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*/ |
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package jsr166e; |
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+ |
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import java.util.Random; |
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/** |
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} |
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/** |
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< |
* Holder for the thread-local hash code. The code is initially |
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< |
* random, but may be set to a different value upon collisions. |
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< |
*/ |
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< |
static final class HashCode { |
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static final Random rng = new Random(); |
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< |
int code; |
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< |
HashCode() { |
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< |
int h = rng.nextInt(); // Avoid zero to allow xorShift rehash |
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< |
code = (h == 0) ? 1 : h; |
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< |
} |
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< |
} |
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< |
|
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< |
/** |
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< |
* The corresponding ThreadLocal class |
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> |
* ThreadLocal holding a single-slot int array holding hash code. |
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> |
* Unlike the JDK8 version of this class, we use a suboptimal |
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> |
* int[] representation to avoid introducing a new type that can |
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> |
* impede class-unloading when ThreadLocals are not removed. |
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*/ |
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< |
static final class ThreadHashCode extends ThreadLocal<HashCode> { |
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< |
public HashCode initialValue() { return new HashCode(); } |
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< |
} |
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> |
static final ThreadLocal<int[]> threadHashCode = new ThreadLocal<int[]>(); |
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/** |
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* Static per-thread hash codes. Shared across all instances to |
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< |
* reduce ThreadLocal pollution and because adjustments due to |
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< |
* collisions in one table are likely to be appropriate for |
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< |
* others. |
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> |
* Generator of new random hash codes |
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*/ |
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< |
static final ThreadHashCode threadHashCode = new ThreadHashCode(); |
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> |
static final Random rng = new Random(); |
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/** Number of CPUS, to place bound on table size */ |
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static final int NCPU = Runtime.getRuntime().availableProcessors(); |
| 185 |
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* @param hc the hash code holder |
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* @param wasUncontended false if CAS failed before call |
| 187 |
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*/ |
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< |
final void retryUpdate(long x, HashCode hc, boolean wasUncontended) { |
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< |
int h = hc.code; |
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> |
final void retryUpdate(long x, int[] hc, boolean wasUncontended) { |
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> |
int h; |
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> |
if (hc == null) { |
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> |
threadHashCode.set(hc = new int[1]); // Initialize randomly |
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> |
int r = rng.nextInt(); // Avoid zero to allow xorShift rehash |
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> |
h = hc[0] = (r == 0) ? 1 : r; |
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> |
} |
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> |
else |
| 196 |
> |
h = hc[0]; |
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boolean collide = false; // True if last slot nonempty |
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for (;;) { |
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Cell[] as; Cell a; int n; long v; |
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h ^= h << 13; // Rehash |
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h ^= h >>> 17; |
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h ^= h << 5; |
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+ |
hc[0] = h; // Record index for next time |
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} |
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else if (busy == 0 && cells == as && casBusy()) { |
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boolean init = false; |
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else if (casBase(v = base, fn(v, x))) |
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break; // Fall back on using base |
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} |
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– |
hc.code = h; // Record index for next time |
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} |
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