J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 3 | * |
| 4 | * This code is free software; you can redistribute it and/or modify it |
| 5 | * under the terms of the GNU General Public License version 2 only, as |
| 6 | * published by the Free Software Foundation. Sun designates this |
| 7 | * particular file as subject to the "Classpath" exception as provided |
| 8 | * by Sun in the LICENSE file that accompanied this code. |
| 9 | * |
| 10 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| 11 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 12 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 13 | * version 2 for more details (a copy is included in the LICENSE file that |
| 14 | * accompanied this code). |
| 15 | * |
| 16 | * You should have received a copy of the GNU General Public License version |
| 17 | * 2 along with this work; if not, write to the Free Software Foundation, |
| 18 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 19 | * |
| 20 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 21 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 22 | * have any questions. |
| 23 | */ |
| 24 | |
| 25 | /* |
| 26 | * This file is available under and governed by the GNU General Public |
| 27 | * License version 2 only, as published by the Free Software Foundation. |
| 28 | * However, the following notice accompanied the original version of this |
| 29 | * file: |
| 30 | * |
| 31 | * Written by Doug Lea with assistance from members of JCP JSR-166 |
| 32 | * Expert Group and released to the public domain, as explained at |
| 33 | * http://creativecommons.org/licenses/publicdomain |
| 34 | */ |
| 35 | |
| 36 | package java.util.concurrent.atomic; |
| 37 | import sun.misc.Unsafe; |
| 38 | import java.lang.reflect.*; |
| 39 | |
| 40 | /** |
| 41 | * A reflection-based utility that enables atomic updates to |
| 42 | * designated {@code volatile long} fields of designated classes. |
| 43 | * This class is designed for use in atomic data structures in which |
| 44 | * several fields of the same node are independently subject to atomic |
| 45 | * updates. |
| 46 | * |
| 47 | * <p>Note that the guarantees of the {@code compareAndSet} |
| 48 | * method in this class are weaker than in other atomic classes. |
| 49 | * Because this class cannot ensure that all uses of the field |
| 50 | * are appropriate for purposes of atomic access, it can |
| 51 | * guarantee atomicity only with respect to other invocations of |
| 52 | * {@code compareAndSet} and {@code set} on the same updater. |
| 53 | * |
| 54 | * @since 1.5 |
| 55 | * @author Doug Lea |
| 56 | * @param <T> The type of the object holding the updatable field |
| 57 | */ |
| 58 | public abstract class AtomicLongFieldUpdater<T> { |
| 59 | /** |
| 60 | * Creates and returns an updater for objects with the given field. |
| 61 | * The Class argument is needed to check that reflective types and |
| 62 | * generic types match. |
| 63 | * |
| 64 | * @param tclass the class of the objects holding the field |
| 65 | * @param fieldName the name of the field to be updated. |
| 66 | * @return the updater |
| 67 | * @throws IllegalArgumentException if the field is not a |
| 68 | * volatile long type. |
| 69 | * @throws RuntimeException with a nested reflection-based |
| 70 | * exception if the class does not hold field or is the wrong type. |
| 71 | */ |
| 72 | public static <U> AtomicLongFieldUpdater<U> newUpdater(Class<U> tclass, String fieldName) { |
| 73 | if (AtomicLong.VM_SUPPORTS_LONG_CAS) |
| 74 | return new CASUpdater<U>(tclass, fieldName); |
| 75 | else |
| 76 | return new LockedUpdater<U>(tclass, fieldName); |
| 77 | } |
| 78 | |
| 79 | /** |
| 80 | * Protected do-nothing constructor for use by subclasses. |
| 81 | */ |
| 82 | protected AtomicLongFieldUpdater() { |
| 83 | } |
| 84 | |
| 85 | /** |
| 86 | * Atomically sets the field of the given object managed by this updater |
| 87 | * to the given updated value if the current value {@code ==} the |
| 88 | * expected value. This method is guaranteed to be atomic with respect to |
| 89 | * other calls to {@code compareAndSet} and {@code set}, but not |
| 90 | * necessarily with respect to other changes in the field. |
| 91 | * |
| 92 | * @param obj An object whose field to conditionally set |
| 93 | * @param expect the expected value |
| 94 | * @param update the new value |
| 95 | * @return true if successful. |
| 96 | * @throws ClassCastException if {@code obj} is not an instance |
| 97 | * of the class possessing the field established in the constructor. |
| 98 | */ |
| 99 | public abstract boolean compareAndSet(T obj, long expect, long update); |
| 100 | |
| 101 | /** |
| 102 | * Atomically sets the field of the given object managed by this updater |
| 103 | * to the given updated value if the current value {@code ==} the |
| 104 | * expected value. This method is guaranteed to be atomic with respect to |
| 105 | * other calls to {@code compareAndSet} and {@code set}, but not |
| 106 | * necessarily with respect to other changes in the field. |
| 107 | * |
| 108 | * <p>May <a href="package-summary.html#Spurious">fail spuriously</a> |
| 109 | * and does not provide ordering guarantees, so is only rarely an |
| 110 | * appropriate alternative to {@code compareAndSet}. |
| 111 | * |
| 112 | * @param obj An object whose field to conditionally set |
| 113 | * @param expect the expected value |
| 114 | * @param update the new value |
| 115 | * @return true if successful. |
| 116 | * @throws ClassCastException if {@code obj} is not an instance |
| 117 | * of the class possessing the field established in the constructor. |
| 118 | */ |
| 119 | public abstract boolean weakCompareAndSet(T obj, long expect, long update); |
| 120 | |
| 121 | /** |
| 122 | * Sets the field of the given object managed by this updater to the |
| 123 | * given updated value. This operation is guaranteed to act as a volatile |
| 124 | * store with respect to subsequent invocations of {@code compareAndSet}. |
| 125 | * |
| 126 | * @param obj An object whose field to set |
| 127 | * @param newValue the new value |
| 128 | */ |
| 129 | public abstract void set(T obj, long newValue); |
| 130 | |
| 131 | /** |
| 132 | * Eventually sets the field of the given object managed by this |
| 133 | * updater to the given updated value. |
| 134 | * |
| 135 | * @param obj An object whose field to set |
| 136 | * @param newValue the new value |
| 137 | * @since 1.6 |
| 138 | */ |
| 139 | public abstract void lazySet(T obj, long newValue); |
| 140 | |
| 141 | /** |
| 142 | * Gets the current value held in the field of the given object managed |
| 143 | * by this updater. |
| 144 | * |
| 145 | * @param obj An object whose field to get |
| 146 | * @return the current value |
| 147 | */ |
| 148 | public abstract long get(T obj); |
| 149 | |
| 150 | /** |
| 151 | * Atomically sets the field of the given object managed by this updater |
| 152 | * to the given value and returns the old value. |
| 153 | * |
| 154 | * @param obj An object whose field to get and set |
| 155 | * @param newValue the new value |
| 156 | * @return the previous value |
| 157 | */ |
| 158 | public long getAndSet(T obj, long newValue) { |
| 159 | for (;;) { |
| 160 | long current = get(obj); |
| 161 | if (compareAndSet(obj, current, newValue)) |
| 162 | return current; |
| 163 | } |
| 164 | } |
| 165 | |
| 166 | /** |
| 167 | * Atomically increments by one the current value of the field of the |
| 168 | * given object managed by this updater. |
| 169 | * |
| 170 | * @param obj An object whose field to get and set |
| 171 | * @return the previous value |
| 172 | */ |
| 173 | public long getAndIncrement(T obj) { |
| 174 | for (;;) { |
| 175 | long current = get(obj); |
| 176 | long next = current + 1; |
| 177 | if (compareAndSet(obj, current, next)) |
| 178 | return current; |
| 179 | } |
| 180 | } |
| 181 | |
| 182 | /** |
| 183 | * Atomically decrements by one the current value of the field of the |
| 184 | * given object managed by this updater. |
| 185 | * |
| 186 | * @param obj An object whose field to get and set |
| 187 | * @return the previous value |
| 188 | */ |
| 189 | public long getAndDecrement(T obj) { |
| 190 | for (;;) { |
| 191 | long current = get(obj); |
| 192 | long next = current - 1; |
| 193 | if (compareAndSet(obj, current, next)) |
| 194 | return current; |
| 195 | } |
| 196 | } |
| 197 | |
| 198 | /** |
| 199 | * Atomically adds the given value to the current value of the field of |
| 200 | * the given object managed by this updater. |
| 201 | * |
| 202 | * @param obj An object whose field to get and set |
| 203 | * @param delta the value to add |
| 204 | * @return the previous value |
| 205 | */ |
| 206 | public long getAndAdd(T obj, long delta) { |
| 207 | for (;;) { |
| 208 | long current = get(obj); |
| 209 | long next = current + delta; |
| 210 | if (compareAndSet(obj, current, next)) |
| 211 | return current; |
| 212 | } |
| 213 | } |
| 214 | |
| 215 | /** |
| 216 | * Atomically increments by one the current value of the field of the |
| 217 | * given object managed by this updater. |
| 218 | * |
| 219 | * @param obj An object whose field to get and set |
| 220 | * @return the updated value |
| 221 | */ |
| 222 | public long incrementAndGet(T obj) { |
| 223 | for (;;) { |
| 224 | long current = get(obj); |
| 225 | long next = current + 1; |
| 226 | if (compareAndSet(obj, current, next)) |
| 227 | return next; |
| 228 | } |
| 229 | } |
| 230 | |
| 231 | /** |
| 232 | * Atomically decrements by one the current value of the field of the |
| 233 | * given object managed by this updater. |
| 234 | * |
| 235 | * @param obj An object whose field to get and set |
| 236 | * @return the updated value |
| 237 | */ |
| 238 | public long decrementAndGet(T obj) { |
| 239 | for (;;) { |
| 240 | long current = get(obj); |
| 241 | long next = current - 1; |
| 242 | if (compareAndSet(obj, current, next)) |
| 243 | return next; |
| 244 | } |
| 245 | } |
| 246 | |
| 247 | /** |
| 248 | * Atomically adds the given value to the current value of the field of |
| 249 | * the given object managed by this updater. |
| 250 | * |
| 251 | * @param obj An object whose field to get and set |
| 252 | * @param delta the value to add |
| 253 | * @return the updated value |
| 254 | */ |
| 255 | public long addAndGet(T obj, long delta) { |
| 256 | for (;;) { |
| 257 | long current = get(obj); |
| 258 | long next = current + delta; |
| 259 | if (compareAndSet(obj, current, next)) |
| 260 | return next; |
| 261 | } |
| 262 | } |
| 263 | |
| 264 | private static class CASUpdater<T> extends AtomicLongFieldUpdater<T> { |
| 265 | private static final Unsafe unsafe = Unsafe.getUnsafe(); |
| 266 | private final long offset; |
| 267 | private final Class<T> tclass; |
| 268 | private final Class cclass; |
| 269 | |
| 270 | CASUpdater(Class<T> tclass, String fieldName) { |
| 271 | Field field = null; |
| 272 | Class caller = null; |
| 273 | int modifiers = 0; |
| 274 | try { |
| 275 | field = tclass.getDeclaredField(fieldName); |
| 276 | caller = sun.reflect.Reflection.getCallerClass(3); |
| 277 | modifiers = field.getModifiers(); |
| 278 | sun.reflect.misc.ReflectUtil.ensureMemberAccess( |
| 279 | caller, tclass, null, modifiers); |
| 280 | sun.reflect.misc.ReflectUtil.checkPackageAccess(tclass); |
| 281 | } catch(Exception ex) { |
| 282 | throw new RuntimeException(ex); |
| 283 | } |
| 284 | |
| 285 | Class fieldt = field.getType(); |
| 286 | if (fieldt != long.class) |
| 287 | throw new IllegalArgumentException("Must be long type"); |
| 288 | |
| 289 | if (!Modifier.isVolatile(modifiers)) |
| 290 | throw new IllegalArgumentException("Must be volatile type"); |
| 291 | |
| 292 | this.cclass = (Modifier.isProtected(modifiers) && |
| 293 | caller != tclass) ? caller : null; |
| 294 | this.tclass = tclass; |
| 295 | offset = unsafe.objectFieldOffset(field); |
| 296 | } |
| 297 | |
| 298 | private void fullCheck(T obj) { |
| 299 | if (!tclass.isInstance(obj)) |
| 300 | throw new ClassCastException(); |
| 301 | if (cclass != null) |
| 302 | ensureProtectedAccess(obj); |
| 303 | } |
| 304 | |
| 305 | public boolean compareAndSet(T obj, long expect, long update) { |
| 306 | if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); |
| 307 | return unsafe.compareAndSwapLong(obj, offset, expect, update); |
| 308 | } |
| 309 | |
| 310 | public boolean weakCompareAndSet(T obj, long expect, long update) { |
| 311 | if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); |
| 312 | return unsafe.compareAndSwapLong(obj, offset, expect, update); |
| 313 | } |
| 314 | |
| 315 | public void set(T obj, long newValue) { |
| 316 | if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); |
| 317 | unsafe.putLongVolatile(obj, offset, newValue); |
| 318 | } |
| 319 | |
| 320 | public void lazySet(T obj, long newValue) { |
| 321 | if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); |
| 322 | unsafe.putOrderedLong(obj, offset, newValue); |
| 323 | } |
| 324 | |
| 325 | public long get(T obj) { |
| 326 | if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); |
| 327 | return unsafe.getLongVolatile(obj, offset); |
| 328 | } |
| 329 | |
| 330 | private void ensureProtectedAccess(T obj) { |
| 331 | if (cclass.isInstance(obj)) { |
| 332 | return; |
| 333 | } |
| 334 | throw new RuntimeException ( |
| 335 | new IllegalAccessException("Class " + |
| 336 | cclass.getName() + |
| 337 | " can not access a protected member of class " + |
| 338 | tclass.getName() + |
| 339 | " using an instance of " + |
| 340 | obj.getClass().getName() |
| 341 | ) |
| 342 | ); |
| 343 | } |
| 344 | } |
| 345 | |
| 346 | |
| 347 | private static class LockedUpdater<T> extends AtomicLongFieldUpdater<T> { |
| 348 | private static final Unsafe unsafe = Unsafe.getUnsafe(); |
| 349 | private final long offset; |
| 350 | private final Class<T> tclass; |
| 351 | private final Class cclass; |
| 352 | |
| 353 | LockedUpdater(Class<T> tclass, String fieldName) { |
| 354 | Field field = null; |
| 355 | Class caller = null; |
| 356 | int modifiers = 0; |
| 357 | try { |
| 358 | field = tclass.getDeclaredField(fieldName); |
| 359 | caller = sun.reflect.Reflection.getCallerClass(3); |
| 360 | modifiers = field.getModifiers(); |
| 361 | sun.reflect.misc.ReflectUtil.ensureMemberAccess( |
| 362 | caller, tclass, null, modifiers); |
| 363 | sun.reflect.misc.ReflectUtil.checkPackageAccess(tclass); |
| 364 | } catch(Exception ex) { |
| 365 | throw new RuntimeException(ex); |
| 366 | } |
| 367 | |
| 368 | Class fieldt = field.getType(); |
| 369 | if (fieldt != long.class) |
| 370 | throw new IllegalArgumentException("Must be long type"); |
| 371 | |
| 372 | if (!Modifier.isVolatile(modifiers)) |
| 373 | throw new IllegalArgumentException("Must be volatile type"); |
| 374 | |
| 375 | this.cclass = (Modifier.isProtected(modifiers) && |
| 376 | caller != tclass) ? caller : null; |
| 377 | this.tclass = tclass; |
| 378 | offset = unsafe.objectFieldOffset(field); |
| 379 | } |
| 380 | |
| 381 | private void fullCheck(T obj) { |
| 382 | if (!tclass.isInstance(obj)) |
| 383 | throw new ClassCastException(); |
| 384 | if (cclass != null) |
| 385 | ensureProtectedAccess(obj); |
| 386 | } |
| 387 | |
| 388 | public boolean compareAndSet(T obj, long expect, long update) { |
| 389 | if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); |
| 390 | synchronized(this) { |
| 391 | long v = unsafe.getLong(obj, offset); |
| 392 | if (v != expect) |
| 393 | return false; |
| 394 | unsafe.putLong(obj, offset, update); |
| 395 | return true; |
| 396 | } |
| 397 | } |
| 398 | |
| 399 | public boolean weakCompareAndSet(T obj, long expect, long update) { |
| 400 | return compareAndSet(obj, expect, update); |
| 401 | } |
| 402 | |
| 403 | public void set(T obj, long newValue) { |
| 404 | if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); |
| 405 | synchronized(this) { |
| 406 | unsafe.putLong(obj, offset, newValue); |
| 407 | } |
| 408 | } |
| 409 | |
| 410 | public void lazySet(T obj, long newValue) { |
| 411 | set(obj, newValue); |
| 412 | } |
| 413 | |
| 414 | public long get(T obj) { |
| 415 | if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); |
| 416 | synchronized(this) { |
| 417 | return unsafe.getLong(obj, offset); |
| 418 | } |
| 419 | } |
| 420 | |
| 421 | private void ensureProtectedAccess(T obj) { |
| 422 | if (cclass.isInstance(obj)) { |
| 423 | return; |
| 424 | } |
| 425 | throw new RuntimeException ( |
| 426 | new IllegalAccessException("Class " + |
| 427 | cclass.getName() + |
| 428 | " can not access a protected member of class " + |
| 429 | tclass.getName() + |
| 430 | " using an instance of " + |
| 431 | obj.getClass().getName() |
| 432 | ) |
| 433 | ); |
| 434 | } |
| 435 | } |
| 436 | } |