org.jctools.queues

Interface MessagePassingQueue<T>

Type Parameters:

T - the event/message type

All Known Implementing Classes:

MpmcArrayQueue, MpmcAtomicArrayQueue, MpmcUnboundedXaddArrayQueue, MpscArrayQueue, MpscAtomicArrayQueue, MpscBlockingConsumerArrayQueue, MpscChunkedArrayQueue, MpscChunkedAtomicArrayQueue, MpscCompoundQueue, MpscGrowableArrayQueue, MpscGrowableAtomicArrayQueue, MpscLinkedAtomicQueue, MpscLinkedQueue, MpscUnboundedArrayQueue, MpscUnboundedAtomicArrayQueue, MpscUnboundedXaddArrayQueue, SpmcArrayQueue, SpmcAtomicArrayQueue, SpscArrayQueue, SpscAtomicArrayQueue, SpscChunkedArrayQueue, SpscChunkedAtomicArrayQueue, SpscGrowableArrayQueue, SpscGrowableAtomicArrayQueue, SpscLinkedAtomicQueue, SpscLinkedQueue, SpscUnboundedArrayQueue, SpscUnboundedAtomicArrayQueue

public interface MessagePassingQueue<T>

Message passing queues are intended for concurrent method passing. A subset of Queue methods are provided with the same semantics, while further functionality which accomodates the concurrent usecase is also on offer.

Message passing queues provide happens before semantics to messages passed through, namely that writes made by the producer before offering the message are visible to the consuming thread after the message has been polled out of the queue.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	MessagePassingQueue.Consumer<T>
static interface	MessagePassingQueue.ExitCondition
static interface	MessagePassingQueue.Supplier<T>
static interface	MessagePassingQueue.WaitStrategy

Field Summary

Fields

Modifier and Type	Field and Description
static int	UNBOUNDED_CAPACITY

Method Summary

Modifier and Type	Method and Description
int	capacity()
void	clear() Removes all items from the queue.
int	drain(MessagePassingQueue.Consumer<T> c) Remove all available item from the queue and hand to consume.
int	drain(MessagePassingQueue.Consumer<T> c, int limit) Remove up to limit elements from the queue and hand to consume.
void	drain(MessagePassingQueue.Consumer<T> c, MessagePassingQueue.WaitStrategy wait, MessagePassingQueue.ExitCondition exit) Remove elements from the queue and hand to consume forever.
int	fill(MessagePassingQueue.Supplier<T> s) Stuff the queue with elements from the supplier.
int	fill(MessagePassingQueue.Supplier<T> s, int limit) Stuff the queue with up to limit elements from the supplier.
void	fill(MessagePassingQueue.Supplier<T> s, MessagePassingQueue.WaitStrategy wait, MessagePassingQueue.ExitCondition exit) Stuff the queue with elements from the supplier forever.
boolean	isEmpty() This method's accuracy is subject to concurrent modifications happening as the observation is carried out.
boolean	offer(T e) Called from a producer thread subject to the restrictions appropriate to the implementation and according to the Queue.offer(Object) interface.
T	peek() Called from the consumer thread subject to the restrictions appropriate to the implementation and according to the Queue.peek() interface.
T	poll() Called from the consumer thread subject to the restrictions appropriate to the implementation and according to the Queue.poll() interface.
boolean	relaxedOffer(T e) Called from a producer thread subject to the restrictions appropriate to the implementation.
T	relaxedPeek() Called from the consumer thread subject to the restrictions appropriate to the implementation.
T	relaxedPoll() Called from the consumer thread subject to the restrictions appropriate to the implementation.
int	size() 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.

Field Detail

UNBOUNDED_CAPACITY

static final int UNBOUNDED_CAPACITY

See Also:

Constant Field Values

Method Detail

offer

boolean offer(T e)

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

T poll()

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

T peek()

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

size

int size()

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).

Returns:

number of messages in the queue, between 0 and Integer.MAX_VALUE but less or equals to capacity (if bounded).

clear

void clear()

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.

isEmpty

boolean isEmpty()

This method's accuracy is subject to concurrent modifications happening as the observation is carried out.

Returns:

true if empty, false otherwise

capacity

int capacity()

Returns:

the capacity of this queue or UNBOUNDED_CAPACITY if not bounded

relaxedOffer

boolean relaxedOffer(T e)

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

T relaxedPoll()

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

T relaxedPeek()

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

int drain(MessagePassingQueue.Consumer<T> c,
          int limit)

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

Throws:

IllegalArgumentException - c is null

IllegalArgumentException - if limit is negative

fill

int fill(MessagePassingQueue.Supplier<T> s,
         int limit)

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

Throws:

IllegalArgumentException - s is null

IllegalArgumentException - if limit is negative

drain

int drain(MessagePassingQueue.Consumer<T> c)

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

Throws:

IllegalArgumentException - c is null

fill

int fill(MessagePassingQueue.Supplier<T> s)

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

Throws:

IllegalArgumentException - s is null

drain

void drain(MessagePassingQueue.Consumer<T> c,
           MessagePassingQueue.WaitStrategy wait,
           MessagePassingQueue.ExitCondition exit)

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.

Throws:

IllegalArgumentException - c OR wait OR exit are null

fill

void fill(MessagePassingQueue.Supplier<T> s,
          MessagePassingQueue.WaitStrategy wait,
          MessagePassingQueue.ExitCondition exit)

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.

Throws:

IllegalArgumentException - s OR wait OR exit are null