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root/jsr166/jsr166/src/main/java/util/ArrayDeque.java

Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.99 by jsr166, Sun Oct 30 16:32:40 2016 UTC vs.
Revision 1.116 by jsr166, Fri Nov 18 16:45:26 2016 UTC

#	Line 60 | Line 60 | import java.util.function.UnaryOperator;
60		public class ArrayDeque<E> extends AbstractCollection<E>
61		implements Deque<E>, Cloneable, Serializable
62		{
63	+	/*
64	+	* VMs excel at optimizing simple array loops where indices are
65	+	* incrementing or decrementing over a valid slice, e.g.
66	+	*
67	+	* for (int i = start; i < end; i++) ... elements[i]
68	+	*
69	+	* Because in a circular array, elements are in general stored in
70	+	* two disjoint such slices, we help the VM by writing unusual
71	+	* nested loops for all traversals over the elements.  Having only
72	+	* one hot inner loop body instead of two or three eases human
73	+	* maintenance and encourages VM loop inlining into the caller.
74	+	*/
75	+
76		/**
77		* The array in which the elements of the deque are stored.
78	<	* We guarantee that all array cells not holding deque elements
79	<	* are always null.
78	>	* All array cells not holding deque elements are always null.
79	>	* The array always has at least one null slot (at tail).
80		*/
81		transient Object[] elements;
82
83		/**
84		* The index of the element at the head of the deque (which is the
85		* element that would be removed by remove() or pop()); or an
86	<	* arbitrary number 0 <= head < elements.length if the deque is empty.
86	>	* arbitrary number 0 <= head < elements.length equal to tail if
87	>	* the deque is empty.
88		*/
89		transient int head;
90
91	<	/** Number of elements in this collection. */
92	<	transient int size;
91	>	/**
92	>	* The index at which the next element would be added to the tail
93	>	* of the deque (via addLast(E), add(E), or push(E));
94	>	* elements[tail] is always null.
95	>	*/
96	>	transient int tail;
97
98		/**
99		* The maximum size of array to allocate.
#	Line 92 | Line 110 | public class ArrayDeque<E> extends Abstr
110		*/
111		private void grow(int needed) {
112		// overflow-conscious code
95	–	// checkInvariants();
113		final int oldCapacity = elements.length;
114		int newCapacity;
115	<	// Double size if small; else grow by 50%
115	>	// Double capacity if small; else grow by 50%
116		int jump = (oldCapacity < 64) ? (oldCapacity + 2) : (oldCapacity >> 1);
117		if (jump < needed
118		|| (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0)
119		newCapacity = newCapacity(needed, jump);
120		elements = Arrays.copyOf(elements, newCapacity);
121	<	if (oldCapacity - head < size) {
121	>	// Exceptionally, here tail == head needs to be disambiguated
122	>	if (tail < head || (tail == head && elements[head] != null)) {
123		// wrap around; slide first leg forward to end of array
124		int newSpace = newCapacity - oldCapacity;
125		System.arraycopy(elements, head,
#	Line 136 | Line 154 | public class ArrayDeque<E> extends Abstr
154		* @since TBD
155		*/
156		/* public */ void ensureCapacity(int minCapacity) {
157	<	if (minCapacity > elements.length)
158	<	grow(minCapacity - elements.length);
157	>	int needed;
158	>	if ((needed = (minCapacity + 1 - elements.length)) > 0)
159	>	grow(needed);
160		// checkInvariants();
161		}
162
#	Line 147 | Line 166 | public class ArrayDeque<E> extends Abstr
166		* @since TBD
167		*/
168		/* public */ void trimToSize() {
169	<	if (size < elements.length) {
170	<	elements = toArray();
169	>	int size;
170	>	if ((size = size()) + 1 < elements.length) {
171	>	elements = toArray(new Object[size + 1]);
172		head = 0;
173	+	tail = size;
174		}
175		// checkInvariants();
176		}
#	Line 169 | Line 190 | public class ArrayDeque<E> extends Abstr
190		* @param numElements lower bound on initial capacity of the deque
191		*/
192		public ArrayDeque(int numElements) {
193	<	elements = new Object[numElements];
193	>	elements =
194	>	new Object[(numElements < 1) ? 1 :
195	>	(numElements == Integer.MAX_VALUE) ? Integer.MAX_VALUE :
196	>	numElements + 1];
197		}
198
199		/**
#	Line 183 | Line 207 | public class ArrayDeque<E> extends Abstr
207		* @throws NullPointerException if the specified collection is null
208		*/
209		public ArrayDeque(Collection<? extends E> c) {
210	<	Object[] es = c.toArray();
211	<	// defend against c.toArray (incorrectly) not returning Object[]
188	<	// (see e.g. https://bugs.openjdk.java.net/browse/JDK-6260652)
189	<	if (es.getClass() != Object[].class)
190	<	es = Arrays.copyOf(es, es.length, Object[].class);
191	<	for (Object obj : es)
192	<	Objects.requireNonNull(obj);
193	<	this.elements = es;
194	<	this.size = es.length;
210	>	this(c.size());
211	>	addAll(c);
212		}
213
214		/**
#	Line 213 | Line 230 | public class ArrayDeque<E> extends Abstr
230		}
231
232		/**
233	<	* Adds i and j, mod modulus.
234	<	* Precondition and postcondition: 0 <= i < modulus, 0 <= j <= modulus.
233	>	* Circularly adds the given distance to index i, mod modulus.
234	>	* Precondition: 0 <= i < modulus, 0 <= distance <= modulus.
235	>	* @return index 0 <= i < modulus
236		*/
237	<	static final int add(int i, int j, int modulus) {
238	<	if ((i += j) - modulus >= 0) i -= modulus;
237	>	static final int add(int i, int distance, int modulus) {
238	>	if ((i += distance) - modulus >= 0) distance -= modulus;
239		return i;
240		}
241
242		/**
243	<	* Returns the array index of the last element.
244	<	* May return invalid index -1 if there are no elements.
243	>	* Subtracts j from i, mod modulus.
244	>	* Index i must be logically ahead of index j.
245	>	* Precondition: 0 <= i < modulus, 0 <= j < modulus.
246	>	* @return the "circular distance" from j to i; corner case i == j
247	>	* is diambiguated to "empty", returning 0.
248		*/
249	<	final int tail() {
250	<	return add(head, size - 1, elements.length);
249	>	static final int sub(int i, int j, int modulus) {
250	>	if ((i -= j) < 0) i += modulus;
251	>	return i;
252		}
253
254		/**
255		* Returns element at array index i.
256	+	* This is a slight abuse of generics, accepted by javac.
257		*/
258		@SuppressWarnings("unchecked")
259	<	private E elementAt(int i) {
260	<	return (E) elements[i];
259	>	static final <E> E elementAt(Object[] es, int i) {
260	>	return (E) es[i];
261		}
262
263		/**
264		* A version of elementAt that checks for null elements.
265		* This check doesn't catch all possible comodifications,
266	<	* but does catch ones that corrupt traversal.  It's a little
244	<	* surprising that javac allows this abuse of generics.
266	>	* but does catch ones that corrupt traversal.
267		*/
268		static final <E> E nonNullElementAt(Object[] es, int i) {
269		@SuppressWarnings("unchecked") E e = (E) es[i];
#	Line 261 | Line 283 | public class ArrayDeque<E> extends Abstr
283		* @throws NullPointerException if the specified element is null
284		*/
285		public void addFirst(E e) {
286	<	// checkInvariants();
287	<	Objects.requireNonNull(e);
288	<	Object[] es;
289	<	int capacity, h;
290	<	final int s;
269	<	if ((s = size) == (capacity = (es = elements).length)) {
286	>	if (e == null)
287	>	throw new NullPointerException();
288	>	final Object[] es = elements;
289	>	es[head = dec(head, es.length)] = e;
290	>	if (head == tail)
291		grow(1);
271	–	capacity = (es = elements).length;
272	–	}
273	–	if ((h = head - 1) < 0) h = capacity - 1;
274	–	es[head = h] = e;
275	–	size = s + 1;
292		// checkInvariants();
293		}
294
#	Line 285 | Line 301 | public class ArrayDeque<E> extends Abstr
301		* @throws NullPointerException if the specified element is null
302		*/
303		public void addLast(E e) {
304	<	// checkInvariants();
305	<	Objects.requireNonNull(e);
306	<	Object[] es;
307	<	int capacity;
308	<	final int s;
293	<	if ((s = size) == (capacity = (es = elements).length)) {
304	>	if (e == null)
305	>	throw new NullPointerException();
306	>	final Object[] es = elements;
307	>	es[tail] = e;
308	>	if (head == (tail = inc(tail, es.length)))
309		grow(1);
295	–	capacity = (es = elements).length;
296	–	}
297	–	es[add(head, s, capacity)] = e;
298	–	size = s + 1;
310		// checkInvariants();
311		}
312
#	Line 311 | Line 322 | public class ArrayDeque<E> extends Abstr
322		*         of its elements are null
323		*/
324		public boolean addAll(Collection<? extends E> c) {
325	<	final int s = size, needed = c.size() - (elements.length - s);
326	<	if (needed > 0)
325	>	final int s = size(), needed;
326	>	if ((needed = s + c.size() - elements.length + 1) > 0)
327		grow(needed);
328	<	c.forEach((e) -> addLast(e));
328	>	c.forEach(this::addLast);
329		// checkInvariants();
330	<	return size > s;
330	>	return size() > s;
331		}
332
333		/**
#	Line 347 | Line 358 | public class ArrayDeque<E> extends Abstr
358		* @throws NoSuchElementException {@inheritDoc}
359		*/
360		public E removeFirst() {
350	–	// checkInvariants();
361		E e = pollFirst();
362		if (e == null)
363		throw new NoSuchElementException();
364	+	// checkInvariants();
365		return e;
366		}
367
#	Line 358 | Line 369 | public class ArrayDeque<E> extends Abstr
369		* @throws NoSuchElementException {@inheritDoc}
370		*/
371		public E removeLast() {
361	–	// checkInvariants();
372		E e = pollLast();
373		if (e == null)
374		throw new NoSuchElementException();
375	+	// checkInvariants();
376		return e;
377		}
378
379		public E pollFirst() {
380	+	final Object[] es;
381	+	final int h;
382	+	E e = elementAt(es = elements, h = head);
383	+	if (e != null) {
384	+	es[h] = null;
385	+	head = inc(h, es.length);
386	+	}
387		// checkInvariants();
370	–	int s, h;
371	–	if ((s = size) <= 0)
372	–	return null;
373	–	final Object[] es = elements;
374	–	@SuppressWarnings("unchecked") E e = (E) es[h = head];
375	–	es[h] = null;
376	–	if (++h >= es.length) h = 0;
377	–	head = h;
378	–	size = s - 1;
388		return e;
389		}
390
391		public E pollLast() {
392	+	final Object[] es;
393	+	final int t;
394	+	E e = elementAt(es = elements, t = dec(tail, es.length));
395	+	if (e != null)
396	+	es[tail = t] = null;
397		// checkInvariants();
384	–	final int s, tail;
385	–	if ((s = size) <= 0)
386	–	return null;
387	–	final Object[] es = elements;
388	–	@SuppressWarnings("unchecked")
389	–	E e = (E) es[tail = add(head, s - 1, es.length)];
390	–	es[tail] = null;
391	–	size = s - 1;
398		return e;
399		}
400
#	Line 396 | Line 402 | public class ArrayDeque<E> extends Abstr
402		* @throws NoSuchElementException {@inheritDoc}
403		*/
404		public E getFirst() {
405	+	E e = elementAt(elements, head);
406	+	if (e == null)
407	+	throw new NoSuchElementException();
408		// checkInvariants();
409	<	if (size <= 0) throw new NoSuchElementException();
401	<	return elementAt(head);
409	>	return e;
410		}
411
412		/**
413		* @throws NoSuchElementException {@inheritDoc}
414		*/
407	–	@SuppressWarnings("unchecked")
415		public E getLast() {
409	–	// checkInvariants();
410	–	final int s;
411	–	if ((s = size) <= 0) throw new NoSuchElementException();
416		final Object[] es = elements;
417	<	return (E) es[add(head, s - 1, es.length)];
417	>	E e = elementAt(es, dec(tail, es.length));
418	>	if (e == null)
419	>	throw new NoSuchElementException();
420	>	// checkInvariants();
421	>	return e;
422		}
423
424		public E peekFirst() {
425		// checkInvariants();
426	<	return (size <= 0) ? null : elementAt(head);
426	>	return elementAt(elements, head);
427		}
428
421	–	@SuppressWarnings("unchecked")
429		public E peekLast() {
430		// checkInvariants();
431	<	final int s;
432	<	if ((s = size) <= 0) return null;
426	<	final Object[] es = elements;
427	<	return (E) es[add(head, s - 1, es.length)];
431	>	final Object[] es;
432	>	return elementAt(es = elements, dec(tail, es.length));
433		}
434
435		/**
#	Line 442 | Line 447 | public class ArrayDeque<E> extends Abstr
447		public boolean removeFirstOccurrence(Object o) {
448		if (o != null) {
449		final Object[] es = elements;
450	<	int i, end, to, todo;
451	<	todo = (end = (i = head) + size)
447	<	- (to = (es.length - end >= 0) ? end : es.length);
448	<	for (;; to = todo, i = 0, todo = 0) {
450	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
451	>	; i = 0, to = end) {
452		for (; i < to; i++)
453		if (o.equals(es[i])) {
454		delete(i);
455		return true;
456		}
457	<	if (todo == 0) break;
457	>	if (to == end) break;
458		}
459		}
460		return false;
#	Line 472 | Line 475 | public class ArrayDeque<E> extends Abstr
475		public boolean removeLastOccurrence(Object o) {
476		if (o != null) {
477		final Object[] es = elements;
478	<	int i, to, end, todo;
479	<	todo = (to = ((end = (i = tail()) - size) >= -1) ? end : -1) - end;
480	<	for (;; to = (i = es.length - 1) - todo, todo = 0) {
478	<	for (; i > to; i--)
478	>	for (int i = tail, end = head, to = (i >= end) ? end : 0;
479	>	; i = es.length, to = end) {
480	>	for (i--; i > to - 1; i--)
481		if (o.equals(es[i])) {
482		delete(i);
483		return true;
484		}
485	<	if (todo == 0) break;
485	>	if (to == end) break;
486		}
487		}
488		return false;
#	Line 608 | Line 610 | public class ArrayDeque<E> extends Abstr
610		* <p>This method is called delete rather than remove to emphasize
611		* that its semantics differ from those of {@link List#remove(int)}.
612		*
613	<	* @return true if elements moved backwards
613	>	* @return true if elements near tail moved backwards
614		*/
615		boolean delete(int i) {
616		// checkInvariants();
617		final Object[] es = elements;
618		final int capacity = es.length;
619		final int h = head;
620	<	int front;              // number of elements before to-be-deleted elt
621	<	if ((front = i - h) < 0) front += capacity;
622	<	final int back = size - front - 1; // number of elements after
620	>	// number of elements before to-be-deleted elt
621	>	final int front = sub(i, h, capacity);
622	>	final int back = size() - front - 1; // number of elements after
623		if (front < back) {
624		// move front elements forwards
625		if (h <= i) {
#	Line 628 | Line 630 | public class ArrayDeque<E> extends Abstr
630		System.arraycopy(es, h, es, h + 1, front - (i + 1));
631		}
632		es[h] = null;
633	<	if ((head = (h + 1)) >= capacity) head = 0;
632	<	size--;
633	>	head = inc(h, capacity);
634		// checkInvariants();
635		return false;
636		} else {
637		// move back elements backwards
638	<	int tail = tail();
638	>	tail = dec(tail, capacity);
639		if (i <= tail) {
640		System.arraycopy(es, i + 1, es, i, back);
641		} else { // Wrap around
#	Line 644 | Line 645 | public class ArrayDeque<E> extends Abstr
645		System.arraycopy(es, 1, es, 0, back - firstLeg - 1);
646		}
647		es[tail] = null;
647	–	size--;
648		// checkInvariants();
649		return true;
650		}
#	Line 658 | Line 658 | public class ArrayDeque<E> extends Abstr
658		* @return the number of elements in this deque
659		*/
660		public int size() {
661	<	return size;
661	>	return sub(tail, head, elements.length);
662		}
663
664		/**
#	Line 667 | Line 667 | public class ArrayDeque<E> extends Abstr
667		* @return {@code true} if this deque contains no elements
668		*/
669		public boolean isEmpty() {
670	<	return size == 0;
670	>	return head == tail;
671		}
672
673		/**
#	Line 691 | Line 691 | public class ArrayDeque<E> extends Abstr
691		int cursor;
692
693		/** Number of elements yet to be returned. */
694	<	int remaining = size;
694	>	int remaining = size();
695
696		/**
697		* Index of element returned by most recent call to next.
#	Line 711 | Line 711 | public class ArrayDeque<E> extends Abstr
711		final Object[] es = elements;
712		E e = nonNullElementAt(es, cursor);
713		lastRet = cursor;
714	<	if (++cursor >= es.length) cursor = 0;
714	>	cursor = inc(cursor, es.length);
715		remaining--;
716		return e;
717		}
718
719		void postDelete(boolean leftShifted) {
720		if (leftShifted)
721	<	if (--cursor < 0) cursor = elements.length - 1;
721	>	cursor = dec(cursor, elements.length);
722		}
723
724		public final void remove() {
#	Line 730 | Line 730 | public class ArrayDeque<E> extends Abstr
730
731		public void forEachRemaining(Consumer<? super E> action) {
732		Objects.requireNonNull(action);
733	<	final int k;
734	<	if ((k = remaining) > 0) {
735	<	remaining = 0;
736	<	ArrayDeque.forEachRemaining(action, elements, cursor, k);
737	<	if ((lastRet = cursor + k - 1) >= elements.length)
738	<	lastRet -= elements.length;
733	>	int r;
734	>	if ((r = remaining) <= 0)
735	>	return;
736	>	remaining = 0;
737	>	final Object[] es = elements;
738	>	if (es[cursor] == null || sub(tail, cursor, es.length) != r)
739	>	throw new ConcurrentModificationException();
740	>	for (int i = cursor, end = tail, to = (i <= end) ? end : es.length;
741	>	; i = 0, to = end) {
742	>	for (; i < to; i++)
743	>	action.accept(elementAt(es, i));
744	>	if (to == end) {
745	>	if (end != tail)
746	>	throw new ConcurrentModificationException();
747	>	lastRet = dec(end, es.length);
748	>	break;
749	>	}
750		}
751		}
752		}
753
754		private class DescendingIterator extends DeqIterator {
755	<	DescendingIterator() { cursor = tail(); }
755	>	DescendingIterator() { cursor = dec(tail, elements.length); }
756
757		public final E next() {
758		if (remaining <= 0)
#	Line 749 | Line 760 | public class ArrayDeque<E> extends Abstr
760		final Object[] es = elements;
761		E e = nonNullElementAt(es, cursor);
762		lastRet = cursor;
763	<	if (--cursor < 0) cursor = es.length - 1;
763	>	cursor = dec(cursor, es.length);
764		remaining--;
765		return e;
766		}
767
768		void postDelete(boolean leftShifted) {
769		if (!leftShifted)
770	<	if (++cursor >= elements.length) cursor = 0;
770	>	cursor = inc(cursor, elements.length);
771		}
772
773		public final void forEachRemaining(Consumer<? super E> action) {
774		Objects.requireNonNull(action);
775	<	final int k;
776	<	if ((k = remaining) > 0) {
777	<	remaining = 0;
778	<	final Object[] es = elements;
779	<	int i, end, to, todo;
780	<	todo = (to = ((end = (i = cursor) - k) >= -1) ? end : -1) - end;
781	<	for (;; to = (i = es.length - 1) - todo, todo = 0) {
782	<	for (; i > to; i--)
783	<	action.accept(nonNullElementAt(es, i));
784	<	if (todo == 0) break;
775	>	int r;
776	>	if ((r = remaining) <= 0)
777	>	return;
778	>	remaining = 0;
779	>	final Object[] es = elements;
780	>	if (es[cursor] == null || sub(cursor, head, es.length) + 1 != r)
781	>	throw new ConcurrentModificationException();
782	>	for (int i = cursor, end = head, to = (i >= end) ? end : 0;
783	>	; i = es.length - 1, to = end) {
784	>	// hotspot generates faster code than for: i >= to !
785	>	for (; i > to - 1; i--)
786	>	action.accept(elementAt(es, i));
787	>	if (to == end) {
788	>	if (end != head)
789	>	throw new ConcurrentModificationException();
790	>	lastRet = end;
791	>	break;
792		}
775	–	if ((lastRet = cursor - (k - 1)) < 0)
776	–	lastRet += es.length;
793		}
794		}
795		}
#	Line 792 | Line 808 | public class ArrayDeque<E> extends Abstr
808		* @since 1.8
809		*/
810		public Spliterator<E> spliterator() {
811	<	return new ArrayDequeSpliterator();
811	>	return new DeqSpliterator();
812		}
813
814	<	final class ArrayDequeSpliterator implements Spliterator<E> {
815	<	private int cursor;
816	<	private int remaining; // -1 until late-binding first use
814	>	final class DeqSpliterator implements Spliterator<E> {
815	>	private int fence;      // -1 until first use
816	>	private int cursor;     // current index, modified on traverse/split
817
818		/** Constructs late-binding spliterator over all elements. */
819	<	ArrayDequeSpliterator() {
820	<	this.remaining = -1;
819	>	DeqSpliterator() {
820	>	this.fence = -1;
821		}
822
823	<	/** Constructs spliterator over the given slice. */
824	<	ArrayDequeSpliterator(int cursor, int count) {
825	<	this.cursor = cursor;
826	<	this.remaining = count;
823	>	/** Constructs spliterator over the given range. */
824	>	DeqSpliterator(int origin, int fence) {
825	>	this.cursor = origin;
826	>	this.fence = fence;
827		}
828
829	<	/** Ensures late-binding initialization; then returns remaining. */
830	<	private int remaining() {
831	<	if (remaining < 0) {
829	>	/** Ensures late-binding initialization; then returns fence. */
830	>	private int getFence() { // force initialization
831	>	int t;
832	>	if ((t = fence) < 0) {
833	>	t = fence = tail;
834		cursor = head;
817	–	remaining = size;
835		}
836	<	return remaining;
836	>	return t;
837		}
838
839	<	public ArrayDequeSpliterator trySplit() {
840	<	final int mid;
841	<	if ((mid = remaining() >> 1) > 0) {
842	<	int oldCursor = cursor;
843	<	cursor = add(cursor, mid, elements.length);
844	<	remaining -= mid;
828	<	return new ArrayDequeSpliterator(oldCursor, mid);
829	<	}
830	<	return null;
839	>	public DeqSpliterator trySplit() {
840	>	final Object[] es = elements;
841	>	final int i, n;
842	>	return ((n = sub(getFence(), i = cursor, es.length) >> 1) <= 0)
843	>	? null
844	>	: new DeqSpliterator(i, cursor = add(i, n, es.length));
845		}
846
847		public void forEachRemaining(Consumer<? super E> action) {
848	<	Objects.requireNonNull(action);
849	<	final int k = remaining(); // side effect!
850	<	remaining = 0;
851	<	ArrayDeque.forEachRemaining(action, elements, cursor, k);
848	>	if (action == null)
849	>	throw new NullPointerException();
850	>	final int end = getFence(), cursor = this.cursor;
851	>	final Object[] es = elements;
852	>	if (cursor != end) {
853	>	this.cursor = end;
854	>	// null check at both ends of range is sufficient
855	>	if (es[cursor] == null || es[dec(end, es.length)] == null)
856	>	throw new ConcurrentModificationException();
857	>	for (int i = cursor, to = (i <= end) ? end : es.length;
858	>	; i = 0, to = end) {
859	>	for (; i < to; i++)
860	>	action.accept(elementAt(es, i));
861	>	if (to == end) break;
862	>	}
863	>	}
864		}
865
866		public boolean tryAdvance(Consumer<? super E> action) {
867	<	Objects.requireNonNull(action);
868	<	final int k;
869	<	if ((k = remaining()) <= 0)
867	>	if (action == null)
868	>	throw new NullPointerException();
869	>	final int t, i;
870	>	if ((t = getFence()) == (i = cursor))
871		return false;
872	<	action.accept(nonNullElementAt(elements, cursor));
873	<	if (++cursor >= elements.length) cursor = 0;
874	<	remaining = k - 1;
872	>	final Object[] es = elements;
873	>	cursor = inc(i, es.length);
874	>	action.accept(nonNullElementAt(es, i));
875		return true;
876		}
877
878		public long estimateSize() {
879	<	return remaining();
879	>	return sub(getFence(), cursor, elements.length);
880		}
881
882		public int characteristics() {
#	Line 860 | Line 887 | public class ArrayDeque<E> extends Abstr
887		}
888		}
889
863	–	@SuppressWarnings("unchecked")
890		public void forEach(Consumer<? super E> action) {
891		Objects.requireNonNull(action);
892		final Object[] es = elements;
893	<	int i, end, to, todo;
894	<	todo = (end = (i = head) + size)
869	<	- (to = (es.length - end >= 0) ? end : es.length);
870	<	for (;; to = todo, i = 0, todo = 0) {
893	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
894	>	; i = 0, to = end) {
895		for (; i < to; i++)
896	<	action.accept((E) es[i]);
897	<	if (todo == 0) break;
896	>	action.accept(elementAt(es, i));
897	>	if (to == end) {
898	>	if (end != tail) throw new ConcurrentModificationException();
899	>	break;
900	>	}
901		}
902		// checkInvariants();
903		}
904
905		/**
879	–	* Calls action on remaining elements, starting at index i and
880	–	* traversing in ascending order.  A variant of forEach that also
881	–	* checks for concurrent modification, for use in iterators.
882	–	*/
883	–	static <E> void forEachRemaining(
884	–	Consumer<? super E> action, Object[] es, int i, int remaining) {
885	–	int end, to, todo;
886	–	todo = (end = i + remaining)
887	–	- (to = (es.length - end >= 0) ? end : es.length);
888	–	for (;; to = todo, i = 0, todo = 0) {
889	–	for (; i < to; i++)
890	–	action.accept(nonNullElementAt(es, i));
891	–	if (todo == 0) break;
892	–	}
893	–	}
894	–
895	–	/**
906		* Replaces each element of this deque with the result of applying the
907		* operator to that element, as specified by {@link List#replaceAll}.
908		*
909		* @param operator the operator to apply to each element
910		* @since TBD
911		*/
902	–	@SuppressWarnings("unchecked")
912		/* public */ void replaceAll(UnaryOperator<E> operator) {
913		Objects.requireNonNull(operator);
914		final Object[] es = elements;
915	<	int i, end, to, todo;
916	<	todo = (end = (i = head) + size)
908	<	- (to = (es.length - end >= 0) ? end : es.length);
909	<	for (;; to = todo, i = 0, todo = 0) {
915	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
916	>	; i = 0, to = end) {
917		for (; i < to; i++)
918	<	es[i] = operator.apply((E) es[i]);
919	<	if (todo == 0) break;
918	>	es[i] = operator.apply(elementAt(es, i));
919	>	if (to == end) {
920	>	if (end != tail) throw new ConcurrentModificationException();
921	>	break;
922	>	}
923		}
924		// checkInvariants();
925		}
#	Line 942 | Line 952 | public class ArrayDeque<E> extends Abstr
952		private boolean bulkRemove(Predicate<? super E> filter) {
953		// checkInvariants();
954		final Object[] es = elements;
955	+	// Optimize for initial run of survivors
956	+	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
957	+	; i = 0, to = end) {
958	+	for (; i < to; i++)
959	+	if (filter.test(elementAt(es, i)))
960	+	return bulkRemoveModified(filter, i);
961	+	if (to == end) {
962	+	if (end != tail) throw new ConcurrentModificationException();
963	+	break;
964	+	}
965	+	}
966	+	return false;
967	+	}
968	+
969	+	// A tiny bit set implementation
970	+
971	+	private static long[] nBits(int n) {
972	+	return new long[((n - 1) >> 6) + 1];
973	+	}
974	+	private static void setBit(long[] bits, int i) {
975	+	bits[i >> 6] |= 1L << i;
976	+	}
977	+	private static boolean isClear(long[] bits, int i) {
978	+	return (bits[i >> 6] & (1L << i)) == 0;
979	+	}
980	+
981	+	/**
982	+	* Helper for bulkRemove, in case of at least one deletion.
983	+	* Tolerate predicates that reentrantly access the collection for
984	+	* read (but writers still get CME), so traverse once to find
985	+	* elements to delete, a second pass to physically expunge.
986	+	*
987	+	* @param beg valid index of first element to be deleted
988	+	*/
989	+	private boolean bulkRemoveModified(
990	+	Predicate<? super E> filter, final int beg) {
991	+	final Object[] es = elements;
992		final int capacity = es.length;
993	<	int i = head, j = i, remaining = size, deleted = 0;
994	<	try {
995	<	for (; remaining > 0; remaining--) {
996	<	@SuppressWarnings("unchecked") E e = (E) es[i];
997	<	if (filter.test(e))
998	<	deleted++;
999	<	else {
1000	<	if (j != i)
1001	<	es[j] = e;
1002	<	if (++j >= capacity) j = 0;
1003	<	}
1004	<	if (++i >= capacity) i = 0;
993	>	final int end = tail;
994	>	final long[] deathRow = nBits(sub(end, beg, capacity));
995	>	deathRow[0] = 1L;   // set bit 0
996	>	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
997	>	; i = 0, to = end, k -= capacity) {
998	>	for (; i < to; i++)
999	>	if (filter.test(elementAt(es, i)))
1000	>	setBit(deathRow, i - k);
1001	>	if (to == end) break;
1002	>	}
1003	>	// a two-finger traversal, with hare i reading, tortoise w writing
1004	>	int w = beg;
1005	>	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
1006	>	; w = 0) { // w rejoins i on second leg
1007	>	// In this loop, i and w are on the same leg, with i > w
1008	>	for (; i < to; i++)
1009	>	if (isClear(deathRow, i - k))
1010	>	es[w++] = es[i];
1011	>	if (to == end) break;
1012	>	// In this loop, w is on the first leg, i on the second
1013	>	for (i = 0, to = end, k -= capacity; i < to && w < capacity; i++)
1014	>	if (isClear(deathRow, i - k))
1015	>	es[w++] = es[i];
1016	>	if (i >= to) {
1017	>	if (w == capacity) w = 0; // "corner" case
1018	>	break;
1019		}
959	–	return deleted > 0;
960	–	} catch (Throwable ex) {
961	–	if (deleted > 0)
962	–	for (; remaining > 0; remaining--) {
963	–	es[j] = es[i];
964	–	if (++i >= capacity) i = 0;
965	–	if (++j >= capacity) j = 0;
966	–	}
967	–	throw ex;
968	–	} finally {
969	–	size -= deleted;
970	–	clearSlice(es, j, deleted);
971	–	// checkInvariants();
1020		}
1021	+	if (end != tail) throw new ConcurrentModificationException();
1022	+	circularClear(es, tail = w, end);
1023	+	// checkInvariants();
1024	+	return true;
1025		}
1026
1027		/**
#	Line 983 | Line 1035 | public class ArrayDeque<E> extends Abstr
1035		public boolean contains(Object o) {
1036		if (o != null) {
1037		final Object[] es = elements;
1038	<	int i, end, to, todo;
1039	<	todo = (end = (i = head) + size)
988	<	- (to = (es.length - end >= 0) ? end : es.length);
989	<	for (;; to = todo, i = 0, todo = 0) {
1038	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1039	>	; i = 0, to = end) {
1040		for (; i < to; i++)
1041		if (o.equals(es[i]))
1042		return true;
1043	<	if (todo == 0) break;
1043	>	if (to == end) break;
1044		}
1045		}
1046		return false;
#	Line 1018 | Line 1068 | public class ArrayDeque<E> extends Abstr
1068		* The deque will be empty after this call returns.
1069		*/
1070		public void clear() {
1071	<	clearSlice(elements, head, size);
1072	<	size = head = 0;
1071	>	circularClear(elements, head, tail);
1072	>	head = tail = 0;
1073		// checkInvariants();
1074		}
1075
1076		/**
1077	<	* Nulls out count elements, starting at array index i.
1077	>	* Nulls out slots starting at array index i, upto index end.
1078		*/
1079	<	private static void clearSlice(Object[] es, int i, int count) {
1080	<	int end, to, todo;
1081	<	todo = (end = i + count)
1032	<	- (to = (es.length - end >= 0) ? end : es.length);
1033	<	for (;; to = todo, i = 0, todo = 0) {
1079	>	private static void circularClear(Object[] es, int i, int end) {
1080	>	for (int to = (i <= end) ? end : es.length;
1081	>	; i = 0, to = end) {
1082		Arrays.fill(es, i, to, null);
1083	<	if (todo == 0) break;
1083	>	if (to == end) break;
1084		}
1085		}
1086
#	Line 1055 | Line 1103 | public class ArrayDeque<E> extends Abstr
1103
1104		private <T> T[] toArray(Class<T[]> klazz) {
1105		final Object[] es = elements;
1058	–	final int capacity = es.length;
1059	–	final int head = this.head, end = head + size;
1106		final T[] a;
1107	<	if (end >= 0) {
1107	>	final int size = size(), head = this.head, end;
1108	>	final int len = Math.min(size, es.length - head);
1109	>	if ((end = head + size) >= 0) {
1110		a = Arrays.copyOfRange(es, head, end, klazz);
1111		} else {
1112		// integer overflow!
1113		a = Arrays.copyOfRange(es, 0, size, klazz);
1114	<	System.arraycopy(es, head, a, 0, capacity - head);
1114	>	System.arraycopy(es, head, a, 0, len);
1115		}
1116	<	if (end - capacity > 0)
1117	<	System.arraycopy(es, 0, a, capacity - head, end - capacity);
1116	>	if (tail < head)
1117	>	System.arraycopy(es, 0, a, len, tail);
1118		return a;
1119		}
1120
#	Line 1109 | Line 1157 | public class ArrayDeque<E> extends Abstr
1157		@SuppressWarnings("unchecked")
1158		public <T> T[] toArray(T[] a) {
1159		final int size;
1160	<	if ((size = this.size) > a.length)
1160	>	if ((size = size()) > a.length)
1161		return toArray((Class<T[]>) a.getClass());
1162		final Object[] es = elements;
1163	<	final int head = this.head, end = head + size;
1164	<	final int front = (es.length - end >= 0) ? size : es.length - head;
1165	<	System.arraycopy(es, head, a, 0, front);
1166	<	if (front < size)
1167	<	System.arraycopy(es, 0, a, front, size - front);
1163	>	for (int i = head, j = 0, len = Math.min(size, es.length - i);
1164	>	; i = 0, len = tail) {
1165	>	System.arraycopy(es, i, a, j, len);
1166	>	if ((j += len) == size) break;
1167	>	}
1168		if (size < a.length)
1169		a[size] = null;
1170		return a;
#	Line 1156 | Line 1204 | public class ArrayDeque<E> extends Abstr
1204		s.defaultWriteObject();
1205
1206		// Write out size
1207	<	s.writeInt(size);
1207	>	s.writeInt(size());
1208
1209		// Write out elements in order.
1210		final Object[] es = elements;
1211	<	int i, end, to, todo;
1212	<	todo = (end = (i = head) + size)
1165	<	- (to = (es.length - end >= 0) ? end : es.length);
1166	<	for (;; to = todo, i = 0, todo = 0) {
1211	>	for (int i = head, end = tail, to = (i <= end) ? end : es.length;
1212	>	; i = 0, to = end) {
1213		for (; i < to; i++)
1214		s.writeObject(es[i]);
1215	<	if (todo == 0) break;
1215	>	if (to == end) break;
1216		}
1217		}
1218
#	Line 1182 | Line 1228 | public class ArrayDeque<E> extends Abstr
1228		s.defaultReadObject();
1229
1230		// Read in size and allocate array
1231	<	elements = new Object[size = s.readInt()];
1231	>	int size = s.readInt();
1232	>	elements = new Object[size + 1];
1233	>	this.tail = size;
1234
1235		// Read in all elements in the proper order.
1236		for (int i = 0; i < size; i++)
#	Line 1191 | Line 1239 | public class ArrayDeque<E> extends Abstr
1239
1240		/** debugging */
1241		void checkInvariants() {
1242	+	// Use head and tail fields with empty slot at tail strategy.
1243	+	// head == tail disambiguates to "empty".
1244		try {
1245		int capacity = elements.length;
1246	<	// assert size >= 0 && size <= capacity;
1247	<	// assert head >= 0;
1248	<	// assert capacity == 0 || head < capacity;
1249	<	// assert size == 0 || elements[head] != null;
1250	<	// assert size == 0 || elements[tail()] != null;
1251	<	// assert size == capacity || elements[dec(head, capacity)] == null;
1252	<	// assert size == capacity || elements[inc(tail(), capacity)] == null;
1246	>	// assert head >= 0 && head < capacity;
1247	>	// assert tail >= 0 && tail < capacity;
1248	>	// assert capacity > 0;
1249	>	// assert size() < capacity;
1250	>	// assert head == tail || elements[head] != null;
1251	>	// assert elements[tail] == null;
1252	>	// assert head == tail || elements[dec(tail, capacity)] != null;
1253		} catch (Throwable t) {
1254	<	System.err.printf("head=%d size=%d capacity=%d%n",
1255	<	head, size, elements.length);
1254	>	System.err.printf("head=%d tail=%d capacity=%d%n",
1255	>	head, tail, elements.length);
1256		System.err.printf("elements=%s%n",
1257		Arrays.toString(elements));
1258		throw t;

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