| /* |
| * 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; |
| } |
| } |
| |
| } |