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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.109 by jsr166, Sat Nov 5 16:21:06 2016 UTC vs.
Revision 1.135 by jsr166, Mon Oct 1 00:10:52 2018 UTC

#	Line 9 | Line 9 | import java.io.Serializable;
9		import java.util.function.Consumer;
10		import java.util.function.Predicate;
11		import java.util.function.UnaryOperator;
12	+	import jdk.internal.misc.SharedSecrets;
13
14		/**
15		* Resizable-array implementation of the {@link Deque} interface.  Array
#	Line 50 | Line 51 | import java.util.function.UnaryOperator;
51		* Iterator} interfaces.
52		*
53		* <p>This class is a member of the
54	<	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
54	>	* <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
55		* Java Collections Framework</a>.
56		*
57		* @author  Josh Bloch and Doug Lea
#	Line 68 | Line 69 | public class ArrayDeque<E> extends Abstr
69		*
70		* Because in a circular array, elements are in general stored in
71		* two disjoint such slices, we help the VM by writing unusual
72	<	* nested loops for all traversals over the elements.
72	>	* nested loops for all traversals over the elements.  Having only
73	>	* one hot inner loop body instead of two or three eases human
74	>	* maintenance and encourages VM loop inlining into the caller.
75		*/
76
77		/**
78		* The array in which the elements of the deque are stored.
79	<	* We guarantee that all array cells not holding deque elements
80	<	* are always null.
79	>	* All array cells not holding deque elements are always null.
80	>	* The array always has at least one null slot (at tail).
81		*/
82		transient Object[] elements;
83
#	Line 88 | Line 91 | public class ArrayDeque<E> extends Abstr
91
92		/**
93		* The index at which the next element would be added to the tail
94	<	* of the deque (via addLast(E), add(E), or push(E)).
94	>	* of the deque (via addLast(E), add(E), or push(E));
95	>	* elements[tail] is always null.
96		*/
97		transient int tail;
98
#	Line 114 | Line 118 | public class ArrayDeque<E> extends Abstr
118		if (jump < needed
119		|| (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0)
120		newCapacity = newCapacity(needed, jump);
121	<	elements = Arrays.copyOf(elements, newCapacity);
121	>	final Object[] es = elements = Arrays.copyOf(elements, newCapacity);
122		// Exceptionally, here tail == head needs to be disambiguated
123	<	if (tail < head || (tail == head && elements[head] != null)) {
123	>	if (tail < head || (tail == head && es[head] != null)) {
124		// wrap around; slide first leg forward to end of array
125		int newSpace = newCapacity - oldCapacity;
126	<	System.arraycopy(elements, head,
127	<	elements, head + newSpace,
126	>	System.arraycopy(es, head,
127	>	es, head + newSpace,
128		oldCapacity - head);
129	<	Arrays.fill(elements, head, head + newSpace, null);
130	<	head += newSpace;
129	>	for (int i = head, to = (head += newSpace); i < to; i++)
130	>	es[i] = null;
131		}
132		// checkInvariants();
133		}
#	Line 177 | Line 181 | public class ArrayDeque<E> extends Abstr
181		* sufficient to hold 16 elements.
182		*/
183		public ArrayDeque() {
184	<	elements = new Object[16];
184	>	elements = new Object[16 + 1];
185		}
186
187		/**
#	Line 187 | Line 191 | public class ArrayDeque<E> extends Abstr
191		* @param numElements lower bound on initial capacity of the deque
192		*/
193		public ArrayDeque(int numElements) {
194	<	elements = new Object[Math.max(1, numElements + 1)];
194	>	elements =
195	>	new Object[(numElements < 1) ? 1 :
196	>	(numElements == Integer.MAX_VALUE) ? Integer.MAX_VALUE :
197	>	numElements + 1];
198		}
199
200		/**
#	Line 201 | Line 208 | public class ArrayDeque<E> extends Abstr
208		* @throws NullPointerException if the specified collection is null
209		*/
210		public ArrayDeque(Collection<? extends E> c) {
211	<	elements = new Object[c.size() + 1];
212	<	addAll(c);
211	>	this(c.size());
212	>	copyElements(c);
213		}
214
215		/**
216	<	* Increments i, mod modulus.
216	>	* Circularly increments i, mod modulus.
217		* Precondition and postcondition: 0 <= i < modulus.
218		*/
219		static final int inc(int i, int modulus) {
#	Line 215 | Line 222 | public class ArrayDeque<E> extends Abstr
222		}
223
224		/**
225	<	* Decrements i, mod modulus.
225	>	* Circularly decrements i, mod modulus.
226		* Precondition and postcondition: 0 <= i < modulus.
227		*/
228		static final int dec(int i, int modulus) {
#	Line 224 | Line 231 | public class ArrayDeque<E> extends Abstr
231		}
232
233		/**
234	<	* Adds i and j, mod modulus.
235	<	* Precondition and postcondition: 0 <= i < modulus, 0 <= j <= modulus.
234	>	* Circularly adds the given distance to index i, mod modulus.
235	>	* Precondition: 0 <= i < modulus, 0 <= distance <= modulus.
236	>	* @return index 0 <= i < modulus
237		*/
238	<	static final int add(int i, int j, int modulus) {
239	<	if ((i += j) - modulus >= 0) i -= modulus;
238	>	static final int inc(int i, int distance, int modulus) {
239	>	if ((i += distance) - modulus >= 0) i -= modulus;
240		return i;
241		}
242
243		/**
244		* Subtracts j from i, mod modulus.
245	<	* Index i must be logically ahead of j.
246	<	* Returns the "circular distance" from j to i.
247	<	* Precondition and postcondition: 0 <= i < modulus, 0 <= j < modulus.
245	>	* Index i must be logically ahead of index j.
246	>	* Precondition: 0 <= i < modulus, 0 <= j < modulus.
247	>	* @return the "circular distance" from j to i; corner case i == j
248	>	* is disambiguated to "empty", returning 0.
249		*/
250		static final int sub(int i, int j, int modulus) {
251		if ((i -= j) < 0) i += modulus;
#	Line 305 | Line 314 | public class ArrayDeque<E> extends Abstr
314		/**
315		* Adds all of the elements in the specified collection at the end
316		* of this deque, as if by calling {@link #addLast} on each one,
317	<	* in the order that they are returned by the collection's
309	<	* iterator.
317	>	* in the order that they are returned by the collection's iterator.
318		*
319		* @param c the elements to be inserted into this deque
320		* @return {@code true} if this deque changed as a result of the call
#	Line 314 | 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;
326	<	if ((needed = s + c.size() - elements.length + 1) > 0)
325	>	final int s, needed;
326	>	if ((needed = (s = size()) + c.size() + 1 - elements.length) > 0)
327		grow(needed);
328	<	c.forEach((e) -> addLast(e));
328	>	copyElements(c);
329		// checkInvariants();
330		return size() > s;
331		}
332
333	+	private void copyElements(Collection<? extends E> c) {
334	+	c.forEach(this::addLast);
335	+	}
336	+
337		/**
338		* Inserts the specified element at the front of this deque.
339		*
#	Line 469 | Line 481 | public class ArrayDeque<E> extends Abstr
481		final Object[] es = elements;
482		for (int i = tail, end = head, to = (i >= end) ? end : 0;
483		; i = es.length, to = end) {
484	<	while (--i >= to)
484	>	for (i--; i > to - 1; i--)
485		if (o.equals(es[i])) {
486		delete(i);
487		return true;
#	Line 512 | Line 524 | public class ArrayDeque<E> extends Abstr
524		/**
525		* Retrieves and removes the head of the queue represented by this deque.
526		*
527	<	* This method differs from {@link #poll poll} only in that it throws an
528	<	* exception if this deque is empty.
527	>	* This method differs from {@link #poll() poll()} only in that it
528	>	* throws an exception if this deque is empty.
529		*
530		* <p>This method is equivalent to {@link #removeFirst}.
531		*
#	Line 608 | Line 620 | public class ArrayDeque<E> extends Abstr
620		// checkInvariants();
621		final Object[] es = elements;
622		final int capacity = es.length;
623	<	final int h = head;
623	>	final int h, t;
624		// number of elements before to-be-deleted elt
625	<	final int front = sub(i, h, capacity);
626	<	final int back = size() - front - 1; // number of elements after
625	>	final int front = sub(i, h = head, capacity);
626	>	// number of elements after to-be-deleted elt
627	>	final int back = sub(t = tail, i, capacity) - 1;
628		if (front < back) {
629		// move front elements forwards
630		if (h <= i) {
#	Line 627 | Line 640 | public class ArrayDeque<E> extends Abstr
640		return false;
641		} else {
642		// move back elements backwards
643	<	tail = dec(tail, capacity);
643	>	tail = dec(t, capacity);
644		if (i <= tail) {
645		System.arraycopy(es, i + 1, es, i, back);
646		} else { // Wrap around
647	<	int firstLeg = capacity - (i + 1);
635	<	System.arraycopy(es, i + 1, es, i, firstLeg);
647	>	System.arraycopy(es, i + 1, es, i, capacity - (i + 1));
648		es[capacity - 1] = es[0];
649	<	System.arraycopy(es, 1, es, 0, back - firstLeg - 1);
649	>	System.arraycopy(es, 1, es, 0, t - 1);
650		}
651		es[tail] = null;
652		// checkInvariants();
#	Line 702 | Line 714 | public class ArrayDeque<E> extends Abstr
714		throw new NoSuchElementException();
715		final Object[] es = elements;
716		E e = nonNullElementAt(es, cursor);
717	<	lastRet = cursor;
706	<	cursor = inc(cursor, es.length);
717	>	cursor = inc(lastRet = cursor, es.length);
718		remaining--;
719		return e;
720		}
#	Line 751 | Line 762 | public class ArrayDeque<E> extends Abstr
762		throw new NoSuchElementException();
763		final Object[] es = elements;
764		E e = nonNullElementAt(es, cursor);
765	<	lastRet = cursor;
755	<	cursor = dec(cursor, es.length);
765	>	cursor = dec(lastRet = cursor, es.length);
766		remaining--;
767		return e;
768		}
#	Line 773 | Line 783 | public class ArrayDeque<E> extends Abstr
783		throw new ConcurrentModificationException();
784		for (int i = cursor, end = head, to = (i >= end) ? end : 0;
785		; i = es.length - 1, to = end) {
786	<	for (; i >= to; i--)
786	>	// hotspot generates faster code than for: i >= to !
787	>	for (; i > to - 1; i--)
788		action.accept(elementAt(es, i));
789		if (to == end) {
790		if (end != head)
791		throw new ConcurrentModificationException();
792	<	lastRet = head;
792	>	lastRet = end;
793		break;
794		}
795		}
#	Line 813 | Line 824 | public class ArrayDeque<E> extends Abstr
824
825		/** Constructs spliterator over the given range. */
826		DeqSpliterator(int origin, int fence) {
827	+	// assert 0 <= origin && origin < elements.length;
828	+	// assert 0 <= fence && fence < elements.length;
829		this.cursor = origin;
830		this.fence = fence;
831		}
#	Line 832 | Line 845 | public class ArrayDeque<E> extends Abstr
845		final int i, n;
846		return ((n = sub(getFence(), i = cursor, es.length) >> 1) <= 0)
847		? null
848	<	: new DeqSpliterator(i, cursor = add(i, n, es.length));
848	>	: new DeqSpliterator(i, cursor = inc(i, n, es.length));
849		}
850
851		public void forEachRemaining(Consumer<? super E> action) {
#	Line 855 | Line 868 | public class ArrayDeque<E> extends Abstr
868		}
869
870		public boolean tryAdvance(Consumer<? super E> action) {
871	<	if (action == null)
872	<	throw new NullPointerException();
873	<	int t, i;
874	<	if ((t = fence) < 0) t = getFence();
875	<	if (t == (i = cursor))
871	>	Objects.requireNonNull(action);
872	>	final Object[] es = elements;
873	>	if (fence < 0) { fence = tail; cursor = head; } // late-binding
874	>	final int i;
875	>	if ((i = cursor) == fence)
876		return false;
877	<	final Object[] es;
865	<	action.accept(nonNullElementAt(es = elements, i));
877	>	E e = nonNullElementAt(es, i);
878		cursor = inc(i, es.length);
879	+	action.accept(e);
880		return true;
881		}
882
#	Line 879 | Line 892 | public class ArrayDeque<E> extends Abstr
892		}
893		}
894
895	+	/**
896	+	* @throws NullPointerException {@inheritDoc}
897	+	*/
898		public void forEach(Consumer<? super E> action) {
899		Objects.requireNonNull(action);
900		final Object[] es = elements;
#	Line 949 | Line 965 | public class ArrayDeque<E> extends Abstr
965		; i = 0, to = end) {
966		for (; i < to; i++)
967		if (filter.test(elementAt(es, i)))
968	<	return bulkRemoveModified(filter, i, to);
968	>	return bulkRemoveModified(filter, i);
969		if (to == end) {
970		if (end != tail) throw new ConcurrentModificationException();
971		break;
#	Line 958 | Line 974 | public class ArrayDeque<E> extends Abstr
974		return false;
975		}
976
977	+	// A tiny bit set implementation
978	+
979	+	private static long[] nBits(int n) {
980	+	return new long[((n - 1) >> 6) + 1];
981	+	}
982	+	private static void setBit(long[] bits, int i) {
983	+	bits[i >> 6] |= 1L << i;
984	+	}
985	+	private static boolean isClear(long[] bits, int i) {
986	+	return (bits[i >> 6] & (1L << i)) == 0;
987	+	}
988	+
989		/**
990		* Helper for bulkRemove, in case of at least one deletion.
991	<	* @param i valid index of first element to be deleted
991	>	* Tolerate predicates that reentrantly access the collection for
992	>	* read (but writers still get CME), so traverse once to find
993	>	* elements to delete, a second pass to physically expunge.
994	>	*
995	>	* @param beg valid index of first element to be deleted
996		*/
997		private boolean bulkRemoveModified(
998	<	Predicate<? super E> filter, int i, int to) {
998	>	Predicate<? super E> filter, final int beg) {
999		final Object[] es = elements;
1000		final int capacity = es.length;
969	–	// a two-finger algorithm, with hare i reading, tortoise j writing
970	–	int j = i++;
1001		final int end = tail;
1002	<	try {
1003	<	for (;; j = 0) {    // j rejoins i on second leg
1004	<	E e;
1005	<	// In this loop, i and j are on the same leg, with i > j
1006	<	for (; i < to; i++)
1007	<	if (!filter.test(e = elementAt(es, i)))
1008	<	es[j++] = e;
1009	<	if (to == end) break;
1010	<	// In this loop, j is on the first leg, i on the second
1011	<	for (i = 0, to = end; i < to && j < capacity; i++)
1012	<	if (!filter.test(e = elementAt(es, i)))
1013	<	es[j++] = e;
1014	<	if (i >= to) {
1015	<	if (j == capacity) j = 0; // "corner" case
1016	<	break;
1017	<	}
1002	>	final long[] deathRow = nBits(sub(end, beg, capacity));
1003	>	deathRow[0] = 1L;   // set bit 0
1004	>	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
1005	>	; i = 0, to = end, k -= capacity) {
1006	>	for (; i < to; i++)
1007	>	if (filter.test(elementAt(es, i)))
1008	>	setBit(deathRow, i - k);
1009	>	if (to == end) break;
1010	>	}
1011	>	// a two-finger traversal, with hare i reading, tortoise w writing
1012	>	int w = beg;
1013	>	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
1014	>	; w = 0) { // w rejoins i on second leg
1015	>	// In this loop, i and w are on the same leg, with i > w
1016	>	for (; i < to; i++)
1017	>	if (isClear(deathRow, i - k))
1018	>	es[w++] = es[i];
1019	>	if (to == end) break;
1020	>	// In this loop, w is on the first leg, i on the second
1021	>	for (i = 0, to = end, k -= capacity; i < to && w < capacity; i++)
1022	>	if (isClear(deathRow, i - k))
1023	>	es[w++] = es[i];
1024	>	if (i >= to) {
1025	>	if (w == capacity) w = 0; // "corner" case
1026	>	break;
1027		}
989	–	return true;
990	–	} catch (Throwable ex) {
991	–	// copy remaining elements
992	–	for (; i != end; i = inc(i, capacity), j = inc(j, capacity))
993	–	es[j] = es[i];
994	–	throw ex;
995	–	} finally {
996	–	if (end != tail) throw new ConcurrentModificationException();
997	–	circularClear(es, tail = j, end);
998	–	// checkInvariants();
1028		}
1029	+	if (end != tail) throw new ConcurrentModificationException();
1030	+	circularClear(es, tail = w, end);
1031	+	// checkInvariants();
1032	+	return true;
1033		}
1034
1035		/**
#	Line 1050 | Line 1083 | public class ArrayDeque<E> extends Abstr
1083
1084		/**
1085		* Nulls out slots starting at array index i, upto index end.
1086	+	* Condition i == end means "empty" - nothing to do.
1087		*/
1088		private static void circularClear(Object[] es, int i, int end) {
1089	+	// assert 0 <= i && i < es.length;
1090	+	// assert 0 <= end && end < es.length;
1091		for (int to = (i <= end) ? end : es.length;
1092		; i = 0, to = end) {
1093	<	Arrays.fill(es, i, to, null);
1093	>	for (; i < to; i++) es[i] = null;
1094		if (to == end) break;
1095		}
1096		}
#	Line 1079 | Line 1115 | public class ArrayDeque<E> extends Abstr
1115		private <T> T[] toArray(Class<T[]> klazz) {
1116		final Object[] es = elements;
1117		final T[] a;
1118	<	final int size = size(), head = this.head, end;
1119	<	final int len = Math.min(size, es.length - head);
1120	<	if ((end = head + size) >= 0) {
1118	>	final int head = this.head, tail = this.tail, end;
1119	>	if ((end = tail + ((head <= tail) ? 0 : es.length)) >= 0) {
1120	>	// Uses null extension feature of copyOfRange
1121		a = Arrays.copyOfRange(es, head, end, klazz);
1122		} else {
1123		// integer overflow!
1124	<	a = Arrays.copyOfRange(es, 0, size, klazz);
1125	<	System.arraycopy(es, head, a, 0, len);
1124	>	a = Arrays.copyOfRange(es, 0, end - head, klazz);
1125	>	System.arraycopy(es, head, a, 0, es.length - head);
1126		}
1127	<	if (tail < head)
1128	<	System.arraycopy(es, 0, a, len, tail);
1127	>	if (end != tail)
1128	>	System.arraycopy(es, 0, a, es.length - head, tail);
1129		return a;
1130		}
1131
#	Line 1204 | Line 1240 | public class ArrayDeque<E> extends Abstr
1240
1241		// Read in size and allocate array
1242		int size = s.readInt();
1243	+	SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, size + 1);
1244		elements = new Object[size + 1];
1245		this.tail = size;
1246
#	Line 1214 | Line 1251 | public class ArrayDeque<E> extends Abstr
1251
1252		/** debugging */
1253		void checkInvariants() {
1254	+	// Use head and tail fields with empty slot at tail strategy.
1255	+	// head == tail disambiguates to "empty".
1256		try {
1257		int capacity = elements.length;
1258	<	// assert head >= 0 && head < capacity;
1259	<	// assert tail >= 0 && tail < capacity;
1258	>	// assert 0 <= head && head < capacity;
1259	>	// assert 0 <= tail && tail < capacity;
1260		// assert capacity > 0;
1261		// assert size() < capacity;
1262		// assert head == tail || elements[head] != null;

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