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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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|
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package java.util.concurrent; |
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|
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import java.util.AbstractQueue; |
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import java.util.Collection; |
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import java.util.Iterator; |
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import java.util.NoSuchElementException; |
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import java.util.Objects; |
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import java.util.Spliterator; |
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import java.util.Spliterators; |
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import java.util.concurrent.locks.Condition; |
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import java.util.concurrent.locks.ReentrantLock; |
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import java.util.function.Consumer; |
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import java.util.function.Predicate; |
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|
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/** |
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* An optionally-bounded {@linkplain BlockingDeque blocking deque} based on |
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* linked nodes. |
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* |
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* <p>The optional capacity bound constructor argument serves as a |
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* way to prevent excessive expansion. The capacity, if unspecified, |
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* is equal to {@link Integer#MAX_VALUE}. Linked nodes are |
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* dynamically created upon each insertion unless this would bring the |
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* deque above capacity. |
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* |
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* <p>Most operations run in constant time (ignoring time spent |
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* blocking). Exceptions include {@link #remove(Object) remove}, |
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* {@link #removeFirstOccurrence removeFirstOccurrence}, {@link |
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* #removeLastOccurrence removeLastOccurrence}, {@link #contains |
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* contains}, {@link #iterator iterator.remove()}, and the bulk |
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* operations, all of which run in linear time. |
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* |
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* <p>This class and its iterator implement all of the <em>optional</em> |
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* methods of the {@link Collection} and {@link Iterator} interfaces. |
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* |
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* <p>This class is a member of the |
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* <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework"> |
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* Java Collections Framework</a>. |
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* |
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* @since 1.6 |
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* @author Doug Lea |
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* @param <E> the type of elements held in this deque |
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*/ |
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public class LinkedBlockingDeque<E> |
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extends AbstractQueue<E> |
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implements BlockingDeque<E>, java.io.Serializable { |
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|
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/* |
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* Implemented as a simple doubly-linked list protected by a |
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* single lock and using conditions to manage blocking. |
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* |
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* To implement weakly consistent iterators, it appears we need to |
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* keep all Nodes GC-reachable from a predecessor dequeued Node. |
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* That would cause two problems: |
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* - allow a rogue Iterator to cause unbounded memory retention |
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* - cause cross-generational linking of old Nodes to new Nodes if |
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* a Node was tenured while live, which generational GCs have a |
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* hard time dealing with, causing repeated major collections. |
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* However, only non-deleted Nodes need to be reachable from |
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* dequeued Nodes, and reachability does not necessarily have to |
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* be of the kind understood by the GC. We use the trick of |
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* linking a Node that has just been dequeued to itself. Such a |
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* self-link implicitly means to jump to "first" (for next links) |
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* or "last" (for prev links). |
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*/ |
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|
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/* |
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* We have "diamond" multiple interface/abstract class inheritance |
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* here, and that introduces ambiguities. Often we want the |
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* BlockingDeque javadoc combined with the AbstractQueue |
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* implementation, so a lot of method specs are duplicated here. |
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*/ |
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|
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private static final long serialVersionUID = -387911632671998426L; |
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|
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/** Doubly-linked list node class */ |
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static final class Node<E> { |
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/** |
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* The item, or null if this node has been removed. |
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*/ |
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E item; |
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|
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/** |
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* One of: |
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* - the real predecessor Node |
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* - this Node, meaning the predecessor is tail |
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* - null, meaning there is no predecessor |
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*/ |
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Node<E> prev; |
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|
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/** |
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* One of: |
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* - the real successor Node |
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* - this Node, meaning the successor is head |
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* - null, meaning there is no successor |
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*/ |
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Node<E> next; |
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|
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Node(E x) { |
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item = x; |
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} |
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} |
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|
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/** |
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* Pointer to first node. |
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* Invariant: (first == null && last == null) || |
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* (first.prev == null && first.item != null) |
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*/ |
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transient Node<E> first; |
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|
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/** |
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* Pointer to last node. |
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* Invariant: (first == null && last == null) || |
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* (last.next == null && last.item != null) |
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*/ |
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transient Node<E> last; |
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|
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/** Number of items in the deque */ |
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private transient int count; |
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|
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/** Maximum number of items in the deque */ |
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private final int capacity; |
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|
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/** Main lock guarding all access */ |
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final ReentrantLock lock = new ReentrantLock(); |
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|
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/** Condition for waiting takes */ |
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@SuppressWarnings("serial") // Classes implementing Condition may be serializable. |
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private final Condition notEmpty = lock.newCondition(); |
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|
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/** Condition for waiting puts */ |
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@SuppressWarnings("serial") // Classes implementing Condition may be serializable. |
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private final Condition notFull = lock.newCondition(); |
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|
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/** |
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* Creates a {@code LinkedBlockingDeque} with a capacity of |
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* {@link Integer#MAX_VALUE}. |
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*/ |
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public LinkedBlockingDeque() { |
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this(Integer.MAX_VALUE); |
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} |
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|
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/** |
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* Creates a {@code LinkedBlockingDeque} with the given (fixed) capacity. |
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* |
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* @param capacity the capacity of this deque |
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* @throws IllegalArgumentException if {@code capacity} is less than 1 |
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*/ |
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public LinkedBlockingDeque(int capacity) { |
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if (capacity <= 0) throw new IllegalArgumentException(); |
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this.capacity = capacity; |
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} |
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|
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/** |
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* Creates a {@code LinkedBlockingDeque} with a capacity of |
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* {@link Integer#MAX_VALUE}, initially containing the elements of |
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* the given collection, added in traversal order of the |
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* collection's iterator. |
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* |
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* @param c the collection of elements to initially contain |
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* @throws NullPointerException if the specified collection or any |
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* of its elements are null |
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*/ |
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public LinkedBlockingDeque(Collection<? extends E> c) { |
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this(Integer.MAX_VALUE); |
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addAll(c); |
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} |
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|
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|
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// Basic linking and unlinking operations, called only while holding lock |
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|
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/** |
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* Links node as first element, or returns false if full. |
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*/ |
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private boolean linkFirst(Node<E> node) { |
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// assert lock.isHeldByCurrentThread(); |
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if (count >= capacity) |
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return false; |
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Node<E> f = first; |
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node.next = f; |
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first = node; |
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if (last == null) |
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last = node; |
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else |
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f.prev = node; |
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++count; |
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notEmpty.signal(); |
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return true; |
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} |
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|
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/** |
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* Links node as last element, or returns false if full. |
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*/ |
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private boolean linkLast(Node<E> node) { |
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// assert lock.isHeldByCurrentThread(); |
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if (count >= capacity) |
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return false; |
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Node<E> l = last; |
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node.prev = l; |
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last = node; |
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if (first == null) |
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first = node; |
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else |
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l.next = node; |
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++count; |
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notEmpty.signal(); |
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return true; |
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} |
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|
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/** |
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* Removes and returns first element, or null if empty. |
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*/ |
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private E unlinkFirst() { |
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// assert lock.isHeldByCurrentThread(); |
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Node<E> f = first; |
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if (f == null) |
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return null; |
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Node<E> n = f.next; |
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E item = f.item; |
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f.item = null; |
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f.next = f; // help GC |
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first = n; |
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if (n == null) |
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last = null; |
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else |
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n.prev = null; |
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--count; |
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notFull.signal(); |
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return item; |
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} |
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|
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/** |
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* Removes and returns last element, or null if empty. |
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*/ |
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private E unlinkLast() { |
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// assert lock.isHeldByCurrentThread(); |
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Node<E> l = last; |
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if (l == null) |
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return null; |
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Node<E> p = l.prev; |
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E item = l.item; |
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l.item = null; |
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l.prev = l; // help GC |
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last = p; |
250 |
if (p == null) |
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first = null; |
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else |
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p.next = null; |
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--count; |
255 |
notFull.signal(); |
256 |
return item; |
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} |
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|
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/** |
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* Unlinks x. |
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*/ |
262 |
void unlink(Node<E> x) { |
263 |
// assert lock.isHeldByCurrentThread(); |
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// assert x.item != null; |
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Node<E> p = x.prev; |
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Node<E> n = x.next; |
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if (p == null) { |
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unlinkFirst(); |
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} else if (n == null) { |
270 |
unlinkLast(); |
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} else { |
272 |
p.next = n; |
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n.prev = p; |
274 |
x.item = null; |
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// Don't mess with x's links. They may still be in use by |
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// an iterator. |
277 |
--count; |
278 |
notFull.signal(); |
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} |
280 |
} |
281 |
|
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// BlockingDeque methods |
283 |
|
284 |
/** |
285 |
* @throws IllegalStateException if this deque is full |
286 |
* @throws NullPointerException {@inheritDoc} |
287 |
*/ |
288 |
public void addFirst(E e) { |
289 |
if (!offerFirst(e)) |
290 |
throw new IllegalStateException("Deque full"); |
291 |
} |
292 |
|
293 |
/** |
294 |
* @throws IllegalStateException if this deque is full |
295 |
* @throws NullPointerException {@inheritDoc} |
296 |
*/ |
297 |
public void addLast(E e) { |
298 |
if (!offerLast(e)) |
299 |
throw new IllegalStateException("Deque full"); |
300 |
} |
301 |
|
302 |
/** |
303 |
* @throws NullPointerException {@inheritDoc} |
304 |
*/ |
305 |
public boolean offerFirst(E e) { |
306 |
if (e == null) throw new NullPointerException(); |
307 |
Node<E> node = new Node<E>(e); |
308 |
final ReentrantLock lock = this.lock; |
309 |
lock.lock(); |
310 |
try { |
311 |
return linkFirst(node); |
312 |
} finally { |
313 |
// checkInvariants(); |
314 |
lock.unlock(); |
315 |
} |
316 |
} |
317 |
|
318 |
/** |
319 |
* @throws NullPointerException {@inheritDoc} |
320 |
*/ |
321 |
public boolean offerLast(E e) { |
322 |
if (e == null) throw new NullPointerException(); |
323 |
Node<E> node = new Node<E>(e); |
324 |
final ReentrantLock lock = this.lock; |
325 |
lock.lock(); |
326 |
try { |
327 |
return linkLast(node); |
328 |
} finally { |
329 |
// checkInvariants(); |
330 |
lock.unlock(); |
331 |
} |
332 |
} |
333 |
|
334 |
/** |
335 |
* @throws NullPointerException {@inheritDoc} |
336 |
* @throws InterruptedException {@inheritDoc} |
337 |
*/ |
338 |
public void putFirst(E e) throws InterruptedException { |
339 |
if (e == null) throw new NullPointerException(); |
340 |
Node<E> node = new Node<E>(e); |
341 |
final ReentrantLock lock = this.lock; |
342 |
lock.lock(); |
343 |
try { |
344 |
while (!linkFirst(node)) |
345 |
notFull.await(); |
346 |
} finally { |
347 |
// checkInvariants(); |
348 |
lock.unlock(); |
349 |
} |
350 |
} |
351 |
|
352 |
/** |
353 |
* @throws NullPointerException {@inheritDoc} |
354 |
* @throws InterruptedException {@inheritDoc} |
355 |
*/ |
356 |
public void putLast(E e) throws InterruptedException { |
357 |
if (e == null) throw new NullPointerException(); |
358 |
Node<E> node = new Node<E>(e); |
359 |
final ReentrantLock lock = this.lock; |
360 |
lock.lock(); |
361 |
try { |
362 |
while (!linkLast(node)) |
363 |
notFull.await(); |
364 |
} finally { |
365 |
// checkInvariants(); |
366 |
lock.unlock(); |
367 |
} |
368 |
} |
369 |
|
370 |
/** |
371 |
* @throws NullPointerException {@inheritDoc} |
372 |
* @throws InterruptedException {@inheritDoc} |
373 |
*/ |
374 |
public boolean offerFirst(E e, long timeout, TimeUnit unit) |
375 |
throws InterruptedException { |
376 |
if (e == null) throw new NullPointerException(); |
377 |
Node<E> node = new Node<E>(e); |
378 |
long nanos = unit.toNanos(timeout); |
379 |
final ReentrantLock lock = this.lock; |
380 |
lock.lockInterruptibly(); |
381 |
try { |
382 |
while (!linkFirst(node)) { |
383 |
if (nanos <= 0L) |
384 |
return false; |
385 |
nanos = notFull.awaitNanos(nanos); |
386 |
} |
387 |
return true; |
388 |
} finally { |
389 |
// checkInvariants(); |
390 |
lock.unlock(); |
391 |
} |
392 |
} |
393 |
|
394 |
/** |
395 |
* @throws NullPointerException {@inheritDoc} |
396 |
* @throws InterruptedException {@inheritDoc} |
397 |
*/ |
398 |
public boolean offerLast(E e, long timeout, TimeUnit unit) |
399 |
throws InterruptedException { |
400 |
if (e == null) throw new NullPointerException(); |
401 |
Node<E> node = new Node<E>(e); |
402 |
long nanos = unit.toNanos(timeout); |
403 |
final ReentrantLock lock = this.lock; |
404 |
lock.lockInterruptibly(); |
405 |
try { |
406 |
while (!linkLast(node)) { |
407 |
if (nanos <= 0L) |
408 |
return false; |
409 |
nanos = notFull.awaitNanos(nanos); |
410 |
} |
411 |
return true; |
412 |
} finally { |
413 |
// checkInvariants(); |
414 |
lock.unlock(); |
415 |
} |
416 |
} |
417 |
|
418 |
/** |
419 |
* @throws NoSuchElementException {@inheritDoc} |
420 |
*/ |
421 |
public E removeFirst() { |
422 |
E x = pollFirst(); |
423 |
if (x == null) throw new NoSuchElementException(); |
424 |
return x; |
425 |
} |
426 |
|
427 |
/** |
428 |
* @throws NoSuchElementException {@inheritDoc} |
429 |
*/ |
430 |
public E removeLast() { |
431 |
E x = pollLast(); |
432 |
if (x == null) throw new NoSuchElementException(); |
433 |
return x; |
434 |
} |
435 |
|
436 |
public E pollFirst() { |
437 |
final ReentrantLock lock = this.lock; |
438 |
lock.lock(); |
439 |
try { |
440 |
return unlinkFirst(); |
441 |
} finally { |
442 |
// checkInvariants(); |
443 |
lock.unlock(); |
444 |
} |
445 |
} |
446 |
|
447 |
public E pollLast() { |
448 |
final ReentrantLock lock = this.lock; |
449 |
lock.lock(); |
450 |
try { |
451 |
return unlinkLast(); |
452 |
} finally { |
453 |
// checkInvariants(); |
454 |
lock.unlock(); |
455 |
} |
456 |
} |
457 |
|
458 |
public E takeFirst() throws InterruptedException { |
459 |
final ReentrantLock lock = this.lock; |
460 |
lock.lock(); |
461 |
try { |
462 |
E x; |
463 |
while ( (x = unlinkFirst()) == null) |
464 |
notEmpty.await(); |
465 |
return x; |
466 |
} finally { |
467 |
// checkInvariants(); |
468 |
lock.unlock(); |
469 |
} |
470 |
} |
471 |
|
472 |
public E takeLast() throws InterruptedException { |
473 |
final ReentrantLock lock = this.lock; |
474 |
lock.lock(); |
475 |
try { |
476 |
E x; |
477 |
while ( (x = unlinkLast()) == null) |
478 |
notEmpty.await(); |
479 |
return x; |
480 |
} finally { |
481 |
// checkInvariants(); |
482 |
lock.unlock(); |
483 |
} |
484 |
} |
485 |
|
486 |
public E pollFirst(long timeout, TimeUnit unit) |
487 |
throws InterruptedException { |
488 |
long nanos = unit.toNanos(timeout); |
489 |
final ReentrantLock lock = this.lock; |
490 |
lock.lockInterruptibly(); |
491 |
try { |
492 |
E x; |
493 |
while ( (x = unlinkFirst()) == null) { |
494 |
if (nanos <= 0L) |
495 |
return null; |
496 |
nanos = notEmpty.awaitNanos(nanos); |
497 |
} |
498 |
return x; |
499 |
} finally { |
500 |
// checkInvariants(); |
501 |
lock.unlock(); |
502 |
} |
503 |
} |
504 |
|
505 |
public E pollLast(long timeout, TimeUnit unit) |
506 |
throws InterruptedException { |
507 |
long nanos = unit.toNanos(timeout); |
508 |
final ReentrantLock lock = this.lock; |
509 |
lock.lockInterruptibly(); |
510 |
try { |
511 |
E x; |
512 |
while ( (x = unlinkLast()) == null) { |
513 |
if (nanos <= 0L) |
514 |
return null; |
515 |
nanos = notEmpty.awaitNanos(nanos); |
516 |
} |
517 |
return x; |
518 |
} finally { |
519 |
// checkInvariants(); |
520 |
lock.unlock(); |
521 |
} |
522 |
} |
523 |
|
524 |
/** |
525 |
* @throws NoSuchElementException {@inheritDoc} |
526 |
*/ |
527 |
public E getFirst() { |
528 |
E x = peekFirst(); |
529 |
if (x == null) throw new NoSuchElementException(); |
530 |
return x; |
531 |
} |
532 |
|
533 |
/** |
534 |
* @throws NoSuchElementException {@inheritDoc} |
535 |
*/ |
536 |
public E getLast() { |
537 |
E x = peekLast(); |
538 |
if (x == null) throw new NoSuchElementException(); |
539 |
return x; |
540 |
} |
541 |
|
542 |
public E peekFirst() { |
543 |
final ReentrantLock lock = this.lock; |
544 |
lock.lock(); |
545 |
try { |
546 |
return (first == null) ? null : first.item; |
547 |
} finally { |
548 |
// checkInvariants(); |
549 |
lock.unlock(); |
550 |
} |
551 |
} |
552 |
|
553 |
public E peekLast() { |
554 |
final ReentrantLock lock = this.lock; |
555 |
lock.lock(); |
556 |
try { |
557 |
return (last == null) ? null : last.item; |
558 |
} finally { |
559 |
// checkInvariants(); |
560 |
lock.unlock(); |
561 |
} |
562 |
} |
563 |
|
564 |
public boolean removeFirstOccurrence(Object o) { |
565 |
if (o == null) return false; |
566 |
final ReentrantLock lock = this.lock; |
567 |
lock.lock(); |
568 |
try { |
569 |
for (Node<E> p = first; p != null; p = p.next) { |
570 |
if (o.equals(p.item)) { |
571 |
unlink(p); |
572 |
return true; |
573 |
} |
574 |
} |
575 |
return false; |
576 |
} finally { |
577 |
// checkInvariants(); |
578 |
lock.unlock(); |
579 |
} |
580 |
} |
581 |
|
582 |
public boolean removeLastOccurrence(Object o) { |
583 |
if (o == null) return false; |
584 |
final ReentrantLock lock = this.lock; |
585 |
lock.lock(); |
586 |
try { |
587 |
for (Node<E> p = last; p != null; p = p.prev) { |
588 |
if (o.equals(p.item)) { |
589 |
unlink(p); |
590 |
return true; |
591 |
} |
592 |
} |
593 |
return false; |
594 |
} finally { |
595 |
// checkInvariants(); |
596 |
lock.unlock(); |
597 |
} |
598 |
} |
599 |
|
600 |
// BlockingQueue methods |
601 |
|
602 |
/** |
603 |
* Inserts the specified element at the end of this deque unless it would |
604 |
* violate capacity restrictions. When using a capacity-restricted deque, |
605 |
* it is generally preferable to use method {@link #offer(Object) offer}. |
606 |
* |
607 |
* <p>This method is equivalent to {@link #addLast}. |
608 |
* |
609 |
* @throws IllegalStateException if this deque is full |
610 |
* @throws NullPointerException if the specified element is null |
611 |
*/ |
612 |
public boolean add(E e) { |
613 |
addLast(e); |
614 |
return true; |
615 |
} |
616 |
|
617 |
/** |
618 |
* @throws NullPointerException if the specified element is null |
619 |
*/ |
620 |
public boolean offer(E e) { |
621 |
return offerLast(e); |
622 |
} |
623 |
|
624 |
/** |
625 |
* @throws NullPointerException {@inheritDoc} |
626 |
* @throws InterruptedException {@inheritDoc} |
627 |
*/ |
628 |
public void put(E e) throws InterruptedException { |
629 |
putLast(e); |
630 |
} |
631 |
|
632 |
/** |
633 |
* @throws NullPointerException {@inheritDoc} |
634 |
* @throws InterruptedException {@inheritDoc} |
635 |
*/ |
636 |
public boolean offer(E e, long timeout, TimeUnit unit) |
637 |
throws InterruptedException { |
638 |
return offerLast(e, timeout, unit); |
639 |
} |
640 |
|
641 |
/** |
642 |
* Retrieves and removes the head of the queue represented by this deque. |
643 |
* This method differs from {@link #poll() poll()} only in that it throws an |
644 |
* exception if this deque is empty. |
645 |
* |
646 |
* <p>This method is equivalent to {@link #removeFirst() removeFirst}. |
647 |
* |
648 |
* @return the head of the queue represented by this deque |
649 |
* @throws NoSuchElementException if this deque is empty |
650 |
*/ |
651 |
public E remove() { |
652 |
return removeFirst(); |
653 |
} |
654 |
|
655 |
public E poll() { |
656 |
return pollFirst(); |
657 |
} |
658 |
|
659 |
public E take() throws InterruptedException { |
660 |
return takeFirst(); |
661 |
} |
662 |
|
663 |
public E poll(long timeout, TimeUnit unit) throws InterruptedException { |
664 |
return pollFirst(timeout, unit); |
665 |
} |
666 |
|
667 |
/** |
668 |
* Retrieves, but does not remove, the head of the queue represented by |
669 |
* this deque. This method differs from {@link #peek() peek()} only in that |
670 |
* it throws an exception if this deque is empty. |
671 |
* |
672 |
* <p>This method is equivalent to {@link #getFirst() getFirst}. |
673 |
* |
674 |
* @return the head of the queue represented by this deque |
675 |
* @throws NoSuchElementException if this deque is empty |
676 |
*/ |
677 |
public E element() { |
678 |
return getFirst(); |
679 |
} |
680 |
|
681 |
public E peek() { |
682 |
return peekFirst(); |
683 |
} |
684 |
|
685 |
/** |
686 |
* Returns the number of additional elements that this deque can ideally |
687 |
* (in the absence of memory or resource constraints) accept without |
688 |
* blocking. This is always equal to the initial capacity of this deque |
689 |
* less the current {@code size} of this deque. |
690 |
* |
691 |
* <p>Note that you <em>cannot</em> always tell if an attempt to insert |
692 |
* an element will succeed by inspecting {@code remainingCapacity} |
693 |
* because it may be the case that another thread is about to |
694 |
* insert or remove an element. |
695 |
*/ |
696 |
public int remainingCapacity() { |
697 |
final ReentrantLock lock = this.lock; |
698 |
lock.lock(); |
699 |
try { |
700 |
return capacity - count; |
701 |
} finally { |
702 |
// checkInvariants(); |
703 |
lock.unlock(); |
704 |
} |
705 |
} |
706 |
|
707 |
/** |
708 |
* @throws UnsupportedOperationException {@inheritDoc} |
709 |
* @throws ClassCastException {@inheritDoc} |
710 |
* @throws NullPointerException {@inheritDoc} |
711 |
* @throws IllegalArgumentException {@inheritDoc} |
712 |
*/ |
713 |
public int drainTo(Collection<? super E> c) { |
714 |
return drainTo(c, Integer.MAX_VALUE); |
715 |
} |
716 |
|
717 |
/** |
718 |
* @throws UnsupportedOperationException {@inheritDoc} |
719 |
* @throws ClassCastException {@inheritDoc} |
720 |
* @throws NullPointerException {@inheritDoc} |
721 |
* @throws IllegalArgumentException {@inheritDoc} |
722 |
*/ |
723 |
public int drainTo(Collection<? super E> c, int maxElements) { |
724 |
Objects.requireNonNull(c); |
725 |
if (c == this) |
726 |
throw new IllegalArgumentException(); |
727 |
if (maxElements <= 0) |
728 |
return 0; |
729 |
final ReentrantLock lock = this.lock; |
730 |
lock.lock(); |
731 |
try { |
732 |
int n = Math.min(maxElements, count); |
733 |
for (int i = 0; i < n; i++) { |
734 |
c.add(first.item); // In this order, in case add() throws. |
735 |
unlinkFirst(); |
736 |
} |
737 |
return n; |
738 |
} finally { |
739 |
// checkInvariants(); |
740 |
lock.unlock(); |
741 |
} |
742 |
} |
743 |
|
744 |
// Stack methods |
745 |
|
746 |
/** |
747 |
* @throws IllegalStateException if this deque is full |
748 |
* @throws NullPointerException {@inheritDoc} |
749 |
*/ |
750 |
public void push(E e) { |
751 |
addFirst(e); |
752 |
} |
753 |
|
754 |
/** |
755 |
* @throws NoSuchElementException {@inheritDoc} |
756 |
*/ |
757 |
public E pop() { |
758 |
return removeFirst(); |
759 |
} |
760 |
|
761 |
// Collection methods |
762 |
|
763 |
/** |
764 |
* Removes the first occurrence of the specified element from this deque. |
765 |
* If the deque does not contain the element, it is unchanged. |
766 |
* More formally, removes the first element {@code e} such that |
767 |
* {@code o.equals(e)} (if such an element exists). |
768 |
* Returns {@code true} if this deque contained the specified element |
769 |
* (or equivalently, if this deque changed as a result of the call). |
770 |
* |
771 |
* <p>This method is equivalent to |
772 |
* {@link #removeFirstOccurrence(Object) removeFirstOccurrence}. |
773 |
* |
774 |
* @param o element to be removed from this deque, if present |
775 |
* @return {@code true} if this deque changed as a result of the call |
776 |
*/ |
777 |
public boolean remove(Object o) { |
778 |
return removeFirstOccurrence(o); |
779 |
} |
780 |
|
781 |
/** |
782 |
* Returns the number of elements in this deque. |
783 |
* |
784 |
* @return the number of elements in this deque |
785 |
*/ |
786 |
public int size() { |
787 |
final ReentrantLock lock = this.lock; |
788 |
lock.lock(); |
789 |
try { |
790 |
return count; |
791 |
} finally { |
792 |
// checkInvariants(); |
793 |
lock.unlock(); |
794 |
} |
795 |
} |
796 |
|
797 |
/** |
798 |
* Returns {@code true} if this deque contains the specified element. |
799 |
* More formally, returns {@code true} if and only if this deque contains |
800 |
* at least one element {@code e} such that {@code o.equals(e)}. |
801 |
* |
802 |
* @param o object to be checked for containment in this deque |
803 |
* @return {@code true} if this deque contains the specified element |
804 |
*/ |
805 |
public boolean contains(Object o) { |
806 |
if (o == null) return false; |
807 |
final ReentrantLock lock = this.lock; |
808 |
lock.lock(); |
809 |
try { |
810 |
for (Node<E> p = first; p != null; p = p.next) |
811 |
if (o.equals(p.item)) |
812 |
return true; |
813 |
return false; |
814 |
} finally { |
815 |
// checkInvariants(); |
816 |
lock.unlock(); |
817 |
} |
818 |
} |
819 |
|
820 |
/** |
821 |
* Appends all of the elements in the specified collection to the end of |
822 |
* this deque, in the order that they are returned by the specified |
823 |
* collection's iterator. Attempts to {@code addAll} of a deque to |
824 |
* itself result in {@code IllegalArgumentException}. |
825 |
* |
826 |
* @param c the elements to be inserted into this deque |
827 |
* @return {@code true} if this deque changed as a result of the call |
828 |
* @throws NullPointerException if the specified collection or any |
829 |
* of its elements are null |
830 |
* @throws IllegalArgumentException if the collection is this deque |
831 |
* @throws IllegalStateException if this deque is full |
832 |
* @see #add(Object) |
833 |
*/ |
834 |
public boolean addAll(Collection<? extends E> c) { |
835 |
if (c == this) |
836 |
// As historically specified in AbstractQueue#addAll |
837 |
throw new IllegalArgumentException(); |
838 |
|
839 |
// Copy c into a private chain of Nodes |
840 |
Node<E> beg = null, end = null; |
841 |
int n = 0; |
842 |
for (E e : c) { |
843 |
Objects.requireNonNull(e); |
844 |
n++; |
845 |
Node<E> newNode = new Node<E>(e); |
846 |
if (beg == null) |
847 |
beg = end = newNode; |
848 |
else { |
849 |
end.next = newNode; |
850 |
newNode.prev = end; |
851 |
end = newNode; |
852 |
} |
853 |
} |
854 |
if (beg == null) |
855 |
return false; |
856 |
|
857 |
// Atomically append the chain at the end |
858 |
final ReentrantLock lock = this.lock; |
859 |
lock.lock(); |
860 |
try { |
861 |
if (count + n <= capacity) { |
862 |
beg.prev = last; |
863 |
if (first == null) |
864 |
first = beg; |
865 |
else |
866 |
last.next = beg; |
867 |
last = end; |
868 |
count += n; |
869 |
notEmpty.signalAll(); |
870 |
return true; |
871 |
} |
872 |
} finally { |
873 |
// checkInvariants(); |
874 |
lock.unlock(); |
875 |
} |
876 |
// Fall back to historic non-atomic implementation, failing |
877 |
// with IllegalStateException when the capacity is exceeded. |
878 |
return super.addAll(c); |
879 |
} |
880 |
|
881 |
/** |
882 |
* Returns an array containing all of the elements in this deque, in |
883 |
* proper sequence (from first to last element). |
884 |
* |
885 |
* <p>The returned array will be "safe" in that no references to it are |
886 |
* maintained by this deque. (In other words, this method must allocate |
887 |
* a new array). The caller is thus free to modify the returned array. |
888 |
* |
889 |
* <p>This method acts as bridge between array-based and collection-based |
890 |
* APIs. |
891 |
* |
892 |
* @return an array containing all of the elements in this deque |
893 |
*/ |
894 |
@SuppressWarnings("unchecked") |
895 |
public Object[] toArray() { |
896 |
final ReentrantLock lock = this.lock; |
897 |
lock.lock(); |
898 |
try { |
899 |
Object[] a = new Object[count]; |
900 |
int k = 0; |
901 |
for (Node<E> p = first; p != null; p = p.next) |
902 |
a[k++] = p.item; |
903 |
return a; |
904 |
} finally { |
905 |
// checkInvariants(); |
906 |
lock.unlock(); |
907 |
} |
908 |
} |
909 |
|
910 |
/** |
911 |
* Returns an array containing all of the elements in this deque, in |
912 |
* proper sequence; the runtime type of the returned array is that of |
913 |
* the specified array. If the deque fits in the specified array, it |
914 |
* is returned therein. Otherwise, a new array is allocated with the |
915 |
* runtime type of the specified array and the size of this deque. |
916 |
* |
917 |
* <p>If this deque fits in the specified array with room to spare |
918 |
* (i.e., the array has more elements than this deque), the element in |
919 |
* the array immediately following the end of the deque is set to |
920 |
* {@code null}. |
921 |
* |
922 |
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
923 |
* array-based and collection-based APIs. Further, this method allows |
924 |
* precise control over the runtime type of the output array, and may, |
925 |
* under certain circumstances, be used to save allocation costs. |
926 |
* |
927 |
* <p>Suppose {@code x} is a deque known to contain only strings. |
928 |
* The following code can be used to dump the deque into a newly |
929 |
* allocated array of {@code String}: |
930 |
* |
931 |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
932 |
* |
933 |
* Note that {@code toArray(new Object[0])} is identical in function to |
934 |
* {@code toArray()}. |
935 |
* |
936 |
* @param a the array into which the elements of the deque are to |
937 |
* be stored, if it is big enough; otherwise, a new array of the |
938 |
* same runtime type is allocated for this purpose |
939 |
* @return an array containing all of the elements in this deque |
940 |
* @throws ArrayStoreException if the runtime type of the specified array |
941 |
* is not a supertype of the runtime type of every element in |
942 |
* this deque |
943 |
* @throws NullPointerException if the specified array is null |
944 |
*/ |
945 |
@SuppressWarnings("unchecked") |
946 |
public <T> T[] toArray(T[] a) { |
947 |
final ReentrantLock lock = this.lock; |
948 |
lock.lock(); |
949 |
try { |
950 |
if (a.length < count) |
951 |
a = (T[])java.lang.reflect.Array.newInstance |
952 |
(a.getClass().getComponentType(), count); |
953 |
|
954 |
int k = 0; |
955 |
for (Node<E> p = first; p != null; p = p.next) |
956 |
a[k++] = (T)p.item; |
957 |
if (a.length > k) |
958 |
a[k] = null; |
959 |
return a; |
960 |
} finally { |
961 |
// checkInvariants(); |
962 |
lock.unlock(); |
963 |
} |
964 |
} |
965 |
|
966 |
public String toString() { |
967 |
return Helpers.collectionToString(this); |
968 |
} |
969 |
|
970 |
/** |
971 |
* Atomically removes all of the elements from this deque. |
972 |
* The deque will be empty after this call returns. |
973 |
*/ |
974 |
public void clear() { |
975 |
final ReentrantLock lock = this.lock; |
976 |
lock.lock(); |
977 |
try { |
978 |
for (Node<E> f = first; f != null; ) { |
979 |
f.item = null; |
980 |
Node<E> n = f.next; |
981 |
f.prev = null; |
982 |
f.next = null; |
983 |
f = n; |
984 |
} |
985 |
first = last = null; |
986 |
count = 0; |
987 |
notFull.signalAll(); |
988 |
} finally { |
989 |
// checkInvariants(); |
990 |
lock.unlock(); |
991 |
} |
992 |
} |
993 |
|
994 |
/** |
995 |
* Used for any element traversal that is not entirely under lock. |
996 |
* Such traversals must handle both: |
997 |
* - dequeued nodes (p.next == p) |
998 |
* - (possibly multiple) interior removed nodes (p.item == null) |
999 |
*/ |
1000 |
Node<E> succ(Node<E> p) { |
1001 |
if (p == (p = p.next)) |
1002 |
p = first; |
1003 |
return p; |
1004 |
} |
1005 |
|
1006 |
/** |
1007 |
* Returns an iterator over the elements in this deque in proper sequence. |
1008 |
* The elements will be returned in order from first (head) to last (tail). |
1009 |
* |
1010 |
* <p>The returned iterator is |
1011 |
* <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>. |
1012 |
* |
1013 |
* @return an iterator over the elements in this deque in proper sequence |
1014 |
*/ |
1015 |
public Iterator<E> iterator() { |
1016 |
return new Itr(); |
1017 |
} |
1018 |
|
1019 |
/** |
1020 |
* Returns an iterator over the elements in this deque in reverse |
1021 |
* sequential order. The elements will be returned in order from |
1022 |
* last (tail) to first (head). |
1023 |
* |
1024 |
* <p>The returned iterator is |
1025 |
* <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>. |
1026 |
* |
1027 |
* @return an iterator over the elements in this deque in reverse order |
1028 |
*/ |
1029 |
public Iterator<E> descendingIterator() { |
1030 |
return new DescendingItr(); |
1031 |
} |
1032 |
|
1033 |
/** |
1034 |
* Base class for LinkedBlockingDeque iterators. |
1035 |
*/ |
1036 |
private abstract class AbstractItr implements Iterator<E> { |
1037 |
/** |
1038 |
* The next node to return in next(). |
1039 |
*/ |
1040 |
Node<E> next; |
1041 |
|
1042 |
/** |
1043 |
* nextItem holds on to item fields because once we claim that |
1044 |
* an element exists in hasNext(), we must return item read |
1045 |
* under lock even if it was in the process of being removed |
1046 |
* when hasNext() was called. |
1047 |
*/ |
1048 |
E nextItem; |
1049 |
|
1050 |
/** |
1051 |
* Node returned by most recent call to next. Needed by remove. |
1052 |
* Reset to null if this element is deleted by a call to remove. |
1053 |
*/ |
1054 |
private Node<E> lastRet; |
1055 |
|
1056 |
abstract Node<E> firstNode(); |
1057 |
abstract Node<E> nextNode(Node<E> n); |
1058 |
|
1059 |
private Node<E> succ(Node<E> p) { |
1060 |
if (p == (p = nextNode(p))) |
1061 |
p = firstNode(); |
1062 |
return p; |
1063 |
} |
1064 |
|
1065 |
AbstractItr() { |
1066 |
// set to initial position |
1067 |
final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
1068 |
lock.lock(); |
1069 |
try { |
1070 |
if ((next = firstNode()) != null) |
1071 |
nextItem = next.item; |
1072 |
} finally { |
1073 |
// checkInvariants(); |
1074 |
lock.unlock(); |
1075 |
} |
1076 |
} |
1077 |
|
1078 |
public boolean hasNext() { |
1079 |
return next != null; |
1080 |
} |
1081 |
|
1082 |
public E next() { |
1083 |
Node<E> p; |
1084 |
if ((p = next) == null) |
1085 |
throw new NoSuchElementException(); |
1086 |
lastRet = p; |
1087 |
E x = nextItem; |
1088 |
final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
1089 |
lock.lock(); |
1090 |
try { |
1091 |
E e = null; |
1092 |
for (p = nextNode(p); p != null && (e = p.item) == null; ) |
1093 |
p = succ(p); |
1094 |
next = p; |
1095 |
nextItem = e; |
1096 |
} finally { |
1097 |
// checkInvariants(); |
1098 |
lock.unlock(); |
1099 |
} |
1100 |
return x; |
1101 |
} |
1102 |
|
1103 |
public void forEachRemaining(Consumer<? super E> action) { |
1104 |
// A variant of forEachFrom |
1105 |
Objects.requireNonNull(action); |
1106 |
Node<E> p; |
1107 |
if ((p = next) == null) return; |
1108 |
lastRet = p; |
1109 |
next = null; |
1110 |
final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
1111 |
final int batchSize = 64; |
1112 |
Object[] es = null; |
1113 |
int n, len = 1; |
1114 |
do { |
1115 |
lock.lock(); |
1116 |
try { |
1117 |
if (es == null) { |
1118 |
p = nextNode(p); |
1119 |
for (Node<E> q = p; q != null; q = succ(q)) |
1120 |
if (q.item != null && ++len == batchSize) |
1121 |
break; |
1122 |
es = new Object[len]; |
1123 |
es[0] = nextItem; |
1124 |
nextItem = null; |
1125 |
n = 1; |
1126 |
} else |
1127 |
n = 0; |
1128 |
for (; p != null && n < len; p = succ(p)) |
1129 |
if ((es[n] = p.item) != null) { |
1130 |
lastRet = p; |
1131 |
n++; |
1132 |
} |
1133 |
} finally { |
1134 |
// checkInvariants(); |
1135 |
lock.unlock(); |
1136 |
} |
1137 |
for (int i = 0; i < n; i++) { |
1138 |
@SuppressWarnings("unchecked") E e = (E) es[i]; |
1139 |
action.accept(e); |
1140 |
} |
1141 |
} while (n > 0 && p != null); |
1142 |
} |
1143 |
|
1144 |
public void remove() { |
1145 |
Node<E> n = lastRet; |
1146 |
if (n == null) |
1147 |
throw new IllegalStateException(); |
1148 |
lastRet = null; |
1149 |
final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
1150 |
lock.lock(); |
1151 |
try { |
1152 |
if (n.item != null) |
1153 |
unlink(n); |
1154 |
} finally { |
1155 |
// checkInvariants(); |
1156 |
lock.unlock(); |
1157 |
} |
1158 |
} |
1159 |
} |
1160 |
|
1161 |
/** Forward iterator */ |
1162 |
private class Itr extends AbstractItr { |
1163 |
Itr() {} // prevent access constructor creation |
1164 |
Node<E> firstNode() { return first; } |
1165 |
Node<E> nextNode(Node<E> n) { return n.next; } |
1166 |
} |
1167 |
|
1168 |
/** Descending iterator */ |
1169 |
private class DescendingItr extends AbstractItr { |
1170 |
DescendingItr() {} // prevent access constructor creation |
1171 |
Node<E> firstNode() { return last; } |
1172 |
Node<E> nextNode(Node<E> n) { return n.prev; } |
1173 |
} |
1174 |
|
1175 |
/** |
1176 |
* A customized variant of Spliterators.IteratorSpliterator. |
1177 |
* Keep this class in sync with (very similar) LBQSpliterator. |
1178 |
*/ |
1179 |
private final class LBDSpliterator implements Spliterator<E> { |
1180 |
static final int MAX_BATCH = 1 << 25; // max batch array size; |
1181 |
Node<E> current; // current node; null until initialized |
1182 |
int batch; // batch size for splits |
1183 |
boolean exhausted; // true when no more nodes |
1184 |
long est = size(); // size estimate |
1185 |
|
1186 |
LBDSpliterator() {} |
1187 |
|
1188 |
public long estimateSize() { return est; } |
1189 |
|
1190 |
public Spliterator<E> trySplit() { |
1191 |
Node<E> h; |
1192 |
if (!exhausted && |
1193 |
((h = current) != null || (h = first) != null) |
1194 |
&& h.next != null) { |
1195 |
int n = batch = Math.min(batch + 1, MAX_BATCH); |
1196 |
Object[] a = new Object[n]; |
1197 |
final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
1198 |
int i = 0; |
1199 |
Node<E> p = current; |
1200 |
lock.lock(); |
1201 |
try { |
1202 |
if (p != null || (p = first) != null) |
1203 |
for (; p != null && i < n; p = succ(p)) |
1204 |
if ((a[i] = p.item) != null) |
1205 |
i++; |
1206 |
} finally { |
1207 |
// checkInvariants(); |
1208 |
lock.unlock(); |
1209 |
} |
1210 |
if ((current = p) == null) { |
1211 |
est = 0L; |
1212 |
exhausted = true; |
1213 |
} |
1214 |
else if ((est -= i) < 0L) |
1215 |
est = 0L; |
1216 |
if (i > 0) |
1217 |
return Spliterators.spliterator |
1218 |
(a, 0, i, (Spliterator.ORDERED | |
1219 |
Spliterator.NONNULL | |
1220 |
Spliterator.CONCURRENT)); |
1221 |
} |
1222 |
return null; |
1223 |
} |
1224 |
|
1225 |
public boolean tryAdvance(Consumer<? super E> action) { |
1226 |
Objects.requireNonNull(action); |
1227 |
if (!exhausted) { |
1228 |
E e = null; |
1229 |
final ReentrantLock lock = LinkedBlockingDeque.this.lock; |
1230 |
lock.lock(); |
1231 |
try { |
1232 |
Node<E> p; |
1233 |
if ((p = current) != null || (p = first) != null) |
1234 |
do { |
1235 |
e = p.item; |
1236 |
p = succ(p); |
1237 |
} while (e == null && p != null); |
1238 |
if ((current = p) == null) |
1239 |
exhausted = true; |
1240 |
} finally { |
1241 |
// checkInvariants(); |
1242 |
lock.unlock(); |
1243 |
} |
1244 |
if (e != null) { |
1245 |
action.accept(e); |
1246 |
return true; |
1247 |
} |
1248 |
} |
1249 |
return false; |
1250 |
} |
1251 |
|
1252 |
public void forEachRemaining(Consumer<? super E> action) { |
1253 |
Objects.requireNonNull(action); |
1254 |
if (!exhausted) { |
1255 |
exhausted = true; |
1256 |
Node<E> p = current; |
1257 |
current = null; |
1258 |
forEachFrom(action, p); |
1259 |
} |
1260 |
} |
1261 |
|
1262 |
public int characteristics() { |
1263 |
return (Spliterator.ORDERED | |
1264 |
Spliterator.NONNULL | |
1265 |
Spliterator.CONCURRENT); |
1266 |
} |
1267 |
} |
1268 |
|
1269 |
/** |
1270 |
* Returns a {@link Spliterator} over the elements in this deque. |
1271 |
* |
1272 |
* <p>The returned spliterator is |
1273 |
* <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>. |
1274 |
* |
1275 |
* <p>The {@code Spliterator} reports {@link Spliterator#CONCURRENT}, |
1276 |
* {@link Spliterator#ORDERED}, and {@link Spliterator#NONNULL}. |
1277 |
* |
1278 |
* @implNote |
1279 |
* The {@code Spliterator} implements {@code trySplit} to permit limited |
1280 |
* parallelism. |
1281 |
* |
1282 |
* @return a {@code Spliterator} over the elements in this deque |
1283 |
* @since 1.8 |
1284 |
*/ |
1285 |
public Spliterator<E> spliterator() { |
1286 |
return new LBDSpliterator(); |
1287 |
} |
1288 |
|
1289 |
/** |
1290 |
* @throws NullPointerException {@inheritDoc} |
1291 |
*/ |
1292 |
public void forEach(Consumer<? super E> action) { |
1293 |
Objects.requireNonNull(action); |
1294 |
forEachFrom(action, null); |
1295 |
} |
1296 |
|
1297 |
/** |
1298 |
* Runs action on each element found during a traversal starting at p. |
1299 |
* If p is null, traversal starts at head. |
1300 |
*/ |
1301 |
void forEachFrom(Consumer<? super E> action, Node<E> p) { |
1302 |
// Extract batches of elements while holding the lock; then |
1303 |
// run the action on the elements while not |
1304 |
final ReentrantLock lock = this.lock; |
1305 |
final int batchSize = 64; // max number of elements per batch |
1306 |
Object[] es = null; // container for batch of elements |
1307 |
int n, len = 0; |
1308 |
do { |
1309 |
lock.lock(); |
1310 |
try { |
1311 |
if (es == null) { |
1312 |
if (p == null) p = first; |
1313 |
for (Node<E> q = p; q != null; q = succ(q)) |
1314 |
if (q.item != null && ++len == batchSize) |
1315 |
break; |
1316 |
es = new Object[len]; |
1317 |
} |
1318 |
for (n = 0; p != null && n < len; p = succ(p)) |
1319 |
if ((es[n] = p.item) != null) |
1320 |
n++; |
1321 |
} finally { |
1322 |
// checkInvariants(); |
1323 |
lock.unlock(); |
1324 |
} |
1325 |
for (int i = 0; i < n; i++) { |
1326 |
@SuppressWarnings("unchecked") E e = (E) es[i]; |
1327 |
action.accept(e); |
1328 |
} |
1329 |
} while (n > 0 && p != null); |
1330 |
} |
1331 |
|
1332 |
/** |
1333 |
* @throws NullPointerException {@inheritDoc} |
1334 |
*/ |
1335 |
public boolean removeIf(Predicate<? super E> filter) { |
1336 |
Objects.requireNonNull(filter); |
1337 |
return bulkRemove(filter); |
1338 |
} |
1339 |
|
1340 |
/** |
1341 |
* @throws NullPointerException {@inheritDoc} |
1342 |
*/ |
1343 |
public boolean removeAll(Collection<?> c) { |
1344 |
Objects.requireNonNull(c); |
1345 |
return bulkRemove(e -> c.contains(e)); |
1346 |
} |
1347 |
|
1348 |
/** |
1349 |
* @throws NullPointerException {@inheritDoc} |
1350 |
*/ |
1351 |
public boolean retainAll(Collection<?> c) { |
1352 |
Objects.requireNonNull(c); |
1353 |
return bulkRemove(e -> !c.contains(e)); |
1354 |
} |
1355 |
|
1356 |
/** Implementation of bulk remove methods. */ |
1357 |
@SuppressWarnings("unchecked") |
1358 |
private boolean bulkRemove(Predicate<? super E> filter) { |
1359 |
boolean removed = false; |
1360 |
final ReentrantLock lock = this.lock; |
1361 |
Node<E> p = null; |
1362 |
Node<E>[] nodes = null; |
1363 |
int n, len = 0; |
1364 |
do { |
1365 |
// 1. Extract batch of up to 64 elements while holding the lock. |
1366 |
lock.lock(); |
1367 |
try { |
1368 |
if (nodes == null) { // first batch; initialize |
1369 |
p = first; |
1370 |
for (Node<E> q = p; q != null; q = succ(q)) |
1371 |
if (q.item != null && ++len == 64) |
1372 |
break; |
1373 |
nodes = (Node<E>[]) new Node<?>[len]; |
1374 |
} |
1375 |
for (n = 0; p != null && n < len; p = succ(p)) |
1376 |
nodes[n++] = p; |
1377 |
} finally { |
1378 |
// checkInvariants(); |
1379 |
lock.unlock(); |
1380 |
} |
1381 |
|
1382 |
// 2. Run the filter on the elements while lock is free. |
1383 |
long deathRow = 0L; // "bitset" of size 64 |
1384 |
for (int i = 0; i < n; i++) { |
1385 |
final E e; |
1386 |
if ((e = nodes[i].item) != null && filter.test(e)) |
1387 |
deathRow |= 1L << i; |
1388 |
} |
1389 |
|
1390 |
// 3. Remove any filtered elements while holding the lock. |
1391 |
if (deathRow != 0) { |
1392 |
lock.lock(); |
1393 |
try { |
1394 |
for (int i = 0; i < n; i++) { |
1395 |
final Node<E> q; |
1396 |
if ((deathRow & (1L << i)) != 0L |
1397 |
&& (q = nodes[i]).item != null) { |
1398 |
unlink(q); |
1399 |
removed = true; |
1400 |
} |
1401 |
nodes[i] = null; // help GC |
1402 |
} |
1403 |
} finally { |
1404 |
// checkInvariants(); |
1405 |
lock.unlock(); |
1406 |
} |
1407 |
} |
1408 |
} while (n > 0 && p != null); |
1409 |
return removed; |
1410 |
} |
1411 |
|
1412 |
/** |
1413 |
* Saves this deque to a stream (that is, serializes it). |
1414 |
* |
1415 |
* @param s the stream |
1416 |
* @throws java.io.IOException if an I/O error occurs |
1417 |
* @serialData The capacity (int), followed by elements (each an |
1418 |
* {@code Object}) in the proper order, followed by a null |
1419 |
*/ |
1420 |
private void writeObject(java.io.ObjectOutputStream s) |
1421 |
throws java.io.IOException { |
1422 |
final ReentrantLock lock = this.lock; |
1423 |
lock.lock(); |
1424 |
try { |
1425 |
// Write out capacity and any hidden stuff |
1426 |
s.defaultWriteObject(); |
1427 |
// Write out all elements in the proper order. |
1428 |
for (Node<E> p = first; p != null; p = p.next) |
1429 |
s.writeObject(p.item); |
1430 |
// Use trailing null as sentinel |
1431 |
s.writeObject(null); |
1432 |
} finally { |
1433 |
// checkInvariants(); |
1434 |
lock.unlock(); |
1435 |
} |
1436 |
} |
1437 |
|
1438 |
/** |
1439 |
* Reconstitutes this deque from a stream (that is, deserializes it). |
1440 |
* @param s the stream |
1441 |
* @throws ClassNotFoundException if the class of a serialized object |
1442 |
* could not be found |
1443 |
* @throws java.io.IOException if an I/O error occurs |
1444 |
*/ |
1445 |
private void readObject(java.io.ObjectInputStream s) |
1446 |
throws java.io.IOException, ClassNotFoundException { |
1447 |
s.defaultReadObject(); |
1448 |
count = 0; |
1449 |
first = null; |
1450 |
last = null; |
1451 |
// Read in all elements and place in queue |
1452 |
for (;;) { |
1453 |
@SuppressWarnings("unchecked") E item = (E)s.readObject(); |
1454 |
if (item == null) |
1455 |
break; |
1456 |
add(item); |
1457 |
} |
1458 |
} |
1459 |
|
1460 |
void checkInvariants() { |
1461 |
// assert lock.isHeldByCurrentThread(); |
1462 |
// Nodes may get self-linked or lose their item, but only |
1463 |
// after being unlinked and becoming unreachable from first. |
1464 |
for (Node<E> p = first; p != null; p = p.next) { |
1465 |
// assert p.next != p; |
1466 |
// assert p.item != null; |
1467 |
} |
1468 |
} |
1469 |
|
1470 |
} |