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Comparing jsr166/src/jsr166e/ConcurrentHashMapV8.java (file contents):
Revision 1.26 by jsr166, Wed Sep 21 11:42:08 2011 UTC vs.
Revision 1.27 by dl, Sun Oct 2 22:01:06 2011 UTC

#	Line 98 | Line 98 | public class ConcurrentHashMapV8<K, V>
98		private static final long serialVersionUID = 7249069246763182397L;
99
100		/**
101	<	* A function computing a mapping from the given key to a value,
102	<	* or {@code null} if there is no mapping. This is a place-holder
103	<	* for an upcoming JDK8 interface.
101	>	* A function computing a mapping from the given key to a value.
102	>	* This is a place-holder for an upcoming JDK8 interface.
103		*/
104		public static interface MappingFunction<K, V> {
105		/**
106	<	* Returns a value for the given key, or null if there is no
108	<	* mapping. If this function throws an (unchecked) exception,
109	<	* the exception is rethrown to its caller, and no mapping is
110	<	* recorded.  Because this function is invoked within
111	<	* atomicity control, the computation should be short and
112	<	* simple. The most common usage is to construct a new object
113	<	* serving as an initial mapped value.
106	>	* Returns a non-null value for the given key.
107		*
108		* @param key the (non-null) key
109	<	* @return a value, or null if none
109	>	* @return a non-null value
110		*/
111		V map(K key);
112		}
113
114	+	/**
115	+	* A function computing a new mapping given a key and its current
116	+	* mapped value (or {@code null} if there is no current
117	+	* mapping). This is a place-holder for an upcoming JDK8
118	+	* interface.
119	+	*/
120	+	public static interface RemappingFunction<K, V> {
121	+	/**
122	+	* Returns a new value given a key and its current value.
123	+	*
124	+	* @param key the (non-null) key
125	+	* @param value the current value, or null if there is no mapping
126	+	* @return a non-null value
127	+	*/
128	+	V remap(K key, V value);
129	+	}
130	+
131		/*
132		* Overview:
133		*
#	Line 134 | Line 144 | public class ConcurrentHashMapV8<K, V>
144		* work off Object types. And similarly, so do the internal
145		* methods of auxiliary iterator and view classes.  All public
146		* generic typed methods relay in/out of these internal methods,
147	<	* supplying null-checks and casts as needed.
147	>	* supplying null-checks and casts as needed. This also allows
148	>	* many of the public methods to be factored into a smaller number
149	>	* of internal methods (although sadly not so for the five
150	>	* sprawling variants of put-related operations).
151		*
152		* The table is lazily initialized to a power-of-two size upon the
153		* first insertion.  Each bin in the table contains a list of
154	<	* Nodes (most often, zero or one Node).  Table accesses require
155	<	* volatile/atomic reads, writes, and CASes.  Because there is no
156	<	* other way to arrange this without adding further indirections,
157	<	* we use intrinsics (sun.misc.Unsafe) operations.  The lists of
158	<	* nodes within bins are always accurately traversable under
159	<	* volatile reads, so long as lookups check hash code and
160	<	* non-nullness of value before checking key equality.
154	>	* Nodes (most often, the list has only zero or one Node).  Table
155	>	* accesses require volatile/atomic reads, writes, and CASes.
156	>	* Because there is no other way to arrange this without adding
157	>	* further indirections, we use intrinsics (sun.misc.Unsafe)
158	>	* operations.  The lists of nodes within bins are always
159	>	* accurately traversable under volatile reads, so long as lookups
160	>	* check hash code and non-nullness of value before checking key
161	>	* equality.
162		*
163		* We use the top two bits of Node hash fields for control
164		* purposes -- they are available anyway because of addressing
165		* constraints.  As explained further below, these top bits are
166	<	* usd as follows:
166	>	* used as follows:
167		*  00 - Normal
168		*  01 - Locked
169		*  11 - Locked and may have a thread waiting for lock
#	Line 158 | Line 172 | public class ConcurrentHashMapV8<K, V>
172		* The lower 30 bits of each Node's hash field contain a
173		* transformation (for better randomization -- method "spread") of
174		* the key's hash code, except for forwarding nodes, for which the
175	<	* lower bits are zero (and so always have hash field == "MOVED").
175	>	* lower bits are zero (and so always have hash field == MOVED).
176		*
177	<	* Insertion (via put or putIfAbsent) of the first node in an
177	>	* Insertion (via put or its variants) of the first node in an
178		* empty bin is performed by just CASing it to the bin.  This is
179		* by far the most common case for put operations.  Other update
180		* operations (insert, delete, and replace) require locks.  We do
#	Line 179 | Line 193 | public class ConcurrentHashMapV8<K, V>
193		* validate that it is still the first node after locking it, and
194		* retry if not. Because new nodes are always appended to lists,
195		* once a node is first in a bin, it remains first until deleted
196	<	* or the bin becomes invalidated.  However, operations that only
197	<	* conditionally update may inspect nodes until the point of
198	<	* update. This is a converse of sorts to the lazy locking
199	<	* technique described by Herlihy & Shavit.
196	>	* or the bin becomes invalidated (upon resizing).  However,
197	>	* operations that only conditionally update may inspect nodes
198	>	* until the point of update. This is a converse of sorts to the
199	>	* lazy locking technique described by Herlihy & Shavit.
200		*
201		* The main disadvantage of per-bin locks is that other update
202		* operations on other nodes in a bin list protected by the same
#	Line 266 | Line 280 | public class ConcurrentHashMapV8<K, V>
280		* The element count is maintained using a LongAdder, which avoids
281		* contention on updates but can encounter cache thrashing if read
282		* too frequently during concurrent access. To avoid reading so
283	<	* often, resizing is normally attempted only upon adding to a bin
284	<	* already holding two or more nodes. Under uniform hash
285	<	* distributions, the probability of this occurring at threshold
286	<	* is around 13%, meaning that only about 1 in 8 puts check
287	<	* threshold (and after resizing, many fewer do so). But this
288	<	* approximation has high variance for small table sizes, so we
289	<	* check on any collision for sizes <= 64.
283	>	* often, resizing is attempted either when a bin lock is
284	>	* contended, or upon adding to a bin already holding two or more
285	>	* nodes (checked before adding in the xIfAbsent methods, after
286	>	* adding in others). Under uniform hash distributions, the
287	>	* probability of this occurring at threshold is around 13%,
288	>	* meaning that only about 1 in 8 puts check threshold (and after
289	>	* resizing, many fewer do so). But this approximation has high
290	>	* variance for small table sizes, so we check on any collision
291	>	* for sizes <= 64. The bulk putAll operation further reduces
292	>	* contention by only committing count updates upon these size
293	>	* checks.
294		*
295		* Maintaining API and serialization compatibility with previous
296		* versions of this class introduces several oddities. Mainly: We
#	Line 496 | Line 514 | public class ConcurrentHashMapV8<K, V>
514		*/
515		private static final int spread(int h) {
516		// Apply base step of MurmurHash; see http://code.google.com/p/smhasher/
517	+	// Despite two multiplies, this is often faster than others
518	+	// with comparable bit-spread properties.
519		h ^= h >>> 16;
520		h *= 0x85ebca6b;
521		h ^= h >>> 13;
#	Line 522 | Line 542 | public class ConcurrentHashMapV8<K, V>
542		return null;
543		}
544
545	<	/** Implementation for put and putIfAbsent */
546	<	private final Object internalPut(Object k, Object v, boolean replace) {
545	>	/**
546	>	* Implementation for the four public remove/replace methods:
547	>	* Replaces node value with v, conditional upon match of cv if
548	>	* non-null.  If resulting value is null, delete.
549	>	*/
550	>	private final Object internalReplace(Object k, Object v, Object cv) {
551		int h = spread(k.hashCode());
552	<	Object oldVal = null;               // previous value or null if none
552	>	Object oldVal = null;
553		for (Node[] tab = table;;) {
554	<	int i; Node f; int fh; Object fk, fv;
554	>	Node f; int i, fh;
555	>	if (tab == null ||
556	>	(f = tabAt(tab, i = (tab.length - 1) & h)) == null)
557	>	break;
558	>	else if ((fh = f.hash) == MOVED)
559	>	tab = (Node[])f.key;
560	>	else if ((fh & HASH_BITS) != h && f.next == null) // precheck
561	>	break;                          // rules out possible existence
562	>	else if ((fh & LOCKED) != 0) {
563	>	checkForResize();               // try resizing if can't get lock
564	>	f.tryAwaitLock(tab, i);
565	>	}
566	>	else if (f.casHash(fh, fh | LOCKED)) {
567	>	boolean validated = false;
568	>	boolean deleted = false;
569	>	try {
570	>	if (tabAt(tab, i) == f) {
571	>	validated = true;
572	>	for (Node e = f, pred = null;;) {
573	>	Object ek, ev;
574	>	if ((e.hash & HASH_BITS) == h &&
575	>	((ev = e.val) != null) &&
576	>	((ek = e.key) == k || k.equals(ek))) {
577	>	if (cv == null || cv == ev || cv.equals(ev)) {
578	>	oldVal = ev;
579	>	if ((e.val = v) == null) {
580	>	deleted = true;
581	>	Node en = e.next;
582	>	if (pred != null)
583	>	pred.next = en;
584	>	else
585	>	setTabAt(tab, i, en);
586	>	}
587	>	}
588	>	break;
589	>	}
590	>	pred = e;
591	>	if ((e = e.next) == null)
592	>	break;
593	>	}
594	>	}
595	>	} finally {
596	>	if (!f.casHash(fh | LOCKED, fh)) {
597	>	f.hash = fh;
598	>	synchronized(f) { f.notifyAll(); };
599	>	}
600	>	}
601	>	if (validated) {
602	>	if (deleted)
603	>	counter.add(-1L);
604	>	break;
605	>	}
606	>	}
607	>	}
608	>	return oldVal;
609	>	}
610	>
611	>	/*
612	>	* Internal versions of the five insertion methods, each a
613	>	* little more complicated than the last. All have
614	>	* the same basic structure as the first (internalPut):
615	>	*  1. If table uninitialized, create
616	>	*  2. If bin empty, try to CAS new node
617	>	*  3. If bin stale, use new table
618	>	*  4. Lock and validate; if valid, scan and add or update
619	>	*
620	>	* The others interweave other checks and/or alternative actions:
621	>	*  * Plain put checks for and performs resize after insertion.
622	>	*  * putIfAbsent prescans for mapping without lock (and fails to add
623	>	*    if present), which also makes pre-emptive resize checks worthwhile.
624	>	*  * computeIfAbsent extends form used in putIfAbsent with additional
625	>	*    mechanics to deal with, calls, potential exceptions and null
626	>	*    returns from function call.
627	>	*  * compute uses the same function-call mechanics, but without
628	>	*    the prescans
629	>	*  * putAll attempts to pre-allocate enough table space
630	>	*    and more lazily performs count updates and checks.
631	>	*
632	>	* Someday when details settle down a bit more, it might be worth
633	>	* some factoring to reduce sprawl.
634	>	*/
635	>
636	>	/** Implementation for put */
637	>	private final Object internalPut(Object k, Object v) {
638	>	int h = spread(k.hashCode());
639	>	boolean checkSize = false;
640	>	for (Node[] tab = table;;) {
641	>	int i; Node f; int fh;
642		if (tab == null)
643		tab = initTable();
644		else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
#	Line 536 | Line 647 | public class ConcurrentHashMapV8<K, V>
647		}
648		else if ((fh = f.hash) == MOVED)
649		tab = (Node[])f.key;
650	<	else if (!replace && (fh & HASH_BITS) == h && (fv = f.val) != null &&
651	<	((fk = f.key) == k || k.equals(fk))) {
541	<	oldVal = fv;                // precheck 1st node for putIfAbsent
542	<	break;
543	<	}
544	<	else if ((fh & LOCKED) != 0)
650	>	else if ((fh & LOCKED) != 0) {
651	>	checkForResize();
652		f.tryAwaitLock(tab, i);
653	+	}
654		else if (f.casHash(fh, fh | LOCKED)) {
655	+	Object oldVal = null;
656		boolean validated = false;
657	<	boolean checkSize = false;
549	<	try {
657	>	try {                        // needed in case equals() throws
658		if (tabAt(tab, i) == f) {
659		validated = true;    // retry if 1st already deleted
660		for (Node e = f;;) {
#	Line 555 | Line 663 | public class ConcurrentHashMapV8<K, V>
663		(ev = e.val) != null &&
664		((ek = e.key) == k || k.equals(ek))) {
665		oldVal = ev;
666	<	if (replace)
559	<	e.val = v;
666	>	e.val = v;
667		break;
668		}
669		Node last = e;
#	Line 575 | Line 682 | public class ConcurrentHashMapV8<K, V>
682		}
683		}
684		if (validated) {
685	<	int sc;
686	<	if (checkSize && tab.length < MAXIMUM_CAPACITY &&
580	<	(sc = sizeCtl) >= 0 && counter.sum() >= (long)sc)
581	<	growTable();
685	>	if (oldVal != null)
686	>	return oldVal;
687		break;
688		}
689		}
690		}
691	<	if (oldVal == null)
692	<	counter.increment();             // update counter outside of locks
693	<	return oldVal;
691	>	counter.add(1L);
692	>	if (checkSize)
693	>	checkForResize();
694	>	return null;
695		}
696
697	<	/**
698	<	* Implementation for the four public remove/replace methods:
593	<	* Replaces node value with v, conditional upon match of cv if
594	<	* non-null.  If resulting value is null, delete.
595	<	*/
596	<	private final Object internalReplace(Object k, Object v, Object cv) {
697	>	/** Implementation for putIfAbsent */
698	>	private final Object internalPutIfAbsent(Object k, Object v) {
699		int h = spread(k.hashCode());
598	–	Object oldVal = null;
700		for (Node[] tab = table;;) {
701	<	Node f; int i, fh;
702	<	if (tab == null ||
703	<	(f = tabAt(tab, i = (tab.length - 1) & h)) == null)
704	<	break;
701	>	int i; Node f; int fh; Object fk, fv;
702	>	if (tab == null)
703	>	tab = initTable();
704	>	else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
705	>	if (casTabAt(tab, i, null, new Node(h, k, v, null)))
706	>	break;
707	>	}
708		else if ((fh = f.hash) == MOVED)
709		tab = (Node[])f.key;
710	<	else if ((fh & HASH_BITS) != h && f.next == null) // precheck
711	<	break;                          // rules out possible existence
712	<	else if ((fh & LOCKED) != 0)
713	<	f.tryAwaitLock(tab, i);
714	<	else if (f.casHash(fh, fh | LOCKED)) {
715	<	boolean validated = false;
716	<	boolean deleted = false;
717	<	try {
718	<	if (tabAt(tab, i) == f) {
719	<	validated = true;
720	<	for (Node e = f, pred = null;;) {
721	<	Object ek, ev;
722	<	if ((e.hash & HASH_BITS) == h &&
723	<	((ev = e.val) != null) &&
724	<	((ek = e.key) == k || k.equals(ek))) {
725	<	if (cv == null || cv == ev || cv.equals(ev)) {
710	>	else if ((fh & HASH_BITS) == h && (fv = f.val) != null &&
711	>	((fk = f.key) == k || k.equals(fk)))
712	>	return fv;
713	>	else {
714	>	Node g = f.next;
715	>	if (g != null) { // at least 2 nodes -- search and maybe resize
716	>	for (Node e = g;;) {
717	>	Object ek, ev;
718	>	if ((e.hash & HASH_BITS) == h && (ev = e.val) != null &&
719	>	((ek = e.key) == k || k.equals(ek)))
720	>	return ev;
721	>	if ((e = e.next) == null) {
722	>	checkForResize();
723	>	break;
724	>	}
725	>	}
726	>	}
727	>	if (((fh = f.hash) & LOCKED) != 0) {
728	>	checkForResize();
729	>	f.tryAwaitLock(tab, i);
730	>	}
731	>	else if (tabAt(tab, i) == f && f.casHash(fh, fh | LOCKED)) {
732	>	Object oldVal = null;
733	>	boolean validated = false;
734	>	try {
735	>	if (tabAt(tab, i) == f) {
736	>	validated = true;
737	>	for (Node e = f;;) {
738	>	Object ek, ev;
739	>	if ((e.hash & HASH_BITS) == h &&
740	>	(ev = e.val) != null &&
741	>	((ek = e.key) == k || k.equals(ek))) {
742		oldVal = ev;
743	<	if ((e.val = v) == null) {
744	<	deleted = true;
745	<	Node en = e.next;
746	<	if (pred != null)
747	<	pred.next = en;
748	<	else
629	<	setTabAt(tab, i, en);
630	<	}
743	>	break;
744	>	}
745	>	Node last = e;
746	>	if ((e = e.next) == null) {
747	>	last.next = new Node(h, k, v, null);
748	>	break;
749		}
632	–	break;
750		}
751	<	pred = e;
752	<	if ((e = e.next) == null)
753	<	break;
751	>	}
752	>	} finally {
753	>	if (!f.casHash(fh | LOCKED, fh)) {
754	>	f.hash = fh;
755	>	synchronized(f) { f.notifyAll(); };
756		}
757		}
758	<	} finally {
759	<	if (!f.casHash(fh | LOCKED, fh)) {
760	<	f.hash = fh;
761	<	synchronized (f) { f.notifyAll(); };
758	>	if (validated) {
759	>	if (oldVal != null)
760	>	return oldVal;
761	>	break;
762		}
763		}
764	<	if (validated) {
765	<	if (deleted)
766	<	counter.decrement();
764	>	}
765	>	}
766	>	counter.add(1L);
767	>	return null;
768	>	}
769	>
770	>	/** Implementation for computeIfAbsent */
771	>	private final Object internalComputeIfAbsent(K k,
772	>	MappingFunction<? super K, ?> mf) {
773	>	int h = spread(k.hashCode());
774	>	Object val = null;
775	>	for (Node[] tab = table;;) {
776	>	Node f; int i, fh; Object fk, fv;
777	>	if (tab == null)
778	>	tab = initTable();
779	>	else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
780	>	Node node = new Node(fh = h | LOCKED, k, null, null);
781	>	boolean validated = false;
782	>	if (casTabAt(tab, i, null, node)) {
783	>	validated = true;
784	>	try {
785	>	if ((val = mf.map(k)) != null)
786	>	node.val = val;
787	>	} finally {
788	>	if (val == null)
789	>	setTabAt(tab, i, null);
790	>	if (!node.casHash(fh, h)) {
791	>	node.hash = h;
792	>	synchronized(node) { node.notifyAll(); };
793	>	}
794	>	}
795	>	}
796	>	if (validated)
797		break;
798	+	}
799	+	else if ((fh = f.hash) == MOVED)
800	+	tab = (Node[])f.key;
801	+	else if ((fh & HASH_BITS) == h && (fv = f.val) != null &&
802	+	((fk = f.key) == k || k.equals(fk)))
803	+	return fv;
804	+	else {
805	+	Node g = f.next;
806	+	if (g != null) {
807	+	for (Node e = g;;) {
808	+	Object ek, ev;
809	+	if ((e.hash & HASH_BITS) == h && (ev = e.val) != null &&
810	+	((ek = e.key) == k || k.equals(ek)))
811	+	return ev;
812	+	if ((e = e.next) == null) {
813	+	checkForResize();
814	+	break;
815	+	}
816	+	}
817	+	}
818	+	if (((fh = f.hash) & LOCKED) != 0) {
819	+	checkForResize();
820	+	f.tryAwaitLock(tab, i);
821	+	}
822	+	else if (tabAt(tab, i) == f && f.casHash(fh, fh | LOCKED)) {
823	+	boolean validated = false;
824	+	try {
825	+	if (tabAt(tab, i) == f) {
826	+	validated = true;
827	+	for (Node e = f;;) {
828	+	Object ek, ev;
829	+	if ((e.hash & HASH_BITS) == h &&
830	+	(ev = e.val) != null &&
831	+	((ek = e.key) == k || k.equals(ek))) {
832	+	val = ev;
833	+	break;
834	+	}
835	+	Node last = e;
836	+	if ((e = e.next) == null) {
837	+	if ((val = mf.map(k)) != null)
838	+	last.next = new Node(h, k, val, null);
839	+	break;
840	+	}
841	+	}
842	+	}
843	+	} finally {
844	+	if (!f.casHash(fh | LOCKED, fh)) {
845	+	f.hash = fh;
846	+	synchronized(f) { f.notifyAll(); };
847	+	}
848	+	}
849	+	if (validated)
850	+	break;
851		}
852		}
853		}
854	<	return oldVal;
854	>	if (val == null)
855	>	throw new NullPointerException();
856	>	counter.add(1L);
857	>	return val;
858		}
859
860	<	/** Implementation for computeIfAbsent and compute. Like put, but messier. */
656	<	// Todo: Somehow reinstate non-termination check
860	>	/** Implementation for compute */
861		@SuppressWarnings("unchecked")
862	<	private final V internalCompute(K k,
863	<	MappingFunction<? super K, ? extends V> fn,
660	<	boolean replace) {
862	>	private final Object internalCompute(K k,
863	>	RemappingFunction<? super K, V> mf) {
864		int h = spread(k.hashCode());
865	<	V val = null;
865	>	Object val = null;
866		boolean added = false;
867	<	Node[] tab = table;
868	<	outer:for (;;) {
869	<	Node f; int i, fh; Object fk, fv;
867	>	boolean checkSize = false;
868	>	for (Node[] tab = table;;) {
869	>	Node f; int i, fh;
870		if (tab == null)
871		tab = initTable();
872		else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null) {
#	Line 672 | Line 875 | public class ConcurrentHashMapV8<K, V>
875		if (casTabAt(tab, i, null, node)) {
876		validated = true;
877		try {
878	<	val = fn.map(k);
676	<	if (val != null) {
878	>	if ((val = mf.remap(k, null)) != null) {
879		node.val = val;
880		added = true;
881		}
#	Line 691 | Line 893 | public class ConcurrentHashMapV8<K, V>
893		}
894		else if ((fh = f.hash) == MOVED)
895		tab = (Node[])f.key;
896	<	else if (!replace && (fh & HASH_BITS) == h && (fv = f.val) != null &&
897	<	((fk = f.key) == k || k.equals(fk))) {
696	<	if (tabAt(tab, i) == f) {
697	<	val = (V)fv;
698	<	break;
699	<	}
700	<	}
701	<	else if ((fh & LOCKED) != 0)
896	>	else if ((fh & LOCKED) != 0) {
897	>	checkForResize();
898		f.tryAwaitLock(tab, i);
899	+	}
900		else if (f.casHash(fh, fh | LOCKED)) {
901		boolean validated = false;
705	–	boolean checkSize = false;
902		try {
903		if (tabAt(tab, i) == f) {
904		validated = true;
905		for (Node e = f;;) {
906	<	Object ek, ev, v;
906	>	Object ek, ev;
907		if ((e.hash & HASH_BITS) == h &&
908		(ev = e.val) != null &&
909		((ek = e.key) == k || k.equals(ek))) {
910	<	if (replace && (v = fn.map(k)) != null)
911	<	ev = e.val = v;
912	<	val = (V)ev;
910	>	val = mf.remap(k, (V)ev);
911	>	if (val != null)
912	>	e.val = val;
913		break;
914		}
915		Node last = e;
916		if ((e = e.next) == null) {
917	<	if ((val = fn.map(k)) != null) {
917	>	if ((val = mf.remap(k, null)) != null) {
918		last.next = new Node(h, k, val, null);
919		added = true;
920		if (last != f || tab.length <= 64)
#	Line 734 | Line 930 | public class ConcurrentHashMapV8<K, V>
930		synchronized (f) { f.notifyAll(); };
931		}
932		}
933	<	if (validated) {
738	<	int sc;
739	<	if (checkSize && tab.length < MAXIMUM_CAPACITY &&
740	<	(sc = sizeCtl) >= 0 && counter.sum() >= (long)sc)
741	<	growTable();
933	>	if (validated)
934		break;
743	–	}
935		}
936		}
937	<	if (added)
938	<	counter.increment();
937	>	if (added) {
938	>	counter.add(1L);
939	>	if (checkSize)
940	>	checkForResize();
941	>	}
942	>	else if (val == null)
943	>	throw new NullPointerException();
944		return val;
945		}
946
947	<	/**
948	<	* Implementation for clear. Steps through each bin, removing all nodes.
949	<	*/
950	<	private final void internalClear() {
951	<	long delta = 0L; // negative number of deletions
952	<	int i = 0;
953	<	Node[] tab = table;
954	<	while (tab != null && i < tab.length) {
955	<	int fh;
956	<	Node f = tabAt(tab, i);
957	<	if (f == null)
958	<	++i;
959	<	else if ((fh = f.hash) == MOVED)
960	<	tab = (Node[])f.key;
961	<	else if ((fh & LOCKED) != 0)
962	<	f.tryAwaitLock(tab, i);
963	<	else if (f.casHash(fh, fh | LOCKED)) {
964	<	boolean validated = false;
965	<	try {
966	<	if (tabAt(tab, i) == f) {
967	<	validated = true;
968	<	for (Node e = f; e != null; e = e.next) {
773	<	if (e.val != null) { // currently always true
774	<	e.val = null;
775	<	--delta;
776	<	}
947	>	/** Implementation for putAll */
948	>	private final void internalPutAll(Map<?, ?> m) {
949	>	tryPresize(m.size());
950	>	long delta = 0L;     // number of uncommitted additions
951	>	boolean npe = false; // to throw exception on exit for nulls
952	>	try {                // to clean up counts on other exceptions
953	>	for (Map.Entry<?, ?> entry : m.entrySet()) {
954	>	Object k, v;
955	>	if (entry == null || (k = entry.getKey()) == null ||
956	>	(v = entry.getValue()) == null) {
957	>	npe = true;
958	>	break;
959	>	}
960	>	int h = spread(k.hashCode());
961	>	for (Node[] tab = table;;) {
962	>	int i; Node f; int fh;
963	>	if (tab == null)
964	>	tab = initTable();
965	>	else if ((f = tabAt(tab, i = (tab.length - 1) & h)) == null){
966	>	if (casTabAt(tab, i, null, new Node(h, k, v, null))) {
967	>	++delta;
968	>	break;
969		}
778	–	setTabAt(tab, i, null);
970		}
971	<	} finally {
972	<	if (!f.casHash(fh | LOCKED, fh)) {
973	<	f.hash = fh;
974	<	synchronized (f) { f.notifyAll(); };
971	>	else if ((fh = f.hash) == MOVED)
972	>	tab = (Node[])f.key;
973	>	else if ((fh & LOCKED) != 0) {
974	>	counter.add(delta);
975	>	delta = 0L;
976	>	checkForResize();
977	>	f.tryAwaitLock(tab, i);
978	>	}
979	>	else if (f.casHash(fh, fh | LOCKED)) {
980	>	boolean validated = false;
981	>	boolean tooLong = false;
982	>	try {
983	>	if (tabAt(tab, i) == f) {
984	>	validated = true;
985	>	for (Node e = f;;) {
986	>	Object ek, ev;
987	>	if ((e.hash & HASH_BITS) == h &&
988	>	(ev = e.val) != null &&
989	>	((ek = e.key) == k || k.equals(ek))) {
990	>	e.val = v;
991	>	break;
992	>	}
993	>	Node last = e;
994	>	if ((e = e.next) == null) {
995	>	++delta;
996	>	last.next = new Node(h, k, v, null);
997	>	break;
998	>	}
999	>	tooLong = true;
1000	>	}
1001	>	}
1002	>	} finally {
1003	>	if (!f.casHash(fh | LOCKED, fh)) {
1004	>	f.hash = fh;
1005	>	synchronized(f) { f.notifyAll(); };
1006	>	}
1007	>	}
1008	>	if (validated) {
1009	>	if (tooLong) {
1010	>	counter.add(delta);
1011	>	delta = 0L;
1012	>	checkForResize();
1013	>	}
1014	>	break;
1015	>	}
1016		}
1017		}
786	–	if (validated)
787	–	++i;
1018		}
1019	+	} finally {
1020	+	if (delta != 0)
1021	+	counter.add(delta);
1022		}
1023	<	counter.add(delta);
1023	>	if (npe)
1024	>	throw new NullPointerException();
1025		}
1026
1027	<	/* ----------------Table Initialization and Resizing -------------- */
1027	>	/* ---------------- Table Initialization and Resizing -------------- */
1028
1029		/**
1030		* Returns a power of two table size for the given desired capacity.
#	Line 819 | Line 1053 | public class ConcurrentHashMapV8<K, V>
1053		if ((tab = table) == null) {
1054		int n = (sc > 0) ? sc : DEFAULT_CAPACITY;
1055		tab = table = new Node[n];
1056	<	sc = n - (n >>> 2) - 1;
1056	>	sc = n - (n >>> 2);
1057		}
1058		} finally {
1059		sizeCtl = sc;
#	Line 831 | Line 1065 | public class ConcurrentHashMapV8<K, V>
1065		}
1066
1067		/**
1068	<	* If not already resizing, creates next table and transfers bins.
1069	<	* Rechecks occupancy after a transfer to see if another resize is
1070	<	* already needed because resizings are lagging additions.
1071	<	*/
1072	<	private final void growTable() {
1073	<	int sc = sizeCtl;
1074	<	if (sc >= 0 && UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
1068	>	* If table is too small and not already resizing, creates next
1069	>	* table and transfers bins.  Rechecks occupancy after a transfer
1070	>	* to see if another resize is already needed because resizings
1071	>	* are lagging additions.
1072	>	*/
1073	>	private final void checkForResize() {
1074	>	Node[] tab; int n, sc;
1075	>	while ((tab = table) != null &&
1076	>	(n = tab.length) < MAXIMUM_CAPACITY &&
1077	>	(sc = sizeCtl) >= 0 && counter.sum() >= (long)sc &&
1078	>	UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
1079		try {
1080	<	Node[] tab; int n;
843	<	while ((tab = table) != null &&
844	<	(n = tab.length) > 0 && n < MAXIMUM_CAPACITY &&
845	<	counter.sum() >= (long)sc) {
1080	>	if (tab == table) {
1081		table = rebuild(tab);
1082	<	sc = (n << 1) - (n >>> 1) - 1;
1082	>	sc = (n << 1) - (n >>> 1);
1083		}
1084		} finally {
1085		sizeCtl = sc;
#	Line 852 | Line 1087 | public class ConcurrentHashMapV8<K, V>
1087		}
1088		}
1089
1090	+	/**
1091	+	* Tries to presize table to accommodate the given number of elements.
1092	+	*
1093	+	* @param size number of elements (doesn't need to be perfectly accurate)
1094	+	*/
1095	+	private final void tryPresize(int size) {
1096	+	int c = (size >= (MAXIMUM_CAPACITY >>> 1)) ? MAXIMUM_CAPACITY :
1097	+	tableSizeFor(size + (size >>> 1) + 1);
1098	+	int sc;
1099	+	while ((sc = sizeCtl) >= 0) {
1100	+	Node[] tab = table; int n;
1101	+	if (tab == null || (n = tab.length) == 0) {
1102	+	n = (sc > c)? sc : c;
1103	+	if (UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
1104	+	try {
1105	+	if (table == tab) {
1106	+	table = new Node[n];
1107	+	sc = n - (n >>> 2);
1108	+	}
1109	+	} finally {
1110	+	sizeCtl = sc;
1111	+	}
1112	+	}
1113	+	}
1114	+	else if (c <= sc || n >= MAXIMUM_CAPACITY)
1115	+	break;
1116	+	else if (UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
1117	+	try {
1118	+	if (table == tab) {
1119	+	table = rebuild(tab);
1120	+	sc = (n << 1) - (n >>> 1);
1121	+	}
1122	+	} finally {
1123	+	sizeCtl = sc;
1124	+	}
1125	+	}
1126	+	}
1127	+	}
1128	+
1129		/*
1130		* Moves and/or copies the nodes in each bin to new table. See
1131		* above for explanation.
#	Line 961 | Line 1235 | public class ConcurrentHashMapV8<K, V>
1235		}
1236		}
1237
1238	+	/**
1239	+	* Implementation for clear. Steps through each bin, removing all
1240	+	* nodes.
1241	+	*/
1242	+	private final void internalClear() {
1243	+	long delta = 0L; // negative number of deletions
1244	+	int i = 0;
1245	+	Node[] tab = table;
1246	+	while (tab != null && i < tab.length) {
1247	+	int fh;
1248	+	Node f = tabAt(tab, i);
1249	+	if (f == null)
1250	+	++i;
1251	+	else if ((fh = f.hash) == MOVED)
1252	+	tab = (Node[])f.key;
1253	+	else if ((fh & LOCKED) != 0) {
1254	+	counter.add(delta); // opportunistically update count
1255	+	delta = 0L;
1256	+	f.tryAwaitLock(tab, i);
1257	+	}
1258	+	else if (f.casHash(fh, fh | LOCKED)) {
1259	+	boolean validated = false;
1260	+	try {
1261	+	if (tabAt(tab, i) == f) {
1262	+	validated = true;
1263	+	for (Node e = f; e != null; e = e.next) {
1264	+	if (e.val != null) { // currently always true
1265	+	e.val = null;
1266	+	--delta;
1267	+	}
1268	+	}
1269	+	setTabAt(tab, i, null);
1270	+	}
1271	+	} finally {
1272	+	if (!f.casHash(fh | LOCKED, fh)) {
1273	+	f.hash = fh;
1274	+	synchronized(f) { f.notifyAll(); };
1275	+	}
1276	+	}
1277	+	if (validated)
1278	+	++i;
1279	+	}
1280	+	}
1281	+	if (delta != 0)
1282	+	counter.add(delta);
1283	+	}
1284	+
1285	+
1286		/* ----------------Table Traversal -------------- */
1287
1288		/**
#	Line 982 | Line 1304 | public class ConcurrentHashMapV8<K, V>
1304		* value, or key-value pairs as return values of Iterator.next(),
1305		* and encapsulate the it.next check as hasNext();
1306		*
1307	<	* The iterator visits each valid node that was reachable upon
1308	<	* iterator construction once. It might miss some that were added
1309	<	* to a bin after the bin was visited, which is OK wrt consistency
1310	<	* guarantees. Maintaining this property in the face of possible
1311	<	* ongoing resizes requires a fair amount of bookkeeping state
1312	<	* that is difficult to optimize away amidst volatile accesses.
1313	<	* Even so, traversal maintains reasonable throughput.
1307	>	* The iterator visits once each still-valid node that was
1308	>	* reachable upon iterator construction. It might miss some that
1309	>	* were added to a bin after the bin was visited, which is OK wrt
1310	>	* consistency guarantees. Maintaining this property in the face
1311	>	* of possible ongoing resizes requires a fair amount of
1312	>	* bookkeeping state that is difficult to optimize away amidst
1313	>	* volatile accesses.  Even so, traversal maintains reasonable
1314	>	* throughput.
1315		*
1316		* Normally, iteration proceeds bin-by-bin traversing lists.
1317		* However, if the table has been resized, then all future steps
#	Line 1026 | Line 1349 | public class ConcurrentHashMapV8<K, V>
1349		this.tab = tab;
1350		baseSize = (tab == null) ? 0 : tab.length;
1351		baseLimit = (hi <= baseSize) ? hi : baseSize;
1352	<	index = baseIndex = lo;
1352	>	index = baseIndex = (lo >= 0) ? lo : 0;
1353		next = null;
1354		advance();
1355		}
#	Line 1090 | Line 1413 | public class ConcurrentHashMapV8<K, V>
1413		public ConcurrentHashMapV8(Map<? extends K, ? extends V> m) {
1414		this.counter = new LongAdder();
1415		this.sizeCtl = DEFAULT_CAPACITY;
1416	<	putAll(m);
1416	>	internalPutAll(m);
1417		}
1418
1419		/**
#	Line 1257 | Line 1580 | public class ConcurrentHashMapV8<K, V>
1580		public V put(K key, V value) {
1581		if (key == null || value == null)
1582		throw new NullPointerException();
1583	<	return (V)internalPut(key, value, true);
1583	>	return (V)internalPut(key, value);
1584		}
1585
1586		/**
#	Line 1271 | Line 1594 | public class ConcurrentHashMapV8<K, V>
1594		public V putIfAbsent(K key, V value) {
1595		if (key == null || value == null)
1596		throw new NullPointerException();
1597	<	return (V)internalPut(key, value, false);
1597	>	return (V)internalPutIfAbsent(key, value);
1598		}
1599
1600		/**
#	Line 1282 | Line 1605 | public class ConcurrentHashMapV8<K, V>
1605		* @param m mappings to be stored in this map
1606		*/
1607		public void putAll(Map<? extends K, ? extends V> m) {
1608	<	if (m == null)
1286	<	throw new NullPointerException();
1287	<	/*
1288	<	* If uninitialized, try to preallocate big enough table
1289	<	*/
1290	<	if (table == null) {
1291	<	int size = m.size();
1292	<	int n = (size >= (MAXIMUM_CAPACITY >>> 1)) ? MAXIMUM_CAPACITY :
1293	<	tableSizeFor(size + (size >>> 1) + 1);
1294	<	int sc = sizeCtl;
1295	<	if (n < sc)
1296	<	n = sc;
1297	<	if (sc >= 0 &&
1298	<	UNSAFE.compareAndSwapInt(this, sizeCtlOffset, sc, -1)) {
1299	<	try {
1300	<	if (table == null) {
1301	<	table = new Node[n];
1302	<	sc = n - (n >>> 2) - 1;
1303	<	}
1304	<	} finally {
1305	<	sizeCtl = sc;
1306	<	}
1307	<	}
1308	<	}
1309	<	for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) {
1310	<	Object ek = e.getKey(), ev = e.getValue();
1311	<	if (ek == null || ev == null)
1312	<	throw new NullPointerException();
1313	<	internalPut(ek, ev, true);
1314	<	}
1608	>	internalPutAll(m);
1609		}
1610
1611		/**
1612		* If the specified key is not already associated with a value,
1613	<	* computes its value using the given mappingFunction, and if
1614	<	* non-null, enters it into the map.  This is equivalent to
1615	<	*  <pre> {@code
1613	>	* computes its value using the given mappingFunction and
1614	>	* enters it into the map.  This is equivalent to
1615	>	* <pre> {@code
1616		* if (map.containsKey(key))
1617		*   return map.get(key);
1618		* value = mappingFunction.map(key);
1619	<	* if (value != null)
1326	<	*   map.put(key, value);
1619	>	* map.put(key, value);
1620		* return value;}</pre>
1621		*
1622	<	* except that the action is performed atomically.  Some attempted
1623	<	* update operations on this map by other threads may be blocked
1624	<	* while computation is in progress, so the computation should be
1625	<	* short and simple, and must not attempt to update any other
1626	<	* mappings of this Map. The most appropriate usage is to
1627	<	* construct a new object serving as an initial mapped value, or
1628	<	* memoized result, as in:
1622	>	* except that the action is performed atomically.  If the
1623	>	* function returns {@code null} (in which case a {@code
1624	>	* NullPointerException} is thrown), or the function itself throws
1625	>	* an (unchecked) exception, the exception is rethrown to its
1626	>	* caller, and no mapping is recorded.  Some attempted update
1627	>	* operations on this map by other threads may be blocked while
1628	>	* computation is in progress, so the computation should be short
1629	>	* and simple, and must not attempt to update any other mappings
1630	>	* of this Map. The most appropriate usage is to construct a new
1631	>	* object serving as an initial mapped value, or memoized result,
1632	>	* as in:
1633	>	*
1634		*  <pre> {@code
1635		* map.computeIfAbsent(key, new MappingFunction<K, V>() {
1636		*   public V map(K k) { return new Value(f(k)); }});}</pre>
#	Line 1340 | Line 1638 | public class ConcurrentHashMapV8<K, V>
1638		* @param key key with which the specified value is to be associated
1639		* @param mappingFunction the function to compute a value
1640		* @return the current (existing or computed) value associated with
1641	<	*         the specified key, or {@code null} if the computation
1642	<	*         returned {@code null}
1643	<	* @throws NullPointerException if the specified key or mappingFunction
1346	<	*         is null
1641	>	*         the specified key.
1642	>	* @throws NullPointerException if the specified key, mappingFunction,
1643	>	*         or computed value is null
1644		* @throws IllegalStateException if the computation detectably
1645		*         attempts a recursive update to this map that would
1646		*         otherwise never complete
1647		* @throws RuntimeException or Error if the mappingFunction does so,
1648		*         in which case the mapping is left unestablished
1649		*/
1650	+	@SuppressWarnings("unchecked")
1651		public V computeIfAbsent(K key, MappingFunction<? super K, ? extends V> mappingFunction) {
1652		if (key == null || mappingFunction == null)
1653		throw new NullPointerException();
1654	<	return internalCompute(key, mappingFunction, false);
1654	>	return (V)internalComputeIfAbsent(key, mappingFunction);
1655		}
1656
1657		/**
1658	<	* Computes the value associated with the given key using the given
1659	<	* mappingFunction, and if non-null, enters it into the map.  This
1660	<	* is equivalent to
1658	>	* Computes and enters a new mapping value given a key and
1659	>	* its current mapped value (or {@code null} if there is no current
1660	>	* mapping). This is equivalent to
1661		*  <pre> {@code
1662	<	* value = mappingFunction.map(key);
1663	<	* if (value != null)
1366	<	*   map.put(key, value);
1367	<	* else
1368	<	*   value = map.get(key);
1369	<	* return value;}</pre>
1662	>	*  map.put(key, remappingFunction.remap(key, map.get(key));
1663	>	* }</pre>
1664		*
1665	<	* except that the action is performed atomically.  Some attempted
1665	>	* except that the action is performed atomically.  If the
1666	>	* function returns {@code null} (in which case a {@code
1667	>	* NullPointerException} is thrown), or the function itself throws
1668	>	* an (unchecked) exception, the exception is rethrown to its
1669	>	* caller, and current mapping is left unchanged.  Some attempted
1670		* update operations on this map by other threads may be blocked
1671		* while computation is in progress, so the computation should be
1672		* short and simple, and must not attempt to update any other
1673	<	* mappings of this Map.
1673	>	* mappings of this Map. For example, to either create or
1674	>	* append new messages to a value mapping:
1675	>	*
1676	>	* <pre> {@code
1677	>	* Map<Key, String> map = ...;
1678	>	* final String msg = ...;
1679	>	* map.compute(key, new RemappingFunction<Key, String>() {
1680	>	*   public String remap(Key k, String v) {
1681	>	*    return (v == null) ? msg : v + msg;});}</pre>
1682		*
1683		* @param key key with which the specified value is to be associated
1684	<	* @param mappingFunction the function to compute a value
1685	<	* @return the current value associated with
1686	<	*         the specified key, or {@code null} if the computation
1687	<	*         returned {@code null} and the value was not otherwise present
1688	<	* @throws NullPointerException if the specified key or mappingFunction
1383	<	*         is null
1684	>	* @param remappingFunction the function to compute a value
1685	>	* @return the new value associated with
1686	>	*         the specified key.
1687	>	* @throws NullPointerException if the specified key or remappingFunction
1688	>	*         or computed value is null
1689		* @throws IllegalStateException if the computation detectably
1690		*         attempts a recursive update to this map that would
1691		*         otherwise never complete
1692		* @throws RuntimeException or Error if the mappingFunction does so,
1693		*         in which case the mapping is unchanged
1694		*/
1695	<	public V compute(K key, MappingFunction<? super K, ? extends V> mappingFunction) {
1696	<	if (key == null || mappingFunction == null)
1695	>	@SuppressWarnings("unchecked")
1696	>	public V compute(K key, RemappingFunction<? super K, V> remappingFunction) {
1697	>	if (key == null || remappingFunction == null)
1698		throw new NullPointerException();
1699	<	return internalCompute(key, mappingFunction, true);
1699	>	return (V)internalCompute(key, remappingFunction);
1700		}
1701
1702		/**
#	Line 2103 | Line 2409 | public class ConcurrentHashMapV8<K, V>
2409		}
2410		if (!init) { // Can only happen if unsafely published.
2411		while (p != null) {
2412	<	internalPut(p.key, p.val, true);
2412	>	internalPut(p.key, p.val);
2413		p = p.next;
2414		}
2415		}

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