--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.base/share/classes/java/util/concurrent/LinkedBlockingDeque.java Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,1462 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation. Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * 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/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.util.AbstractQueue;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.Objects;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Consumer;
+import java.util.function.Predicate;
+
+/**
+ * An optionally-bounded {@linkplain BlockingDeque blocking deque} based on
+ * linked nodes.
+ *
+ * <p>The optional capacity bound constructor argument serves as a
+ * way to prevent excessive expansion. The capacity, if unspecified,
+ * is equal to {@link Integer#MAX_VALUE}. Linked nodes are
+ * dynamically created upon each insertion unless this would bring the
+ * deque above capacity.
+ *
+ * <p>Most operations run in constant time (ignoring time spent
+ * blocking). Exceptions include {@link #remove(Object) remove},
+ * {@link #removeFirstOccurrence removeFirstOccurrence}, {@link
+ * #removeLastOccurrence removeLastOccurrence}, {@link #contains
+ * contains}, {@link #iterator iterator.remove()}, and the bulk
+ * operations, all of which run in linear time.
+ *
+ * <p>This class and its iterator implement all of the <em>optional</em>
+ * methods of the {@link Collection} and {@link Iterator} interfaces.
+ *
+ * <p>This class is a member of the
+ * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
+ * Java Collections Framework</a>.
+ *
+ * @since 1.6
+ * @author Doug Lea
+ * @param <E> the type of elements held in this deque
+ */
+public class LinkedBlockingDeque<E>
+ extends AbstractQueue<E>
+ implements BlockingDeque<E>, java.io.Serializable {
+
+ /*
+ * Implemented as a simple doubly-linked list protected by a
+ * single lock and using conditions to manage blocking.
+ *
+ * To implement weakly consistent iterators, it appears we need to
+ * keep all Nodes GC-reachable from a predecessor dequeued Node.
+ * That would cause two problems:
+ * - allow a rogue Iterator to cause unbounded memory retention
+ * - cause cross-generational linking of old Nodes to new Nodes if
+ * a Node was tenured while live, which generational GCs have a
+ * hard time dealing with, causing repeated major collections.
+ * However, only non-deleted Nodes need to be reachable from
+ * dequeued Nodes, and reachability does not necessarily have to
+ * be of the kind understood by the GC. We use the trick of
+ * linking a Node that has just been dequeued to itself. Such a
+ * self-link implicitly means to jump to "first" (for next links)
+ * or "last" (for prev links).
+ */
+
+ /*
+ * We have "diamond" multiple interface/abstract class inheritance
+ * here, and that introduces ambiguities. Often we want the
+ * BlockingDeque javadoc combined with the AbstractQueue
+ * implementation, so a lot of method specs are duplicated here.
+ */
+
+ private static final long serialVersionUID = -387911632671998426L;
+
+ /** Doubly-linked list node class */
+ static final class Node<E> {
+ /**
+ * The item, or null if this node has been removed.
+ */
+ E item;
+
+ /**
+ * One of:
+ * - the real predecessor Node
+ * - this Node, meaning the predecessor is tail
+ * - null, meaning there is no predecessor
+ */
+ Node<E> prev;
+
+ /**
+ * One of:
+ * - the real successor Node
+ * - this Node, meaning the successor is head
+ * - null, meaning there is no successor
+ */
+ Node<E> next;
+
+ Node(E x) {
+ item = x;
+ }
+ }
+
+ /**
+ * Pointer to first node.
+ * Invariant: (first == null && last == null) ||
+ * (first.prev == null && first.item != null)
+ */
+ transient Node<E> first;
+
+ /**
+ * Pointer to last node.
+ * Invariant: (first == null && last == null) ||
+ * (last.next == null && last.item != null)
+ */
+ transient Node<E> last;
+
+ /** Number of items in the deque */
+ private transient int count;
+
+ /** Maximum number of items in the deque */
+ private final int capacity;
+
+ /** Main lock guarding all access */
+ final ReentrantLock lock = new ReentrantLock();
+
+ /** Condition for waiting takes */
+ private final Condition notEmpty = lock.newCondition();
+
+ /** Condition for waiting puts */
+ private final Condition notFull = lock.newCondition();
+
+ /**
+ * Creates a {@code LinkedBlockingDeque} with a capacity of
+ * {@link Integer#MAX_VALUE}.
+ */
+ public LinkedBlockingDeque() {
+ this(Integer.MAX_VALUE);
+ }
+
+ /**
+ * Creates a {@code LinkedBlockingDeque} with the given (fixed) capacity.
+ *
+ * @param capacity the capacity of this deque
+ * @throws IllegalArgumentException if {@code capacity} is less than 1
+ */
+ public LinkedBlockingDeque(int capacity) {
+ if (capacity <= 0) throw new IllegalArgumentException();
+ this.capacity = capacity;
+ }
+
+ /**
+ * Creates a {@code LinkedBlockingDeque} with a capacity of
+ * {@link Integer#MAX_VALUE}, initially containing the elements of
+ * the given collection, added in traversal order of the
+ * collection's iterator.
+ *
+ * @param c the collection of elements to initially contain
+ * @throws NullPointerException if the specified collection or any
+ * of its elements are null
+ */
+ public LinkedBlockingDeque(Collection<? extends E> c) {
+ this(Integer.MAX_VALUE);
+ addAll(c);
+ }
+
+
+ // Basic linking and unlinking operations, called only while holding lock
+
+ /**
+ * Links node as first element, or returns false if full.
+ */
+ private boolean linkFirst(Node<E> node) {
+ // assert lock.isHeldByCurrentThread();
+ if (count >= capacity)
+ return false;
+ Node<E> f = first;
+ node.next = f;
+ first = node;
+ if (last == null)
+ last = node;
+ else
+ f.prev = node;
+ ++count;
+ notEmpty.signal();
+ return true;
+ }
+
+ /**
+ * Links node as last element, or returns false if full.
+ */
+ private boolean linkLast(Node<E> node) {
+ // assert lock.isHeldByCurrentThread();
+ if (count >= capacity)
+ return false;
+ Node<E> l = last;
+ node.prev = l;
+ last = node;
+ if (first == null)
+ first = node;
+ else
+ l.next = node;
+ ++count;
+ notEmpty.signal();
+ return true;
+ }
+
+ /**
+ * Removes and returns first element, or null if empty.
+ */
+ private E unlinkFirst() {
+ // assert lock.isHeldByCurrentThread();
+ Node<E> f = first;
+ if (f == null)
+ return null;
+ Node<E> n = f.next;
+ E item = f.item;
+ f.item = null;
+ f.next = f; // help GC
+ first = n;
+ if (n == null)
+ last = null;
+ else
+ n.prev = null;
+ --count;
+ notFull.signal();
+ return item;
+ }
+
+ /**
+ * Removes and returns last element, or null if empty.
+ */
+ private E unlinkLast() {
+ // assert lock.isHeldByCurrentThread();
+ Node<E> l = last;
+ if (l == null)
+ return null;
+ Node<E> p = l.prev;
+ E item = l.item;
+ l.item = null;
+ l.prev = l; // help GC
+ last = p;
+ if (p == null)
+ first = null;
+ else
+ p.next = null;
+ --count;
+ notFull.signal();
+ return item;
+ }
+
+ /**
+ * Unlinks x.
+ */
+ void unlink(Node<E> x) {
+ // assert lock.isHeldByCurrentThread();
+ // assert x.item != null;
+ Node<E> p = x.prev;
+ Node<E> n = x.next;
+ if (p == null) {
+ unlinkFirst();
+ } else if (n == null) {
+ unlinkLast();
+ } else {
+ p.next = n;
+ n.prev = p;
+ x.item = null;
+ // Don't mess with x's links. They may still be in use by
+ // an iterator.
+ --count;
+ notFull.signal();
+ }
+ }
+
+ // BlockingDeque methods
+
+ /**
+ * @throws IllegalStateException if this deque is full
+ * @throws NullPointerException {@inheritDoc}
+ */
+ public void addFirst(E e) {
+ if (!offerFirst(e))
+ throw new IllegalStateException("Deque full");
+ }
+
+ /**
+ * @throws IllegalStateException if this deque is full
+ * @throws NullPointerException {@inheritDoc}
+ */
+ public void addLast(E e) {
+ if (!offerLast(e))
+ throw new IllegalStateException("Deque full");
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ */
+ public boolean offerFirst(E e) {
+ if (e == null) throw new NullPointerException();
+ Node<E> node = new Node<E>(e);
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ return linkFirst(node);
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ */
+ public boolean offerLast(E e) {
+ if (e == null) throw new NullPointerException();
+ Node<E> node = new Node<E>(e);
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ return linkLast(node);
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ * @throws InterruptedException {@inheritDoc}
+ */
+ public void putFirst(E e) throws InterruptedException {
+ if (e == null) throw new NullPointerException();
+ Node<E> node = new Node<E>(e);
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ while (!linkFirst(node))
+ notFull.await();
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ * @throws InterruptedException {@inheritDoc}
+ */
+ public void putLast(E e) throws InterruptedException {
+ if (e == null) throw new NullPointerException();
+ Node<E> node = new Node<E>(e);
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ while (!linkLast(node))
+ notFull.await();
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ * @throws InterruptedException {@inheritDoc}
+ */
+ public boolean offerFirst(E e, long timeout, TimeUnit unit)
+ throws InterruptedException {
+ if (e == null) throw new NullPointerException();
+ Node<E> node = new Node<E>(e);
+ long nanos = unit.toNanos(timeout);
+ final ReentrantLock lock = this.lock;
+ lock.lockInterruptibly();
+ try {
+ while (!linkFirst(node)) {
+ if (nanos <= 0L)
+ return false;
+ nanos = notFull.awaitNanos(nanos);
+ }
+ return true;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ * @throws InterruptedException {@inheritDoc}
+ */
+ public boolean offerLast(E e, long timeout, TimeUnit unit)
+ throws InterruptedException {
+ if (e == null) throw new NullPointerException();
+ Node<E> node = new Node<E>(e);
+ long nanos = unit.toNanos(timeout);
+ final ReentrantLock lock = this.lock;
+ lock.lockInterruptibly();
+ try {
+ while (!linkLast(node)) {
+ if (nanos <= 0L)
+ return false;
+ nanos = notFull.awaitNanos(nanos);
+ }
+ return true;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * @throws NoSuchElementException {@inheritDoc}
+ */
+ public E removeFirst() {
+ E x = pollFirst();
+ if (x == null) throw new NoSuchElementException();
+ return x;
+ }
+
+ /**
+ * @throws NoSuchElementException {@inheritDoc}
+ */
+ public E removeLast() {
+ E x = pollLast();
+ if (x == null) throw new NoSuchElementException();
+ return x;
+ }
+
+ public E pollFirst() {
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ return unlinkFirst();
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public E pollLast() {
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ return unlinkLast();
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public E takeFirst() throws InterruptedException {
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ E x;
+ while ( (x = unlinkFirst()) == null)
+ notEmpty.await();
+ return x;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public E takeLast() throws InterruptedException {
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ E x;
+ while ( (x = unlinkLast()) == null)
+ notEmpty.await();
+ return x;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public E pollFirst(long timeout, TimeUnit unit)
+ throws InterruptedException {
+ long nanos = unit.toNanos(timeout);
+ final ReentrantLock lock = this.lock;
+ lock.lockInterruptibly();
+ try {
+ E x;
+ while ( (x = unlinkFirst()) == null) {
+ if (nanos <= 0L)
+ return null;
+ nanos = notEmpty.awaitNanos(nanos);
+ }
+ return x;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public E pollLast(long timeout, TimeUnit unit)
+ throws InterruptedException {
+ long nanos = unit.toNanos(timeout);
+ final ReentrantLock lock = this.lock;
+ lock.lockInterruptibly();
+ try {
+ E x;
+ while ( (x = unlinkLast()) == null) {
+ if (nanos <= 0L)
+ return null;
+ nanos = notEmpty.awaitNanos(nanos);
+ }
+ return x;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * @throws NoSuchElementException {@inheritDoc}
+ */
+ public E getFirst() {
+ E x = peekFirst();
+ if (x == null) throw new NoSuchElementException();
+ return x;
+ }
+
+ /**
+ * @throws NoSuchElementException {@inheritDoc}
+ */
+ public E getLast() {
+ E x = peekLast();
+ if (x == null) throw new NoSuchElementException();
+ return x;
+ }
+
+ public E peekFirst() {
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ return (first == null) ? null : first.item;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public E peekLast() {
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ return (last == null) ? null : last.item;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public boolean removeFirstOccurrence(Object o) {
+ if (o == null) return false;
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ for (Node<E> p = first; p != null; p = p.next) {
+ if (o.equals(p.item)) {
+ unlink(p);
+ return true;
+ }
+ }
+ return false;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public boolean removeLastOccurrence(Object o) {
+ if (o == null) return false;
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ for (Node<E> p = last; p != null; p = p.prev) {
+ if (o.equals(p.item)) {
+ unlink(p);
+ return true;
+ }
+ }
+ return false;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ // BlockingQueue methods
+
+ /**
+ * Inserts the specified element at the end of this deque unless it would
+ * violate capacity restrictions. When using a capacity-restricted deque,
+ * it is generally preferable to use method {@link #offer(Object) offer}.
+ *
+ * <p>This method is equivalent to {@link #addLast}.
+ *
+ * @throws IllegalStateException if this deque is full
+ * @throws NullPointerException if the specified element is null
+ */
+ public boolean add(E e) {
+ addLast(e);
+ return true;
+ }
+
+ /**
+ * @throws NullPointerException if the specified element is null
+ */
+ public boolean offer(E e) {
+ return offerLast(e);
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ * @throws InterruptedException {@inheritDoc}
+ */
+ public void put(E e) throws InterruptedException {
+ putLast(e);
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ * @throws InterruptedException {@inheritDoc}
+ */
+ public boolean offer(E e, long timeout, TimeUnit unit)
+ throws InterruptedException {
+ return offerLast(e, timeout, unit);
+ }
+
+ /**
+ * Retrieves and removes the head of the queue represented by this deque.
+ * This method differs from {@link #poll() poll()} only in that it throws an
+ * exception if this deque is empty.
+ *
+ * <p>This method is equivalent to {@link #removeFirst() removeFirst}.
+ *
+ * @return the head of the queue represented by this deque
+ * @throws NoSuchElementException if this deque is empty
+ */
+ public E remove() {
+ return removeFirst();
+ }
+
+ public E poll() {
+ return pollFirst();
+ }
+
+ public E take() throws InterruptedException {
+ return takeFirst();
+ }
+
+ public E poll(long timeout, TimeUnit unit) throws InterruptedException {
+ return pollFirst(timeout, unit);
+ }
+
+ /**
+ * Retrieves, but does not remove, the head of the queue represented by
+ * this deque. This method differs from {@link #peek() peek()} only in that
+ * it throws an exception if this deque is empty.
+ *
+ * <p>This method is equivalent to {@link #getFirst() getFirst}.
+ *
+ * @return the head of the queue represented by this deque
+ * @throws NoSuchElementException if this deque is empty
+ */
+ public E element() {
+ return getFirst();
+ }
+
+ public E peek() {
+ return peekFirst();
+ }
+
+ /**
+ * Returns the number of additional elements that this deque can ideally
+ * (in the absence of memory or resource constraints) accept without
+ * blocking. This is always equal to the initial capacity of this deque
+ * less the current {@code size} of this deque.
+ *
+ * <p>Note that you <em>cannot</em> always tell if an attempt to insert
+ * an element will succeed by inspecting {@code remainingCapacity}
+ * because it may be the case that another thread is about to
+ * insert or remove an element.
+ */
+ public int remainingCapacity() {
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ return capacity - count;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * @throws UnsupportedOperationException {@inheritDoc}
+ * @throws ClassCastException {@inheritDoc}
+ * @throws NullPointerException {@inheritDoc}
+ * @throws IllegalArgumentException {@inheritDoc}
+ */
+ public int drainTo(Collection<? super E> c) {
+ return drainTo(c, Integer.MAX_VALUE);
+ }
+
+ /**
+ * @throws UnsupportedOperationException {@inheritDoc}
+ * @throws ClassCastException {@inheritDoc}
+ * @throws NullPointerException {@inheritDoc}
+ * @throws IllegalArgumentException {@inheritDoc}
+ */
+ public int drainTo(Collection<? super E> c, int maxElements) {
+ Objects.requireNonNull(c);
+ if (c == this)
+ throw new IllegalArgumentException();
+ if (maxElements <= 0)
+ return 0;
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ int n = Math.min(maxElements, count);
+ for (int i = 0; i < n; i++) {
+ c.add(first.item); // In this order, in case add() throws.
+ unlinkFirst();
+ }
+ return n;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ // Stack methods
+
+ /**
+ * @throws IllegalStateException if this deque is full
+ * @throws NullPointerException {@inheritDoc}
+ */
+ public void push(E e) {
+ addFirst(e);
+ }
+
+ /**
+ * @throws NoSuchElementException {@inheritDoc}
+ */
+ public E pop() {
+ return removeFirst();
+ }
+
+ // Collection methods
+
+ /**
+ * Removes the first occurrence of the specified element from this deque.
+ * If the deque does not contain the element, it is unchanged.
+ * More formally, removes the first element {@code e} such that
+ * {@code o.equals(e)} (if such an element exists).
+ * Returns {@code true} if this deque contained the specified element
+ * (or equivalently, if this deque changed as a result of the call).
+ *
+ * <p>This method is equivalent to
+ * {@link #removeFirstOccurrence(Object) removeFirstOccurrence}.
+ *
+ * @param o element to be removed from this deque, if present
+ * @return {@code true} if this deque changed as a result of the call
+ */
+ public boolean remove(Object o) {
+ return removeFirstOccurrence(o);
+ }
+
+ /**
+ * Returns the number of elements in this deque.
+ *
+ * @return the number of elements in this deque
+ */
+ public int size() {
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ return count;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * Returns {@code true} if this deque contains the specified element.
+ * More formally, returns {@code true} if and only if this deque contains
+ * at least one element {@code e} such that {@code o.equals(e)}.
+ *
+ * @param o object to be checked for containment in this deque
+ * @return {@code true} if this deque contains the specified element
+ */
+ public boolean contains(Object o) {
+ if (o == null) return false;
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ for (Node<E> p = first; p != null; p = p.next)
+ if (o.equals(p.item))
+ return true;
+ return false;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * Appends all of the elements in the specified collection to the end of
+ * this deque, in the order that they are returned by the specified
+ * collection's iterator. Attempts to {@code addAll} of a deque to
+ * itself result in {@code IllegalArgumentException}.
+ *
+ * @param c the elements to be inserted into this deque
+ * @return {@code true} if this deque changed as a result of the call
+ * @throws NullPointerException if the specified collection or any
+ * of its elements are null
+ * @throws IllegalArgumentException if the collection is this deque
+ * @throws IllegalStateException if this deque is full
+ * @see #add(Object)
+ */
+ public boolean addAll(Collection<? extends E> c) {
+ if (c == this)
+ // As historically specified in AbstractQueue#addAll
+ throw new IllegalArgumentException();
+
+ // Copy c into a private chain of Nodes
+ Node<E> beg = null, end = null;
+ int n = 0;
+ for (E e : c) {
+ Objects.requireNonNull(e);
+ n++;
+ Node<E> newNode = new Node<E>(e);
+ if (beg == null)
+ beg = end = newNode;
+ else {
+ end.next = newNode;
+ newNode.prev = end;
+ end = newNode;
+ }
+ }
+ if (beg == null)
+ return false;
+
+ // Atomically append the chain at the end
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ if (count + n <= capacity) {
+ beg.prev = last;
+ if (first == null)
+ first = beg;
+ else
+ last.next = beg;
+ last = end;
+ count += n;
+ notEmpty.signalAll();
+ return true;
+ }
+ } finally {
+ lock.unlock();
+ }
+ // Fall back to historic non-atomic implementation, failing
+ // with IllegalStateException when the capacity is exceeded.
+ return super.addAll(c);
+ }
+
+ /**
+ * Returns an array containing all of the elements in this deque, in
+ * proper sequence (from first to last element).
+ *
+ * <p>The returned array will be "safe" in that no references to it are
+ * maintained by this deque. (In other words, this method must allocate
+ * a new array). The caller is thus free to modify the returned array.
+ *
+ * <p>This method acts as bridge between array-based and collection-based
+ * APIs.
+ *
+ * @return an array containing all of the elements in this deque
+ */
+ @SuppressWarnings("unchecked")
+ public Object[] toArray() {
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ Object[] a = new Object[count];
+ int k = 0;
+ for (Node<E> p = first; p != null; p = p.next)
+ a[k++] = p.item;
+ return a;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * Returns an array containing all of the elements in this deque, in
+ * proper sequence; the runtime type of the returned array is that of
+ * the specified array. If the deque fits in the specified array, it
+ * is returned therein. Otherwise, a new array is allocated with the
+ * runtime type of the specified array and the size of this deque.
+ *
+ * <p>If this deque fits in the specified array with room to spare
+ * (i.e., the array has more elements than this deque), the element in
+ * the array immediately following the end of the deque is set to
+ * {@code null}.
+ *
+ * <p>Like the {@link #toArray()} method, this method acts as bridge between
+ * array-based and collection-based APIs. Further, this method allows
+ * precise control over the runtime type of the output array, and may,
+ * under certain circumstances, be used to save allocation costs.
+ *
+ * <p>Suppose {@code x} is a deque known to contain only strings.
+ * The following code can be used to dump the deque into a newly
+ * allocated array of {@code String}:
+ *
+ * <pre> {@code String[] y = x.toArray(new String[0]);}</pre>
+ *
+ * Note that {@code toArray(new Object[0])} is identical in function to
+ * {@code toArray()}.
+ *
+ * @param a the array into which the elements of the deque are to
+ * be stored, if it is big enough; otherwise, a new array of the
+ * same runtime type is allocated for this purpose
+ * @return an array containing all of the elements in this deque
+ * @throws ArrayStoreException if the runtime type of the specified array
+ * is not a supertype of the runtime type of every element in
+ * this deque
+ * @throws NullPointerException if the specified array is null
+ */
+ @SuppressWarnings("unchecked")
+ public <T> T[] toArray(T[] a) {
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ if (a.length < count)
+ a = (T[])java.lang.reflect.Array.newInstance
+ (a.getClass().getComponentType(), count);
+
+ int k = 0;
+ for (Node<E> p = first; p != null; p = p.next)
+ a[k++] = (T)p.item;
+ if (a.length > k)
+ a[k] = null;
+ return a;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public String toString() {
+ return Helpers.collectionToString(this);
+ }
+
+ /**
+ * Atomically removes all of the elements from this deque.
+ * The deque will be empty after this call returns.
+ */
+ public void clear() {
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ for (Node<E> f = first; f != null; ) {
+ f.item = null;
+ Node<E> n = f.next;
+ f.prev = null;
+ f.next = null;
+ f = n;
+ }
+ first = last = null;
+ count = 0;
+ notFull.signalAll();
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * Used for any element traversal that is not entirely under lock.
+ * Such traversals must handle both:
+ * - dequeued nodes (p.next == p)
+ * - (possibly multiple) interior removed nodes (p.item == null)
+ */
+ Node<E> succ(Node<E> p) {
+ if (p == (p = p.next))
+ p = first;
+ return p;
+ }
+
+ /**
+ * Returns an iterator over the elements in this deque in proper sequence.
+ * The elements will be returned in order from first (head) to last (tail).
+ *
+ * <p>The returned iterator is
+ * <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.
+ *
+ * @return an iterator over the elements in this deque in proper sequence
+ */
+ public Iterator<E> iterator() {
+ return new Itr();
+ }
+
+ /**
+ * Returns an iterator over the elements in this deque in reverse
+ * sequential order. The elements will be returned in order from
+ * last (tail) to first (head).
+ *
+ * <p>The returned iterator is
+ * <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.
+ *
+ * @return an iterator over the elements in this deque in reverse order
+ */
+ public Iterator<E> descendingIterator() {
+ return new DescendingItr();
+ }
+
+ /**
+ * Base class for LinkedBlockingDeque iterators.
+ */
+ private abstract class AbstractItr implements Iterator<E> {
+ /**
+ * The next node to return in next().
+ */
+ Node<E> next;
+
+ /**
+ * nextItem holds on to item fields because once we claim that
+ * an element exists in hasNext(), we must return item read
+ * under lock even if it was in the process of being removed
+ * when hasNext() was called.
+ */
+ E nextItem;
+
+ /**
+ * Node returned by most recent call to next. Needed by remove.
+ * Reset to null if this element is deleted by a call to remove.
+ */
+ private Node<E> lastRet;
+
+ abstract Node<E> firstNode();
+ abstract Node<E> nextNode(Node<E> n);
+
+ private Node<E> succ(Node<E> p) {
+ if (p == (p = nextNode(p)))
+ p = firstNode();
+ return p;
+ }
+
+ AbstractItr() {
+ // set to initial position
+ final ReentrantLock lock = LinkedBlockingDeque.this.lock;
+ lock.lock();
+ try {
+ if ((next = firstNode()) != null)
+ nextItem = next.item;
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ public boolean hasNext() {
+ return next != null;
+ }
+
+ public E next() {
+ Node<E> p;
+ if ((p = next) == null)
+ throw new NoSuchElementException();
+ lastRet = p;
+ E x = nextItem;
+ final ReentrantLock lock = LinkedBlockingDeque.this.lock;
+ lock.lock();
+ try {
+ E e = null;
+ for (p = nextNode(p); p != null && (e = p.item) == null; )
+ p = succ(p);
+ next = p;
+ nextItem = e;
+ } finally {
+ lock.unlock();
+ }
+ return x;
+ }
+
+ public void forEachRemaining(Consumer<? super E> action) {
+ // A variant of forEachFrom
+ Objects.requireNonNull(action);
+ Node<E> p;
+ if ((p = next) == null) return;
+ lastRet = p;
+ next = null;
+ final ReentrantLock lock = LinkedBlockingDeque.this.lock;
+ final int batchSize = 64;
+ Object[] es = null;
+ int n, len = 1;
+ do {
+ lock.lock();
+ try {
+ if (es == null) {
+ p = nextNode(p);
+ for (Node<E> q = p; q != null; q = succ(q))
+ if (q.item != null && ++len == batchSize)
+ break;
+ es = new Object[len];
+ es[0] = nextItem;
+ nextItem = null;
+ n = 1;
+ } else
+ n = 0;
+ for (; p != null && n < len; p = succ(p))
+ if ((es[n] = p.item) != null) {
+ lastRet = p;
+ n++;
+ }
+ } finally {
+ lock.unlock();
+ }
+ for (int i = 0; i < n; i++) {
+ @SuppressWarnings("unchecked") E e = (E) es[i];
+ action.accept(e);
+ }
+ } while (n > 0 && p != null);
+ }
+
+ public void remove() {
+ Node<E> n = lastRet;
+ if (n == null)
+ throw new IllegalStateException();
+ lastRet = null;
+ final ReentrantLock lock = LinkedBlockingDeque.this.lock;
+ lock.lock();
+ try {
+ if (n.item != null)
+ unlink(n);
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
+
+ /** Forward iterator */
+ private class Itr extends AbstractItr {
+ Itr() {} // prevent access constructor creation
+ Node<E> firstNode() { return first; }
+ Node<E> nextNode(Node<E> n) { return n.next; }
+ }
+
+ /** Descending iterator */
+ private class DescendingItr extends AbstractItr {
+ DescendingItr() {} // prevent access constructor creation
+ Node<E> firstNode() { return last; }
+ Node<E> nextNode(Node<E> n) { return n.prev; }
+ }
+
+ /**
+ * A customized variant of Spliterators.IteratorSpliterator.
+ * Keep this class in sync with (very similar) LBQSpliterator.
+ */
+ private final class LBDSpliterator implements Spliterator<E> {
+ static final int MAX_BATCH = 1 << 25; // max batch array size;
+ Node<E> current; // current node; null until initialized
+ int batch; // batch size for splits
+ boolean exhausted; // true when no more nodes
+ long est = size(); // size estimate
+
+ LBDSpliterator() {}
+
+ public long estimateSize() { return est; }
+
+ public Spliterator<E> trySplit() {
+ Node<E> h;
+ if (!exhausted &&
+ ((h = current) != null || (h = first) != null)
+ && h.next != null) {
+ int n = batch = Math.min(batch + 1, MAX_BATCH);
+ Object[] a = new Object[n];
+ final ReentrantLock lock = LinkedBlockingDeque.this.lock;
+ int i = 0;
+ Node<E> p = current;
+ lock.lock();
+ try {
+ if (p != null || (p = first) != null)
+ for (; p != null && i < n; p = succ(p))
+ if ((a[i] = p.item) != null)
+ i++;
+ } finally {
+ lock.unlock();
+ }
+ if ((current = p) == null) {
+ est = 0L;
+ exhausted = true;
+ }
+ else if ((est -= i) < 0L)
+ est = 0L;
+ if (i > 0)
+ return Spliterators.spliterator
+ (a, 0, i, (Spliterator.ORDERED |
+ Spliterator.NONNULL |
+ Spliterator.CONCURRENT));
+ }
+ return null;
+ }
+
+ public boolean tryAdvance(Consumer<? super E> action) {
+ Objects.requireNonNull(action);
+ if (!exhausted) {
+ E e = null;
+ final ReentrantLock lock = LinkedBlockingDeque.this.lock;
+ lock.lock();
+ try {
+ Node<E> p;
+ if ((p = current) != null || (p = first) != null)
+ do {
+ e = p.item;
+ p = succ(p);
+ } while (e == null && p != null);
+ if ((current = p) == null)
+ exhausted = true;
+ } finally {
+ lock.unlock();
+ }
+ if (e != null) {
+ action.accept(e);
+ return true;
+ }
+ }
+ return false;
+ }
+
+ public void forEachRemaining(Consumer<? super E> action) {
+ Objects.requireNonNull(action);
+ if (!exhausted) {
+ exhausted = true;
+ Node<E> p = current;
+ current = null;
+ forEachFrom(action, p);
+ }
+ }
+
+ public int characteristics() {
+ return (Spliterator.ORDERED |
+ Spliterator.NONNULL |
+ Spliterator.CONCURRENT);
+ }
+ }
+
+ /**
+ * Returns a {@link Spliterator} over the elements in this deque.
+ *
+ * <p>The returned spliterator is
+ * <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.
+ *
+ * <p>The {@code Spliterator} reports {@link Spliterator#CONCURRENT},
+ * {@link Spliterator#ORDERED}, and {@link Spliterator#NONNULL}.
+ *
+ * @implNote
+ * The {@code Spliterator} implements {@code trySplit} to permit limited
+ * parallelism.
+ *
+ * @return a {@code Spliterator} over the elements in this deque
+ * @since 1.8
+ */
+ public Spliterator<E> spliterator() {
+ return new LBDSpliterator();
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ */
+ public void forEach(Consumer<? super E> action) {
+ Objects.requireNonNull(action);
+ forEachFrom(action, null);
+ }
+
+ /**
+ * Runs action on each element found during a traversal starting at p.
+ * If p is null, traversal starts at head.
+ */
+ void forEachFrom(Consumer<? super E> action, Node<E> p) {
+ // Extract batches of elements while holding the lock; then
+ // run the action on the elements while not
+ final ReentrantLock lock = this.lock;
+ final int batchSize = 64; // max number of elements per batch
+ Object[] es = null; // container for batch of elements
+ int n, len = 0;
+ do {
+ lock.lock();
+ try {
+ if (es == null) {
+ if (p == null) p = first;
+ for (Node<E> q = p; q != null; q = succ(q))
+ if (q.item != null && ++len == batchSize)
+ break;
+ es = new Object[len];
+ }
+ for (n = 0; p != null && n < len; p = succ(p))
+ if ((es[n] = p.item) != null)
+ n++;
+ } finally {
+ lock.unlock();
+ }
+ for (int i = 0; i < n; i++) {
+ @SuppressWarnings("unchecked") E e = (E) es[i];
+ action.accept(e);
+ }
+ } while (n > 0 && p != null);
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ */
+ public boolean removeIf(Predicate<? super E> filter) {
+ Objects.requireNonNull(filter);
+ return bulkRemove(filter);
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ */
+ public boolean removeAll(Collection<?> c) {
+ Objects.requireNonNull(c);
+ return bulkRemove(e -> c.contains(e));
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ */
+ public boolean retainAll(Collection<?> c) {
+ Objects.requireNonNull(c);
+ return bulkRemove(e -> !c.contains(e));
+ }
+
+ /** Implementation of bulk remove methods. */
+ @SuppressWarnings("unchecked")
+ private boolean bulkRemove(Predicate<? super E> filter) {
+ boolean removed = false;
+ Node<E> p = null;
+ final ReentrantLock lock = this.lock;
+ Node<E>[] nodes = null;
+ int n, len = 0;
+ do {
+ // 1. Extract batch of up to 64 elements while holding the lock.
+ long deathRow = 0; // "bitset" of size 64
+ lock.lock();
+ try {
+ if (nodes == null) {
+ if (p == null) p = first;
+ for (Node<E> q = p; q != null; q = succ(q))
+ if (q.item != null && ++len == 64)
+ break;
+ nodes = (Node<E>[]) new Node<?>[len];
+ }
+ for (n = 0; p != null && n < len; p = succ(p))
+ nodes[n++] = p;
+ } finally {
+ lock.unlock();
+ }
+
+ // 2. Run the filter on the elements while lock is free.
+ for (int i = 0; i < n; i++) {
+ final E e;
+ if ((e = nodes[i].item) != null && filter.test(e))
+ deathRow |= 1L << i;
+ }
+
+ // 3. Remove any filtered elements while holding the lock.
+ if (deathRow != 0) {
+ lock.lock();
+ try {
+ for (int i = 0; i < n; i++) {
+ final Node<E> q;
+ if ((deathRow & (1L << i)) != 0L
+ && (q = nodes[i]).item != null) {
+ unlink(q);
+ removed = true;
+ }
+ }
+ } finally {
+ lock.unlock();
+ }
+ }
+ } while (n > 0 && p != null);
+ return removed;
+ }
+
+ /**
+ * Saves this deque to a stream (that is, serializes it).
+ *
+ * @param s the stream
+ * @throws java.io.IOException if an I/O error occurs
+ * @serialData The capacity (int), followed by elements (each an
+ * {@code Object}) in the proper order, followed by a null
+ */
+ private void writeObject(java.io.ObjectOutputStream s)
+ throws java.io.IOException {
+ final ReentrantLock lock = this.lock;
+ lock.lock();
+ try {
+ // Write out capacity and any hidden stuff
+ s.defaultWriteObject();
+ // Write out all elements in the proper order.
+ for (Node<E> p = first; p != null; p = p.next)
+ s.writeObject(p.item);
+ // Use trailing null as sentinel
+ s.writeObject(null);
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /**
+ * Reconstitutes this deque from a stream (that is, deserializes it).
+ * @param s the stream
+ * @throws ClassNotFoundException if the class of a serialized object
+ * could not be found
+ * @throws java.io.IOException if an I/O error occurs
+ */
+ private void readObject(java.io.ObjectInputStream s)
+ throws java.io.IOException, ClassNotFoundException {
+ s.defaultReadObject();
+ count = 0;
+ first = null;
+ last = null;
+ // Read in all elements and place in queue
+ for (;;) {
+ @SuppressWarnings("unchecked") E item = (E)s.readObject();
+ if (item == null)
+ break;
+ add(item);
+ }
+ }
+
+ void checkInvariants() {
+ // assert lock.isHeldByCurrentThread();
+ // Nodes may get self-linked or lose their item, but only
+ // after being unlinked and becoming unreachable from first.
+ for (Node<E> p = first; p != null; p = p.next) {
+ // assert p.next != p;
+ // assert p.item != null;
+ }
+ }
+
+}