Class SpmcArrayQueue<E>

java.lang.Object
java.util.AbstractCollection<E>
java.util.AbstractQueue<E>
org.jctools.queues.SpmcArrayQueue<E>
All Implemented Interfaces:
Iterable<E>, Collection<E>, Queue<E>, IndexedQueueSizeUtil.IndexedQueue, MessagePassingQueue<E>, QueueProgressIndicators, SupportsIterator
public class SpmcArrayQueue<E> extends AbstractQueue<E>

  • Field Details

    • C_INDEX_OFFSET

      protected static final long C_INDEX_OFFSET

    • P_INDEX_OFFSET

      protected static final long P_INDEX_OFFSET

    • mask

      protected final long mask

    • buffer

      protected final E[] buffer

  • Constructor Details

    • SpmcArrayQueue

      public SpmcArrayQueue(int capacity)

  • Method Details

    • offer

      public boolean offer(E e)
      Description copied from interface: MessagePassingQueue
      Called from a producer thread subject to the restrictions appropriate to the implementation and according to the Queue.offer(Object) interface.
      Parameters:
      e - not null, will throw NPE if it is
      Returns:
      true if element was inserted into the queue, false iff full

    • poll

      public E poll()
      Description copied from interface: MessagePassingQueue
      Called from the consumer thread subject to the restrictions appropriate to the implementation and according to the Queue.poll() interface.
      Returns:
      a message from the queue if one is available, null iff empty

    • peek

      public E peek()
      Description copied from interface: MessagePassingQueue
      Called from the consumer thread subject to the restrictions appropriate to the implementation and according to the Queue.peek() interface.
      Returns:
      a message from the queue if one is available, null iff empty

    • relaxedOffer

      public boolean relaxedOffer(E e)
      Description copied from interface: MessagePassingQueue
      Called from a producer thread subject to the restrictions appropriate to the implementation. As opposed to Queue.offer(Object) this method may return false without the queue being full.
      Parameters:
      e - not null, will throw NPE if it is
      Returns:
      true if element was inserted into the queue, false if unable to offer

    • relaxedPoll

      public E relaxedPoll()
      Description copied from interface: MessagePassingQueue
      Called from the consumer thread subject to the restrictions appropriate to the implementation. As opposed to Queue.poll() this method may return null without the queue being empty.
      Returns:
      a message from the queue if one is available, null if unable to poll

    • relaxedPeek

      public E relaxedPeek()
      Description copied from interface: MessagePassingQueue
      Called from the consumer thread subject to the restrictions appropriate to the implementation. As opposed to Queue.peek() this method may return null without the queue being empty.
      Returns:
      a message from the queue if one is available, null if unable to peek

    • drain

      public int drain(MessagePassingQueue.Consumer<E> c, int limit)
      Description copied from interface: MessagePassingQueue
      Remove up to limit elements from the queue and hand to consume. This should be semantically similar to: 

        M m;
  int i = 0;
  for(;i < limit && (m = relaxedPoll()) != null; i++){
    c.accept(m);
  }
  return i;

      There's no strong commitment to the queue being empty at the end of a drain. Called from a consumer thread subject to the restrictions appropriate to the implementation.

      WARNING: Explicit assumptions are made with regards to MessagePassingQueue.Consumer.accept(T) make sure you have read and understood these before using this method.

      Returns:
      the number of polled elements

    • fill

      public int fill(MessagePassingQueue.Supplier<E> s, int limit)
      Description copied from interface: MessagePassingQueue
      Stuff the queue with up to limit elements from the supplier. Semantically similar to: 

        for(int i=0; i < limit && relaxedOffer(s.get()); i++);

      There's no strong commitment to the queue being full at the end of a fill. Called from a producer thread subject to the restrictions appropriate to the implementation. WARNING: Explicit assumptions are made with regards to MessagePassingQueue.Supplier.get() make sure you have read and understood these before using this method.

      Returns:
      the number of offered elements

    • drain

      public int drain(MessagePassingQueue.Consumer<E> c)
      Description copied from interface: MessagePassingQueue
      Remove all available item from the queue and hand to consume. This should be semantically similar to: 
      M m;
while((m = relaxedPoll()) != null){
c.accept(m);
}
      There's no strong commitment to the queue being empty at the end of a drain. Called from a consumer thread subject to the restrictions appropriate to the implementation.

      WARNING: Explicit assumptions are made with regards to MessagePassingQueue.Consumer.accept(T) make sure you have read and understood these before using this method.

      Returns:
      the number of polled elements

    • fill

      public int fill(MessagePassingQueue.Supplier<E> s)
      Description copied from interface: MessagePassingQueue
      Stuff the queue with elements from the supplier. Semantically similar to: 
      while(relaxedOffer(s.get());
      There's no strong commitment to the queue being full at the end of a fill. Called from a producer thread subject to the restrictions appropriate to the implementation.

      Unbounded queues will fill up the queue with a fixed amount rather than fill up to oblivion. WARNING: Explicit assumptions are made with regards to MessagePassingQueue.Supplier.get() make sure you have read and understood these before using this method.

      Returns:
      the number of offered elements

    • drain

      public void drain(MessagePassingQueue.Consumer<E> c, MessagePassingQueue.WaitStrategy w, MessagePassingQueue.ExitCondition exit)
      Description copied from interface: MessagePassingQueue
      Remove elements from the queue and hand to consume forever. Semantically similar to: 

       int idleCounter = 0;
 while (exit.keepRunning()) {
     E e = relaxedPoll();
     if(e==null){
         idleCounter = wait.idle(idleCounter);
         continue;
     }
     idleCounter = 0;
     c.accept(e);
 }

      Called from a consumer thread subject to the restrictions appropriate to the implementation.

      WARNING: Explicit assumptions are made with regards to MessagePassingQueue.Consumer.accept(T) make sure you have read and understood these before using this method.

    • fill

      public void fill(MessagePassingQueue.Supplier<E> s, MessagePassingQueue.WaitStrategy w, MessagePassingQueue.ExitCondition e)
      Description copied from interface: MessagePassingQueue
      Stuff the queue with elements from the supplier forever. Semantically similar to: 

      
 int idleCounter = 0;
 while (exit.keepRunning()) {
     E e = s.get();
     while (!relaxedOffer(e)) {
         idleCounter = wait.idle(idleCounter);
         continue;
     }
     idleCounter = 0;
 }

      Called from a producer thread subject to the restrictions appropriate to the implementation. The main difference being that implementors MUST assure room in the queue is available BEFORE calling MessagePassingQueue.Supplier.get(). WARNING: Explicit assumptions are made with regards to MessagePassingQueue.Supplier.get() make sure you have read and understood these before using this method.

    • lvProducerIndexCache

      protected final long lvProducerIndexCache()

    • svProducerIndexCache

      protected final void svProducerIndexCache(long newValue)

    • lvConsumerIndex

      public final long lvConsumerIndex()

    • lvProducerIndex

      public final long lvProducerIndex()

    • size

      public int size()
      Description copied from interface: MessagePassingQueue
      This method's accuracy is subject to concurrent modifications happening as the size is estimated and as such is a best effort rather than absolute value. For some implementations this method may be O(n) rather than O(1).
      Specified by:
      size in interface Collection<E>
      Specified by:
      size in interface MessagePassingQueue<E>
      Specified by:
      size in class AbstractCollection<E>
      Returns:
      number of messages in the queue, between 0 and Integer.MAX_VALUE but less or equals to capacity (if bounded).

    • isEmpty

      public boolean isEmpty()
      Description copied from interface: MessagePassingQueue
      This method's accuracy is subject to concurrent modifications happening as the observation is carried out.
      Specified by:
      isEmpty in interface Collection<E>
      Specified by:
      isEmpty in interface MessagePassingQueue<E>
      Overrides:
      isEmpty in class AbstractCollection<E>
      Returns:
      true if empty, false otherwise

    • toString

      public String toString()
      Overrides:
      toString in class AbstractCollection<E>

    • clear

      public void clear()
      Description copied from interface: MessagePassingQueue
      Removes all items from the queue. Called from the consumer thread subject to the restrictions appropriate to the implementation and according to the Collection.clear() interface.
      Specified by:
      clear in interface Collection<E>
      Specified by:
      clear in interface MessagePassingQueue<E>
      Overrides:
      clear in class AbstractQueue<E>

    • capacity

      public int capacity()
      Specified by:
      capacity in interface IndexedQueueSizeUtil.IndexedQueue
      Specified by:
      capacity in interface MessagePassingQueue<E>
      Returns:
      the capacity of this queue or MessagePassingQueue.UNBOUNDED_CAPACITY if not bounded

    • currentProducerIndex

      public long currentProducerIndex()
      Description copied from interface: QueueProgressIndicators
      This method has no concurrent visibility semantics. The value returned may be negative. Under normal circumstances 2 consecutive calls to this method can offer an idea of progress made by producer threads by subtracting the 2 results though in extreme cases (if producers have progressed by more than 2^64) this may also fail.
      This value will normally indicate number of elements passed into the queue, but may under some circumstances be a derivative of that figure. This method should not be used to derive size or emptiness.
      Specified by:
      currentProducerIndex in interface QueueProgressIndicators
      Returns:
      the current value of the producer progress index

    • currentConsumerIndex

      public long currentConsumerIndex()
      Description copied from interface: QueueProgressIndicators
      This method has no concurrent visibility semantics. The value returned may be negative. Under normal circumstances 2 consecutive calls to this method can offer an idea of progress made by consumer threads by subtracting the 2 results though in extreme cases (if consumers have progressed by more than 2^64) this may also fail.
      This value will normally indicate number of elements taken out of the queue, but may under some circumstances be a derivative of that figure. This method should not be used to derive size or emptiness.
      Specified by:
      currentConsumerIndex in interface QueueProgressIndicators
      Returns:
      the current value of the consumer progress index

    • iterator

      public Iterator<E> iterator()
      Get an iterator for this queue. This method is thread safe.

      The iterator provides a best-effort snapshot of the elements in the queue. The returned iterator is not guaranteed to return elements in queue order, and races with the consumer thread may cause gaps in the sequence of returned elements. Like {link #relaxedPoll}, the iterator may not immediately return newly inserted elements.

      Specified by:
      iterator in interface Collection<E>
      Specified by:
      iterator in interface Iterable<E>
      Specified by:
      iterator in class AbstractCollection<E>
      Returns:
      The iterator.