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Diffstat (limited to 'external/jsr166/java/util/concurrent/ConcurrentSkipListSet.java')
| -rw-r--r-- | external/jsr166/java/util/concurrent/ConcurrentSkipListSet.java | 456 |
1 files changed, 456 insertions, 0 deletions
diff --git a/external/jsr166/java/util/concurrent/ConcurrentSkipListSet.java b/external/jsr166/java/util/concurrent/ConcurrentSkipListSet.java new file mode 100644 index 000000000..7da50d593 --- /dev/null +++ b/external/jsr166/java/util/concurrent/ConcurrentSkipListSet.java @@ -0,0 +1,456 @@ +/* + * Written by Doug Lea with assistance from members of JCP JSR-166 + * Expert Group and released to the public domain, as explained at + * http://creativecommons.org/licenses/publicdomain + */ + +package java.util.concurrent; +import java.util.*; +import sun.misc.Unsafe; + +/** + * A scalable concurrent {@link NavigableSet} implementation based on + * a {@link ConcurrentSkipListMap}. The elements of the set are kept + * sorted according to their {@linkplain Comparable natural ordering}, + * or by a {@link Comparator} provided at set creation time, depending + * on which constructor is used. + * + * <p>This implementation provides expected average <i>log(n)</i> time + * cost for the <tt>contains</tt>, <tt>add</tt>, and <tt>remove</tt> + * operations and their variants. Insertion, removal, and access + * operations safely execute concurrently by multiple threads. + * Iterators are <i>weakly consistent</i>, returning elements + * reflecting the state of the set at some point at or since the + * creation of the iterator. They do <em>not</em> throw {@link + * ConcurrentModificationException}, and may proceed concurrently with + * other operations. Ascending ordered views and their iterators are + * faster than descending ones. + * + * <p>Beware that, unlike in most collections, the <tt>size</tt> + * method is <em>not</em> a constant-time operation. Because of the + * asynchronous nature of these sets, determining the current number + * of elements requires a traversal of the elements. Additionally, the + * bulk operations <tt>addAll</tt>, <tt>removeAll</tt>, + * <tt>retainAll</tt>, and <tt>containsAll</tt> are <em>not</em> + * guaranteed to be performed atomically. For example, an iterator + * operating concurrently with an <tt>addAll</tt> operation might view + * only some of the added elements. + * + * <p>This class and its iterators implement all of the + * <em>optional</em> methods of the {@link Set} and {@link Iterator} + * interfaces. Like most other concurrent collection implementations, + * this class does not permit the use of <tt>null</tt> elements, + * because <tt>null</tt> arguments and return values cannot be reliably + * distinguished from the absence of elements. + * + * <p>This class is a member of the + * <a href="{@docRoot}/../technotes/guides/collections/index.html"> + * Java Collections Framework</a>. + * + * @author Doug Lea + * @param <E> the type of elements maintained by this set + * @since 1.6 + */ +public class ConcurrentSkipListSet<E> + extends AbstractSet<E> + implements NavigableSet<E>, Cloneable, java.io.Serializable { + + private static final long serialVersionUID = -2479143111061671589L; + + /** + * The underlying map. Uses Boolean.TRUE as value for each + * element. This field is declared final for the sake of thread + * safety, which entails some ugliness in clone() + */ + private final ConcurrentNavigableMap<E,Object> m; + + /** + * Constructs a new, empty set that orders its elements according to + * their {@linkplain Comparable natural ordering}. + */ + public ConcurrentSkipListSet() { + m = new ConcurrentSkipListMap<E,Object>(); + } + + /** + * Constructs a new, empty set that orders its elements according to + * the specified comparator. + * + * @param comparator the comparator that will be used to order this set. + * If <tt>null</tt>, the {@linkplain Comparable natural + * ordering} of the elements will be used. + */ + public ConcurrentSkipListSet(Comparator<? super E> comparator) { + m = new ConcurrentSkipListMap<E,Object>(comparator); + } + + /** + * Constructs a new set containing the elements in the specified + * collection, that orders its elements according to their + * {@linkplain Comparable natural ordering}. + * + * @param c The elements that will comprise the new set + * @throws ClassCastException if the elements in <tt>c</tt> are + * not {@link Comparable}, or are not mutually comparable + * @throws NullPointerException if the specified collection or any + * of its elements are null + */ + public ConcurrentSkipListSet(Collection<? extends E> c) { + m = new ConcurrentSkipListMap<E,Object>(); + addAll(c); + } + + /** + * Constructs a new set containing the same elements and using the + * same ordering as the specified sorted set. + * + * @param s sorted set whose elements will comprise the new set + * @throws NullPointerException if the specified sorted set or any + * of its elements are null + */ + public ConcurrentSkipListSet(SortedSet<E> s) { + m = new ConcurrentSkipListMap<E,Object>(s.comparator()); + addAll(s); + } + + /** + * For use by submaps + */ + ConcurrentSkipListSet(ConcurrentNavigableMap<E,Object> m) { + this.m = m; + } + + /** + * Returns a shallow copy of this <tt>ConcurrentSkipListSet</tt> + * instance. (The elements themselves are not cloned.) + * + * @return a shallow copy of this set + */ + public ConcurrentSkipListSet<E> clone() { + ConcurrentSkipListSet<E> clone = null; + try { + clone = (ConcurrentSkipListSet<E>) super.clone(); + clone.setMap(new ConcurrentSkipListMap(m)); + } catch (CloneNotSupportedException e) { + throw new InternalError(); + } + + return clone; + } + + /* ---------------- Set operations -------------- */ + + /** + * Returns the number of elements in this set. If this set + * contains more than <tt>Integer.MAX_VALUE</tt> elements, it + * returns <tt>Integer.MAX_VALUE</tt>. + * + * <p>Beware that, unlike in most collections, this method is + * <em>NOT</em> a constant-time operation. Because of the + * asynchronous nature of these sets, determining the current + * number of elements requires traversing them all to count them. + * Additionally, it is possible for the size to change during + * execution of this method, in which case the returned result + * will be inaccurate. Thus, this method is typically not very + * useful in concurrent applications. + * + * @return the number of elements in this set + */ + public int size() { + return m.size(); + } + + /** + * Returns <tt>true</tt> if this set contains no elements. + * @return <tt>true</tt> if this set contains no elements + */ + public boolean isEmpty() { + return m.isEmpty(); + } + + /** + * Returns <tt>true</tt> if this set contains the specified element. + * More formally, returns <tt>true</tt> if and only if this set + * contains an element <tt>e</tt> such that <tt>o.equals(e)</tt>. + * + * @param o object to be checked for containment in this set + * @return <tt>true</tt> if this set contains the specified element + * @throws ClassCastException if the specified element cannot be + * compared with the elements currently in this set + * @throws NullPointerException if the specified element is null + */ + public boolean contains(Object o) { + return m.containsKey(o); + } + + /** + * Adds the specified element to this set if it is not already present. + * More formally, adds the specified element <tt>e</tt> to this set if + * the set contains no element <tt>e2</tt> such that <tt>e.equals(e2)</tt>. + * If this set already contains the element, the call leaves the set + * unchanged and returns <tt>false</tt>. + * + * @param e element to be added to this set + * @return <tt>true</tt> if this set did not already contain the + * specified element + * @throws ClassCastException if <tt>e</tt> cannot be compared + * with the elements currently in this set + * @throws NullPointerException if the specified element is null + */ + public boolean add(E e) { + return m.putIfAbsent(e, Boolean.TRUE) == null; + } + + /** + * Removes the specified element from this set if it is present. + * More formally, removes an element <tt>e</tt> such that + * <tt>o.equals(e)</tt>, if this set contains such an element. + * Returns <tt>true</tt> if this set contained the element (or + * equivalently, if this set changed as a result of the call). + * (This set will not contain the element once the call returns.) + * + * @param o object to be removed from this set, if present + * @return <tt>true</tt> if this set contained the specified element + * @throws ClassCastException if <tt>o</tt> cannot be compared + * with the elements currently in this set + * @throws NullPointerException if the specified element is null + */ + public boolean remove(Object o) { + return m.remove(o, Boolean.TRUE); + } + + /** + * Removes all of the elements from this set. + */ + public void clear() { + m.clear(); + } + + /** + * Returns an iterator over the elements in this set in ascending order. + * + * @return an iterator over the elements in this set in ascending order + */ + public Iterator<E> iterator() { + return m.navigableKeySet().iterator(); + } + + /** + * Returns an iterator over the elements in this set in descending order. + * + * @return an iterator over the elements in this set in descending order + */ + public Iterator<E> descendingIterator() { + return m.descendingKeySet().iterator(); + } + + + /* ---------------- AbstractSet Overrides -------------- */ + + /** + * Compares the specified object with this set for equality. Returns + * <tt>true</tt> if the specified object is also a set, the two sets + * have the same size, and every member of the specified set is + * contained in this set (or equivalently, every member of this set is + * contained in the specified set). This definition ensures that the + * equals method works properly across different implementations of the + * set interface. + * + * @param o the object to be compared for equality with this set + * @return <tt>true</tt> if the specified object is equal to this set + */ + public boolean equals(Object o) { + // Override AbstractSet version to avoid calling size() + if (o == this) + return true; + if (!(o instanceof Set)) + return false; + Collection<?> c = (Collection<?>) o; + try { + return containsAll(c) && c.containsAll(this); + } catch (ClassCastException unused) { + return false; + } catch (NullPointerException unused) { + return false; + } + } + + /** + * Removes from this set all of its elements that are contained in + * the specified collection. If the specified collection is also + * a set, this operation effectively modifies this set so that its + * value is the <i>asymmetric set difference</i> of the two sets. + * + * @param c collection containing elements to be removed from this set + * @return <tt>true</tt> if this set changed as a result of the call + * @throws ClassCastException if the types of one or more elements in this + * set are incompatible with the specified collection + * @throws NullPointerException if the specified collection or any + * of its elements are null + */ + public boolean removeAll(Collection<?> c) { + // Override AbstractSet version to avoid unnecessary call to size() + boolean modified = false; + for (Iterator<?> i = c.iterator(); i.hasNext(); ) + if (remove(i.next())) + modified = true; + return modified; + } + + /* ---------------- Relational operations -------------- */ + + /** + * @throws ClassCastException {@inheritDoc} + * @throws NullPointerException if the specified element is null + */ + public E lower(E e) { + return m.lowerKey(e); + } + + /** + * @throws ClassCastException {@inheritDoc} + * @throws NullPointerException if the specified element is null + */ + public E floor(E e) { + return m.floorKey(e); + } + + /** + * @throws ClassCastException {@inheritDoc} + * @throws NullPointerException if the specified element is null + */ + public E ceiling(E e) { + return m.ceilingKey(e); + } + + /** + * @throws ClassCastException {@inheritDoc} + * @throws NullPointerException if the specified element is null + */ + public E higher(E e) { + return m.higherKey(e); + } + + public E pollFirst() { + Map.Entry<E,Object> e = m.pollFirstEntry(); + return e == null? null : e.getKey(); + } + + public E pollLast() { + Map.Entry<E,Object> e = m.pollLastEntry(); + return e == null? null : e.getKey(); + } + + + /* ---------------- SortedSet operations -------------- */ + + + public Comparator<? super E> comparator() { + return m.comparator(); + } + + /** + * @throws NoSuchElementException {@inheritDoc} + */ + public E first() { + return m.firstKey(); + } + + /** + * @throws NoSuchElementException {@inheritDoc} + */ + public E last() { + return m.lastKey(); + } + + /** + * @throws ClassCastException {@inheritDoc} + * @throws NullPointerException if {@code fromElement} or + * {@code toElement} is null + * @throws IllegalArgumentException {@inheritDoc} + */ + public NavigableSet<E> subSet(E fromElement, + boolean fromInclusive, + E toElement, + boolean toInclusive) { + return new ConcurrentSkipListSet<E> + (m.subMap(fromElement, fromInclusive, + toElement, toInclusive)); + } + + /** + * @throws ClassCastException {@inheritDoc} + * @throws NullPointerException if {@code toElement} is null + * @throws IllegalArgumentException {@inheritDoc} + */ + public NavigableSet<E> headSet(E toElement, boolean inclusive) { + return new ConcurrentSkipListSet<E>(m.headMap(toElement, inclusive)); + } + + /** + * @throws ClassCastException {@inheritDoc} + * @throws NullPointerException if {@code fromElement} is null + * @throws IllegalArgumentException {@inheritDoc} + */ + public NavigableSet<E> tailSet(E fromElement, boolean inclusive) { + return new ConcurrentSkipListSet<E>(m.tailMap(fromElement, inclusive)); + } + + /** + * @throws ClassCastException {@inheritDoc} + * @throws NullPointerException if {@code fromElement} or + * {@code toElement} is null + * @throws IllegalArgumentException {@inheritDoc} + */ + public NavigableSet<E> subSet(E fromElement, E toElement) { + return subSet(fromElement, true, toElement, false); + } + + /** + * @throws ClassCastException {@inheritDoc} + * @throws NullPointerException if {@code toElement} is null + * @throws IllegalArgumentException {@inheritDoc} + */ + public NavigableSet<E> headSet(E toElement) { + return headSet(toElement, false); + } + + /** + * @throws ClassCastException {@inheritDoc} + * @throws NullPointerException if {@code fromElement} is null + * @throws IllegalArgumentException {@inheritDoc} + */ + public NavigableSet<E> tailSet(E fromElement) { + return tailSet(fromElement, true); + } + + /** + * Returns a reverse order view of the elements contained in this set. + * The descending set is backed by this set, so changes to the set are + * reflected in the descending set, and vice-versa. + * + * <p>The returned set has an ordering equivalent to + * <tt>{@link Collections#reverseOrder(Comparator) Collections.reverseOrder}(comparator())</tt>. + * The expression {@code s.descendingSet().descendingSet()} returns a + * view of {@code s} essentially equivalent to {@code s}. + * + * @return a reverse order view of this set + */ + public NavigableSet<E> descendingSet() { + return new ConcurrentSkipListSet(m.descendingMap()); + } + + // Support for resetting map in clone + private static final Unsafe unsafe = Unsafe.getUnsafe(); + private static final long mapOffset; + static { + try { + mapOffset = unsafe.objectFieldOffset + (ConcurrentSkipListSet.class.getDeclaredField("m")); + } catch (Exception ex) { throw new Error(ex); } + } + private void setMap(ConcurrentNavigableMap<E,Object> map) { + unsafe.putObjectVolatile(this, mapOffset, map); + } + +} |