package rsc.parallel;
import java.util.Queue;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.atomic.AtomicLongArray;
import java.util.function.Supplier;
import org.reactivestreams.Publisher;
import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;
import rsc.documentation.FusionMode;
import rsc.documentation.FusionSupport;
import rsc.flow.Fuseable;
import rsc.util.BackpressureHelper;
import rsc.util.ExceptionHelper;
import rsc.subscriber.SubscriptionHelper;
/**
* Dispatches the values from upstream in a round robin fashion to subscribers which are
* ready to consume elements. A value from upstream is sent to only one of the subscribers.
*
* @param <T> the value type
*/
@FusionSupport(input = { FusionMode.SYNC, FusionMode.ASYNC })
public final class ParallelOrderedSource<T> extends ParallelOrderedBase<T> {
final Publisher<? extends T> source;
final int parallelism;
final int prefetch;
final Supplier<Queue<T>> queueSupplier;
public ParallelOrderedSource(Publisher<? extends T> source, int parallelism, int prefetch, Supplier<Queue<T>> queueSupplier) {
this.source = source;
this.parallelism = parallelism;
this.prefetch = prefetch;
this.queueSupplier = queueSupplier;
}
@Override
public int parallelism() {
return parallelism;
}
@Override
public void subscribeOrdered(Subscriber<? super OrderedItem<T>>[] subscribers) {
if (!validate(subscribers)) {
return;
}
source.subscribe(new ParallelDispatcher<>(subscribers, prefetch, queueSupplier));
}
static final class ParallelDispatcher<T> implements Subscriber<T> {
final Subscriber<? super OrderedItem<T>>[] subscribers;
final AtomicLongArray requests;
final long[] emissions;
final int prefetch;
final int limit;
final Supplier<Queue<T>> queueSupplier;
Subscription s;
Queue<T> queue;
Throwable error;
volatile boolean done;
int index;
volatile boolean cancelled;
volatile int wip;
@SuppressWarnings("rawtypes")
static final AtomicIntegerFieldUpdater<ParallelDispatcher> WIP =
AtomicIntegerFieldUpdater.newUpdater(ParallelDispatcher.class, "wip");
/**
* Counts how many subscribers were setup to delay triggering the
* drain of upstream until all of them have been setup.
*/
volatile int subscriberCount;
@SuppressWarnings("rawtypes")
static final AtomicIntegerFieldUpdater<ParallelDispatcher> SUBSCRIBER_COUNT =
AtomicIntegerFieldUpdater.newUpdater(ParallelDispatcher.class, "subscriberCount");
int produced;
int sourceMode;
long primaryIndex;
public ParallelDispatcher(Subscriber<? super OrderedItem<T>>[] subscribers, int prefetch, Supplier<Queue<T>> queueSupplier) {
this.subscribers = subscribers;
this.prefetch = prefetch;
this.queueSupplier = queueSupplier;
this.limit = prefetch - (prefetch >> 2);
this.requests = new AtomicLongArray(subscribers.length);
this.emissions = new long[subscribers.length];
}
@Override
public void onSubscribe(Subscription s) {
if (SubscriptionHelper.validate(this.s, s)) {
this.s = s;
if (s instanceof Fuseable.QueueSubscription) {
@SuppressWarnings("unchecked")
Fuseable.QueueSubscription<T> qs = (Fuseable.QueueSubscription<T>) s;
int m = qs.requestFusion(Fuseable.ANY);
if (m == Fuseable.SYNC) {
sourceMode = m;
queue = qs;
done = true;
setupSubscribers();
drain();
return;
} else
if (m == Fuseable.ASYNC) {
sourceMode = m;
queue = qs;
setupSubscribers();
s.request(prefetch);
return;
}
}
queue = queueSupplier.get();
setupSubscribers();
s.request(prefetch);
}
}
void setupSubscribers() {
int m = subscribers.length;
for (int i = 0; i < m; i++) {
if (cancelled) {
return;
}
int j = i;
SUBSCRIBER_COUNT.lazySet(this, i + 1);
subscribers[i].onSubscribe(new Subscription() {
@Override
public void request(long n) {
if (SubscriptionHelper.validate(n)) {
AtomicLongArray ra = requests;
for (;;) {
long r = ra.get(j);
if (r == Long.MAX_VALUE) {
return;
}
long u = BackpressureHelper.addCap(r, n);
if (ra.compareAndSet(j, r, u)) {
break;
}
}
if (subscriberCount == m) {
drain();
}
}
}
@Override
public void cancel() {
ParallelDispatcher.this.cancel();
}
});
}
}
@Override
public void onNext(T t) {
if (sourceMode == Fuseable.NONE) {
if (!queue.offer(t)) {
cancel();
onError(new IllegalStateException("Queue is full?"));
return;
}
}
drain();
}
@Override
public void onError(Throwable t) {
error = t;
done = true;
drain();
}
@Override
public void onComplete() {
done = true;
drain();
}
void cancel() {
if (!cancelled) {
cancelled = true;
this.s.cancel();
if (WIP.getAndIncrement(this) == 0) {
queue.clear();
}
}
}
void drainAsync() {
int missed = 1;
Queue<T> q = queue;
Subscriber<? super OrderedItem<T>>[] a = this.subscribers;
AtomicLongArray r = this.requests;
long[] e = this.emissions;
int n = e.length;
int idx = index;
int consumed = produced;
long pi = primaryIndex;
for (;;) {
int notReady = 0;
for (;;) {
if (cancelled) {
q.clear();
return;
}
boolean d = done;
if (d) {
Throwable ex = error;
if (ex != null) {
q.clear();
for (Subscriber<?> s : a) {
s.onError(ex);
}
return;
}
}
boolean empty = q.isEmpty();
if (d && empty) {
for (Subscriber<?> s : a) {
s.onComplete();
}
return;
}
if (empty) {
break;
}
long ridx = r.get(idx);
long eidx = e[idx];
if (ridx != eidx) {
T v = q.poll();
a[idx].onNext(PrimaryOrderedItem.of(v, pi++));
e[idx] = eidx + 1;
int c = ++consumed;
if (c == limit) {
consumed = 0;
s.request(c);
}
notReady = 0;
} else {
notReady++;
}
idx++;
if (idx == n) {
idx = 0;
}
if (notReady == n) {
break;
}
}
int w = wip;
if (w == missed) {
index = idx;
produced = consumed;
primaryIndex = pi;
missed = WIP.addAndGet(this, -missed);
if (missed == 0) {
break;
}
} else {
missed = w;
}
}
}
void drainSync() {
int missed = 1;
Queue<T> q = queue;
Subscriber<? super OrderedItem<T>>[] a = this.subscribers;
AtomicLongArray r = this.requests;
long[] e = this.emissions;
int n = e.length;
int idx = index;
long pi = primaryIndex;
for (;;) {
int notReady = 0;
for (;;) {
if (cancelled) {
return;
}
boolean empty;
try {
empty = q.isEmpty();
} catch (Throwable ex) {
ExceptionHelper.throwIfFatal(ex);
s.cancel();
for (Subscriber<?> s : a) {
s.onError(ex);
}
return;
}
if (empty) {
for (Subscriber<?> s : a) {
s.onComplete();
}
return;
}
long ridx = r.get(idx);
long eidx = e[idx];
if (ridx != eidx) {
T v;
try {
v = q.poll();
} catch (Throwable ex) {
ExceptionHelper.throwIfFatal(ex);
s.cancel();
for (Subscriber<?> s : a) {
s.onError(ex);
}
return;
}
a[idx].onNext(PrimaryOrderedItem.of(v, pi++));
e[idx] = eidx + 1;
notReady = 0;
} else {
notReady++;
}
idx++;
if (idx == n) {
idx = 0;
}
if (notReady == n) {
break;
}
}
int w = wip;
if (w == missed) {
index = idx;
primaryIndex = pi;
missed = WIP.addAndGet(this, -missed);
if (missed == 0) {
break;
}
} else {
missed = w;
}
}
}
void drain() {
if (WIP.getAndIncrement(this) != 0) {
return;
}
if (sourceMode == Fuseable.SYNC) {
drainSync();
} else {
drainAsync();
}
}
}
}
