@Override
public T poll() {
long ci = consumerIndex;
int offset = (int) ci & mask;
T value = get(offset);
if (value == null) {
return null;
}
CONSUMER_INDEX.lazySet(this, ci + 1);
lazySet(offset, null);
return value;
}
protected void downstreamRequest(long n) {
for (; ; ) {
long r = requested;
long u;
if (r != Long.MAX_VALUE && n == Long.MAX_VALUE) {
u = Long.MAX_VALUE;
} else if (r + n < 0) {
u = Long.MAX_VALUE;
} else {
u = r + n;
}
if (REQUESTED.compareAndSet(this, r, u)) {
break;
}
}
drain();
}
@Override
public boolean offer(T value) {
if (value == null) {
throw new NullPointerException();
}
long pi = producerIndex;
int m = mask;
int fullCheck = (int) (pi + capacitySkip) & m;
if (get(fullCheck) != null) {
return false;
}
int offset = (int) pi & m;
PRODUCER_INDEX.lazySet(this, pi + 1);
lazySet(offset, value);
return true;
}
/**
* A single-producer single-consumer bounded queue with exact capacity tracking.
*
* <p>This means that a queue of 10 will allow exactly 10 offers, however, the underlying storage is
* still power-of-2.
*
* <p>The implementation uses field updaters and thus should be platform-safe.
*/
public final class SpscExactAtomicArrayQueue<T> extends AtomicReferenceArray<T>
implements Queue<T> {
/** */
private static final long serialVersionUID = 6210984603741293445L;
final int mask;
final int capacitySkip;
volatile long producerIndex;
volatile long consumerIndex;
@SuppressWarnings("rawtypes")
static final AtomicLongFieldUpdater<SpscExactAtomicArrayQueue> PRODUCER_INDEX =
AtomicLongFieldUpdater.newUpdater(SpscExactAtomicArrayQueue.class, "producerIndex");
@SuppressWarnings("rawtypes")
static final AtomicLongFieldUpdater<SpscExactAtomicArrayQueue> CONSUMER_INDEX =
AtomicLongFieldUpdater.newUpdater(SpscExactAtomicArrayQueue.class, "consumerIndex");
public SpscExactAtomicArrayQueue(int capacity) {
super(Pow2.roundToPowerOfTwo(capacity));
int len = length();
this.mask = len - 1;
this.capacitySkip = len - capacity;
}
@Override
public boolean offer(T value) {
if (value == null) {
throw new NullPointerException();
}
long pi = producerIndex;
int m = mask;
int fullCheck = (int) (pi + capacitySkip) & m;
if (get(fullCheck) != null) {
return false;
}
int offset = (int) pi & m;
PRODUCER_INDEX.lazySet(this, pi + 1);
lazySet(offset, value);
return true;
}
@Override
public T poll() {
long ci = consumerIndex;
int offset = (int) ci & mask;
T value = get(offset);
if (value == null) {
return null;
}
CONSUMER_INDEX.lazySet(this, ci + 1);
lazySet(offset, null);
return value;
}
@Override
public T peek() {
return get((int) consumerIndex & mask);
}
@Override
public void clear() {
while (poll() != null || !isEmpty()) ;
}
@Override
public boolean isEmpty() {
return producerIndex == consumerIndex;
}
@Override
public int size() {
long ci = consumerIndex;
for (; ; ) {
long pi = producerIndex;
long ci2 = consumerIndex;
if (ci == ci2) {
return (int) (pi - ci2);
}
ci = ci2;
}
}
@Override
public boolean contains(Object o) {
throw new UnsupportedOperationException();
}
@Override
public Iterator<T> iterator() {
throw new UnsupportedOperationException();
}
@Override
public Object[] toArray() {
throw new UnsupportedOperationException();
}
@Override
public <E> E[] toArray(E[] a) {
throw new UnsupportedOperationException();
}
@Override
public boolean remove(Object o) {
throw new UnsupportedOperationException();
}
@Override
public boolean containsAll(Collection<?> c) {
throw new UnsupportedOperationException();
}
@Override
public boolean addAll(Collection<? extends T> c) {
throw new UnsupportedOperationException();
}
@Override
public boolean removeAll(Collection<?> c) {
throw new UnsupportedOperationException();
}
@Override
public boolean retainAll(Collection<?> c) {
throw new UnsupportedOperationException();
}
@Override
public boolean add(T e) {
throw new UnsupportedOperationException();
}
@Override
public T remove() {
throw new UnsupportedOperationException();
}
@Override
public T element() {
throw new UnsupportedOperationException();
}
}
/**
* A single-producer single-consumer array-backed queue which can allocate new arrays in case the
* consumer is slower than the producer.
*/
public final class SpscLinkedArrayQueue<T> implements Queue<T> {
static final int MAX_LOOK_AHEAD_STEP =
Integer.getInteger("jctools.spsc.max.lookahead.step", 4096);
protected volatile long producerIndex;
@SuppressWarnings("rawtypes")
static final AtomicLongFieldUpdater<SpscLinkedArrayQueue> PRODUCER_INDEX =
AtomicLongFieldUpdater.newUpdater(SpscLinkedArrayQueue.class, "producerIndex");
protected int producerLookAheadStep;
protected long producerLookAhead;
protected int producerMask;
protected AtomicReferenceArray<Object> producerBuffer;
protected int consumerMask;
protected AtomicReferenceArray<Object> consumerBuffer;
protected volatile long consumerIndex;
@SuppressWarnings("rawtypes")
static final AtomicLongFieldUpdater<SpscLinkedArrayQueue> CONSUMER_INDEX =
AtomicLongFieldUpdater.newUpdater(SpscLinkedArrayQueue.class, "consumerIndex");
private static final Object HAS_NEXT = new Object();
public SpscLinkedArrayQueue(final int bufferSize) {
int p2capacity = Pow2.roundToPowerOfTwo(bufferSize);
int mask = p2capacity - 1;
AtomicReferenceArray<Object> buffer = new AtomicReferenceArray<>(p2capacity + 1);
producerBuffer = buffer;
producerMask = mask;
adjustLookAheadStep(p2capacity);
consumerBuffer = buffer;
consumerMask = mask;
producerLookAhead = mask - 1; // we know it's all empty to start with
soProducerIndex(0L);
}
/**
* {@inheritDoc}
*
* <p>This implementation is correct for single producer thread use only.
*/
@Override
public final boolean offer(final T e) {
// local load of field to avoid repeated loads after volatile reads
final AtomicReferenceArray<Object> buffer = producerBuffer;
final long index = lpProducerIndex();
final int mask = producerMask;
final int offset = calcWrappedOffset(index, mask);
if (index < producerLookAhead) {
return writeToQueue(buffer, e, index, offset);
} else {
final int lookAheadStep = producerLookAheadStep;
// go around the buffer or resize if full (unless we hit max capacity)
int lookAheadElementOffset = calcWrappedOffset(index + lookAheadStep, mask);
if (null == lvElement(buffer, lookAheadElementOffset)) { // LoadLoad
producerLookAhead = index + lookAheadStep - 1; // joy, there's plenty of room
return writeToQueue(buffer, e, index, offset);
} else if (null
== lvElement(buffer, calcWrappedOffset(index + 1, mask))) { // buffer is not full
return writeToQueue(buffer, e, index, offset);
} else {
resize(buffer, index, offset, e, mask); // add a buffer and link old to new
return true;
}
}
}
private boolean writeToQueue(
final AtomicReferenceArray<Object> buffer, final T e, final long index, final int offset) {
soProducerIndex(index + 1); // this ensures atomic write of long on 32bit platforms
soElement(buffer, offset, e); // StoreStore
return true;
}
private void resize(
final AtomicReferenceArray<Object> oldBuffer,
final long currIndex,
final int offset,
final T e,
final long mask) {
final int capacity = oldBuffer.length();
final AtomicReferenceArray<Object> newBuffer = new AtomicReferenceArray<>(capacity);
producerBuffer = newBuffer;
producerLookAhead = currIndex + mask - 1;
soProducerIndex(currIndex + 1); // this ensures correctness on 32bit platforms
soElement(newBuffer, offset, e); // StoreStore
soNext(oldBuffer, newBuffer);
soElement(oldBuffer, offset, HAS_NEXT); // new buffer is visible after element is
// inserted
}
private void soNext(AtomicReferenceArray<Object> curr, AtomicReferenceArray<Object> next) {
soElement(curr, calcDirectOffset(curr.length() - 1), next);
}
@SuppressWarnings("unchecked")
private AtomicReferenceArray<Object> lvNext(AtomicReferenceArray<Object> curr) {
return (AtomicReferenceArray<Object>) lvElement(curr, calcDirectOffset(curr.length() - 1));
}
/**
* {@inheritDoc}
*
* <p>This implementation is correct for single consumer thread use only.
*/
@SuppressWarnings("unchecked")
@Override
public final T poll() {
// local load of field to avoid repeated loads after volatile reads
final AtomicReferenceArray<Object> buffer = consumerBuffer;
final long index = lpConsumerIndex();
final int mask = consumerMask;
final int offset = calcWrappedOffset(index, mask);
final Object e = lvElement(buffer, offset); // LoadLoad
boolean isNextBuffer = e == HAS_NEXT;
if (null != e && !isNextBuffer) {
soConsumerIndex(index + 1); // this ensures correctness on 32bit platforms
soElement(buffer, offset, null); // StoreStore
return (T) e;
} else if (isNextBuffer) {
return newBufferPoll(lvNext(buffer), index, mask);
}
return null;
}
@SuppressWarnings("unchecked")
private T newBufferPoll(
AtomicReferenceArray<Object> nextBuffer, final long index, final int mask) {
consumerBuffer = nextBuffer;
final int offsetInNew = calcWrappedOffset(index, mask);
final T n = (T) lvElement(nextBuffer, offsetInNew); // LoadLoad
if (null == n) {
return null;
} else {
soConsumerIndex(index + 1); // this ensures correctness on 32bit platforms
soElement(nextBuffer, offsetInNew, null); // StoreStore
return n;
}
}
/**
* {@inheritDoc}
*
* <p>This implementation is correct for single consumer thread use only.
*/
@SuppressWarnings("unchecked")
@Override
public final T peek() {
final AtomicReferenceArray<Object> buffer = consumerBuffer;
final long index = lpConsumerIndex();
final int mask = consumerMask;
final int offset = calcWrappedOffset(index, mask);
final Object e = lvElement(buffer, offset); // LoadLoad
if (e == HAS_NEXT) {
return newBufferPeek(lvNext(buffer), index, mask);
}
return (T) e;
}
@Override
public void clear() {
while (poll() != null || !isEmpty()) ;
}
@SuppressWarnings("unchecked")
private T newBufferPeek(
AtomicReferenceArray<Object> nextBuffer, final long index, final int mask) {
consumerBuffer = nextBuffer;
final int offsetInNew = calcWrappedOffset(index, mask);
return (T) lvElement(nextBuffer, offsetInNew); // LoadLoad
}
@Override
public final int size() {
/*
* It is possible for a thread to be interrupted or reschedule between the read of the producer and
* consumer indices, therefore protection is required to ensure size is within valid range. In the
* event of concurrent polls/offers to this method the size is OVER estimated as we read consumer
* index BEFORE the producer index.
*/
long after = lvConsumerIndex();
while (true) {
final long before = after;
final long currentProducerIndex = lvProducerIndex();
after = lvConsumerIndex();
if (before == after) {
return (int) (currentProducerIndex - after);
}
}
}
@Override
public boolean isEmpty() {
return lvProducerIndex() == lvConsumerIndex();
}
private void adjustLookAheadStep(int capacity) {
producerLookAheadStep = Math.min(capacity / 4, MAX_LOOK_AHEAD_STEP);
}
private long lvProducerIndex() {
return producerIndex;
}
private long lvConsumerIndex() {
return consumerIndex;
}
private long lpProducerIndex() {
return producerIndex;
}
private long lpConsumerIndex() {
return consumerIndex;
}
private void soProducerIndex(long v) {
PRODUCER_INDEX.lazySet(this, v);
}
private void soConsumerIndex(long v) {
CONSUMER_INDEX.lazySet(this, v);
}
private static final int calcWrappedOffset(long index, int mask) {
return calcDirectOffset((int) index & mask);
}
private static final int calcDirectOffset(int index) {
return index;
}
private static final void soElement(AtomicReferenceArray<Object> buffer, int offset, Object e) {
buffer.lazySet(offset, e);
}
private static final <E> Object lvElement(AtomicReferenceArray<Object> buffer, int offset) {
return buffer.get(offset);
}
@Override
public final Iterator<T> iterator() {
throw new UnsupportedOperationException();
}
@Override
public boolean contains(Object o) {
throw new UnsupportedOperationException();
}
@Override
public Object[] toArray() {
throw new UnsupportedOperationException();
}
@Override
public <E> E[] toArray(E[] a) {
throw new UnsupportedOperationException();
}
@Override
public boolean remove(Object o) {
throw new UnsupportedOperationException();
}
@Override
public boolean containsAll(Collection<?> c) {
throw new UnsupportedOperationException();
}
@Override
public boolean addAll(Collection<? extends T> c) {
throw new UnsupportedOperationException();
}
@Override
public boolean removeAll(Collection<?> c) {
throw new UnsupportedOperationException();
}
@Override
public boolean retainAll(Collection<?> c) {
throw new UnsupportedOperationException();
}
@Override
public boolean add(T e) {
throw new UnsupportedOperationException();
}
@Override
public T remove() {
throw new UnsupportedOperationException();
}
@Override
public T element() {
throw new UnsupportedOperationException();
}
/**
* Offer two elements at the same time.
*
* <p>Don't use the regular offer() with this at all!
*
* @param first
* @param second
* @return
*/
public boolean offer(T first, T second) {
final AtomicReferenceArray<Object> buffer = producerBuffer;
final long p = producerIndex;
final int m = producerMask;
int pi = calcWrappedOffset(p + 2, m);
if (null == lvElement(buffer, pi)) {
pi = calcWrappedOffset(p, m);
soElement(buffer, pi + 1, second);
soProducerIndex(p + 2);
soElement(buffer, pi, first);
} else {
final int capacity = buffer.length();
final AtomicReferenceArray<Object> newBuffer = new AtomicReferenceArray<>(capacity);
producerBuffer = newBuffer;
pi = calcWrappedOffset(p, m);
soElement(newBuffer, pi + 1, second); // StoreStore
soElement(newBuffer, pi, first);
soNext(buffer, newBuffer);
soProducerIndex(p + 2); // this ensures correctness on 32bit platforms
soElement(buffer, pi, HAS_NEXT); // new buffer is visible after element is
}
return true;
}
}
private void soConsumerIndex(long v) {
CONSUMER_INDEX.lazySet(this, v);
}
private void soProducerIndex(long v) {
PRODUCER_INDEX.lazySet(this, v);
}
static final class SourceSubscriber<T> extends Subscriber<Observable<? extends T>> {
final NotificationLite<T> nl = NotificationLite.instance();
final int maxConcurrency;
final Subscriber<T> s;
final CompositeSubscription csub;
final Object guard;
volatile int wip;
@SuppressWarnings("rawtypes")
static final AtomicIntegerFieldUpdater<SourceSubscriber> WIP =
AtomicIntegerFieldUpdater.newUpdater(SourceSubscriber.class, "wip");
volatile int sourceIndex;
@SuppressWarnings("rawtypes")
static final AtomicIntegerFieldUpdater<SourceSubscriber> SOURCE_INDEX =
AtomicIntegerFieldUpdater.newUpdater(SourceSubscriber.class, "sourceIndex");
/** Guarded by guard. */
int active;
/** Guarded by guard. */
final Queue<Observable<? extends T>> queue;
/** Indicates the emitting phase. Guarded by this. */
boolean emitting;
/** Counts the missed emitting calls. Guarded by this. */
int missedEmitting;
/** The last buffer index in the round-robin drain scheme. Accessed while emitting == true. */
int lastIndex;
/** Guarded by itself. */
final List<MergeItemSubscriber> subscribers;
volatile long requested;
@SuppressWarnings("rawtypes")
static final AtomicLongFieldUpdater<SourceSubscriber> REQUESTED =
AtomicLongFieldUpdater.newUpdater(SourceSubscriber.class, "requested");
public SourceSubscriber(int maxConcurrency, Subscriber<T> s, CompositeSubscription csub) {
super(s);
this.maxConcurrency = maxConcurrency;
this.s = s;
this.csub = csub;
this.guard = new Object();
this.queue = new ArrayDeque<Observable<? extends T>>(maxConcurrency);
this.subscribers = Collections.synchronizedList(new ArrayList<MergeItemSubscriber>());
this.wip = 1;
}
@Override
public void onStart() {
request(maxConcurrency);
}
@Override
public void onNext(Observable<? extends T> t) {
synchronized (guard) {
queue.add(t);
}
subscribeNext();
}
void subscribeNext() {
Observable<? extends T> t;
synchronized (guard) {
t = queue.peek();
if (t == null || active >= maxConcurrency) {
return;
}
active++;
queue.poll();
}
MergeItemSubscriber itemSub = new MergeItemSubscriber(SOURCE_INDEX.getAndIncrement(this));
subscribers.add(itemSub);
csub.add(itemSub);
WIP.incrementAndGet(this);
t.unsafeSubscribe(itemSub);
request(1);
}
@Override
public void onError(Throwable e) {
Object[] active;
synchronized (subscribers) {
active = subscribers.toArray();
subscribers.clear();
}
try {
s.onError(e);
unsubscribe();
} finally {
for (Object o : active) {
@SuppressWarnings("unchecked")
MergeItemSubscriber a = (MergeItemSubscriber) o;
a.release();
}
}
}
@Override
public void onCompleted() {
WIP.decrementAndGet(this);
drain();
}
protected void downstreamRequest(long n) {
for (; ; ) {
long r = requested;
long u;
if (r != Long.MAX_VALUE && n == Long.MAX_VALUE) {
u = Long.MAX_VALUE;
} else if (r + n < 0) {
u = Long.MAX_VALUE;
} else {
u = r + n;
}
if (REQUESTED.compareAndSet(this, r, u)) {
break;
}
}
drain();
}
protected void drain() {
synchronized (this) {
if (emitting) {
missedEmitting++;
return;
}
emitting = true;
missedEmitting = 0;
}
final List<SourceSubscriber<T>.MergeItemSubscriber> subs = subscribers;
final Subscriber<T> child = s;
Object[] active = new Object[subs.size()];
do {
long r;
outer:
while ((r = requested) > 0) {
int idx = lastIndex;
synchronized (subs) {
if (subs.size() == active.length) {
active = subs.toArray(active);
} else {
active = subs.toArray();
}
}
int resumeIndex = 0;
int j = 0;
for (Object o : active) {
@SuppressWarnings("unchecked")
MergeItemSubscriber e = (MergeItemSubscriber) o;
if (e.index == idx) {
resumeIndex = j;
break;
}
j++;
}
int sumConsumed = 0;
for (int i = 0; i < active.length; i++) {
j = (i + resumeIndex) % active.length;
@SuppressWarnings("unchecked")
final MergeItemSubscriber e = (MergeItemSubscriber) active[j];
final RxRingBuffer b = e.buffer;
lastIndex = e.index;
if (!e.once && b.peek() == null) {
subs.remove(e);
synchronized (guard) {
this.active--;
}
csub.remove(e);
e.release();
subscribeNext();
WIP.decrementAndGet(this);
continue outer;
}
int consumed = 0;
Object v;
while (r > 0 && (v = b.poll()) != null) {
nl.accept(child, v);
if (child.isUnsubscribed()) {
return;
}
r--;
consumed++;
}
if (consumed > 0) {
sumConsumed += consumed;
REQUESTED.addAndGet(this, -consumed);
e.requestMore(consumed);
}
if (r == 0) {
break outer;
}
}
if (sumConsumed == 0) {
break;
}
}
if (active.length == 0) {
if (wip == 0) {
child.onCompleted();
return;
}
}
synchronized (this) {
if (missedEmitting == 0) {
emitting = false;
break;
}
missedEmitting = 0;
}
} while (true);
}
final class MergeItemSubscriber extends Subscriber<T> {
volatile boolean once = true;
final int index;
final RxRingBuffer buffer;
public MergeItemSubscriber(int index) {
buffer = RxRingBuffer.getSpmcInstance();
this.index = index;
}
@Override
public void onStart() {
request(RxRingBuffer.SIZE);
}
@Override
public void onNext(T t) {
try {
buffer.onNext(t);
} catch (MissingBackpressureException ex) {
onError(ex);
return;
}
drain();
}
@Override
public void onError(Throwable e) {
SourceSubscriber.this.onError(e);
}
@Override
public void onCompleted() {
if (once) {
once = false;
drain();
}
}
/** Request more from upstream. */
void requestMore(long n) {
request(n);
}
void release() {
// NO-OP for now
buffer.release();
}
}
}
protected void drain() {
synchronized (this) {
if (emitting) {
missedEmitting++;
return;
}
emitting = true;
missedEmitting = 0;
}
final List<SourceSubscriber<T>.MergeItemSubscriber> subs = subscribers;
final Subscriber<T> child = s;
Object[] active = new Object[subs.size()];
do {
long r;
outer:
while ((r = requested) > 0) {
int idx = lastIndex;
synchronized (subs) {
if (subs.size() == active.length) {
active = subs.toArray(active);
} else {
active = subs.toArray();
}
}
int resumeIndex = 0;
int j = 0;
for (Object o : active) {
@SuppressWarnings("unchecked")
MergeItemSubscriber e = (MergeItemSubscriber) o;
if (e.index == idx) {
resumeIndex = j;
break;
}
j++;
}
int sumConsumed = 0;
for (int i = 0; i < active.length; i++) {
j = (i + resumeIndex) % active.length;
@SuppressWarnings("unchecked")
final MergeItemSubscriber e = (MergeItemSubscriber) active[j];
final RxRingBuffer b = e.buffer;
lastIndex = e.index;
if (!e.once && b.peek() == null) {
subs.remove(e);
synchronized (guard) {
this.active--;
}
csub.remove(e);
e.release();
subscribeNext();
WIP.decrementAndGet(this);
continue outer;
}
int consumed = 0;
Object v;
while (r > 0 && (v = b.poll()) != null) {
nl.accept(child, v);
if (child.isUnsubscribed()) {
return;
}
r--;
consumed++;
}
if (consumed > 0) {
sumConsumed += consumed;
REQUESTED.addAndGet(this, -consumed);
e.requestMore(consumed);
}
if (r == 0) {
break outer;
}
}
if (sumConsumed == 0) {
break;
}
}
if (active.length == 0) {
if (wip == 0) {
child.onCompleted();
return;
}
}
synchronized (this) {
if (missedEmitting == 0) {
emitting = false;
break;
}
missedEmitting = 0;
}
} while (true);
}
