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Comparing jsr166/src/main/java/util/concurrent/ConcurrentHashMap.java (file contents):
Revision 1.307 by jsr166, Sun Mar 11 18:00:05 2018 UTC vs.
Revision 1.324 by dl, Fri Mar 18 16:01:41 2022 UTC

#	Line 224 | Line 224 | import jdk.internal.misc.Unsafe;
224		* <p>All arguments to all task methods must be non-null.
225		*
226		* <p>This class is a member of the
227	<	* <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
227	>	* <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
228		* Java Collections Framework</a>.
229		*
230		* @since 1.5
#	Line 356 | Line 356 | public class ConcurrentHashMap<K,V> exte
356		* cases where old nodes can be reused because their next fields
357		* won't change.  On average, only about one-sixth of them need
358		* cloning when a table doubles. The nodes they replace will be
359	<	* garbage collectable as soon as they are no longer referenced by
359	>	* garbage collectible as soon as they are no longer referenced by
360		* any reader thread that may be in the midst of concurrently
361		* traversing table.  Upon transfer, the old table bin contains
362		* only a special forwarding node (with hash field "MOVED") that
#	Line 673 | Line 673 | public class ConcurrentHashMap<K,V> exte
673		* See Hackers Delight, sec 3.2
674		*/
675		private static final int tableSizeFor(int c) {
676	<	int n = c - 1;
677	<	n |= n >>> 1;
678	<	n |= n >>> 2;
679	<	n |= n >>> 4;
680	<	n |= n >>> 8;
681	<	n |= n >>> 16;
676	>	int n = -1 >>> Integer.numberOfLeadingZeros(c - 1);
677		return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
678		}
679
#	Line 733 | Line 728 | public class ConcurrentHashMap<K,V> exte
728
729		@SuppressWarnings("unchecked")
730		static final <K,V> Node<K,V> tabAt(Node<K,V>[] tab, int i) {
731	<	return (Node<K,V>)U.getObjectAcquire(tab, ((long)i << ASHIFT) + ABASE);
731	>	return (Node<K,V>)U.getReferenceAcquire(tab, ((long)i << ASHIFT) + ABASE);
732		}
733
734		static final <K,V> boolean casTabAt(Node<K,V>[] tab, int i,
735		Node<K,V> c, Node<K,V> v) {
736	<	return U.compareAndSetObject(tab, ((long)i << ASHIFT) + ABASE, c, v);
736	>	return U.compareAndSetReference(tab, ((long)i << ASHIFT) + ABASE, c, v);
737		}
738
739		static final <K,V> void setTabAt(Node<K,V>[] tab, int i, Node<K,V> v) {
740	<	U.putObjectRelease(tab, ((long)i << ASHIFT) + ABASE, v);
740	>	U.putReferenceRelease(tab, ((long)i << ASHIFT) + ABASE, v);
741		}
742
743		/* ---------------- Fields -------------- */
#	Line 815 | Line 810 | public class ConcurrentHashMap<K,V> exte
810		* elements is negative
811		*/
812		public ConcurrentHashMap(int initialCapacity) {
813	<	if (initialCapacity < 0)
819	<	throw new IllegalArgumentException();
820	<	int cap = ((initialCapacity >= (MAXIMUM_CAPACITY >>> 1)) ?
821	<	MAXIMUM_CAPACITY :
822	<	tableSizeFor(initialCapacity + (initialCapacity >>> 1) + 1));
823	<	this.sizeCtl = cap;
813	>	this(initialCapacity, LOAD_FACTOR, 1);
814		}
815
816		/**
#	Line 854 | Line 844 | public class ConcurrentHashMap<K,V> exte
844
845		/**
846		* Creates a new, empty map with an initial table size based on
847	<	* the given number of elements ({@code initialCapacity}), table
848	<	* density ({@code loadFactor}), and number of concurrently
847	>	* the given number of elements ({@code initialCapacity}), initial
848	>	* table density ({@code loadFactor}), and number of concurrently
849		* updating threads ({@code concurrencyLevel}).
850		*
851		* @param initialCapacity the initial capacity. The implementation
#	Line 1444 | Line 1434 | public class ConcurrentHashMap<K,V> exte
1434		if (size == 0L)
1435		sizeCtl = 0;
1436		else {
1437	<	int n;
1438	<	if (size >= (long)(MAXIMUM_CAPACITY >>> 1))
1439	<	n = MAXIMUM_CAPACITY;
1450	<	else {
1451	<	int sz = (int)size;
1452	<	n = tableSizeFor(sz + (sz >>> 1) + 1);
1453	<	}
1437	>	long ts = (long)(1.0 + size / LOAD_FACTOR);
1438	>	int n = (ts >= (long)MAXIMUM_CAPACITY) ?
1439	>	MAXIMUM_CAPACITY : tableSizeFor((int)ts);
1440		@SuppressWarnings("unchecked")
1441		Node<K,V>[] tab = (Node<K,V>[])new Node<?,?>[n];
1442		int mask = n - 1;
#	Line 1652 | Line 1638 | public class ConcurrentHashMap<K,V> exte
1638		* If the specified key is not already associated with a value,
1639		* attempts to compute its value using the given mapping function
1640		* and enters it into this map unless {@code null}.  The entire
1641	<	* method invocation is performed atomically, so the function is
1642	<	* applied at most once per key.  Some attempted update operations
1643	<	* on this map by other threads may be blocked while computation
1644	<	* is in progress, so the computation should be short and simple,
1645	<	* and must not attempt to update any other mappings of this map.
1641	>	* method invocation is performed atomically.  The supplied
1642	>	* function is invoked exactly once per invocation of this method
1643	>	* if the key is absent, else not at all.  Some attempted update
1644	>	* operations on this map by other threads may be blocked while
1645	>	* computation is in progress, so the computation should be short
1646	>	* and simple.
1647	>	*
1648	>	* <p>The mapping function must not modify this map during computation.
1649		*
1650		* @param key key with which the specified value is to be associated
1651		* @param mappingFunction the function to compute a value
#	Line 1763 | Line 1752 | public class ConcurrentHashMap<K,V> exte
1752		* If the value for the specified key is present, attempts to
1753		* compute a new mapping given the key and its current mapped
1754		* value.  The entire method invocation is performed atomically.
1755	<	* Some attempted update operations on this map by other threads
1756	<	* may be blocked while computation is in progress, so the
1757	<	* computation should be short and simple, and must not attempt to
1758	<	* update any other mappings of this map.
1755	>	* The supplied function is invoked exactly once per invocation of
1756	>	* this method if the key is present, else not at all.  Some
1757	>	* attempted update operations on this map by other threads may be
1758	>	* blocked while computation is in progress, so the computation
1759	>	* should be short and simple.
1760	>	*
1761	>	* <p>The remapping function must not modify this map during computation.
1762		*
1763		* @param key key with which a value may be associated
1764		* @param remappingFunction the function to compute a value
#	Line 1855 | Line 1847 | public class ConcurrentHashMap<K,V> exte
1847		* Attempts to compute a mapping for the specified key and its
1848		* current mapped value (or {@code null} if there is no current
1849		* mapping). The entire method invocation is performed atomically.
1850	<	* Some attempted update operations on this map by other threads
1851	<	* may be blocked while computation is in progress, so the
1852	<	* computation should be short and simple, and must not attempt to
1853	<	* update any other mappings of this Map.
1850	>	* The supplied function is invoked exactly once per invocation of
1851	>	* this method.  Some attempted update operations on this map by
1852	>	* other threads may be blocked while computation is in progress,
1853	>	* so the computation should be short and simple.
1854	>	*
1855	>	* <p>The remapping function must not modify this map during computation.
1856		*
1857		* @param key key with which the specified value is to be associated
1858		* @param remappingFunction the function to compute a value
#	Line 2319 | Line 2313 | public class ConcurrentHashMap<K,V> exte
2313		Node<K,V>[] tab, nt; int n, sc;
2314		while (s >= (long)(sc = sizeCtl) && (tab = table) != null &&
2315		(n = tab.length) < MAXIMUM_CAPACITY) {
2316	<	int rs = resizeStamp(n);
2316	>	int rs = resizeStamp(n) << RESIZE_STAMP_SHIFT;
2317		if (sc < 0) {
2318	<	if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 ||
2319	<	sc == rs + MAX_RESIZERS || (nt = nextTable) == null ||
2326	<	transferIndex <= 0)
2318	>	if (sc == rs + MAX_RESIZERS || sc == rs + 1 ||
2319	>	(nt = nextTable) == null || transferIndex <= 0)
2320		break;
2321		if (U.compareAndSetInt(this, SIZECTL, sc, sc + 1))
2322		transfer(tab, nt);
2323		}
2324	<	else if (U.compareAndSetInt(this, SIZECTL, sc,
2332	<	(rs << RESIZE_STAMP_SHIFT) + 2))
2324	>	else if (U.compareAndSetInt(this, SIZECTL, sc, rs + 2))
2325		transfer(tab, null);
2326		s = sumCount();
2327		}
#	Line 2343 | Line 2335 | public class ConcurrentHashMap<K,V> exte
2335		Node<K,V>[] nextTab; int sc;
2336		if (tab != null && (f instanceof ForwardingNode) &&
2337		(nextTab = ((ForwardingNode<K,V>)f).nextTable) != null) {
2338	<	int rs = resizeStamp(tab.length);
2338	>	int rs = resizeStamp(tab.length) << RESIZE_STAMP_SHIFT;
2339		while (nextTab == nextTable && table == tab &&
2340		(sc = sizeCtl) < 0) {
2341	<	if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 ||
2342	<	sc == rs + MAX_RESIZERS || transferIndex <= 0)
2341	>	if (sc == rs + MAX_RESIZERS || sc == rs + 1 ||
2342	>	transferIndex <= 0)
2343		break;
2344		if (U.compareAndSetInt(this, SIZECTL, sc, sc + 1)) {
2345		transfer(tab, nextTab);
#	Line 2527 | Line 2519 | public class ConcurrentHashMap<K,V> exte
2519		setTabAt(tab, i, fwd);
2520		advance = true;
2521		}
2522	+	else if (f instanceof ReservationNode)
2523	+	throw new IllegalStateException("Recursive update");
2524		}
2525		}
2526		}
#	Line 3271 | Line 3265 | public class ConcurrentHashMap<K,V> exte
3265		return true;
3266		}
3267
3268	<	private static final Unsafe U = Unsafe.getUnsafe();
3269	<	private static final long LOCKSTATE;
3276	<	static {
3277	<	try {
3278	<	LOCKSTATE = U.objectFieldOffset
3279	<	(TreeBin.class.getDeclaredField("lockState"));
3280	<	} catch (ReflectiveOperationException e) {
3281	<	throw new ExceptionInInitializerError(e);
3282	<	}
3283	<	}
3268	>	private static final long LOCKSTATE
3269	>	= U.objectFieldOffset(TreeBin.class, "lockState");
3270		}
3271
3272		/* ----------------Table Traversal -------------- */
#	Line 4577 | Line 4563 | public class ConcurrentHashMap<K,V> exte
4563		public static class KeySetView<K,V> extends CollectionView<K,V,K>
4564		implements Set<K>, java.io.Serializable {
4565		private static final long serialVersionUID = 7249069246763182397L;
4566	+	@SuppressWarnings("serial") // Conditionally serializable
4567		private final V value;
4568		KeySetView(ConcurrentHashMap<K,V> map, V value) {  // non-public
4569		super(map);
#	Line 6337 | Line 6324 | public class ConcurrentHashMap<K,V> exte
6324
6325		// Unsafe mechanics
6326		private static final Unsafe U = Unsafe.getUnsafe();
6327	<	private static final long SIZECTL;
6328	<	private static final long TRANSFERINDEX;
6329	<	private static final long BASECOUNT;
6330	<	private static final long CELLSBUSY;
6331	<	private static final long CELLVALUE;
6332	<	private static final int ABASE;
6327	>	private static final long SIZECTL
6328	>	= U.objectFieldOffset(ConcurrentHashMap.class, "sizeCtl");
6329	>	private static final long TRANSFERINDEX
6330	>	= U.objectFieldOffset(ConcurrentHashMap.class, "transferIndex");
6331	>	private static final long BASECOUNT
6332	>	= U.objectFieldOffset(ConcurrentHashMap.class, "baseCount");
6333	>	private static final long CELLSBUSY
6334	>	= U.objectFieldOffset(ConcurrentHashMap.class, "cellsBusy");
6335	>	private static final long CELLVALUE
6336	>	= U.objectFieldOffset(CounterCell.class, "value");
6337	>	private static final int ABASE = U.arrayBaseOffset(Node[].class);
6338		private static final int ASHIFT;
6339
6340		static {
6341	<	try {
6342	<	SIZECTL = U.objectFieldOffset
6343	<	(ConcurrentHashMap.class.getDeclaredField("sizeCtl"));
6344	<	TRANSFERINDEX = U.objectFieldOffset
6353	<	(ConcurrentHashMap.class.getDeclaredField("transferIndex"));
6354	<	BASECOUNT = U.objectFieldOffset
6355	<	(ConcurrentHashMap.class.getDeclaredField("baseCount"));
6356	<	CELLSBUSY = U.objectFieldOffset
6357	<	(ConcurrentHashMap.class.getDeclaredField("cellsBusy"));
6358	<
6359	<	CELLVALUE = U.objectFieldOffset
6360	<	(CounterCell.class.getDeclaredField("value"));
6361	<
6362	<	ABASE = U.arrayBaseOffset(Node[].class);
6363	<	int scale = U.arrayIndexScale(Node[].class);
6364	<	if ((scale & (scale - 1)) != 0)
6365	<	throw new Error("array index scale not a power of two");
6366	<	ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
6367	<	} catch (ReflectiveOperationException e) {
6368	<	throw new ExceptionInInitializerError(e);
6369	<	}
6341	>	int scale = U.arrayIndexScale(Node[].class);
6342	>	if ((scale & (scale - 1)) != 0)
6343	>	throw new ExceptionInInitializerError("array index scale not a power of two");
6344	>	ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
6345
6346		// Reduce the risk of rare disastrous classloading in first call to
6347		// LockSupport.park: https://bugs.openjdk.java.net/browse/JDK-8074773
6348		Class<?> ensureLoaded = LockSupport.class;
6349	+
6350	+	// Eager class load observed to help JIT during startup
6351	+	ensureLoaded = ReservationNode.class;
6352		}
6353		}

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