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Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.108 by jsr166, Sat Nov 5 14:41:14 2016 UTC vs.
Revision 1.138 by jsr166, Fri Aug 30 18:05:38 2019 UTC

#	Line 8 | Line 8 | package java.util;
8		import java.io.Serializable;
9		import java.util.function.Consumer;
10		import java.util.function.Predicate;
11	<	import java.util.function.UnaryOperator;
11	>	// OPENJDK import jdk.internal.access.SharedSecrets;
12
13		/**
14		* Resizable-array implementation of the {@link Deque} interface.  Array
#	Line 50 | Line 50 | import java.util.function.UnaryOperator;
50		* Iterator} interfaces.
51		*
52		* <p>This class is a member of the
53	<	* <a href="{@docRoot}/../technotes/guides/collections/index.html">
53	>	* <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
54		* Java Collections Framework</a>.
55		*
56		* @author  Josh Bloch and Doug Lea
#	Line 68 | Line 68 | public class ArrayDeque<E> extends Abstr
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.
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
#	Line 88 | Line 90 | public class ArrayDeque<E> extends Abstr
90
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)).
93	>	* of the deque (via addLast(E), add(E), or push(E));
94	>	* elements[tail] is always null.
95		*/
96		transient int tail;
97
#	Line 114 | Line 117 | public class ArrayDeque<E> extends Abstr
117		if (jump < needed
118		|| (newCapacity = (oldCapacity + jump)) - MAX_ARRAY_SIZE > 0)
119		newCapacity = newCapacity(needed, jump);
120	<	elements = Arrays.copyOf(elements, newCapacity);
120	>	final Object[] es = elements = Arrays.copyOf(elements, newCapacity);
121		// Exceptionally, here tail == head needs to be disambiguated
122	<	if (tail < head || (tail == head && elements[head] != null)) {
122	>	if (tail < head || (tail == head && es[head] != null)) {
123		// wrap around; slide first leg forward to end of array
124		int newSpace = newCapacity - oldCapacity;
125	<	System.arraycopy(elements, head,
126	<	elements, head + newSpace,
125	>	System.arraycopy(es, head,
126	>	es, head + newSpace,
127		oldCapacity - head);
128	<	Arrays.fill(elements, head, head + newSpace, null);
129	<	head += newSpace;
128	>	for (int i = head, to = (head += newSpace); i < to; i++)
129	>	es[i] = null;
130		}
131		// checkInvariants();
132		}
#	Line 177 | Line 180 | public class ArrayDeque<E> extends Abstr
180		* sufficient to hold 16 elements.
181		*/
182		public ArrayDeque() {
183	<	elements = new Object[16];
183	>	elements = new Object[16 + 1];
184		}
185
186		/**
#	Line 187 | 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[Math.max(1, numElements + 1)];
193	>	elements =
194	>	new Object[(numElements < 1) ? 1 :
195	>	(numElements == Integer.MAX_VALUE) ? Integer.MAX_VALUE :
196	>	numElements + 1];
197		}
198
199		/**
#	Line 201 | 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	<	elements = new Object[c.size() + 1];
211	<	addAll(c);
210	>	this(c.size());
211	>	copyElements(c);
212		}
213
214		/**
215	<	* Increments i, mod modulus.
215	>	* Circularly increments i, mod modulus.
216		* Precondition and postcondition: 0 <= i < modulus.
217		*/
218		static final int inc(int i, int modulus) {
#	Line 215 | Line 221 | public class ArrayDeque<E> extends Abstr
221		}
222
223		/**
224	<	* Decrements i, mod modulus.
224	>	* Circularly decrements i, mod modulus.
225		* Precondition and postcondition: 0 <= i < modulus.
226		*/
227		static final int dec(int i, int modulus) {
#	Line 224 | 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 inc(int i, int distance, int modulus) {
238	>	if ((i += distance) - modulus >= 0) i -= modulus;
239		return i;
240		}
241
242		/**
243		* Subtracts j from i, mod modulus.
244	<	* Index i must be logically ahead of j.
245	<	* Returns the "circular distance" from j to i.
246	<	* Precondition and postcondition: 0 <= i < modulus, 0 <= j < 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 disambiguated to "empty", returning 0.
248		*/
249		static final int sub(int i, int j, int modulus) {
250		if ((i -= j) < 0) i += modulus;
#	Line 244 | Line 252 | public class ArrayDeque<E> extends Abstr
252		}
253
254		/**
247	–	* Returns the array index of the last element.
248	–	* May return invalid index -1 if there are no elements.
249	–	*/
250	–	final int last() {
251	–	return dec(tail, elements.length);
252	–	}
253	–
254	–	/**
255		* Returns element at array index i.
256		* This is a slight abuse of generics, accepted by javac.
257		*/
#	Line 313 | Line 313 | public class ArrayDeque<E> extends Abstr
313		/**
314		* Adds all of the elements in the specified collection at the end
315		* of this deque, as if by calling {@link #addLast} on each one,
316	<	* in the order that they are returned by the collection's
317	<	* iterator.
316	>	* in the order that they are returned by the collection's iterator.
317		*
318		* @param c the elements to be inserted into this deque
319		* @return {@code true} if this deque changed as a result of the call
#	Line 322 | Line 321 | public class ArrayDeque<E> extends Abstr
321		*         of its elements are null
322		*/
323		public boolean addAll(Collection<? extends E> c) {
324	<	final int s = size(), needed;
325	<	if ((needed = s + c.size() - elements.length + 1) > 0)
324	>	final int s, needed;
325	>	if ((needed = (s = size()) + c.size() + 1 - elements.length) > 0)
326		grow(needed);
327	<	c.forEach((e) -> addLast(e));
327	>	copyElements(c);
328		// checkInvariants();
329		return size() > s;
330		}
331
332	+	private void copyElements(Collection<? extends E> c) {
333	+	c.forEach(this::addLast);
334	+	}
335	+
336		/**
337		* Inserts the specified element at the front of this deque.
338		*
#	Line 477 | Line 480 | public class ArrayDeque<E> extends Abstr
480		final Object[] es = elements;
481		for (int i = tail, end = head, to = (i >= end) ? end : 0;
482		; i = es.length, to = end) {
483	<	while (--i >= to)
483	>	for (i--; i > to - 1; i--)
484		if (o.equals(es[i])) {
485		delete(i);
486		return true;
#	Line 520 | Line 523 | public class ArrayDeque<E> extends Abstr
523		/**
524		* Retrieves and removes the head of the queue represented by this deque.
525		*
526	<	* This method differs from {@link #poll poll} only in that it throws an
527	<	* exception if this deque is empty.
526	>	* This method differs from {@link #poll() poll()} only in that it
527	>	* throws an exception if this deque is empty.
528		*
529		* <p>This method is equivalent to {@link #removeFirst}.
530		*
#	Line 616 | Line 619 | public class ArrayDeque<E> extends Abstr
619		// checkInvariants();
620		final Object[] es = elements;
621		final int capacity = es.length;
622	<	final int h = head;
622	>	final int h, t;
623		// number of elements before to-be-deleted elt
624	<	final int front = sub(i, h, capacity);
625	<	final int back = size() - front - 1; // number of elements after
624	>	final int front = sub(i, h = head, capacity);
625	>	// number of elements after to-be-deleted elt
626	>	final int back = sub(t = tail, i, capacity) - 1;
627		if (front < back) {
628		// move front elements forwards
629		if (h <= i) {
#	Line 635 | Line 639 | public class ArrayDeque<E> extends Abstr
639		return false;
640		} else {
641		// move back elements backwards
642	<	tail = dec(tail, capacity);
642	>	tail = dec(t, capacity);
643		if (i <= tail) {
644		System.arraycopy(es, i + 1, es, i, back);
645		} else { // Wrap around
646	<	int firstLeg = capacity - (i + 1);
643	<	System.arraycopy(es, i + 1, es, i, firstLeg);
646	>	System.arraycopy(es, i + 1, es, i, capacity - (i + 1));
647		es[capacity - 1] = es[0];
648	<	System.arraycopy(es, 1, es, 0, back - firstLeg - 1);
648	>	System.arraycopy(es, 1, es, 0, t - 1);
649		}
650		es[tail] = null;
651		// checkInvariants();
#	Line 710 | Line 713 | public class ArrayDeque<E> extends Abstr
713		throw new NoSuchElementException();
714		final Object[] es = elements;
715		E e = nonNullElementAt(es, cursor);
716	<	lastRet = cursor;
714	<	cursor = inc(cursor, es.length);
716	>	cursor = inc(lastRet = cursor, es.length);
717		remaining--;
718		return e;
719		}
#	Line 752 | Line 754 | public class ArrayDeque<E> extends Abstr
754		}
755
756		private class DescendingIterator extends DeqIterator {
757	<	DescendingIterator() { cursor = last(); }
757	>	DescendingIterator() { cursor = dec(tail, elements.length); }
758
759		public final E next() {
760		if (remaining <= 0)
761		throw new NoSuchElementException();
762		final Object[] es = elements;
763		E e = nonNullElementAt(es, cursor);
764	<	lastRet = cursor;
763	<	cursor = dec(cursor, es.length);
764	>	cursor = dec(lastRet = cursor, es.length);
765		remaining--;
766		return e;
767		}
#	Line 781 | Line 782 | public class ArrayDeque<E> extends Abstr
782		throw new ConcurrentModificationException();
783		for (int i = cursor, end = head, to = (i >= end) ? end : 0;
784		; i = es.length - 1, to = end) {
785	<	for (; i >= to; i--)
785	>	// hotspot generates faster code than for: i >= to !
786	>	for (; i > to - 1; i--)
787		action.accept(elementAt(es, i));
788		if (to == end) {
789		if (end != head)
790		throw new ConcurrentModificationException();
791	<	lastRet = head;
791	>	lastRet = end;
792		break;
793		}
794		}
#	Line 821 | Line 823 | public class ArrayDeque<E> extends Abstr
823
824		/** Constructs spliterator over the given range. */
825		DeqSpliterator(int origin, int fence) {
826	+	// assert 0 <= origin && origin < elements.length;
827	+	// assert 0 <= fence && fence < elements.length;
828		this.cursor = origin;
829		this.fence = fence;
830		}
#	Line 840 | Line 844 | public class ArrayDeque<E> extends Abstr
844		final int i, n;
845		return ((n = sub(getFence(), i = cursor, es.length) >> 1) <= 0)
846		? null
847	<	: new DeqSpliterator(i, cursor = add(i, n, es.length));
847	>	: new DeqSpliterator(i, cursor = inc(i, n, es.length));
848		}
849
850		public void forEachRemaining(Consumer<? super E> action) {
#	Line 863 | Line 867 | public class ArrayDeque<E> extends Abstr
867		}
868
869		public boolean tryAdvance(Consumer<? super E> action) {
870	<	if (action == null)
871	<	throw new NullPointerException();
872	<	int t, i;
873	<	if ((t = fence) < 0) t = getFence();
874	<	if (t == (i = cursor))
870	>	Objects.requireNonNull(action);
871	>	final Object[] es = elements;
872	>	if (fence < 0) { fence = tail; cursor = head; } // late-binding
873	>	final int i;
874	>	if ((i = cursor) == fence)
875		return false;
876	<	final Object[] es;
873	<	action.accept(nonNullElementAt(es = elements, i));
876	>	E e = nonNullElementAt(es, i);
877		cursor = inc(i, es.length);
878	+	action.accept(e);
879		return true;
880		}
881
#	Line 887 | Line 891 | public class ArrayDeque<E> extends Abstr
891		}
892		}
893
894	+	/**
895	+	* @throws NullPointerException {@inheritDoc}
896	+	*/
897		public void forEach(Consumer<? super E> action) {
898		Objects.requireNonNull(action);
899		final Object[] es = elements;
#	Line 909 | Line 916 | public class ArrayDeque<E> extends Abstr
916		* @param operator the operator to apply to each element
917		* @since TBD
918		*/
919	<	/* public */ void replaceAll(UnaryOperator<E> operator) {
919	>	/* public */ void replaceAll(java.util.function.UnaryOperator<E> operator) {
920		Objects.requireNonNull(operator);
921		final Object[] es = elements;
922		for (int i = head, end = tail, to = (i <= end) ? end : es.length;
#	Line 957 | Line 964 | public class ArrayDeque<E> extends Abstr
964		; i = 0, to = end) {
965		for (; i < to; i++)
966		if (filter.test(elementAt(es, i)))
967	<	return bulkRemoveModified(filter, i, to);
967	>	return bulkRemoveModified(filter, i);
968		if (to == end) {
969		if (end != tail) throw new ConcurrentModificationException();
970		break;
#	Line 966 | Line 973 | public class ArrayDeque<E> extends Abstr
973		return false;
974		}
975
976	+	// A tiny bit set implementation
977	+
978	+	private static long[] nBits(int n) {
979	+	return new long[((n - 1) >> 6) + 1];
980	+	}
981	+	private static void setBit(long[] bits, int i) {
982	+	bits[i >> 6] |= 1L << i;
983	+	}
984	+	private static boolean isClear(long[] bits, int i) {
985	+	return (bits[i >> 6] & (1L << i)) == 0;
986	+	}
987	+
988		/**
989		* Helper for bulkRemove, in case of at least one deletion.
990	<	* @param i valid index of first element to be deleted
990	>	* Tolerate predicates that reentrantly access the collection for
991	>	* read (but writers still get CME), so traverse once to find
992	>	* elements to delete, a second pass to physically expunge.
993	>	*
994	>	* @param beg valid index of first element to be deleted
995		*/
996		private boolean bulkRemoveModified(
997	<	Predicate<? super E> filter, int i, int to) {
997	>	Predicate<? super E> filter, final int beg) {
998		final Object[] es = elements;
999		final int capacity = es.length;
977	–	// a two-finger algorithm, with hare i reading, tortoise j writing
978	–	int j = i++;
1000		final int end = tail;
1001	<	try {
1002	<	for (;; j = 0) {    // j rejoins i on second leg
1003	<	E e;
1004	<	// In this loop, i and j are on the same leg, with i > j
1005	<	for (; i < to; i++)
1006	<	if (!filter.test(e = elementAt(es, i)))
1007	<	es[j++] = e;
1008	<	if (to == end) break;
1009	<	// In this loop, j is on the first leg, i on the second
1010	<	for (i = 0, to = end; i < to && j < capacity; i++)
1011	<	if (!filter.test(e = elementAt(es, i)))
1012	<	es[j++] = e;
1013	<	if (i >= to) {
1014	<	if (j == capacity) j = 0; // "corner" case
1015	<	break;
1016	<	}
1001	>	final long[] deathRow = nBits(sub(end, beg, capacity));
1002	>	deathRow[0] = 1L;   // set bit 0
1003	>	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
1004	>	; i = 0, to = end, k -= capacity) {
1005	>	for (; i < to; i++)
1006	>	if (filter.test(elementAt(es, i)))
1007	>	setBit(deathRow, i - k);
1008	>	if (to == end) break;
1009	>	}
1010	>	// a two-finger traversal, with hare i reading, tortoise w writing
1011	>	int w = beg;
1012	>	for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg;
1013	>	; w = 0) { // w rejoins i on second leg
1014	>	// In this loop, i and w are on the same leg, with i > w
1015	>	for (; i < to; i++)
1016	>	if (isClear(deathRow, i - k))
1017	>	es[w++] = es[i];
1018	>	if (to == end) break;
1019	>	// In this loop, w is on the first leg, i on the second
1020	>	for (i = 0, to = end, k -= capacity; i < to && w < capacity; i++)
1021	>	if (isClear(deathRow, i - k))
1022	>	es[w++] = es[i];
1023	>	if (i >= to) {
1024	>	if (w == capacity) w = 0; // "corner" case
1025	>	break;
1026		}
997	–	return true;
998	–	} catch (Throwable ex) {
999	–	// copy remaining elements
1000	–	for (; i != end; i = inc(i, capacity), j = inc(j, capacity))
1001	–	es[j] = es[i];
1002	–	throw ex;
1003	–	} finally {
1004	–	if (end != tail) throw new ConcurrentModificationException();
1005	–	circularClear(es, tail = j, end);
1006	–	// checkInvariants();
1027		}
1028	+	if (end != tail) throw new ConcurrentModificationException();
1029	+	circularClear(es, tail = w, end);
1030	+	// checkInvariants();
1031	+	return true;
1032		}
1033
1034		/**
#	Line 1058 | Line 1082 | public class ArrayDeque<E> extends Abstr
1082
1083		/**
1084		* Nulls out slots starting at array index i, upto index end.
1085	+	* Condition i == end means "empty" - nothing to do.
1086		*/
1087		private static void circularClear(Object[] es, int i, int end) {
1088	+	// assert 0 <= i && i < es.length;
1089	+	// assert 0 <= end && end < es.length;
1090		for (int to = (i <= end) ? end : es.length;
1091		; i = 0, to = end) {
1092	<	Arrays.fill(es, i, to, null);
1092	>	for (; i < to; i++) es[i] = null;
1093		if (to == end) break;
1094		}
1095		}
#	Line 1087 | Line 1114 | public class ArrayDeque<E> extends Abstr
1114		private <T> T[] toArray(Class<T[]> klazz) {
1115		final Object[] es = elements;
1116		final T[] a;
1117	<	final int size = size(), head = this.head, end;
1118	<	final int len = Math.min(size, es.length - head);
1119	<	if ((end = head + size) >= 0) {
1117	>	final int head = this.head, tail = this.tail, end;
1118	>	if ((end = tail + ((head <= tail) ? 0 : es.length)) >= 0) {
1119	>	// Uses null extension feature of copyOfRange
1120		a = Arrays.copyOfRange(es, head, end, klazz);
1121		} else {
1122		// integer overflow!
1123	<	a = Arrays.copyOfRange(es, 0, size, klazz);
1124	<	System.arraycopy(es, head, a, 0, len);
1123	>	a = Arrays.copyOfRange(es, 0, end - head, klazz);
1124	>	System.arraycopy(es, head, a, 0, es.length - head);
1125		}
1126	<	if (tail < head)
1127	<	System.arraycopy(es, 0, a, len, tail);
1126	>	if (end != tail)
1127	>	System.arraycopy(es, 0, a, es.length - head, tail);
1128		return a;
1129		}
1130
#	Line 1171 | Line 1198 | public class ArrayDeque<E> extends Abstr
1198		}
1199		}
1200
1201	+	// OPENJDK @java.io.Serial
1202		private static final long serialVersionUID = 2340985798034038923L;
1203
1204		/**
#	Line 1182 | Line 1210 | public class ArrayDeque<E> extends Abstr
1210		* followed by all of its elements (each an object reference) in
1211		* first-to-last order.
1212		*/
1213	+	// OPENJDK @java.io.Serial
1214		private void writeObject(java.io.ObjectOutputStream s)
1215		throws java.io.IOException {
1216		s.defaultWriteObject();
#	Line 1206 | Line 1235 | public class ArrayDeque<E> extends Abstr
1235		*         could not be found
1236		* @throws java.io.IOException if an I/O error occurs
1237		*/
1238	+	// OPENJDK @java.io.Serial
1239		private void readObject(java.io.ObjectInputStream s)
1240		throws java.io.IOException, ClassNotFoundException {
1241		s.defaultReadObject();
1242
1243		// Read in size and allocate array
1244		int size = s.readInt();
1245	+	jsr166.Platform.checkArray(s, Object[].class, size + 1);
1246		elements = new Object[size + 1];
1247		this.tail = size;
1248
#	Line 1222 | Line 1253 | public class ArrayDeque<E> extends Abstr
1253
1254		/** debugging */
1255		void checkInvariants() {
1256	+	// Use head and tail fields with empty slot at tail strategy.
1257	+	// head == tail disambiguates to "empty".
1258		try {
1259		int capacity = elements.length;
1260	<	// assert head >= 0 && head < capacity;
1261	<	// assert tail >= 0 && tail < capacity;
1260	>	// assert 0 <= head && head < capacity;
1261	>	// assert 0 <= tail && tail < capacity;
1262		// assert capacity > 0;
1263		// assert size() < capacity;
1264		// assert head == tail || elements[head] != null;

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