBaseOffset(char[].class); 1013 1014 /** The value of {@code arrayBaseOffset(int[].class)} */ 1015 public static final int ARRAY_INT_BASE_OFFSET 1016 = theUnsafe.arrayBaseOffset(int[].class); 1017 1018 /** The value of {@code arrayBaseOffset(long[].class)} */ 1019 public static final int ARRAY_LONG_BASE_OFFSET 1020 = theUnsafe.arrayBaseOffset(long[].class); 1021 1022 /** The value of {@code arrayBaseOffset(float[].class)} */ 1023 public static final int ARRAY_FLOAT_BASE_OFFSET 1024 = theUnsafe.arrayBaseOffset(float[].class); 1025 1026 /** The value of {@code arrayBaseOffset(double[].class)} */ 1027 public static final int ARRAY_DOUBLE_BASE_OFFSET 1028 = theUnsafe.arrayBaseOffset(double[].class); 1029 1030 /** The value of {@code arrayBaseOffset(Object[].class)} */ 1031 public static final int ARRAY_OBJECT_BASE_OFFSET 1032 = theUnsafe.arrayBaseOffset(Object[].class); 1033 1034 /** 1035 * Reports the scale factor for addressing elements in the storage 1036 * allocation of a given array class. However, arrays of "narrow" types 1037 * will generally not work properly with accessors like {@link 1038 * #getByte(Object, long)}, so the scale factor for such classes is reported 1039 * as zero. 1040 * 1041 * @see #arrayBaseOffset 1042 * @see #getInt(Object, long) 1043 * @see #putInt(Object, long, int) 1044 */ 1045 public int arrayIndexScale(Class<?> arrayClass) { 1046 if (arrayClass == null) { 1047 throw new NullPointerException(); 1048 } 1049 1050 return arrayIndexScale0(arrayClass); 1051 } 1052 1053 1054 /** The value of {@code arrayIndexScale(boolean[].class)} */ 1055 public static final int ARRAY_BOOLEAN_INDEX_SCALE 1056 = theUnsafe.arrayIndexScale(boolean[].class); 1057 1058 /** The value of {@code arrayIndexScale(byte[].class)} */ 1059 public static final int ARRAY_BYTE_INDEX_SCALE 1060 = theUnsafe.arrayIndexScale(byte[].class); 1061 1062 /** The value of {@code arrayIndexScale(short[].class)} */ 1063 public static final int ARRAY_SHORT_INDEX_SCALE 1064 = theUnsafe.arrayIndexScale(short[].class); 1065 1066 /** The value of {@code arrayIndexScale(char[].class)} */ 1067 public static final int ARRAY_CHAR_INDEX_SCALE 1068 = theUnsafe.arrayIndexScale(char[].class); 1069 1070 /** The value of {@code arrayIndexScale(int[].class)} */ 1071 public static final int ARRAY_INT_INDEX_SCALE 1072 = theUnsafe.arrayIndexScale(int[].class); 1073 1074 /** The value of {@code arrayIndexScale(long[].class)} */ 1075 public static final int ARRAY_LONG_INDEX_SCALE 1076 = theUnsafe.arrayIndexScale(long[].class); 1077 1078 /** The value of {@code arrayIndexScale(float[].class)} */ 1079 public static final int ARRAY_FLOAT_INDEX_SCALE 1080 = theUnsafe.arrayIndexScale(float[].class); 1081 1082 /** The value of {@code arrayIndexScale(double[].class)} */ 1083 public static final int ARRAY_DOUBLE_INDEX_SCALE 1084 = theUnsafe.arrayIndexScale(double[].class); 1085 1086 /** The value of {@code arrayIndexScale(Object[].class)} */ 1087 public static final int ARRAY_OBJECT_INDEX_SCALE 1088 = theUnsafe.arrayIndexScale(Object[].class); 1089 1090 /** 1091 * Reports the size in bytes of a native pointer, as stored via {@link 1092 * #putAddress}. This value will be either 4 or 8. Note that the sizes of 1093 * other primitive types (as stored in native memory blocks) is determined 1094 * fully by their information content. 1095 */ 1096 public int addressSize() { 1097 return ADDRESS_SIZE; 1098 } 1099 1100 /** The value of {@code addressSize()} */ 1101 public static final int ADDRESS_SIZE = theUnsafe.addressSize0(); 1102 1103 /** 1104 * Reports the size in bytes of a native memory page (whatever that is). 1105 * This value will always be a power of two. 1106 */ 1107 public native int pageSize(); 1108 1109 1110 /// random trusted operations from JNI: 1111 1112 /** 1113 * Tells the VM to define a class, without security checks. By default, the 1114 * class loader and protection domain come from the caller's class. 1115 */ 1116 public Class<?> defineClass(String name, byte[] b, int off, int len, 1117 ClassLoader loader, 1118 ProtectionDomain protectionDomain) { 1119 if (b == null) { 1120 throw new NullPointerException(); 1121 } 1122 if (len < 0) { 1123 throw new ArrayIndexOutOfBoundsException(); 1124 } 1125 1126 return defineClass0(name, b, off, len, loader, protectionDomain); 1127 } 1128 1129 public native Class<?> defineClass0(String name, byte[] b, int off, int len, 1130 ClassLoader loader, 1131 ProtectionDomain protectionDomain); 1132 1133 /** 1134 * Defines a class but does not make it known to the class loader or system dictionary. 1135 * <p> 1136 * For each CP entry, the corresponding CP patch must either be null or have 1137 * the a format that matches its tag: 1138 * <ul> 1139 * <li>Integer, Long, Float, Double: the corresponding wrapper object type from java.lang 1140 * <li>Utf8: a string (must have suitable syntax if used as signature or name) 1141 * <li>Class: any java.lang.Class object 1142 * <li>String: any object (not just a java.lang.String) 1143 * <li>InterfaceMethodRef: (NYI) a method handle to invoke on that call site's arguments 1144 * </ul> 1145 * @param hostClass context for linkage, access control, protection domain, and class loader 1146 * @param data bytes of a class file 1147 * @param cpPatches where non-null entries exist, they replace corresponding CP entries in data 1148 */ 1149 public Class<?> defineAnonymousClass(Class<?> hostClass, byte[] data, Object[] cpPatches) { 1150 if (hostClass == null || data == null) { 1151 throw new NullPointerException(); 1152 } 1153 1154 return defineAnonymousClass0(hostClass, data, cpPatches); 1155 } 1156 1157 /** 1158 * Allocates an instance but does not run any constructor. 1159 * Initializes the class if it has not yet been. 1160 */ 1161 @ForceInline 1162 public Object allocateInstance(Class<?> cls) throws InstantiationException { 1163 // Interfaces and abstract classes are handled by the intrinsic. 1164 if (cls.isPrimitive() || cls.isArray()) { 1165 throw new InstantiationException(cls.getName()); 1166 } 1167 return allocateInstance0(cls); 1168 } 1169 1170 @HotSpotIntrinsicCandidate 1171 private native Object allocateInstance0(Class<?> cls) throws InstantiationException; 1172 1173 /** 1174 * Allocates an array of a given type, but does not do zeroing. 1175 * <p> 1176 * This method should only be used in the very rare cases where a high-performance code 1177 * overwrites the destination array completely, and compilers cannot assist in zeroing elimination. 1178 * In an overwhelming majority of cases, a normal Java allocation should be used instead. 1179 * <p> 1180 * Users of this method are <b>required</b> to overwrite the initial (garbage) array contents 1181 * before allowing untrusted code, or code in other threads, to observe the reference 1182 * to the newly allocated array. In addition, the publication of the array reference must be 1183 * safe according to the Java Memory Model requirements. 1184 * <p> 1185 * The safest approach to deal with an uninitialized array is to keep the reference to it in local 1186 * variable at least until the initialization is complete, and then publish it <b>once</b>, either 1187 * by writing it to a <em>volatile</em> field, or storing it into a <em>final</em> field in constructor, 1188 * or issuing a {@link #storeFence} before publishing the reference. 1189 * <p> 1190 * @implnote This method can only allocate primitive arrays, to avoid garbage reference 1191 * elements that could break heap integrity. 1192 * 1193 * @param componentType array component type to allocate 1194 * @param length array size to allocate 1195 * @throws IllegalArgumentException if component type is null, or not a primitive class; 1196 * or the length is negative 1197 */ 1198 public Object allocateUninitializedArray(Class<?> componentType, int length) { 1199 if (componentType == null) { 1200 throw new IllegalArgumentException("Component type is null"); 1201 } 1202 if (!componentType.isPrimitive()) { 1203 throw new IllegalArgumentException("Component type is not primitive"); 1204 } 1205 if (length < 0) { 1206 throw new IllegalArgumentException("Negative length"); 1207 } 1208 return allocateUninitializedArray0(componentType, length); 1209 } 1210 1211 @HotSpotIntrinsicCandidate 1212 private Object allocateUninitializedArray0(Class<?> componentType, int length) { 1213 // These fallbacks provide zeroed arrays, but intrinsic is not required to 1214 // return the zeroed arrays. 1215 if (componentType == byte.class) return new byte[length]; 1216 if (componentType == boolean.class) return new boolean[length]; 1217 if (componentType == short.class) return new short[length]; 1218 if (componentType == char.class) return new char[length]; 1219 if (componentType == int.class) return new int[length]; 1220 if (componentType == float.class) return new float[length]; 1221 if (componentType == long.class) return new long[length]; 1222 if (componentType == double.class) return new double[length]; 1223 return null; 1224 } 1225 1226 /** Throws the exception without telling the verifier. */ 1227 public native void throwException(Throwable ee); 1228 1229 /** 1230 * Atomically updates Java variable to {@code x} if it is currently 1231 * holding {@code expected}. 1232 * 1233 * <p>This operation has memory semantics of a {@code volatile} read 1234 * and write. Corresponds to C11 atomic_compare_exchange_strong. 1235 * 1236 * @return {@code true} if successful 1237 */ 1238 @HotSpotIntrinsicCandidate 1239 public final native boolean compareAndSwapObject(Object o, long offset, 1240 Object expected, 1241 Object x); 1242 1243 @HotSpotIntrinsicCandidate 1244 public final native Object compareAndExchangeObjectVolatile(Object o, long offset, 1245 Object expected, 1246 Object x); 1247 1248 @HotSpotIntrinsicCandidate 1249 public final Object compareAndExchangeObjectAcquire(Object o, long offset, 1250 Object expected, 1251 Object x) { 1252 return compareAndExchangeObjectVolatile(o, offset, expected, x); 1253 } 1254 1255 @HotSpotIntrinsicCandidate 1256 public final Object compareAndExchangeObjectRelease(Object o, long offset, 1257 Object expected, 1258 Object x) { 1259 return compareAndExchangeObjectVolatile(o, offset, expected, x); 1260 } 1261 1262 @HotSpotIntrinsicCandidate 1263 public final boolean weakCompareAndSwapObject(Object o, long offset, 1264 Object expected, 1265 Object x) { 1266 return compareAndSwapObject(o, offset, expected, x); 1267 } 1268 1269 @HotSpotIntrinsicCandidate 1270 public final boolean weakCompareAndSwapObjectAcquire(Object o, long offset, 1271 Object expected, 1272 Object x) { 1273 return compareAndSwapObject(o, offset, expected, x); 1274 } 1275 1276 @HotSpotIntrinsicCandidate 1277 public final boolean weakCompareAndSwapObjectRelease(Object o, long offset, 1278 Object expected, 1279 Object x) { 1280 return compareAndSwapObject(o, offset, expected, x); 1281 } 1282 1283 /** 1284 * Atomically updates Java variable to {@code x} if it is currently 1285 * holding {@code expected}. 1286 * 1287 * <p>This operation has memory semantics of a {@code volatile} read 1288 * and write. Corresponds to C11 atomic_compare_exchange_strong. 1289 * 1290 * @return {@code true} if successful 1291 */ 1292 @HotSpotIntrinsicCandidate 1293 public final native boolean compareAndSwapInt(Object o, long offset, 1294 int expected, 1295 int x); 1296 1297 @HotSpotIntrinsicCandidate 1298 public final native int compareAndExchangeIntVolatile(Object o, long offset, 1299 int expected, 1300 int x); 1301 1302 @HotSpotIntrinsicCandidate 1303 public final int compareAndExchangeIntAcquire(Object o, long offset, 1304 int expected, 1305 int x) { 1306 return compareAndExchangeIntVolatile(o, offset, expected, x); 1307 } 1308 1309 @HotSpotIntrinsicCandidate 1310 public final int compareAndExchangeIntRelease(Object o, long offset, 1311 int expected, 1312 int x) { 1313 return compareAndExchangeIntVolatile(o, offset, expected, x); 1314 } 1315 1316 @HotSpotIntrinsicCandidate 1317 public final boolean weakCompareAndSwapInt(Object o, long offset, 1318 int expected, 1319 int x) { 1320 return compareAndSwapInt(o, offset, expected, x); 1321 } 1322 1323 @HotSpotIntrinsicCandidate 1324 public final boolean weakCompareAndSwapIntAcquire(Object o, long offset, 1325 int expected, 1326 int x) { 1327 return compareAndSwapInt(o, offset, expected, x); 1328 } 1329 1330 @HotSpotIntrinsicCandidate 1331 public final boolean weakCompareAndSwapIntRelease(Object o, long offset, 1332 int expected, 1333 int x) { 1334 return compareAndSwapInt(o, offset, expected, x); 1335 } 1336 1337 /** 1338 * Atomically updates Java variable to {@code x} if it is currently 1339 * holding {@code expected}. 1340 * 1341 * <p>This operation has memory semantics of a {@code volatile} read 1342 * and write. Corresponds to C11 atomic_compare_exchange_strong. 1343 * 1344 * @return {@code true} if successful 1345 */ 1346 @HotSpotIntrinsicCandidate 1347 public final native boolean compareAndSwapLong(Object o, long offset, 1348 long expected, 1349 long x); 1350 1351 @HotSpotIntrinsicCandidate 1352 public final native long compareAndExchangeLongVolatile(Object o, long offset, 1353 long expected, 1354 long x); 1355 1356 @HotSpotIntrinsicCandidate 1357 public final long compareAndExchangeLongAcquire(Object o, long offset, 1358 long expected, 1359 long x) { 1360 return compareAndExchangeLongVolatile(o, offset, expected, x); 1361 } 1362 1363 @HotSpotIntrinsicCandidate 1364 public final long compareAndExchangeLongRelease(Object o, long offset, 1365 long expected, 1366 long x) { 1367 return compareAndExchangeLongVolatile(o, offset, expected, x); 1368 } 1369 1370 @HotSpotIntrinsicCandidate 1371 public final boolean weakCompareAndSwapLong(Object o, long offset, 1372 long expected, 1373 long x) { 1374 return compareAndSwapLong(o, offset, expected, x); 1375 } 1376 1377 @HotSpotIntrinsicCandidate 1378 public final boolean weakCompareAndSwapLongAcquire(Object o, long offset, 1379 long expected, 1380 long x) { 1381 return compareAndSwapLong(o, offset, expected, x); 1382 } 1383 1384 @HotSpotIntrinsicCandidate 1385 public final boolean weakCompareAndSwapLongRelease(Object o, long offset, 1386 long expected, 1387 long x) { 1388 return compareAndSwapLong(o, offset, expected, x); 1389 } 1390 1391 /** 1392 * Fetches a reference value from a given Java variable, with volatile 1393 * load semantics. Otherwise identical to {@link #getObject(Object, long)} 1394 */ 1395 @HotSpotIntrinsicCandidate 1396 public native Object getObjectVolatile(Object o, long offset); 1397 1398 /** 1399 * Stores a reference value into a given Java variable, with 1400 * volatile store semantics. Otherwise identical to {@link #putObject(Object, long, Object)} 1401 */ 1402 @HotSpotIntrinsicCandidate 1403 public native void putObjectVolatile(Object o, long offset, Object x); 1404 1405 /** Volatile version of {@link #getInt(Object, long)} */ 1406 @HotSpotIntrinsicCandidate 1407 public native int getIntVolatile(Object o, long offset); 1408 1409 /** Volatile version of {@link #putInt(Object, long, int)} */ 1410 @HotSpotIntrinsicCandidate 1411 public native void putIntVolatile(Object o, long offset, int x); 1412 1413 /** Volatile version of {@link #getBoolean(Object, long)} */ 1414 @HotSpotIntrinsicCandidate 1415 public native boolean getBooleanVolatile(Object o, long offset); 1416 1417 /** Volatile version of {@link #putBoolean(Object, long, boolean)} */ 1418 @HotSpotIntrinsicCandidate 1419 public native void putBooleanVolatile(Object o, long offset, boolean x); 1420 1421 /** Volatile version of {@link #getByte(Object, long)} */ 1422 @HotSpotIntrinsicCandidate 1423 public native byte getByteVolatile(Object o, long offset); 1424 1425 /** Volatile version of {@link #putByte(Object, long, byte)} */ 1426 @HotSpotIntrinsicCandidate 1427 public native void putByteVolatile(Object o, long offset, byte x); 1428 1429 /** Volatile version of {@link #getShort(Object, long)} */ 1430 @HotSpotIntrinsicCandidate 1431 public native short getShortVolatile(Object o, long offset); 1432 1433 /** Volatile version of {@link #putShort(Object, long, short)} */ 1434 @HotSpotIntrinsicCandidate 1435 public native void putShortVolatile(Object o, long offset, short x); 1436 1437 /** Volatile version of {@link #getChar(Object, long)} */ 1438 @HotSpotIntrinsicCandidate 1439 public native char getCharVolatile(Object o, long offset); 1440 1441 /** Volatile version of {@link #putChar(Object, long, char)} */ 1442 @HotSpotIntrinsicCandidate 1443 public native void putCharVolatile(Object o, long offset, char x); 1444 1445 /** Volatile version of {@link #getLong(Object, long)} */ 1446 @HotSpotIntrinsicCandidate 1447 public native long getLongVolatile(Object o, long offset); 1448 1449 /** Volatile version of {@link #putLong(Object, long, long)} */ 1450 @HotSpotIntrinsicCandidate 1451 public native void putLongVolatile(Object o, long offset, long x); 1452 1453 /** Volatile version of {@link #getFloat(Object, long)} */ 1454 @HotSpotIntrinsicCandidate 1455 public native float getFloatVolatile(Object o, long offset); 1456 1457 /** Volatile version of {@link #putFloat(Object, long, float)} */ 1458 @HotSpotIntrinsicCandidate 1459 public native void putFloatVolatile(Object o, long offset, float x); 1460 1461 /** Volatile version of {@link #getDouble(Object, long)} */ 1462 @HotSpotIntrinsicCandidate 1463 public native double getDoubleVolatile(Object o, long offset); 1464 1465 /** Volatile version of {@link #putDouble(Object, long, double)} */ 1466 @HotSpotIntrinsicCandidate 1467 public native void putDoubleVolatile(Object o, long offset, double x); 1468 1469 1470 1471 /** Acquire version of {@link #getObjectVolatile(Object, long)} */ 1472 @HotSpotIntrinsicCandidate 1473 public final Object getObjectAcquire(Object o, long offset) { 1474 return getObjectVolatile(o, offset); 1475 } 1476 1477 /** Acquire version of {@link #getBooleanVolatile(Object, long)} */ 1478 @HotSpotIntrinsicCandidate 1479 public final boolean getBooleanAcquire(Object o, long offset) { 1480 return getBooleanVolatile(o, offset); 1481 } 1482 1483 /** Acquire version of {@link #getByteVolatile(Object, long)} */ 1484 @HotSpotIntrinsicCandidate 1485 public final byte getByteAcquire(Object o, long offset) { 1486 return getByteVolatile(o, offset); 1487 } 1488 1489 /** Acquire version of {@link #getShortVolatile(Object, long)} */ 1490 @HotSpotIntrinsicCandidate 1491 public final short getShortAcquire(Object o, long offset) { 1492 return getShortVolatile(o, offset); 1493 } 1494 1495 /** Acquire version of {@link #getCharVolatile(Object, long)} */ 1496 @HotSpotIntrinsicCandidate 1497 public final char getCharAcquire(Object o, long offset) { 1498 return getCharVolatile(o, offset); 1499 } 1500 1501 /** Acquire version of {@link #getIntVolatile(Object, long)} */ 1502 @HotSpotIntrinsicCandidate 1503 public final int getIntAcquire(Object o, long offset) { 1504 return getIntVolatile(o, offset); 1505 } 1506 1507 /** Acquire version of {@link #getFloatVolatile(Object, long)} */ 1508 @HotSpotIntrinsicCandidate 1509 public final float getFloatAcquire(Object o, long offset) { 1510 return getFloatVolatile(o, offset); 1511 } 1512 1513 /** Acquire version of {@link #getLongVolatile(Object, long)} */ 1514 @HotSpotIntrinsicCandidate 1515 public final long getLongAcquire(Object o, long offset) { 1516 return getLongVolatile(o, offset); 1517 } 1518 1519 /** Acquire version of {@link #getDoubleVolatile(Object, long)} */ 1520 @HotSpotIntrinsicCandidate 1521 public final double getDoubleAcquire(Object o, long offset) { 1522 return getDoubleVolatile(o, offset); 1523 } 1524 1525 /* 1526 * Versions of {@link #putObjectVolatile(Object, long, Object)} 1527 * that do not guarantee immediate visibility of the store to 1528 * other threads. This method is generally only useful if the 1529 * underlying field is a Java volatile (or if an array cell, one 1530 * that is otherwise only accessed using volatile accesses). 1531 * 1532 * Corresponds to C11 atomic_store_explicit(..., memory_order_release). 1533 */ 1534 1535 /** Release version of {@link #putObjectVolatile(Object, long, Object)} */ 1536 @HotSpotIntrinsicCandidate 1537 public final void putObjectRelease(Object o, long offset, Object x) { 1538 putObjectVolatile(o, offset, x); 1539 } 1540 1541 /** Release version of {@link #putBooleanVolatile(Object, long, boolean)} */ 1542 @HotSpotIntrinsicCandidate 1543 public final void putBooleanRelease(Object o, long offset, boolean x) { 1544 putBooleanVolatile(o, offset, x); 1545 } 1546 1547 /** Release version of {@link #putByteVolatile(Object, long, byte)} */ 1548 @HotSpotIntrinsicCandidate 1549 public final void putByteRelease(Object o, long offset, byte x) { 1550 putByteVolatile(o, offset, x); 1551 } 1552 1553 /** Release version of {@link #putShortVolatile(Object, long, short)} */ 1554 @HotSpotIntrinsicCandidate 1555 public final void putShortRelease(Object o, long offset, short x) { 1556 putShortVolatile(o, offset, x); 1557 } 1558 1559 /** Release version of {@link #putCharVolatile(Object, long, char)} */ 1560 @HotSpotIntrinsicCandidate 1561 public final void putCharRelease(Object o, long offset, char x) { 1562 putCharVolatile(o, offset, x); 1563 } 1564 1565 /** Release version of {@link #putIntVolatile(Object, long, int)} */ 1566 @HotSpotIntrinsicCandidate 1567 public final void putIntRelease(Object o, long offset, int x) { 1568 putIntVolatile(o, offset, x); 1569 } 1570 1571 /** Release version of {@link #putFloatVolatile(Object, long, float)} */ 1572 @HotSpotIntrinsicCandidate 1573 public final void putFloatRelease(Object o, long offset, float x) { 1574 putFloatVolatile(o, offset, x); 1575 } 1576 1577 /** Release version of {@link #putLongVolatile(Object, long, long)} */ 1578 @HotSpotIntrinsicCandidate 1579 public final void putLongRelease(Object o, long offset, long x) { 1580 putLongVolatile(o, offset, x); 1581 } 1582 1583 /** Release version of {@link #putDoubleVolatile(Object, long, double)} */ 1584 @HotSpotIntrinsicCandidate 1585 public final void putDoubleRelease(Object o, long offset, double x) { 1586 putDoubleVolatile(o, offset, x); 1587 } 1588 1589 // ------------------------------ Opaque -------------------------------------- 1590 1591 /** Opaque version of {@link #getObjectVolatile(Object, long)} */ 1592 @HotSpotIntrinsicCandidate 1593 public final Object getObjectOpaque(Object o, long offset) { 1594 return getObjectVolatile(o, offset); 1595 } 1596 1597 /** Opaque version of {@link #getBooleanVolatile(Object, long)} */ 1598 @HotSpotIntrinsicCandidate 1599 public final boolean getBooleanOpaque(Object o, long offset) { 1600 return getBooleanVolatile(o, offset); 1601 } 1602 1603 /** Opaque version of {@link #getByteVolatile(Object, long)} */ 1604 @HotSpotIntrinsicCandidate 1605 public final byte getByteOpaque(Object o, long offset) { 1606 return getByteVolatile(o, offset); 1607 } 1608 1609 /** Opaque version of {@link #getShortVolatile(Object, long)} */ 1610 @HotSpotIntrinsicCandidate 1611 public final short getShortOpaque(Object o, long offset) { 1612 return getShortVolatile(o, offset); 1613 } 1614 1615 /** Opaque version of {@link #getCharVolatile(Object, long)} */ 1616 @HotSpotIntrinsicCandidate 1617 public final char getCharOpaque(Object o, long offset) { 1618 return getCharVolatile(o, offset); 1619 } 1620 1621 /** Opaque version of {@link #getIntVolatile(Object, long)} */ 1622 @HotSpotIntrinsicCandidate 1623 public final int getIntOpaque(Object o, long offset) { 1624 return getIntVolatile(o, offset); 1625 } 1626 1627 /** Opaque version of {@link #getFloatVolatile(Object, long)} */ 1628 @HotSpotIntrinsicCandidate 1629 public final float getFloatOpaque(Object o, long offset) { 1630 return getFloatVolatile(o, offset); 1631 } 1632 1633 /** Opaque version of {@link #getLongVolatile(Object, long)} */ 1634 @HotSpotIntrinsicCandidate 1635 public final long getLongOpaque(Object o, long offset) { 1636 return getLongVolatile(o, offset); 1637 } 1638 1639 /** Opaque version of {@link #getDoubleVolatile(Object, long)} */ 1640 @HotSpotIntrinsicCandidate 1641 public final double getDoubleOpaque(Object o, long offset) { 1642 return getDoubleVolatile(o, offset); 1643 } 1644 1645 /** Opaque version of {@link #putObjectVolatile(Object, long, Object)} */ 1646 @HotSpotIntrinsicCandidate 1647 public final void putObjectOpaque(Object o, long offset, Object x) { 1648 putObjectVolatile(o, offset, x); 1649 } 1650 1651 /** Opaque version of {@link #putBooleanVolatile(Object, long, boolean)} */ 1652 @HotSpotIntrinsicCandidate 1653 public final void putBooleanOpaque(Object o, long offset, boolean x) { 1654 putBooleanVolatile(o, offset, x); 1655 } 1656 1657 /** Opaque version of {@link #putByteVolatile(Object, long, byte)} */ 1658 @HotSpotIntrinsicCandidate 1659 public final void putByteOpaque(Object o, long offset, byte x) { 1660 putByteVolatile(o, offset, x); 1661 } 1662 1663 /** Opaque version of {@link #putShortVolatile(Object, long, short)} */ 1664 @HotSpotIntrinsicCandidate 1665 public final void putShortOpaque(Object o, long offset, short x) { 1666 putShortVolatile(o, offset, x); 1667 } 1668 1669 /** Opaque version of {@link #putCharVolatile(Object, long, char)} */ 1670 @HotSpotIntrinsicCandidate 1671 public final void putCharOpaque(Object o, long offset, char x) { 1672 putCharVolatile(o, offset, x); 1673 } 1674 1675 /** Opaque version of {@link #putIntVolatile(Object, long, int)} */ 1676 @HotSpotIntrinsicCandidate 1677 public final void putIntOpaque(Object o, long offset, int x) { 1678 putIntVolatile(o, offset, x); 1679 } 1680 1681 /** Opaque version of {@link #putFloatVolatile(Object, long, float)} */ 1682 @HotSpotIntrinsicCandidate 1683 public final void putFloatOpaque(Object o, long offset, float x) { 1684 putFloatVolatile(o, offset, x); 1685 } 1686 1687 /** Opaque version of {@link #putLongVolatile(Object, long, long)} */ 1688 @HotSpotIntrinsicCandidate 1689 public final void putLongOpaque(Object o, long offset, long x) { 1690 putLongVolatile(o, offset, x); 1691 } 1692 1693 /** Opaque version of {@link #putDoubleVolatile(Object, long, double)} */ 1694 @HotSpotIntrinsicCandidate 1695 public final void putDoubleOpaque(Object o, long offset, double x) { 1696 putDoubleVolatile(o, offset, x); 1697 } 1698 1699 /** 1700 * Unblocks the given thread blocked on {@code park}, or, if it is 1701 * not blocked, causes the subsequent call to {@code park} not to 1702 * block. Note: this operation is "unsafe" solely because the 1703 * caller must somehow ensure that the thread has not been 1704 * destroyed. Nothing special is usually required to ensure this 1705 * when called from Java (in which there will ordinarily be a live 1706 * reference to the thread) but this is not nearly-automatically 1707 * so when calling from native code. 1708 * 1709 * @param thread the thread to unpark. 1710 */ 1711 @HotSpotIntrinsicCandidate 1712 public native void unpark(Object thread); 1713 1714 /** 1715 * Blocks current thread, returning when a balancing 1716 * {@code unpark} occurs, or a balancing {@code unpark} has 1717 * already occurred, or the thread is interrupted, or, if not 1718 * absolute and time is not zero, the given time nanoseconds have 1719 * elapsed, or if absolute, the given deadline in milliseconds 1720 * since Epoch has passed, or spuriously (i.e., returning for no 1721 * "reason"). Note: This operation is in the Unsafe class only 1722 * because {@code unpark} is, so it would be strange to place it 1723 * elsewhere. 1724 */ 1725 @HotSpotIntrinsicCandidate 1726 public native void park(boolean isAbsolute, long time); 1727 1728 /** 1729 * Gets the load average in the system run queue assigned 1730 * to the available processors averaged over various periods of time. 1731 * This method retrieves the given {@code nelem} samples and 1732 * assigns to the elements of the given {@code loadavg} array. 1733 * The system imposes a maximum of 3 samples, representing 1734 * averages over the last 1, 5, and 15 minutes, respectively. 1735 * 1736 * @param loadavg an array of double of size nelems 1737 * @param nelems the number of samples to be retrieved and 1738 * must be 1 to 3. 1739 * 1740 * @return the number of samples actually retrieved; or -1 1741 * if the load average is unobtainable. 1742 */ 1743 public int getLoadAverage(double[] loadavg, int nelems) { 1744 if (nelems < 0 || nelems > 3 || nelems > loadavg.length) { 1745 throw new ArrayIndexOutOfBoundsException(); 1746 } 1747 1748 return getLoadAverage0(loadavg, nelems); 1749 } 1750 1751 // The following contain CAS-based Java implementations used on 1752 // platforms not supporting native instructions 1753 1754 /** 1755 * Atomically adds the given value to the current value of a field 1756 * or array element within the given object {@code o} 1757 * at the given {@code offset}. 1758 * 1759 * @param o object/array to update the field/element in 1760 * @param offset field/element offset 1761 * @param delta the value to add 1762 * @return the previous value 1763 * @since 1.8 1764 */ 1765 @HotSpotIntrinsicCandidate 1766 public final int getAndAddInt(Object o, long offset, int delta) { 1767 int v; 1768 do { 1769 v = getIntVolatile(o, offset); 1770 } while (!compareAndSwapInt(o, offset, v, v + delta)); 1771 return v; 1772 } 1773 1774 /** 1775 * Atomically adds the given value to the current value of a field 1776 * or array element within the given object {@code o} 1777 * at the given {@code offset}. 1778 * 1779 * @param o object/array to update the field/element in 1780 * @param offset field/element offset 1781 * @param delta the value to add 1782 * @return the previous value 1783 * @since 1.8 1784 */ 1785 @HotSpotIntrinsicCandidate 1786 public final long getAndAddLong(Object o, long offset, long delta) { 1787 long v; 1788 do { 1789 v = getLongVolatile(o, offset); 1790 } while (!compareAndSwapLong(o, offset, v, v + delta)); 1791 return v; 1792 } 1793 1794 /** 1795 * Atomically exchanges the given value with the current value of 1796 * a field or array element within the given object {@code o} 1797 * at the given {@code offset}. 1798 * 1799 * @param o object/array to update the field/element in 1800 * @param offset field/element offset 1801 * @param newValue new value 1802 * @return the previous value 1803 * @since 1.8 1804 */ 1805 @HotSpotIntrinsicCandidate 1806 public final int getAndSetInt(Object o, long offset, int newValue) { 1807 int v; 1808 do { 1809 v = getIntVolatile(o, offset); 1810 } while (!compareAndSwapInt(o, offset, v, newValue)); 1811 return v; 1812 } 1813 1814 /** 1815 * Atomically exchanges the given value with the current value of 1816 * a field or array element within the given object {@code o} 1817 * at the given {@code offset}. 1818 * 1819 * @param o object/array to update the field/element in 1820 * @param offset field/element offset 1821 * @param newValue new value 1822 * @return the previous value 1823 * @since 1.8 1824 */ 1825 @HotSpotIntrinsicCandidate 1826 public final long getAndSetLong(Object o, long offset, long newValue) { 1827 long v; 1828 do { 1829 v = getLongVolatile(o, offset); 1830 } while (!compareAndSwapLong(o, offset, v, newValue)); 1831 return v; 1832 } 1833 1834 /** 1835 * Atomically exchanges the given reference value with the current 1836 * reference value of a field or array element within the given 1837 * object {@code o} at the given {@code offset}. 1838 * 1839 * @param o object/array to update the field/element in 1840 * @param offset field/element offset 1841 * @param newValue new value 1842 * @return the previous value 1843 * @since 1.8 1844 */ 1845 @HotSpotIntrinsicCandidate 1846 public final Object getAndSetObject(Object o, long offset, Object newValue) { 1847 Object v; 1848 do { 1849 v = getObjectVolatile(o, offset); 1850 } while (!compareAndSwapObject(o, offset, v, newValue)); 1851 return v; 1852 } 1853 1854 1855 /** 1856 * Ensures that loads before the fence will not be reordered with loads and 1857 * stores after the fence; a "LoadLoad plus LoadStore barrier". 1858 * 1859 * Corresponds to C11 atomic_thread_fence(memory_order_acquire) 1860 * (an "acquire fence"). 1861 * 1862 * A pure LoadLoad fence is not provided, since the addition of LoadStore 1863 * is almost always desired, and most current hardware instructions that 1864 * provide a LoadLoad barrier also provide a LoadStore barrier for free. 1865 * @since 1.8 1866 */ 1867 @HotSpotIntrinsicCandidate 1868 public native void loadFence(); 1869 1870 /** 1871 * Ensures that loads and stores before the fence will not be reordered with 1872 * stores after the fence; a "StoreStore plus LoadStore barrier". 1873 * 1874 * Corresponds to C11 atomic_thread_fence(memory_order_release) 1875 * (a "release fence"). 1876 * 1877 * A pure StoreStore fence is not provided, since the addition of LoadStore 1878 * is almost always desired, and most current hardware instructions that 1879 * provide a StoreStore barrier also provide a LoadStore barrier for free. 1880 * @since 1.8 1881 */ 1882 @HotSpotIntrinsicCandidate 1883 public native void storeFence(); 1884 1885 /** 1886 * Ensures that loads and stores before the fence will not be reordered 1887 * with loads and stores after the fence. Implies the effects of both 1888 * loadFence() and storeFence(), and in addition, the effect of a StoreLoad 1889 * barrier. 1890 * 1891 * Corresponds to C11 atomic_thread_fence(memory_order_seq_cst). 1892 * @since 1.8 1893 */ 1894 @HotSpotIntrinsicCandidate 1895 public native void fullFence(); 1896 1897 /** 1898 * Ensures that loads before the fence will not be reordered with 1899 * loads after the fence. 1900 */ 1901 public final void loadLoadFence() { 1902 loadFence(); 1903 } 1904 1905 /** 1906 * Ensures that stores before the fence will not be reordered with 1907 * stores after the fence. 1908 */ 1909 public final void storeStoreFence() { 1910 storeFence(); 1911 } 1912 1913 1914 /** 1915 * Throws IllegalAccessError; for use by the VM for access control 1916 * error support. 1917 * @since 1.8 1918 */ 1919 private static void throwIllegalAccessError() { 1920 throw new IllegalAccessError(); 1921 } 1922 1923 /** 1924 * @return Returns true if the native byte ordering of this 1925 * platform is big-endian, false if it is little-endian. 1926 */ 1927 public final boolean isBigEndian() { return BE; } 1928 1929 /** 1930 * @return Returns true if this platform is capable of performing 1931 * accesses at addresses which are not aligned for the type of the 1932 * primitive type being accessed, false otherwise. 1933 */ 1934 public final boolean unalignedAccess() { return unalignedAccess; } 1935 1936 /** 1937 * Fetches a value at some byte offset into a given Java object. 1938 * More specifically, fetches a value within the given object 1939 * <code>o</code> at the given offset, or (if <code>o</code> is 1940 * null) from the memory address whose numerical value is the 1941 * given offset. <p> 1942 * 1943 * The specification of this method is the same as {@link 1944 * #getLong(Object, long)} except that the offset does not need to 1945 * have been obtained from {@link #objectFieldOffset} on the 1946 * {@link java.lang.reflect.Field} of some Java field. The value 1947 * in memory is raw data, and need not correspond to any Java 1948 * variable. Unless <code>o</code> is null, the value accessed 1949 * must be entirely within the allocated object. The endianness 1950 * of the value in memory is the endianness of the native platform. 1951 * 1952 * <p> The read will be atomic with respect to the largest power 1953 * of two that divides the GCD of the offset and the storage size. 1954 * For example, getLongUnaligned will make atomic reads of 2-, 4-, 1955 * or 8-byte storage units if the offset is zero mod 2, 4, or 8, 1956 * respectively. There are no other guarantees of atomicity. 1957 * <p> 1958 * 8-byte atomicity is only guaranteed on platforms on which 1959 * support atomic accesses to longs. 1960 * 1961 * @param o Java heap object in which the value resides, if any, else 1962 * null 1963 * @param offset The offset in bytes from the start of the object 1964 * @return the value fetched from the indicated object 1965 * @throws RuntimeException No defined exceptions are thrown, not even 1966 * {@link NullPointerException} 1967 * @since 9 1968 */ 1969 @HotSpotIntrinsicCandidate 1970 public final long getLongUnaligned(Object o, long offset) { 1971 if ((offset & 7) == 0) { 1972 return getLong(o, offset); 1973 } else if ((offset & 3) == 0) { 1974 return makeLong(getInt(o, offset), 1975 getInt(o, offset + 4)); 1976 } else if ((offset & 1) == 0) { 1977 return makeLong(getShort(o, offset), 1978 getShort(o, offset + 2), 1979 getShort(o, offset + 4), 1980 getShort(o, offset + 6)); 1981 } else { 1982 return makeLong(getByte(o, offset), 1983 getByte(o, offset + 1), 1984 getByte(o, offset + 2), 1985 getByte(o, offset + 3), 1986 getByte(o, offset + 4), 1987 getByte(o, offset + 5), 1988 getByte(o, offset + 6), 1989 getByte(o, offset + 7)); 1990 } 1991 } 1992 /** 1993 * As {@link #getLongUnaligned(Object, long)} but with an 1994 * additional argument which specifies the endianness of the value 1995 * as stored in memory. 1996 * 1997 * @param o Java heap object in which the variable resides 1998 * @param offset The offset in bytes from the start of the object 1999 * @param bigEndian The endianness of the value 2000 * @return the value fetched from the indicated object 2001 * @since 9 2002 */ 2003 public final long getLongUnaligned(Object o, long offset, boolean bigEndian) { 2004 return convEndian(bigEndian, getLongUnaligned(o, offset)); 2005 } 2006 2007 /** @see #getLongUnaligned(Object, long) */ 2008 @HotSpotIntrinsicCandidate 2009 public final int getIntUnaligned(Object o, long offset) { 2010 if ((offset & 3) == 0) { 2011 return getInt(o, offset); 2012 } else if ((offset & 1) == 0) { 2013 return makeInt(getShort(o, offset), 2014 getShort(o, offset + 2)); 2015 } else { 2016 return makeInt(getByte(o, offset), 2017 getByte(o, offset + 1), 2018 getByte(o, offset + 2), 2019 getByte(o, offset + 3)); 2020 } 2021 } 2022 /** @see #getLongUnaligned(Object, long, boolean) */ 2023 public final int getIntUnaligned(Object o, long offset, boolean bigEndian) { 2024 return convEndian(bigEndian, getIntUnaligned(o, offset)); 2025 } 2026 2027 /** @see #getLongUnaligned(Object, long) */ 2028 @HotSpotIntrinsicCandidate 2029 public final short getShortUnaligned(Object o, long offset) { 2030 if ((offset & 1) == 0) { 2031 return getShort(o, offset); 2032 } else { 2033 return makeShort(getByte(o, offset), 2034 getByte(o, offset + 1)); 2035 } 2036 } 2037 /** @see #getLongUnaligned(Object, long, boolean) */ 2038 public final short getShortUnaligned(Object o, long offset, boolean bigEndian) { 2039 return convEndian(bigEndian, getShortUnaligned(o, offset)); 2040 } 2041 2042 /** @see #getLongUnaligned(Object, long) */ 2043 @HotSpotIntrinsicCandidate 2044 public final char getCharUnaligned(Object o, long offset) { 2045 if ((offset & 1) == 0) { 2046 return getChar(o, offset); 2047 } else { 2048 return (char)makeShort(getByte(o, offset), 2049 getByte(o, offset + 1)); 2050 } 2051 } 2052 2053 /** @see #getLongUnaligned(Object, long, boolean) */ 2054 public final char getCharUnaligned(Object o, long offset, boolean bigEndian) { 2055 return convEndian(bigEndian, getCharUnaligned(o, offset)); 2056 } 2057 2058 /** 2059 * Stores a value at some byte offset into a given Java object. 2060 * <p> 2061 * The specification of this method is the same as {@link 2062 * #getLong(Object, long)} except that the offset does not need to 2063 * have been obtained from {@link #objectFieldOffset} on the 2064 * {@link java.lang.reflect.Field} of some Java field. The value 2065 * in memory is raw data, and need not correspond to any Java 2066 * variable. The endianness of the value in memory is the 2067 * endianness of the native platform. 2068 * <p> 2069 * The write will be atomic with respect to the largest power of 2070 * two that divides the GCD of the offset and the storage size. 2071 * For example, putLongUnaligned will make atomic writes of 2-, 4-, 2072 * or 8-byte storage units if the offset is zero mod 2, 4, or 8, 2073 * respectively. There are no other guarantees of atomicity. 2074 * <p> 2075 * 8-byte atomicity is only guaranteed on platforms on which 2076 * support atomic accesses to longs. 2077 * 2078 * @param o Java heap object in which the value resides, if any, else 2079 * null 2080 * @param offset The offset in bytes from the start of the object 2081 * @param x the value to store 2082 * @throws RuntimeException No defined exceptions are thrown, not even 2083 * {@link NullPointerException} 2084 * @since 9 2085 */ 2086 @HotSpotIntrinsicCandidate 2087 public final void putLongUnaligned(Object o, long offset, long x) { 2088 if ((offset & 7) == 0) { 2089 putLong(o, offset, x); 2090 } else if ((offset & 3) == 0) { 2091 putLongParts(o, offset, 2092 (int)(x >> 0), 2093 (int)(x >>> 32)); 2094 } else if ((offset & 1) == 0) { 2095 putLongParts(o, offset, 2096 (short)(x >>> 0), 2097 (short)(x >>> 16), 2098 (short)(x >>> 32), 2099 (short)(x >>> 48)); 2100 } else { 2101 putLongParts(o, offset, 2102 (byte)(x >>> 0), 2103 (byte)(x >>> 8), 2104 (byte)(x >>> 16), 2105 (byte)(x >>> 24), 2106 (byte)(x >>> 32), 2107 (byte)(x >>> 40), 2108 (byte)(x >>> 48), 2109 (byte)(x >>> 56)); 2110 } 2111 } 2112 2113 /** 2114 * As {@link #putLongUnaligned(Object, long, long)} but with an additional 2115 * argument which specifies the endianness of the value as stored in memory. 2116 * @param o Java heap object in which the value resides 2117 * @param offset The offset in bytes from the start of the object 2118 * @param x the value to store 2119 * @param bigEndian The endianness of the value 2120 * @throws RuntimeException No defined exceptions are thrown, not even 2121 * {@link NullPointerException} 2122 * @since 9 2123 */ 2124 public final void putLongUnaligned(Object o, long offset, long x, boolean bigEndian) { 2125 putLongUnaligned(o, offset, convEndian(bigEndian, x)); 2126 } 2127 2128 /** @see #putLongUnaligned(Object, long, long) */ 2129 @HotSpotIntrinsicCandidate 2130 public final void putIntUnaligned(Object o, long offset, int x) { 2131 if ((offset & 3) == 0) { 2132 putInt(o, offset, x); 2133 } else if ((offset & 1) == 0) { 2134 putIntParts(o, offset, 2135 (short)(x >> 0), 2136 (short)(x >>> 16)); 2137 } else { 2138 putIntParts(o, offset, 2139 (byte)(x >>> 0), 2140 (byte)(x >>> 8), 2141 (byte)(x >>> 16), 2142 (byte)(x >>> 24)); 2143 } 2144 } 2145 /** @see #putLongUnaligned(Object, long, long, boolean) */ 2146 public final void putIntUnaligned(Object o, long offset, int x, boolean bigEndian) { 2147 putIntUnaligned(o, offset, convEndian(bigEndian, x)); 2148 } 2149 2150 /** @see #putLongUnaligned(Object, long, long) */ 2151 @HotSpotIntrinsicCandidate 2152 public final void putShortUnaligned(Object o, long offset, short x) { 2153 if ((offset & 1) == 0) { 2154 putShort(o, offset, x); 2155 } else { 2156 putShortParts(o, offset, 2157 (byte)(x >>> 0), 2158 (byte)(x >>> 8)); 2159 } 2160 } 2161 /** @see #putLongUnaligned(Object, long, long, boolean) */ 2162 public final void putShortUnaligned(Object o, long offset, short x, boolean bigEndian) { 2163 putShortUnaligned(o, offset, convEndian(bigEndian, x)); 2164 } 2165 2166 /** @see #putLongUnaligned(Object, long, long) */ 2167 @HotSpotIntrinsicCandidate 2168 public final void putCharUnaligned(Object o, long offset, char x) { 2169 putShortUnaligned(o, offset, (short)x); 2170 } 2171 /** @see #putLongUnaligned(Object, long, long, boolean) */ 2172 public final void putCharUnaligned(Object o, long offset, char x, boolean bigEndian) { 2173 putCharUnaligned(o, offset, convEndian(bigEndian, x)); 2174 } 2175 2176 // JVM interface methods 2177 // BE is true iff the native endianness of this platform is big. 2178 private static final boolean BE = theUnsafe.isBigEndian0(); 2179 2180 // unalignedAccess is true iff this platform can perform unaligned accesses. 2181 private static final boolean unalignedAccess = theUnsafe.unalignedAccess0(); 2182 2183 private static int pickPos(int top, int pos) { return BE ? top - pos : pos; } 2184 2185 // These methods construct integers from bytes. The byte ordering 2186 // is the native endianness of this platform. 2187 private static long makeLong(byte i0, byte i1, byte i2, byte i3, byte i4, byte i5, byte i6, byte i7) { 2188 return ((toUnsignedLong(i0) << pickPos(56, 0)) 2189 | (toUnsignedLong(i1) << pickPos(56, 8)) 2190 | (toUnsignedLong(i2) << pickPos(56, 16)) 2191 | (toUnsignedLong(i3) << pickPos(56, 24)) 2192 | (toUnsignedLong(i4) << pickPos(56, 32)) 2193 | (toUnsignedLong(i5) << pickPos(56, 40)) 2194 | (toUnsignedLong(i6) << pickPos(56, 48)) 2195 | (toUnsignedLong(i7) << pickPos(56, 56))); 2196 } 2197 private static long makeLong(short i0, short i1, short i2, short i3) { 2198 return ((toUnsignedLong(i0) << pickPos(48, 0)) 2199 | (toUnsignedLong(i1) << pickPos(48, 16)) 2200 | (toUnsignedLong(i2) << pickPos(48, 32)) 2201 | (toUnsignedLong(i3) << pickPos(48, 48))); 2202 } 2203 private static long makeLong(int i0, int i1) { 2204 return (toUnsignedLong(i0) << pickPos(32, 0)) 2205 | (toUnsignedLong(i1) << pickPos(32, 32)); 2206 } 2207 private static int makeInt(short i0, short i1) { 2208 return (toUnsignedInt(i0) << pickPos(16, 0)) 2209 | (toUnsignedInt(i1) << pickPos(16, 16)); 2210 } 2211 private static int makeInt(byte i0, byte i1, byte i2, byte i3) { 2212 return ((toUnsignedInt(i0) << pickPos(24, 0)) 2213 | (toUnsignedInt(i1) << pickPos(24, 8)) 2214 | (toUnsignedInt(i2) << pickPos(24, 16)) 2215 | (toUnsignedInt(i3) << pickPos(24, 24))); 2216 } 2217 private static short makeShort(byte i0, byte i1) { 2218 return (short)((toUnsignedInt(i0) << pickPos(8, 0)) 2219 | (toUnsignedInt(i1) << pickPos(8, 8))); 2220 } 2221 2222 private static byte pick(byte le, byte be) { return BE ? be : le; } 2223 private static short pick(short le, short be) { return BE ? be : le; } 2224 private static int pick(int le, int be) { return BE ? be : le; } 2225 2226 // These methods write integers to memory from smaller parts 2227 // provided by their caller. The ordering in which these parts 2228 // are written is the native endianness of this platform. 2229 private void putLongParts(Object o, long offset, byte i0, byte i1, byte i2, byte i3, byte i4, byte i5, byte i6, byte i7) { 2230 putByte(o, offset + 0, pick(i0, i7)); 2231 putByte(o, offset + 1, pick(i1, i6)); 2232 putByte(o, offset + 2, pick(i2, i5)); 2233 putByte(o, offset + 3, pick(i3, i4)); 2234 putByte(o, offset + 4, pick(i4, i3)); 2235 putByte(o, offset + 5, pick(i5, i2)); 2236 putByte(o, offset + 6, pick(i6, i1)); 2237 putByte(o, offset + 7, pick(i7, i0)); 2238 } 2239 private void putLongParts(Object o, long offset, short i0, short i1, short i2, short i3) { 2240 putShort(o, offset + 0, pick(i0, i3)); 2241 putShort(o, offset + 2, pick(i1, i2)); 2242 putShort(o, offset + 4, pick(i2, i1)); 2243 putShort(o, offset + 6, pick(i3, i0)); 2244 } 2245 private void putLongParts(Object o, long offset, int i0, int i1) { 2246 putInt(o, offset + 0, pick(i0, i1)); 2247 putInt(o, offset + 4, pick(i1, i0)); 2248 } 2249 private void putIntParts(Object o, long offset, short i0, short i1) { 2250 putShort(o, offset + 0, pick(i0, i1)); 2251 putShort(o, offset + 2, pick(i1, i0)); 2252 } 2253 private void putIntParts(Object o, long offset, byte i0, byte i1, byte i2, byte i3) { 2254 putByte(o, offset + 0, pick(i0, i3)); 2255 putByte(o, offset + 1, pick(i1, i2)); 2256 putByte(o, offset + 2, pick(i2, i1)); 2257 putByte(o, offset + 3, pick(i3, i0)); 2258 } 2259 private void putShortParts(Object o, long offset, byte i0, byte i1) { 2260 putByte(o, offset + 0, pick(i0, i1)); 2261 putByte(o, offset + 1, pick(i1, i0)); 2262 } 2263 2264 // Zero-extend an integer 2265 private static int toUnsignedInt(byte n) { return n & 0xff; } 2266 private static int toUnsignedInt(short n) { return n & 0xffff; } 2267 private static long toUnsignedLong(byte n) { return n & 0xffl; } 2268 private static long toUnsignedLong(short n) { return n & 0xffffl; } 2269 private static long toUnsignedLong(int n) { return n & 0xffffffffl; } 2270 2271 // Maybe byte-reverse an integer 2272 private static char convEndian(boolean big, char n) { return big == BE ? n : Character.reverseBytes(n); } 2273 private static short convEndian(boolean big, short n) { return big == BE ? n : Short.reverseBytes(n) ; } 2274 private static int convEndian(boolean big, int n) { return big == BE ? n : Integer.reverseBytes(n) ; } 2275 private static long convEndian(boolean big, long n) { return big == BE ? n : Long.reverseBytes(n) ; } 2276 2277 2278 2279 private native long allocateMemory0(long bytes); 2280 private native long reallocateMemory0(long address, long bytes); 2281 private native void freeMemory0(long address); 2282 private native void setMemory0(Object o, long offset, long bytes, byte value); 2283 @HotSpotIntrinsicCandidate 2284 private native void copyMemory0(Object srcBase, long srcOffset, Object destBase, long destOffset, long bytes); 2285 private native void copySwapMemory0(Object srcBase, long srcOffset, Object destBase, long destOffset, long bytes, long elemSize); 2286 private native long objectFieldOffset0(Field f); 2287 private native long staticFieldOffset0(Field f); 2288 private native Object staticFieldBase0(Field f); 2289 private native boolean shouldBeInitialized0(Class<?> c); 2290 private native void ensureClassInitialized0(Class<?> c); 2291 private native int arrayBaseOffset0(Class<?> arrayClass); 2292 private native int arrayIndexScale0(Class<?> arrayClass); 2293 private native int addressSize0(); 2294 private native Class<?> defineAnonymousClass0(Class<?> hostClass, byte[] data, Object[] cpPatches); 2295 private native int getLoadAverage0(double[] loadavg, int nelems); 2296 private native boolean unalignedAccess0(); 2297 private native boolean isBigEndian0(); 2298 }