| 125 |
|
* within bins are always accurately traversable under volatile |
| 126 |
|
* reads, so long as lookups check hash code and non-nullness of |
| 127 |
|
* key and value before checking key equality. (All valid hash |
| 128 |
< |
* codes are nonnegative. Negative values are served for special |
| 129 |
< |
* nodes.) |
| 128 |
> |
* codes are nonnegative. Negative values are reserved for special |
| 129 |
> |
* forwarding nodes; see below.) |
| 130 |
|
* |
| 131 |
|
* A bin may be locked during update (insert, delete, and replace) |
| 132 |
|
* operations. We do not want to waste the space required to |
| 172 |
|
* complexity of access and iteration schemes that could admit |
| 173 |
|
* out-of-order or concurrent bin transfers. |
| 174 |
|
* |
| 175 |
< |
* (While not yet implemented, a similar traversal scheme can |
| 176 |
< |
* apply to partial traversals during partitioned aggregate |
| 177 |
< |
* operations. Also, read-only operations give up if ever |
| 178 |
< |
* forwarded to a null table, which provides support for |
| 179 |
< |
* shutdown-style clearing, which is also not currently |
| 180 |
< |
* implemented.) |
| 175 |
> |
* A similar traversal scheme (not yet implemented) can apply to |
| 176 |
> |
* partial traversals during partitioned aggregate operations. |
| 177 |
> |
* Also, read-only operations give up if ever forwarded to a null |
| 178 |
> |
* table, which provides support for shutdown-style clearing, |
| 179 |
> |
* which is also not currently implemented. |
| 180 |
|
* |
| 181 |
|
* The element count is maintained using a LongAdder, which avoids |
| 182 |
|
* contention on updates but can encounter cache thrashing if read |
| 183 |
|
* too frequently during concurrent updates. To avoid reading so |
| 184 |
< |
* often, resizing is attempted only upon adding to a bin already |
| 185 |
< |
* holding two or more nodes. Under the default threshold (0.75), |
| 186 |
< |
* and uniform hash distributions, the probability of this |
| 184 |
> |
* often, resizing is normally attempted only upon adding to a bin |
| 185 |
> |
* already holding two or more nodes. Under the default threshold |
| 186 |
> |
* (0.75), and uniform hash distributions, the probability of this |
| 187 |
|
* occurring at threshold is around 13%, meaning that only about 1 |
| 188 |
|
* in 8 puts check threshold (and after resizing, many fewer do |
| 189 |
< |
* so). To increase the probablity that a resize occurs soon |
| 190 |
< |
* enough, we offset the threshold (see THRESHOLD_OFFSET) by the |
| 191 |
< |
* expected number of puts between checks. This is currently set |
| 192 |
< |
* to 8, in accord with the default load factor. In practice, this |
| 193 |
< |
* is rarely overridden, and in any case is close enough to other |
| 189 |
> |
* so). But this approximation has high variance for small table |
| 190 |
> |
* sizes, so we check on any collision for sizes <= 64. Further, |
| 191 |
> |
* to increase the probablity that a resize occurs soon enough, we |
| 192 |
> |
* offset the threshold (see THRESHOLD_OFFSET) by the expected |
| 193 |
> |
* number of puts between checks. This is currently set to 8, in |
| 194 |
> |
* accord with the default load factor. In practice, this is |
| 195 |
> |
* rarely overridden, and in any case is close enough to other |
| 196 |
|
* plausible values not to waste dynamic probablity computation |
| 197 |
|
* for more precision. |
| 198 |
|
*/ |
| 311 |
|
* implicitly bounds-checked, relying on the invariants that tab |
| 312 |
|
* arrays have non-zero size, and all indices are masked with |
| 313 |
|
* (tab.length - 1) which is never negative and always less than |
| 314 |
< |
* length. The only other usage is in HashIterator.advance, which |
| 315 |
< |
* performs explicit checks. |
| 314 |
> |
* length. The "relaxed" non-volatile forms are used only during |
| 315 |
> |
* table initialization. The only other usage is in |
| 316 |
> |
* HashIterator.advance, which performs explicit checks. |
| 317 |
|
*/ |
| 318 |
|
|
| 319 |
|
static final Node tabAt(Node[] tab, int i) { // used in HashIterator |
| 328 |
|
UNSAFE.putObjectVolatile(tab, ((long)i<<ASHIFT)+ABASE, v); |
| 329 |
|
} |
| 330 |
|
|
| 331 |
+ |
private static final Node relaxedTabAt(Node[] tab, int i) { |
| 332 |
+ |
return (Node)UNSAFE.getObject(tab, ((long)i<<ASHIFT)+ABASE); |
| 333 |
+ |
} |
| 334 |
+ |
|
| 335 |
+ |
private static final void relaxedSetTabAt(Node[] tab, int i, Node v) { |
| 336 |
+ |
UNSAFE.putObject(tab, ((long)i<<ASHIFT)+ABASE, v); |
| 337 |
+ |
} |
| 338 |
+ |
|
| 339 |
|
/* ---------------- Access and update operations -------------- */ |
| 340 |
|
|
| 341 |
< |
/** Implements get and containsKey **/ |
| 342 |
< |
private final Object internalGet(Object k) { |
| 341 |
> |
/** Implementation for get and containsKey **/ |
| 342 |
> |
private final Object internalGet(Object k) { |
| 343 |
|
int h = spread(k.hashCode()); |
| 344 |
|
Node[] tab = table; |
| 345 |
|
retry: while (tab != null) { |
| 351 |
|
if (ev != null && ek != null && (k == ek || k.equals(ek))) |
| 352 |
|
return ev; |
| 353 |
|
} |
| 354 |
< |
if (eh < 0) { // bin was moved during resize |
| 354 |
> |
else if (eh < 0) { // bin was moved during resize |
| 355 |
|
tab = (Node[])e.key; |
| 356 |
|
continue retry; |
| 357 |
|
} |
| 362 |
|
return null; |
| 363 |
|
} |
| 364 |
|
|
| 365 |
< |
/** Implements put and putIfAbsent **/ |
| 365 |
> |
/** Implementation for put and putIfAbsent **/ |
| 366 |
|
private final Object internalPut(Object k, Object v, boolean replace) { |
| 367 |
|
int h = spread(k.hashCode()); |
| 368 |
|
Object oldVal = null; // the previous value or null if none |
| 359 |
– |
Node node = null; // the node created if absent |
| 369 |
|
Node[] tab = table; |
| 370 |
|
for (;;) { |
| 371 |
|
Node e; int i; |
| 372 |
|
if (tab == null) |
| 373 |
|
tab = grow(0); |
| 374 |
|
else if ((e = tabAt(tab, i = (tab.length - 1) & h)) == null) { |
| 375 |
< |
if (node == null) |
| 367 |
< |
node = new Node(h, k, v, null); |
| 368 |
< |
if (casTabAt(tab, i, null, node)) |
| 375 |
> |
if (casTabAt(tab, i, null, new Node(h, k, v, null))) |
| 376 |
|
break; |
| 377 |
|
} |
| 378 |
|
else if (e.hash < 0) |
| 400 |
|
if ((e = e.next) == null) { |
| 401 |
|
if (tabAt(tab, i) == first) { |
| 402 |
|
validated = true; |
| 403 |
< |
if (node == null) |
| 404 |
< |
node = new Node(h, k, v, null); |
| 398 |
< |
last.next = node; |
| 399 |
< |
if (last != first) |
| 403 |
> |
last.next = new Node(h, k, v, null); |
| 404 |
> |
if (last != first || tab.length <= 64) |
| 405 |
|
checkSize = true; |
| 406 |
|
} |
| 407 |
|
break; |
| 481 |
|
return oldVal; |
| 482 |
|
} |
| 483 |
|
|
| 484 |
< |
/** Implements computeIfAbsent */ |
| 484 |
> |
/** Implementation for computeIfAbsent and compute */ |
| 485 |
|
@SuppressWarnings("unchecked") |
| 486 |
< |
private final V computeVal(K k, MappingFunction<? super K, ? extends V> f) { |
| 486 |
> |
private final V internalCompute(K k, |
| 487 |
> |
MappingFunction<? super K, ? extends V> f, |
| 488 |
> |
boolean replace) { |
| 489 |
|
int h = spread(k.hashCode()); |
| 490 |
|
V val = null; |
| 484 |
– |
Node node = null; |
| 491 |
|
boolean added = false; |
| 492 |
|
boolean validated = false; |
| 493 |
|
Node[] tab = table; |
| 496 |
|
if (tab == null) |
| 497 |
|
tab = grow(0); |
| 498 |
|
else if ((e = tabAt(tab, i = (tab.length - 1) & h)) == null) { |
| 499 |
< |
if (node == null) |
| 494 |
< |
node = new Node(h, k, null, null); |
| 499 |
> |
Node node = new Node(h, k, null, null); |
| 500 |
|
synchronized(node) { |
| 501 |
|
if (casTabAt(tab, i, null, node)) { |
| 502 |
|
validated = true; |
| 527 |
|
(k == ek || k.equals(ek))) { |
| 528 |
|
if (tabAt(tab, i) == first) { |
| 529 |
|
validated = true; |
| 530 |
+ |
if (replace && (ev = f.map(k)) != null) |
| 531 |
+ |
e.val = ev; |
| 532 |
|
val = (V)ev; |
| 533 |
|
} |
| 534 |
|
break; |
| 538 |
|
if (tabAt(tab, i) == first) { |
| 539 |
|
validated = true; |
| 540 |
|
if ((val = f.map(k)) != null) { |
| 541 |
< |
if (node == null) |
| 535 |
< |
node = new Node(h, k, val, null); |
| 536 |
< |
else |
| 537 |
< |
node.val = val; |
| 538 |
< |
last.next = node; |
| 539 |
< |
if (last != first) |
| 540 |
< |
checkSize = true; |
| 541 |
> |
last.next = new Node(h, k, val, null); |
| 542 |
|
added = true; |
| 543 |
+ |
if (last != first || tab.length <= 64) |
| 544 |
+ |
checkSize = true; |
| 545 |
|
} |
| 546 |
|
} |
| 547 |
|
break; |
| 598 |
|
} |
| 599 |
|
if (tabAt(tab, i) == e) { |
| 600 |
|
validated = true; |
| 601 |
< |
setTabAt(nextTab, idx, lastRun); |
| 601 |
> |
relaxedSetTabAt(nextTab, idx, lastRun); |
| 602 |
|
for (Node p = e; p != lastRun; p = p.next) { |
| 603 |
|
int h = p.hash; |
| 604 |
|
int j = h & mask; |
| 605 |
< |
Object pk = p.key, pv = p.val; |
| 606 |
< |
Node r = tabAt(nextTab, j); |
| 607 |
< |
setTabAt(nextTab, j, new Node(h, pk, pv, r)); |
| 605 |
> |
Node r = relaxedTabAt(nextTab, j); |
| 606 |
> |
relaxedSetTabAt(nextTab, j, |
| 607 |
> |
new Node(h, p.key, p.val, r)); |
| 608 |
|
} |
| 609 |
|
setTabAt(tab, i, fwd); |
| 610 |
|
} |
| 626 |
|
* @return current table |
| 627 |
|
*/ |
| 628 |
|
private final Node[] grow(int sizeHint) { |
| 626 |
– |
Node[] tab; |
| 629 |
|
if (resizing == 0 && |
| 630 |
|
UNSAFE.compareAndSwapInt(this, resizingOffset, 0, 1)) { |
| 631 |
|
try { |
| 632 |
|
for (;;) { |
| 633 |
|
int cap, n; |
| 634 |
< |
if ((tab = table) == null) { |
| 634 |
> |
Node[] tab = table; |
| 635 |
> |
if (tab == null) { |
| 636 |
|
int c = initCap; |
| 637 |
|
if (c < sizeHint) |
| 638 |
|
c = sizeHint; |
| 656 |
|
if (tab != null) |
| 657 |
|
transfer(tab, nextTab); |
| 658 |
|
table = nextTab; |
| 659 |
< |
if (tab == null || counter.sum() < threshold) { |
| 660 |
< |
tab = nextTab; |
| 659 |
> |
if (tab == null || cap >= MAXIMUM_CAPACITY || |
| 660 |
> |
(sizeHint > 0 && cap >= sizeHint) || |
| 661 |
> |
counter.sum() < threshold) |
| 662 |
|
break; |
| 659 |
– |
} |
| 663 |
|
} |
| 664 |
|
} finally { |
| 665 |
|
resizing = 0; |
| 666 |
|
} |
| 667 |
|
} |
| 668 |
< |
else if ((tab = table) == null) |
| 668 |
> |
else if (table == null) |
| 669 |
|
Thread.yield(); // lost initialization race; just spin |
| 670 |
< |
return tab; |
| 670 |
> |
return table; |
| 671 |
|
} |
| 672 |
|
|
| 673 |
|
/** |
| 674 |
< |
* Implements putAll and constructor with Map argument. Tries to |
| 675 |
< |
* first override initial capacity or grow (once) based on map |
| 676 |
< |
* size to pre-allocate table space. |
| 674 |
> |
* Implementation for putAll and constructor with Map |
| 675 |
> |
* argument. Tries to first override initial capacity or grow |
| 676 |
> |
* based on map size to pre-allocate table space. |
| 677 |
|
*/ |
| 678 |
|
private final void internalPutAll(Map<? extends K, ? extends V> m) { |
| 679 |
|
int s = m.size(); |
| 688 |
|
} |
| 689 |
|
|
| 690 |
|
/** |
| 691 |
< |
* Implements clear. Steps through each bin, removing all nodes. |
| 691 |
> |
* Implementation for clear. Steps through each bin, removing all nodes. |
| 692 |
|
*/ |
| 693 |
|
private final void internalClear() { |
| 694 |
< |
long delta = 0L; // negative of number of deletions |
| 694 |
> |
long deletions = 0L; |
| 695 |
|
int i = 0; |
| 696 |
|
Node[] tab = table; |
| 697 |
|
while (tab != null && i < tab.length) { |
| 708 |
|
do { |
| 709 |
|
if (e.val != null) { |
| 710 |
|
e.val = null; |
| 711 |
< |
--delta; |
| 711 |
> |
++deletions; |
| 712 |
|
} |
| 713 |
|
} while ((e = e.next) != null); |
| 714 |
|
setTabAt(tab, i, null); |
| 715 |
|
} |
| 716 |
|
} |
| 717 |
< |
if (validated) |
| 717 |
> |
if (validated) { |
| 718 |
|
++i; |
| 719 |
+ |
if (deletions > THRESHOLD_OFFSET) { // bound lag in counts |
| 720 |
+ |
counter.add(-deletions); |
| 721 |
+ |
deletions = 0L; |
| 722 |
+ |
} |
| 723 |
+ |
} |
| 724 |
|
} |
| 725 |
|
} |
| 726 |
< |
counter.add(delta); |
| 726 |
> |
if (deletions != 0L) |
| 727 |
> |
counter.add(-deletions); |
| 728 |
|
} |
| 729 |
|
|
| 730 |
|
/** |
| 971 |
|
* @return {@code true} if this map contains no key-value mappings |
| 972 |
|
*/ |
| 973 |
|
public boolean isEmpty() { |
| 974 |
< |
return counter.sum() == 0L; |
| 974 |
> |
return counter.sum() <= 0L; // ignore transient negative values |
| 975 |
|
} |
| 976 |
|
|
| 977 |
|
/** |
| 983 |
|
*/ |
| 984 |
|
public int size() { |
| 985 |
|
long n = counter.sum(); |
| 986 |
< |
return n >= Integer.MAX_VALUE ? Integer.MAX_VALUE : (int)n; |
| 986 |
> |
return n <= 0L? 0 : n >= Integer.MAX_VALUE ? Integer.MAX_VALUE : (int)n; |
| 987 |
|
} |
| 988 |
|
|
| 989 |
|
/** |
| 1112 |
|
* return map.get(key); |
| 1113 |
|
* value = mappingFunction.map(key); |
| 1114 |
|
* if (value != null) |
| 1115 |
< |
* return map.put(key, value); |
| 1116 |
< |
* else |
| 1108 |
< |
* return null; |
| 1115 |
> |
* map.put(key, value); |
| 1116 |
> |
* return value; |
| 1117 |
|
* </pre> |
| 1118 |
|
* |
| 1119 |
|
* except that the action is performed atomically. Some attempted |
| 1120 |
|
* operations on this map by other threads may be blocked while |
| 1121 |
< |
* computation is in progress. Because this function is invoked |
| 1122 |
< |
* within atomicity control, the computation should be short and |
| 1123 |
< |
* simple, and must not attempt to update any other mappings of |
| 1116 |
< |
* this Map. The most common usage is to construct a new object |
| 1121 |
> |
* computation is in progress, so the computation should be short |
| 1122 |
> |
* and simple, and must not attempt to update any other mappings |
| 1123 |
> |
* of this Map. The most common usage is to construct a new object |
| 1124 |
|
* serving as an initial mapped value, or memoized result. |
| 1125 |
|
* |
| 1126 |
|
* @param key key with which the specified value is to be associated |
| 1136 |
|
public V computeIfAbsent(K key, MappingFunction<? super K, ? extends V> mappingFunction) { |
| 1137 |
|
if (key == null || mappingFunction == null) |
| 1138 |
|
throw new NullPointerException(); |
| 1139 |
< |
return computeVal(key, mappingFunction); |
| 1139 |
> |
return internalCompute(key, mappingFunction, false); |
| 1140 |
> |
} |
| 1141 |
> |
|
| 1142 |
> |
/** |
| 1143 |
> |
* Computes the value associated with he given key using the given |
| 1144 |
> |
* mappingFunction, and if non-null, enters it into the map. This |
| 1145 |
> |
* is equivalent to |
| 1146 |
> |
* |
| 1147 |
> |
* <pre> |
| 1148 |
> |
* value = mappingFunction.map(key); |
| 1149 |
> |
* if (value != null) |
| 1150 |
> |
* map.put(key, value); |
| 1151 |
> |
* else |
| 1152 |
> |
* return map.get(key); |
| 1153 |
> |
* </pre> |
| 1154 |
> |
* |
| 1155 |
> |
* except that the action is performed atomically. Some attempted |
| 1156 |
> |
* operations on this map by other threads may be blocked while |
| 1157 |
> |
* computation is in progress, so the computation should be short |
| 1158 |
> |
* and simple, and must not attempt to update any other mappings |
| 1159 |
> |
* of this Map. |
| 1160 |
> |
* |
| 1161 |
> |
* @param key key with which the specified value is to be associated |
| 1162 |
> |
* @param mappingFunction the function to compute a value |
| 1163 |
> |
* @return the current value associated with |
| 1164 |
> |
* the specified key, or {@code null} if the computation |
| 1165 |
> |
* returned {@code null} and the value was not otherwise present. |
| 1166 |
> |
* @throws NullPointerException if the specified key or mappingFunction |
| 1167 |
> |
* is null, |
| 1168 |
> |
* @throws RuntimeException or Error if the mappingFunction does so, |
| 1169 |
> |
* in which case the mapping is unchanged. |
| 1170 |
> |
*/ |
| 1171 |
> |
public V compute(K key, MappingFunction<? super K, ? extends V> mappingFunction) { |
| 1172 |
> |
if (key == null || mappingFunction == null) |
| 1173 |
> |
throw new NullPointerException(); |
| 1174 |
> |
return internalCompute(key, mappingFunction, true); |
| 1175 |
|
} |
| 1176 |
|
|
| 1177 |
|
/** |
| 1319 |
|
} |
| 1320 |
|
|
| 1321 |
|
/** |
| 1322 |
< |
* {@inheritDoc} |
| 1322 |
> |
* Returns the hash code value for this {@link Map}, i.e., |
| 1323 |
> |
* the sum of, for each key-value pair in the map, |
| 1324 |
> |
* {@code key.hashCode() ^ value.hashCode()}. |
| 1325 |
> |
* |
| 1326 |
> |
* @return the hash code value for this map |
| 1327 |
|
*/ |
| 1328 |
|
public int hashCode() { |
| 1329 |
|
return new HashIterator().mapHashCode(); |
| 1330 |
|
} |
| 1331 |
|
|
| 1332 |
|
/** |
| 1333 |
< |
* {@inheritDoc} |
| 1333 |
> |
* Returns a string representation of this map. The string |
| 1334 |
> |
* representation consists of a list of key-value mappings (in no |
| 1335 |
> |
* particular order) enclosed in braces ("{@code {}}"). Adjacent |
| 1336 |
> |
* mappings are separated by the characters {@code ", "} (comma |
| 1337 |
> |
* and space). Each key-value mapping is rendered as the key |
| 1338 |
> |
* followed by an equals sign ("{@code =}") followed by the |
| 1339 |
> |
* associated value. |
| 1340 |
> |
* |
| 1341 |
> |
* @return a string representation of this map |
| 1342 |
|
*/ |
| 1343 |
|
public String toString() { |
| 1344 |
|
return new HashIterator().mapToString(); |
| 1345 |
|
} |
| 1346 |
|
|
| 1347 |
|
/** |
| 1348 |
< |
* {@inheritDoc} |
| 1348 |
> |
* Compares the specified object with this map for equality. |
| 1349 |
> |
* Returns {@code true} if the given object is a map with the same |
| 1350 |
> |
* mappings as this map. This operation may return misleading |
| 1351 |
> |
* results if either map is concurrently modified during execution |
| 1352 |
> |
* of this method. |
| 1353 |
> |
* |
| 1354 |
> |
* @param o object to be compared for equality with this map |
| 1355 |
> |
* @return {@code true} if the specified object is equal to this map |
| 1356 |
|
*/ |
| 1357 |
|
public boolean equals(Object o) { |
| 1358 |
|
if (o == this) |
