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*/ |
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package jsr166e; |
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+ |
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| 9 |
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import java.util.Random; |
| 10 |
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/** |
| 12 |
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* A package-local class holding common representation and mechanics |
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* for classes supporting dynamic striping on 64bit values. The class |
| 14 |
< |
* extends Number so that concrete subclasses can publicly do so. |
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> |
* extends Number so that concrete subclasses must publicly do so. |
| 15 |
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*/ |
| 16 |
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abstract class Striped64 extends Number { |
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/* |
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* |
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* A single spinlock ("busy") is used for initializing and |
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* resizing the table, as well as populating slots with new Cells. |
| 44 |
< |
* There is no need for a blocking lock: When the lock is not |
| 44 |
> |
* There is no need for a blocking lock; when the lock is not |
| 45 |
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* available, threads try other slots (or the base). During these |
| 46 |
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* retries, there is increased contention and reduced locality, |
| 47 |
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* which is still better than alternatives. |
| 112 |
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} |
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|
| 114 |
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/** |
| 115 |
< |
* Holder for the thread-local hash code. The code is initially |
| 116 |
< |
* random, but may be set to a different value upon collisions. |
| 115 |
> |
* ThreadLocal holding a single-slot int array holding hash code. |
| 116 |
> |
* Unlike the JDK8 version of this class, we use a suboptimal |
| 117 |
> |
* int[] representation to avoid introducing a new type that can |
| 118 |
> |
* impede class-unloading when ThreadLocals are not removed. |
| 119 |
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*/ |
| 120 |
< |
static final class HashCode { |
| 118 |
< |
static final Random rng = new Random(); |
| 119 |
< |
int code; |
| 120 |
< |
HashCode() { |
| 121 |
< |
int h = rng.nextInt(); // Avoid zero to allow xorShift rehash |
| 122 |
< |
code = (h == 0) ? 1 : h; |
| 123 |
< |
} |
| 124 |
< |
} |
| 125 |
< |
|
| 126 |
< |
/** |
| 127 |
< |
* The corresponding ThreadLocal class |
| 128 |
< |
*/ |
| 129 |
< |
static final class ThreadHashCode extends ThreadLocal<HashCode> { |
| 130 |
< |
public HashCode initialValue() { return new HashCode(); } |
| 131 |
< |
} |
| 120 |
> |
static final ThreadLocal<int[]> threadHashCode = new ThreadLocal<int[]>(); |
| 121 |
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|
| 122 |
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/** |
| 123 |
< |
* Static per-thread hash codes. Shared across all instances to |
| 135 |
< |
* reduce ThreadLocal pollution and because adjustments due to |
| 136 |
< |
* collisions in one table are likely to be appropriate for |
| 137 |
< |
* others. |
| 123 |
> |
* Generator of new random hash codes |
| 124 |
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*/ |
| 125 |
< |
static final ThreadHashCode threadHashCode = new ThreadHashCode(); |
| 125 |
> |
static final Random rng = new Random(); |
| 126 |
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|
| 127 |
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/** Number of CPUS, to place bound on table size */ |
| 128 |
|
static final int NCPU = Runtime.getRuntime().availableProcessors(); |
| 185 |
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* @param hc the hash code holder |
| 186 |
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* @param wasUncontended false if CAS failed before call |
| 187 |
|
*/ |
| 188 |
< |
final void retryUpdate(long x, HashCode hc, boolean wasUncontended) { |
| 189 |
< |
int h = hc.code; |
| 188 |
> |
final void retryUpdate(long x, int[] hc, boolean wasUncontended) { |
| 189 |
> |
int h; |
| 190 |
> |
if (hc == null) { |
| 191 |
> |
threadHashCode.set(hc = new int[1]); // Initialize randomly |
| 192 |
> |
int r = rng.nextInt(); // Avoid zero to allow xorShift rehash |
| 193 |
> |
h = hc[0] = (r == 0) ? 1 : r; |
| 194 |
> |
} |
| 195 |
> |
else |
| 196 |
> |
h = hc[0]; |
| 197 |
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boolean collide = false; // True if last slot nonempty |
| 198 |
|
for (;;) { |
| 199 |
|
Cell[] as; Cell a; int n; long v; |
| 246 |
|
h ^= h << 13; // Rehash |
| 247 |
|
h ^= h >>> 17; |
| 248 |
|
h ^= h << 5; |
| 249 |
+ |
hc[0] = h; // Record index for next time |
| 250 |
|
} |
| 251 |
|
else if (busy == 0 && cells == as && casBusy()) { |
| 252 |
|
boolean init = false; |
| 266 |
|
else if (casBase(v = base, fn(v, x))) |
| 267 |
|
break; // Fall back on using base |
| 268 |
|
} |
| 275 |
– |
hc.code = h; // Record index for next time |
| 269 |
|
} |
| 270 |
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|
| 271 |
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|
| 312 |
|
private static sun.misc.Unsafe getUnsafe() { |
| 313 |
|
try { |
| 314 |
|
return sun.misc.Unsafe.getUnsafe(); |
| 315 |
< |
} catch (SecurityException se) { |
| 316 |
< |
try { |
| 317 |
< |
return java.security.AccessController.doPrivileged |
| 318 |
< |
(new java.security |
| 319 |
< |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
| 320 |
< |
public sun.misc.Unsafe run() throws Exception { |
| 321 |
< |
java.lang.reflect.Field f = sun.misc |
| 322 |
< |
.Unsafe.class.getDeclaredField("theUnsafe"); |
| 323 |
< |
f.setAccessible(true); |
| 324 |
< |
return (sun.misc.Unsafe) f.get(null); |
| 325 |
< |
}}); |
| 326 |
< |
} catch (java.security.PrivilegedActionException e) { |
| 327 |
< |
throw new RuntimeException("Could not initialize intrinsics", |
| 328 |
< |
e.getCause()); |
| 329 |
< |
} |
| 315 |
> |
} catch (SecurityException tryReflectionInstead) {} |
| 316 |
> |
try { |
| 317 |
> |
return java.security.AccessController.doPrivileged |
| 318 |
> |
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
| 319 |
> |
public sun.misc.Unsafe run() throws Exception { |
| 320 |
> |
Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class; |
| 321 |
> |
for (java.lang.reflect.Field f : k.getDeclaredFields()) { |
| 322 |
> |
f.setAccessible(true); |
| 323 |
> |
Object x = f.get(null); |
| 324 |
> |
if (k.isInstance(x)) |
| 325 |
> |
return k.cast(x); |
| 326 |
> |
} |
| 327 |
> |
throw new NoSuchFieldError("the Unsafe"); |
| 328 |
> |
}}); |
| 329 |
> |
} catch (java.security.PrivilegedActionException e) { |
| 330 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
| 331 |
> |
e.getCause()); |
| 332 |
|
} |
| 333 |
|
} |
| 339 |
– |
|
| 334 |
|
} |
