| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.tomcat.dbcp.pool2.impl; |
| |
| import java.io.Serializable; |
| import java.util.AbstractQueue; |
| import java.util.Collection; |
| import java.util.Deque; |
| import java.util.Iterator; |
| import java.util.NoSuchElementException; |
| import java.util.concurrent.TimeUnit; |
| import java.util.concurrent.locks.Condition; |
| |
| /** |
| * An optionally-bounded {@linkplain java.util.concurrent.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}/../technotes/guides/collections/index.html"> |
| * Java Collections Framework</a>. |
| * |
| * @param <E> the type of elements held in this collection |
| * |
| * Note: This was copied from Apache Harmony and modified to suit the needs of |
| * Commons Pool. |
| * |
| * @since 2.0 |
| */ |
| class LinkedBlockingDeque<E> extends AbstractQueue<E> |
| implements Deque<E>, 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. |
| * |
| * @param <E> node item type |
| */ |
| private 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; |
| |
| /** |
| * Create a new list node. |
| * |
| * @param x The list item |
| * @param p Previous item |
| * @param n Next item |
| */ |
| Node(final E x, final Node<E> p, final Node<E> n) { |
| item = x; |
| prev = p; |
| next = n; |
| } |
| } |
| |
| /** |
| * Pointer to first node. |
| * Invariant: (first == null && last == null) || |
| * (first.prev == null && first.item != null) |
| */ |
| private transient Node<E> first; // @GuardedBy("lock") |
| |
| /** |
| * Pointer to last node. |
| * Invariant: (first == null && last == null) || |
| * (last.next == null && last.item != null) |
| */ |
| private transient Node<E> last; // @GuardedBy("lock") |
| |
| /** Number of items in the deque */ |
| private transient int count; // @GuardedBy("lock") |
| |
| /** Maximum number of items in the deque */ |
| private final int capacity; |
| |
| /** Main lock guarding all access */ |
| private final InterruptibleReentrantLock lock; |
| |
| /** Condition for waiting takes */ |
| private final Condition notEmpty; |
| |
| /** Condition for waiting puts */ |
| private final Condition notFull; |
| |
| /** |
| * Creates a {@code LinkedBlockingDeque} with a capacity of |
| * {@link Integer#MAX_VALUE}. |
| */ |
| public LinkedBlockingDeque() { |
| this(Integer.MAX_VALUE); |
| } |
| |
| /** |
| * Creates a {@code LinkedBlockingDeque} with a capacity of |
| * {@link Integer#MAX_VALUE} and the given fairness policy. |
| * @param fairness true means threads waiting on the deque should be served |
| * as if waiting in a FIFO request queue |
| */ |
| public LinkedBlockingDeque(final boolean fairness) { |
| this(Integer.MAX_VALUE, fairness); |
| } |
| |
| /** |
| * 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(final int capacity) { |
| this(capacity, false); |
| } |
| |
| /** |
| * Creates a {@code LinkedBlockingDeque} with the given (fixed) capacity |
| * and fairness policy. |
| * |
| * @param capacity the capacity of this deque |
| * @param fairness true means threads waiting on the deque should be served |
| * as if waiting in a FIFO request queue |
| * @throws IllegalArgumentException if {@code capacity} is less than 1 |
| */ |
| public LinkedBlockingDeque(final int capacity, final boolean fairness) { |
| if (capacity <= 0) { |
| throw new IllegalArgumentException(); |
| } |
| this.capacity = capacity; |
| lock = new InterruptibleReentrantLock(fairness); |
| notEmpty = lock.newCondition(); |
| notFull = lock.newCondition(); |
| } |
| |
| /** |
| * 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(final Collection<? extends E> c) { |
| this(Integer.MAX_VALUE); |
| lock.lock(); // Never contended, but necessary for visibility |
| try { |
| for (final E e : c) { |
| if (e == null) { |
| throw new NullPointerException(); |
| } |
| if (!linkLast(e)) { |
| throw new IllegalStateException("Deque full"); |
| } |
| } |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| |
| // Basic linking and unlinking operations, called only while holding lock |
| |
| /** |
| * Links provided element as first element, or returns false if full. |
| * |
| * @param e The element to link as the first element. |
| * |
| * @return {@code true} if successful, otherwise {@code false} |
| */ |
| private boolean linkFirst(final E e) { |
| // assert lock.isHeldByCurrentThread(); |
| if (count >= capacity) { |
| return false; |
| } |
| final Node<E> f = first; |
| final Node<E> x = new Node<>(e, null, f); |
| first = x; |
| if (last == null) { |
| last = x; |
| } else { |
| f.prev = x; |
| } |
| ++count; |
| notEmpty.signal(); |
| return true; |
| } |
| |
| /** |
| * Links provided element as last element, or returns false if full. |
| * |
| * @param e The element to link as the last element. |
| * |
| * @return {@code true} if successful, otherwise {@code false} |
| */ |
| private boolean linkLast(final E e) { |
| // assert lock.isHeldByCurrentThread(); |
| if (count >= capacity) { |
| return false; |
| } |
| final Node<E> l = last; |
| final Node<E> x = new Node<>(e, l, null); |
| last = x; |
| if (first == null) { |
| first = x; |
| } else { |
| l.next = x; |
| } |
| ++count; |
| notEmpty.signal(); |
| return true; |
| } |
| |
| /** |
| * Removes and returns the first element, or null if empty. |
| * |
| * @return The first element or {@code null} if empty |
| */ |
| private E unlinkFirst() { |
| // assert lock.isHeldByCurrentThread(); |
| final Node<E> f = first; |
| if (f == null) { |
| return null; |
| } |
| final Node<E> n = f.next; |
| final 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 the last element, or null if empty. |
| * |
| * @return The first element or {@code null} if empty |
| */ |
| private E unlinkLast() { |
| // assert lock.isHeldByCurrentThread(); |
| final Node<E> l = last; |
| if (l == null) { |
| return null; |
| } |
| final Node<E> p = l.prev; |
| final 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 the provided node. |
| * |
| * @param x The node to unlink |
| */ |
| private void unlink(final Node<E> x) { |
| // assert lock.isHeldByCurrentThread(); |
| final Node<E> p = x.prev; |
| final 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 |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public void addFirst(final E e) { |
| if (!offerFirst(e)) { |
| throw new IllegalStateException("Deque full"); |
| } |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public void addLast(final E e) { |
| if (!offerLast(e)) { |
| throw new IllegalStateException("Deque full"); |
| } |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public boolean offerFirst(final E e) { |
| if (e == null) { |
| throw new NullPointerException(); |
| } |
| lock.lock(); |
| try { |
| return linkFirst(e); |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public boolean offerLast(final E e) { |
| if (e == null) { |
| throw new NullPointerException(); |
| } |
| lock.lock(); |
| try { |
| return linkLast(e); |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * Links the provided element as the first in the queue, waiting until there |
| * is space to do so if the queue is full. |
| * |
| * @param e element to link |
| * |
| * @throws NullPointerException if e is null |
| * @throws InterruptedException if the thread is interrupted whilst waiting |
| * for space |
| */ |
| public void putFirst(final E e) throws InterruptedException { |
| if (e == null) { |
| throw new NullPointerException(); |
| } |
| lock.lock(); |
| try { |
| while (!linkFirst(e)) { |
| notFull.await(); |
| } |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * Links the provided element as the last in the queue, waiting until there |
| * is space to do so if the queue is full. |
| * |
| * @param e element to link |
| * |
| * @throws NullPointerException if e is null |
| * @throws InterruptedException if the thread is interrupted whilst waiting |
| * for space |
| */ |
| public void putLast(final E e) throws InterruptedException { |
| if (e == null) { |
| throw new NullPointerException(); |
| } |
| lock.lock(); |
| try { |
| while (!linkLast(e)) { |
| notFull.await(); |
| } |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * Links the provided element as the first in the queue, waiting up to the |
| * specified time to do so if the queue is full. |
| * |
| * @param e element to link |
| * @param timeout length of time to wait |
| * @param unit units that timeout is expressed in |
| * |
| * @return {@code true} if successful, otherwise {@code false} |
| * |
| * @throws NullPointerException if e is null |
| * @throws InterruptedException if the thread is interrupted whilst waiting |
| * for space |
| */ |
| public boolean offerFirst(final E e, final long timeout, final TimeUnit unit) |
| throws InterruptedException { |
| if (e == null) { |
| throw new NullPointerException(); |
| } |
| long nanos = unit.toNanos(timeout); |
| lock.lockInterruptibly(); |
| try { |
| while (!linkFirst(e)) { |
| if (nanos <= 0) { |
| return false; |
| } |
| nanos = notFull.awaitNanos(nanos); |
| } |
| return true; |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * Links the provided element as the last in the queue, waiting up to the |
| * specified time to do so if the queue is full. |
| * |
| * @param e element to link |
| * @param timeout length of time to wait |
| * @param unit units that timeout is expressed in |
| * |
| * @return {@code true} if successful, otherwise {@code false} |
| * |
| * @throws NullPointerException if e is null |
| * @throws InterruptedException if the thread is interrupted whist waiting |
| * for space |
| */ |
| public boolean offerLast(final E e, final long timeout, final TimeUnit unit) |
| throws InterruptedException { |
| if (e == null) { |
| throw new NullPointerException(); |
| } |
| long nanos = unit.toNanos(timeout); |
| lock.lockInterruptibly(); |
| try { |
| while (!linkLast(e)) { |
| if (nanos <= 0) { |
| return false; |
| } |
| nanos = notFull.awaitNanos(nanos); |
| } |
| return true; |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public E removeFirst() { |
| final E x = pollFirst(); |
| if (x == null) { |
| throw new NoSuchElementException(); |
| } |
| return x; |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public E removeLast() { |
| final E x = pollLast(); |
| if (x == null) { |
| throw new NoSuchElementException(); |
| } |
| return x; |
| } |
| |
| @Override |
| public E pollFirst() { |
| lock.lock(); |
| try { |
| return unlinkFirst(); |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| @Override |
| public E pollLast() { |
| lock.lock(); |
| try { |
| return unlinkLast(); |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * Unlinks the first element in the queue, waiting until there is an element |
| * to unlink if the queue is empty. |
| * |
| * @return the unlinked element |
| * @throws InterruptedException if the current thread is interrupted |
| */ |
| public E takeFirst() throws InterruptedException { |
| lock.lock(); |
| try { |
| E x; |
| while ( (x = unlinkFirst()) == null) { |
| notEmpty.await(); |
| } |
| return x; |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * Unlinks the last element in the queue, waiting until there is an element |
| * to unlink if the queue is empty. |
| * |
| * @return the unlinked element |
| * @throws InterruptedException if the current thread is interrupted |
| */ |
| public E takeLast() throws InterruptedException { |
| lock.lock(); |
| try { |
| E x; |
| while ( (x = unlinkLast()) == null) { |
| notEmpty.await(); |
| } |
| return x; |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * Unlinks the first element in the queue, waiting up to the specified time |
| * to do so if the queue is empty. |
| * |
| * @param timeout length of time to wait |
| * @param unit units that timeout is expressed in |
| * |
| * @return the unlinked element |
| * @throws InterruptedException if the current thread is interrupted |
| */ |
| public E pollFirst(final long timeout, final TimeUnit unit) |
| throws InterruptedException { |
| long nanos = unit.toNanos(timeout); |
| lock.lockInterruptibly(); |
| try { |
| E x; |
| while ( (x = unlinkFirst()) == null) { |
| if (nanos <= 0) { |
| return null; |
| } |
| nanos = notEmpty.awaitNanos(nanos); |
| } |
| return x; |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * Unlinks the last element in the queue, waiting up to the specified time |
| * to do so if the queue is empty. |
| * |
| * @param timeout length of time to wait |
| * @param unit units that timeout is expressed in |
| * |
| * @return the unlinked element |
| * @throws InterruptedException if the current thread is interrupted |
| */ |
| public E pollLast(final long timeout, final TimeUnit unit) |
| throws InterruptedException { |
| long nanos = unit.toNanos(timeout); |
| lock.lockInterruptibly(); |
| try { |
| E x; |
| while ( (x = unlinkLast()) == null) { |
| if (nanos <= 0) { |
| return null; |
| } |
| nanos = notEmpty.awaitNanos(nanos); |
| } |
| return x; |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public E getFirst() { |
| final E x = peekFirst(); |
| if (x == null) { |
| throw new NoSuchElementException(); |
| } |
| return x; |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public E getLast() { |
| final E x = peekLast(); |
| if (x == null) { |
| throw new NoSuchElementException(); |
| } |
| return x; |
| } |
| |
| @Override |
| public E peekFirst() { |
| lock.lock(); |
| try { |
| return first == null ? null : first.item; |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| @Override |
| public E peekLast() { |
| lock.lock(); |
| try { |
| return last == null ? null : last.item; |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| @Override |
| public boolean removeFirstOccurrence(final Object o) { |
| if (o == null) { |
| return false; |
| } |
| 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(); |
| } |
| } |
| |
| @Override |
| public boolean removeLastOccurrence(final Object o) { |
| if (o == null) { |
| return false; |
| } |
| 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 |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public boolean add(final E e) { |
| addLast(e); |
| return true; |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public boolean offer(final E e) { |
| return offerLast(e); |
| } |
| |
| /** |
| * Links the provided element as the last in the queue, waiting until there |
| * is space to do so if the queue is full. |
| * |
| * <p>This method is equivalent to {@link #putLast(Object)}. |
| * |
| * @param e element to link |
| * |
| * @throws NullPointerException if e is null |
| * @throws InterruptedException if the thread is interrupted whilst waiting |
| * for space |
| */ |
| public void put(final E e) throws InterruptedException { |
| putLast(e); |
| } |
| |
| /** |
| * Links the provided element as the last in the queue, waiting up to the |
| * specified time to do so if the queue is full. |
| * <p> |
| * This method is equivalent to {@link #offerLast(Object, long, TimeUnit)} |
| * |
| * @param e element to link |
| * @param timeout length of time to wait |
| * @param unit units that timeout is expressed in |
| * |
| * @return {@code true} if successful, otherwise {@code false} |
| * |
| * @throws NullPointerException if e is null |
| * @throws InterruptedException if the thread is interrupted whilst waiting |
| * for space |
| */ |
| public boolean offer(final E e, final long timeout, final 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 |
| */ |
| @Override |
| public E remove() { |
| return removeFirst(); |
| } |
| |
| @Override |
| public E poll() { |
| return pollFirst(); |
| } |
| |
| /** |
| * Unlinks the first element in the queue, waiting until there is an element |
| * to unlink if the queue is empty. |
| * |
| * <p>This method is equivalent to {@link #takeFirst()}. |
| * |
| * @return the unlinked element |
| * @throws InterruptedException if the current thread is interrupted |
| */ |
| public E take() throws InterruptedException { |
| return takeFirst(); |
| } |
| |
| /** |
| * Unlinks the first element in the queue, waiting up to the specified time |
| * to do so if the queue is empty. |
| * |
| * <p>This method is equivalent to {@link #pollFirst(long, TimeUnit)}. |
| * |
| * @param timeout length of time to wait |
| * @param unit units that timeout is expressed in |
| * |
| * @return the unlinked element |
| * @throws InterruptedException if the current thread is interrupted |
| */ |
| public E poll(final long timeout, final 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 |
| */ |
| @Override |
| public E element() { |
| return getFirst(); |
| } |
| |
| @Override |
| 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. |
| * |
| * @return The number of additional elements the queue is able to accept |
| */ |
| public int remainingCapacity() { |
| lock.lock(); |
| try { |
| return capacity - count; |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * Drains the queue to the specified collection. |
| * |
| * @param c The collection to add the elements to |
| * |
| * @return number of elements added to the collection |
| * |
| * @throws UnsupportedOperationException if the add operation is not |
| * supported by the specified collection |
| * @throws ClassCastException if the class of the elements held by this |
| * collection prevents them from being added to the specified |
| * collection |
| * @throws NullPointerException if c is null |
| * @throws IllegalArgumentException if c is this instance |
| */ |
| public int drainTo(final Collection<? super E> c) { |
| return drainTo(c, Integer.MAX_VALUE); |
| } |
| |
| /** |
| * Drains no more than the specified number of elements from the queue to the |
| * specified collection. |
| * |
| * @param c collection to add the elements to |
| * @param maxElements maximum number of elements to remove from the queue |
| * |
| * @return number of elements added to the collection |
| * @throws UnsupportedOperationException if the add operation is not |
| * supported by the specified collection |
| * @throws ClassCastException if the class of the elements held by this |
| * collection prevents them from being added to the specified |
| * collection |
| * @throws NullPointerException if c is null |
| * @throws IllegalArgumentException if c is this instance |
| */ |
| public int drainTo(final Collection<? super E> c, final int maxElements) { |
| if (c == null) { |
| throw new NullPointerException(); |
| } |
| if (c == this) { |
| throw new IllegalArgumentException(); |
| } |
| lock.lock(); |
| try { |
| final 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 |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public void push(final E e) { |
| addFirst(e); |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| 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 |
| */ |
| @Override |
| public boolean remove(final Object o) { |
| return removeFirstOccurrence(o); |
| } |
| |
| /** |
| * Returns the number of elements in this deque. |
| * |
| * @return the number of elements in this deque |
| */ |
| @Override |
| public int size() { |
| 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 |
| */ |
| @Override |
| public boolean contains(final Object o) { |
| if (o == null) { |
| return false; |
| } |
| 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(); |
| } |
| } |
| |
| /* |
| * TODO: Add support for more efficient bulk operations. |
| * |
| * We don't want to acquire the lock for every iteration, but we |
| * also want other threads a chance to interact with the |
| * collection, especially when count is close to capacity. |
| */ |
| |
| // /** |
| // * Adds all of the elements in the specified collection to this |
| // * queue. Attempts to addAll of a queue to itself result in |
| // * {@code IllegalArgumentException}. Further, the behavior of |
| // * this operation is undefined if the specified collection is |
| // * modified while the operation is in progress. |
| // * |
| // * @param c collection containing elements to be added to this queue |
| // * @return {@code true} if this queue changed as a result of the call |
| // * @throws ClassCastException |
| // * @throws NullPointerException |
| // * @throws IllegalArgumentException |
| // * @throws IllegalStateException |
| // * @see #add(Object) |
| // */ |
| // public boolean addAll(Collection<? extends E> c) { |
| // if (c == null) |
| // throw new NullPointerException(); |
| // if (c == this) |
| // throw new IllegalArgumentException(); |
| // final ReentrantLock lock = this.lock; |
| // lock.lock(); |
| // try { |
| // boolean modified = false; |
| // for (E e : c) |
| // if (linkLast(e)) |
| // modified = true; |
| // return modified; |
| // } finally { |
| // lock.unlock(); |
| // } |
| // } |
| |
| /** |
| * 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 |
| */ |
| @Override |
| public Object[] toArray() { |
| lock.lock(); |
| try { |
| final 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(); |
| } |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @SuppressWarnings("unchecked") |
| @Override |
| public <T> T[] toArray(T[] a) { |
| 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(); |
| } |
| } |
| |
| @Override |
| public String toString() { |
| lock.lock(); |
| try { |
| return super.toString(); |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * Atomically removes all of the elements from this deque. |
| * The deque will be empty after this call returns. |
| */ |
| @Override |
| public void clear() { |
| lock.lock(); |
| try { |
| for (Node<E> f = first; f != null;) { |
| f.item = null; |
| final Node<E> n = f.next; |
| f.prev = null; |
| f.next = null; |
| f = n; |
| } |
| first = last = null; |
| count = 0; |
| notFull.signalAll(); |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * 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). |
| * The returned {@code Iterator} is a "weakly consistent" iterator that |
| * will never throw {@link java.util.ConcurrentModificationException |
| * ConcurrentModificationException}, |
| * and guarantees to traverse elements as they existed upon |
| * construction of the iterator, and may (but is not guaranteed to) |
| * reflect any modifications subsequent to construction. |
| * |
| * @return an iterator over the elements in this deque in proper sequence |
| */ |
| @Override |
| public Iterator<E> iterator() { |
| return new Itr(); |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public Iterator<E> descendingIterator() { |
| return new DescendingItr(); |
| } |
| |
| /** |
| * Base class for Iterators for LinkedBlockingDeque |
| */ |
| 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 (in advance()) 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; |
| |
| /** |
| * Obtain the first node to be returned by the iterator. |
| * |
| * @return first node |
| */ |
| abstract Node<E> firstNode(); |
| |
| /** |
| * For a given node, obtain the next node to be returned by the |
| * iterator. |
| * |
| * @param n given node |
| * |
| * @return next node |
| */ |
| abstract Node<E> nextNode(Node<E> n); |
| |
| /** |
| * Create a new iterator. Sets the initial position. |
| */ |
| AbstractItr() { |
| // set to initial position |
| lock.lock(); |
| try { |
| next = firstNode(); |
| nextItem = next == null ? null : next.item; |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * Returns the successor node of the given non-null, but |
| * possibly previously deleted, node. |
| * |
| * @param n node whose successor is sought |
| * @return successor node |
| */ |
| private Node<E> succ(Node<E> n) { |
| // Chains of deleted nodes ending in null or self-links |
| // are possible if multiple interior nodes are removed. |
| for (;;) { |
| final Node<E> s = nextNode(n); |
| if (s == null) { |
| return null; |
| } else if (s.item != null) { |
| return s; |
| } else if (s == n) { |
| return firstNode(); |
| } else { |
| n = s; |
| } |
| } |
| } |
| |
| /** |
| * Advances next. |
| */ |
| void advance() { |
| lock.lock(); |
| try { |
| // assert next != null; |
| next = succ(next); |
| nextItem = next == null ? null : next.item; |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| @Override |
| public boolean hasNext() { |
| return next != null; |
| } |
| |
| @Override |
| public E next() { |
| if (next == null) { |
| throw new NoSuchElementException(); |
| } |
| lastRet = next; |
| final E x = nextItem; |
| advance(); |
| return x; |
| } |
| |
| @Override |
| public void remove() { |
| final Node<E> n = lastRet; |
| if (n == null) { |
| throw new IllegalStateException(); |
| } |
| lastRet = null; |
| lock.lock(); |
| try { |
| if (n.item != null) { |
| unlink(n); |
| } |
| } finally { |
| lock.unlock(); |
| } |
| } |
| } |
| |
| /** Forward iterator */ |
| private class Itr extends AbstractItr { |
| @Override |
| Node<E> firstNode() { return first; } |
| @Override |
| Node<E> nextNode(final Node<E> n) { return n.next; } |
| } |
| |
| /** Descending iterator */ |
| private class DescendingItr extends AbstractItr { |
| @Override |
| Node<E> firstNode() { return last; } |
| @Override |
| Node<E> nextNode(final Node<E> n) { return n.prev; } |
| } |
| |
| /** |
| * Saves the state of this deque to a stream (that is, serialize it). |
| * |
| * @serialData The capacity (int), followed by elements (each an |
| * {@code Object}) in the proper order, followed by a null |
| * @param s the stream |
| */ |
| private void writeObject(final java.io.ObjectOutputStream s) |
| throws java.io.IOException { |
| 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, |
| * deserialize it). |
| * @param s the stream |
| */ |
| private void readObject(final 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") |
| final |
| E item = (E)s.readObject(); |
| if (item == null) { |
| break; |
| } |
| add(item); |
| } |
| } |
| |
| // Monitoring methods |
| |
| /** |
| * Returns true if there are threads waiting to take instances from this deque. See disclaimer on accuracy in |
| * {@link java.util.concurrent.locks.ReentrantLock#hasWaiters(Condition)}. |
| * |
| * @return true if there is at least one thread waiting on this deque's notEmpty condition. |
| */ |
| public boolean hasTakeWaiters() { |
| lock.lock(); |
| try { |
| return lock.hasWaiters(notEmpty); |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * Returns the length of the queue of threads waiting to take instances from this deque. See disclaimer on accuracy |
| * in {@link java.util.concurrent.locks.ReentrantLock#getWaitQueueLength(Condition)}. |
| * |
| * @return number of threads waiting on this deque's notEmpty condition. |
| */ |
| public int getTakeQueueLength() { |
| lock.lock(); |
| try { |
| return lock.getWaitQueueLength(notEmpty); |
| } finally { |
| lock.unlock(); |
| } |
| } |
| |
| /** |
| * Interrupts the threads currently waiting to take an object from the pool. See disclaimer on accuracy in |
| * {@link java.util.concurrent.locks.ReentrantLock#getWaitingThreads(Condition)}. |
| */ |
| public void interuptTakeWaiters() { |
| lock.lock(); |
| try { |
| lock.interruptWaiters(notEmpty); |
| } finally { |
| lock.unlock(); |
| } |
| } |
| } |