Unpadded Atomic generated queues

jctools-core/src/main/java/org/jctools/queues/unpadded/atomic/BaseLinkedUnpaddedAtomicQueue.java

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+/*
+ * Licensed 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.jctools.queues.unpadded.atomic;
+
+import java.util.AbstractQueue;
+import java.util.Iterator;
+import java.util.Queue;
+import java.util.concurrent.atomic.*;
+import org.jctools.queues.*;
+import static org.jctools.queues.unpadded.atomic.AtomicQueueUtil.*;
+
+/**
+ * NOTE: This class was automatically generated by org.jctools.queues.atomic.JavaParsingAtomicLinkedQueueGenerator
+ * which can found in the jctools-build module. The original source file is BaseLinkedQueue.java.
+ */
+abstract class BaseLinkedUnpaddedAtomicQueuePad0<E> extends AbstractQueue<E> implements MessagePassingQueue<E> {
+}
+
+/**
+ * NOTE: This class was automatically generated by org.jctools.queues.atomic.JavaParsingAtomicLinkedQueueGenerator
+ * which can found in the jctools-build module. The original source file is BaseLinkedQueue.java.
+ */
+abstract class BaseLinkedUnpaddedAtomicQueueProducerNodeRef<E> extends BaseLinkedUnpaddedAtomicQueuePad0<E> {
+
+    private static final AtomicReferenceFieldUpdater<BaseLinkedUnpaddedAtomicQueueProducerNodeRef, LinkedQueueAtomicNode> P_NODE_UPDATER = AtomicReferenceFieldUpdater.newUpdater(BaseLinkedUnpaddedAtomicQueueProducerNodeRef.class, LinkedQueueAtomicNode.class, "producerNode");
+
+    private volatile LinkedQueueAtomicNode<E> producerNode;
+
+    final void spProducerNode(LinkedQueueAtomicNode<E> newValue) {
+        P_NODE_UPDATER.lazySet(this, newValue);
+    }
+
+    final void soProducerNode(LinkedQueueAtomicNode<E> newValue) {
+        P_NODE_UPDATER.lazySet(this, newValue);
+    }
+
+    final LinkedQueueAtomicNode<E> lvProducerNode() {
+        return producerNode;
+    }
+
+    final boolean casProducerNode(LinkedQueueAtomicNode<E> expect, LinkedQueueAtomicNode<E> newValue) {
+        return P_NODE_UPDATER.compareAndSet(this, expect, newValue);
+    }
+
+    final LinkedQueueAtomicNode<E> lpProducerNode() {
+        return producerNode;
+    }
+
+    protected final LinkedQueueAtomicNode<E> xchgProducerNode(LinkedQueueAtomicNode<E> newValue) {
+        return P_NODE_UPDATER.getAndSet(this, newValue);
+    }
+}
+
+/**
+ * NOTE: This class was automatically generated by org.jctools.queues.atomic.JavaParsingAtomicLinkedQueueGenerator
+ * which can found in the jctools-build module. The original source file is BaseLinkedQueue.java.
+ */
+abstract class BaseLinkedUnpaddedAtomicQueuePad1<E> extends BaseLinkedUnpaddedAtomicQueueProducerNodeRef<E> {
+}
+
+/**
+ * NOTE: This class was automatically generated by org.jctools.queues.atomic.JavaParsingAtomicLinkedQueueGenerator
+ * which can found in the jctools-build module. The original source file is BaseLinkedQueue.java.
+ */
+abstract class BaseLinkedUnpaddedAtomicQueueConsumerNodeRef<E> extends BaseLinkedUnpaddedAtomicQueuePad1<E> {
+
+    private static final AtomicReferenceFieldUpdater<BaseLinkedUnpaddedAtomicQueueConsumerNodeRef, LinkedQueueAtomicNode> C_NODE_UPDATER = AtomicReferenceFieldUpdater.newUpdater(BaseLinkedUnpaddedAtomicQueueConsumerNodeRef.class, LinkedQueueAtomicNode.class, "consumerNode");
+
+    private volatile LinkedQueueAtomicNode<E> consumerNode;
+
+    final void spConsumerNode(LinkedQueueAtomicNode<E> newValue) {
+        C_NODE_UPDATER.lazySet(this, newValue);
+    }
+
+    @SuppressWarnings("unchecked")
+    final LinkedQueueAtomicNode<E> lvConsumerNode() {
+        return consumerNode;
+    }
+
+    final LinkedQueueAtomicNode<E> lpConsumerNode() {
+        return consumerNode;
+    }
+}
+
+/**
+ * NOTE: This class was automatically generated by org.jctools.queues.atomic.JavaParsingAtomicLinkedQueueGenerator
+ * which can found in the jctools-build module. The original source file is BaseLinkedQueue.java.
+ */
+abstract class BaseLinkedUnpaddedAtomicQueuePad2<E> extends BaseLinkedUnpaddedAtomicQueueConsumerNodeRef<E> {
+}
+
+/**
+ * NOTE: This class was automatically generated by org.jctools.queues.atomic.JavaParsingAtomicLinkedQueueGenerator
+ * which can found in the jctools-build module. The original source file is BaseLinkedQueue.java.
+ *
+ * A base data structure for concurrent linked queues. For convenience also pulled in common single consumer
+ * methods since at this time there's no plan to implement MC.
+ */
+abstract class BaseLinkedUnpaddedAtomicQueue<E> extends BaseLinkedUnpaddedAtomicQueuePad2<E> {
+
+    @Override
+    public final Iterator<E> iterator() {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public String toString() {
+        return this.getClass().getName();
+    }
+
+    protected final LinkedQueueAtomicNode<E> newNode() {
+        return new LinkedQueueAtomicNode<E>();
+    }
+
+    protected final LinkedQueueAtomicNode<E> newNode(E e) {
+        return new LinkedQueueAtomicNode<E>(e);
+    }
+
+    /**
+     * {@inheritDoc} <br>
+     * <p>
+     * IMPLEMENTATION NOTES:<br>
+     * This is an O(n) operation as we run through all the nodes and count them.<br>
+     * The accuracy of the value returned by this method is subject to races with producer/consumer threads. In
+     * particular when racing with the consumer thread this method may under estimate the size.<br>
+     *
+     * @see java.util.Queue#size()
+     */
+    @Override
+    public final int size() {
+        // Read consumer first, this is important because if the producer is node is 'older' than the consumer
+        // the consumer may overtake it (consume past it) invalidating the 'snapshot' notion of size.
+        LinkedQueueAtomicNode<E> chaserNode = lvConsumerNode();
+        LinkedQueueAtomicNode<E> producerNode = lvProducerNode();
+        int size = 0;
+        // must chase the nodes all the way to the producer node, but there's no need to count beyond expected head.
+        while (// don't go passed producer node
+        chaserNode != producerNode && // stop at last node
+        chaserNode != null && // stop at max int
+        size < Integer.MAX_VALUE) {
+            LinkedQueueAtomicNode<E> next;
+            next = chaserNode.lvNext();
+            // check if this node has been consumed, if so return what we have
+            if (next == chaserNode) {
+                return size;
+            }
+            chaserNode = next;
+            size++;
+        }
+        return size;
+    }
+
+    /**
+     * {@inheritDoc} <br>
+     * <p>
+     * IMPLEMENTATION NOTES:<br>
+     * Queue is empty when producerNode is the same as consumerNode. An alternative implementation would be to
+     * observe the producerNode.value is null, which also means an empty queue because only the
+     * consumerNode.value is allowed to be null.
+     *
+     * @see MessagePassingQueue#isEmpty()
+     */
+    @Override
+    public boolean isEmpty() {
+        LinkedQueueAtomicNode<E> consumerNode = lvConsumerNode();
+        LinkedQueueAtomicNode<E> producerNode = lvProducerNode();
+        return consumerNode == producerNode;
+    }
+
+    protected E getSingleConsumerNodeValue(LinkedQueueAtomicNode<E> currConsumerNode, LinkedQueueAtomicNode<E> nextNode) {
+        // we have to null out the value because we are going to hang on to the node
+        final E nextValue = nextNode.getAndNullValue();
+        // Fix up the next ref of currConsumerNode to prevent promoted nodes from keeping new ones alive.
+        // We use a reference to self instead of null because null is already a meaningful value (the next of
+        // producer node is null).
+        currConsumerNode.soNext(currConsumerNode);
+        spConsumerNode(nextNode);
+        // currConsumerNode is now no longer referenced and can be collected
+        return nextValue;
+    }
+
+    /**
+     * {@inheritDoc} <br>
+     * <p>
+     * IMPLEMENTATION NOTES:<br>
+     * Poll is allowed from a SINGLE thread.<br>
+     * Poll is potentially blocking here as the {@link Queue#poll()} does not allow returning {@code null} if the queue is not
+     * empty. This is very different from the original Vyukov guarantees. See {@link #relaxedPoll()} for the original
+     * semantics.<br>
+     * Poll reads {@code consumerNode.next} and:
+     * <ol>
+     * <li>If it is {@code null} AND the queue is empty return {@code null}, <b>if queue is not empty spin wait for
+     * value to become visible</b>.
+     * <li>If it is not {@code null} set it as the consumer node and return it's now evacuated value.
+     * </ol>
+     * This means the consumerNode.value is always {@code null}, which is also the starting point for the queue.
+     * Because {@code null} values are not allowed to be offered this is the only node with it's value set to
+     * {@code null} at any one time.
+     *
+     * @see MessagePassingQueue#poll()
+     * @see java.util.Queue#poll()
+     */
+    @Override
+    public E poll() {
+        final LinkedQueueAtomicNode<E> currConsumerNode = lpConsumerNode();
+        LinkedQueueAtomicNode<E> nextNode = currConsumerNode.lvNext();
+        if (nextNode != null) {
+            return getSingleConsumerNodeValue(currConsumerNode, nextNode);
+        } else if (currConsumerNode != lvProducerNode()) {
+            nextNode = spinWaitForNextNode(currConsumerNode);
+            // got the next node...
+            return getSingleConsumerNodeValue(currConsumerNode, nextNode);
+        }
+        return null;
+    }
+
+    /**
+     * {@inheritDoc} <br>
+     * <p>
+     * IMPLEMENTATION NOTES:<br>
+     * Peek is allowed from a SINGLE thread.<br>
+     * Peek is potentially blocking here as the {@link Queue#peek()} does not allow returning {@code null} if the queue is not
+     * empty. This is very different from the original Vyukov guarantees. See {@link #relaxedPeek()} for the original
+     * semantics.<br>
+     * Poll reads the next node from the consumerNode and:
+     * <ol>
+     * <li>If it is {@code null} AND the queue is empty return {@code null}, <b>if queue is not empty spin wait for
+     * value to become visible</b>.
+     * <li>If it is not {@code null} return it's value.
+     * </ol>
+     *
+     * @see MessagePassingQueue#peek()
+     * @see java.util.Queue#peek()
+     */
+    @Override
+    public E peek() {
+        final LinkedQueueAtomicNode<E> currConsumerNode = lpConsumerNode();
+        LinkedQueueAtomicNode<E> nextNode = currConsumerNode.lvNext();
+        if (nextNode != null) {
+            return nextNode.lpValue();
+        } else if (currConsumerNode != lvProducerNode()) {
+            nextNode = spinWaitForNextNode(currConsumerNode);
+            // got the next node...
+            return nextNode.lpValue();
+        }
+        return null;
+    }
+
+    LinkedQueueAtomicNode<E> spinWaitForNextNode(LinkedQueueAtomicNode<E> currNode) {
+        LinkedQueueAtomicNode<E> nextNode;
+        while ((nextNode = currNode.lvNext()) == null) {
+            // spin, we are no longer wait free
+        }
+        return nextNode;
+    }
+
+    @Override
+    public E relaxedPoll() {
+        final LinkedQueueAtomicNode<E> currConsumerNode = lpConsumerNode();
+        final LinkedQueueAtomicNode<E> nextNode = currConsumerNode.lvNext();
+        if (nextNode != null) {
+            return getSingleConsumerNodeValue(currConsumerNode, nextNode);
+        }
+        return null;
+    }
+
+    @Override
+    public E relaxedPeek() {
+        final LinkedQueueAtomicNode<E> nextNode = lpConsumerNode().lvNext();
+        if (nextNode != null) {
+            return nextNode.lpValue();
+        }
+        return null;
+    }
+
+    @Override
+    public boolean relaxedOffer(E e) {
+        return offer(e);
+    }
+
+    @Override
+    public int drain(Consumer<E> c, int limit) {
+        if (null == c)
+            throw new IllegalArgumentException("c is null");
+        if (limit < 0)
+            throw new IllegalArgumentException("limit is negative: " + limit);
+        if (limit == 0)
+            return 0;
+        LinkedQueueAtomicNode<E> chaserNode = this.lpConsumerNode();
+        for (int i = 0; i < limit; i++) {
+            final LinkedQueueAtomicNode<E> nextNode = chaserNode.lvNext();
+            if (nextNode == null) {
+                return i;
+            }
+            // we have to null out the value because we are going to hang on to the node
+            final E nextValue = getSingleConsumerNodeValue(chaserNode, nextNode);
+            chaserNode = nextNode;
+            c.accept(nextValue);
+        }
+        return limit;
+    }
+
+    @Override
+    public int drain(Consumer<E> c) {
+        return MessagePassingQueueUtil.drain(this, c);
+    }
+
+    @Override
+    public void drain(Consumer<E> c, WaitStrategy wait, ExitCondition exit) {
+        MessagePassingQueueUtil.drain(this, c, wait, exit);
+    }
+
+    @Override
+    public int capacity() {
+        return UNBOUNDED_CAPACITY;
+    }
+}