ViewVC Help

View File | Revision Log | Show Annotations | Download File | Root Listing

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

Comparing jsr166/src/main/java/util/ArrayDeque.java (file contents):
Revision 1.19 by dl, Fri Sep 16 11:15:41 2005 UTC vs.
Revision 1.26 by jsr166, Mon Sep 19 13:42:19 2005 UTC

#	Line 479 | Line 479 | public class ArrayDeque<E> extends Abstr
479		return removeFirst();
480		}
481
482	+	private void checkInvariants() {
483	+	assert elements[tail] == null;
484	+	assert head == tail ? elements[head] == null :
485	+	(elements[head] != null &&
486	+	elements[(tail - 1) & (elements.length - 1)] != null);
487	+	assert elements[(head - 1) & (elements.length - 1)] == null;
488	+	}
489	+
490		/**
491		* Removes the element at the specified position in the elements array,
492		* adjusting head and tail as necessary.  This can result in motion of
#	Line 490 | Line 498 | public class ArrayDeque<E> extends Abstr
498		* @return true if elements moved backwards
499		*/
500		private boolean delete(int i) {
501	<	int mask = elements.length - 1;
501	>	checkInvariants();
502	>	final E[] elements = this.elements;
503	>	final int mask = elements.length - 1;
504	>	final int h = head;
505	>	final int t = tail;
506	>	final int front = (i - h) & mask;
507	>	final int back  = (t - i) & mask;
508
509		// Invariant: head <= i < tail mod circularity
510	<	if (((i - head) & mask) >= ((tail - head) & mask))
510	>	if (front >= ((t - h) & mask))
511		throw new ConcurrentModificationException();
512
513	<	// Case 1: Deque doesn't wrap
514	<	// Case 2: Deque does wrap and removed element is in the head portion
515	<	if (i >= head) {
516	<	System.arraycopy(elements, head, elements, head + 1, i - head);
517	<	elements[head] = null;
518	<	head = (head + 1) & mask;
519	<	return false;
520	<	}
521	<
522	<	// Case 3: Deque wraps and removed element is in the tail portion
523	<	tail--;
524	<	System.arraycopy(elements, i + 1, elements, i, tail - i);
525	<	elements[tail] = null;
526	<	return true;
513	>	// Optimize for least element motion
514	>	if (front < back) {
515	>	if (h <= i) {
516	>	System.arraycopy(elements, h, elements, h + 1, front);
517	>	} else { // Wrap around
518	>	System.arraycopy(elements, 0, elements, 1, i);
519	>	elements[0] = elements[mask];
520	>	System.arraycopy(elements, h, elements, h + 1, mask - h);
521	>	}
522	>	elements[h] = null;
523	>	head = (h + 1) & mask;
524	>	return false;
525	>	} else {
526	>	if (i < t) { // Copy the null tail as well
527	>	System.arraycopy(elements, i + 1, elements, i, back);
528	>	tail = t - 1;
529	>	} else { // Wrap around
530	>	System.arraycopy(elements, i + 1, elements, i, mask - i);
531	>	elements[mask] = elements[0];
532	>	System.arraycopy(elements, 1, elements, 0, t);
533	>	tail = (t - 1) & mask;
534	>	}
535	>	return true;
536	>	}
537		}
538
539		// *** Collection Methods ***
#	Line 571 | Line 595 | public class ArrayDeque<E> extends Abstr
595		}
596
597		public E next() {
574	–	E result;
598		if (cursor == fence)
599		throw new NoSuchElementException();
600	+	E result = elements[cursor];
601		// This check doesn't catch all possible comodifications,
602		// but does catch the ones that corrupt traversal
603	<	if (tail != fence || (result = elements[cursor]) == null)
603	>	if (tail != fence || result == null)
604		throw new ConcurrentModificationException();
605		lastRet = cursor;
606		cursor = (cursor + 1) & (elements.length - 1);
#	Line 586 | Line 610 | public class ArrayDeque<E> extends Abstr
610		public void remove() {
611		if (lastRet < 0)
612		throw new IllegalStateException();
613	<	if (delete(lastRet)) // if left-shifted, undo increment in next()
613	>	if (delete(lastRet)) { // if left-shifted, undo increment in next()
614		cursor = (cursor - 1) & (elements.length - 1);
615	+	fence = tail;
616	+	}
617		lastRet = -1;
592	–	fence = tail;
618		}
619		}
620
596	–
621		private class DescendingIterator implements Iterator<E> {
622		/*
623		* This class is nearly a mirror-image of DeqIterator, using
624	<	* (tail-1) instead of head for initial cursor, (head-1)
625	<	* instead of tail for fence, and elements.length instead of -1
602	<	* for sentinel. It shares the same structure, but not many
603	<	* actual lines of code.
624	>	* tail instead of head for initial cursor, and head instead of
625	>	* tail for fence.
626		*/
627	<	private int cursor = (tail - 1) & (elements.length - 1);
628	<	private int fence =  (head - 1) & (elements.length - 1);
629	<	private int lastRet = elements.length;
627	>	private int cursor = tail;
628	>	private int fence = head;
629	>	private int lastRet = -1;
630
631		public boolean hasNext() {
632		return cursor != fence;
633		}
634
635		public E next() {
614	–	E result;
636		if (cursor == fence)
637		throw new NoSuchElementException();
638	<	if (((head - 1) & (elements.length - 1)) != fence ||
639	<	(result = elements[cursor]) == null)
638	>	cursor = (cursor - 1) & (elements.length - 1);
639	>	E result = elements[cursor];
640	>	if (head != fence || result == null)
641		throw new ConcurrentModificationException();
642		lastRet = cursor;
621	–	cursor = (cursor - 1) & (elements.length - 1);
643		return result;
644		}
645
646		public void remove() {
647	<	if (lastRet >= elements.length)
647	>	if (lastRet < 0)
648		throw new IllegalStateException();
649	<	if (!delete(lastRet))
649	>	if (!delete(lastRet)) {
650		cursor = (cursor + 1) & (elements.length - 1);
651	<	lastRet = elements.length;
652	<	fence = (head - 1) & (elements.length - 1);
651	>	fence = head;
652	>	}
653	>	lastRet = -1;
654		}
655		}
656
#	Line 814 | Line 836 | public class ArrayDeque<E> extends Abstr
836		// Read in all elements in the proper order.
837		for (int i = 0; i < size; i++)
838		elements[i] = (E)s.readObject();
817	–
839		}
840		}

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines