com.github.davidmoten.rx.internal.operators.OrderedMerge Maven / Gradle / Ivy
package com.github.davidmoten.rx.internal.operators;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Comparator;
import java.util.List;
import java.util.Queue;
import java.util.concurrent.atomic.AtomicLong;
import rx.Observable;
import rx.Observable.OnSubscribe;
import rx.Producer;
import rx.Subscriber;
import rx.exceptions.CompositeException;
import rx.exceptions.MissingBackpressureException;
import rx.internal.operators.BackpressureUtils;
import rx.internal.operators.NotificationLite;
import rx.internal.util.RxRingBuffer;
import rx.internal.util.unsafe.MpscLinkedQueue;
/**
* @author David Karnokd
*
* @param
* type of observable
*/
public final class OrderedMerge implements OnSubscribe {
final List> sources;
final Comparator comparator;
final boolean delayErrors;
public static > Observable create(
Collection> sources) {
return create(sources, false);
}
public static Observable create(Collection> sources,
Comparator comparator) {
return create(sources, comparator, false);
}
public static > Observable create(
Collection> sources, boolean delayErrors) {
return Observable.create(new OrderedMerge(sources, new Comparator() {
@Override
public int compare(U o1, U o2) {
return o1.compareTo(o2);
}
}, delayErrors));
}
public static Observable create(Collection> sources,
Comparator comparator, boolean delayErrors) {
return Observable.create(new OrderedMerge(sources, comparator, delayErrors));
}
private OrderedMerge(Collection> sources,
Comparator comparator, boolean delayErrors) {
this.sources = sources instanceof List ? (List>) sources
: new ArrayList>(sources);
this.comparator = comparator;
this.delayErrors = delayErrors;
}
@Override
public void call(Subscriber child) {
@SuppressWarnings("unchecked")
SourceSubscriber[] sources = new SourceSubscriber[this.sources.size()];
MergeProducer mp = new MergeProducer(sources, child, comparator, delayErrors);
for (int i = 0; i < sources.length; i++) {
if (child.isUnsubscribed()) {
return;
}
SourceSubscriber s = new SourceSubscriber(mp);
sources[i] = s;
child.add(s);
}
mp.set(0); // release contents of the array
child.setProducer(mp);
int i = 0;
for (Observable source : this.sources) {
if (child.isUnsubscribed()) {
return;
}
source.unsafeSubscribe(sources[i]);
i++;
}
}
static final class MergeProducer extends AtomicLong implements Producer {
/** */
private static final long serialVersionUID = -812969080497027108L;
final NotificationLite nl = NotificationLite.instance();
final boolean delayErrors;
final Comparator comparator;
@SuppressWarnings("rawtypes")
final SourceSubscriber[] sources;
final Subscriber child;
final Queue errors;
boolean emitting;
boolean missed;
@SuppressWarnings("rawtypes")
public MergeProducer(SourceSubscriber[] sources, Subscriber child,
Comparator comparator, boolean delayErrors) {
this.sources = sources;
this.delayErrors = delayErrors;
this.errors = new MpscLinkedQueue();
this.child = child;
this.comparator = comparator;
}
@Override
public void request(long n) {
BackpressureUtils.getAndAddRequest(this, n);
emit();
}
public void error(Throwable ex) {
errors.offer(ex);
emit();
}
public void emit() {
synchronized (this) {
if (emitting) {
missed = true;
return;
}
emitting = true;
}
// lift into local variables, just in case
@SuppressWarnings("unchecked")
final SourceSubscriber[] sources = this.sources;
final int n = sources.length;
final Subscriber child = this.child;
for (;;) {
if (child.isUnsubscribed()) {
return;
}
// eagerly check for errors
if (!delayErrors && !errors.isEmpty()) {
child.onError(errors.poll());
return;
}
// the current requested
long r = get();
// aggregate total emissions
long e = 0;
// even without request, terminal events can be fired if the
// state is right
if (r == 0) {
int doneCount = 0;
// for each source
for (SourceSubscriber s : sources) {
// if completed earlier
if (s == null) {
doneCount++;
} else {
// or just completed
if (s.done && s.queue.isEmpty()) {
doneCount++;
}
}
}
// if all of them are completed
if (doneCount == n) {
reportErrorOrComplete(child);
return;
}
}
// until there is request
while (r != 0L) {
if (child.isUnsubscribed()) {
return;
}
// eagerly check for errors
if (!delayErrors && !errors.isEmpty()) {
child.onError(errors.poll());
return;
}
// indicates that every active source has at least one value
boolean fullRow = true;
// indicates that at least one value is available
boolean hasAtLeastOne = false;
// holds the smallest of the available values
T minimum = null;
// indicates which source's value is taken so it can be
// polled/replenished
int toPoll = -1;
// number of completed sources
int doneCount = 0;
// for each source
for (int i = 0; i < n; i++) {
SourceSubscriber s = sources[i];
// terminated and emptied sources are ignored
if (s == null) {
doneCount++;
continue;
}
// read the terminal indicator first
boolean d = s.done;
// peek into the queue
Object o = s.queue.peek();
// no value available
if (o == null) {
// because it terminated?
if (d) {
sources[i] = null;
doneCount++;
continue;
}
// otherwise, indicate not all queues are ready
fullRow = false;
break;
}
// if we already found a value, compare it against the
// current
if (hasAtLeastOne) {
T v = nl.getValue(o);
int c = comparator.compare(minimum, v);
if (c > 0) {
minimum = v;
toPoll = i;
}
} else {
// this is the first value found
minimum = nl.getValue(o);
hasAtLeastOne = true;
toPoll = i;
}
}
// in case all of the sources completed
if (doneCount == n) {
reportErrorOrComplete(child);
return;
}
// if there was a full row of available values
if (fullRow) {
// given the winner
if (toPoll >= 0) {
SourceSubscriber s = sources[toPoll];
// remove the winning value from its queue
s.queue.poll();
// request replenishment
s.requestMore(1);
}
// emit the smallest
child.onNext(minimum);
// decrement the available request and increment the
// emit count
if (r != Long.MAX_VALUE) {
r--;
e++;
}
} else {
// if some sources weren't ready, just quit
break;
}
}
// if there was emission, adjust the downstream request amount
if (e != 0L) {
addAndGet(-e);
}
synchronized (this) {
if (!missed) {
emitting = false;
return;
}
missed = false;
}
}
}
void reportErrorOrComplete(Subscriber child) {
if (delayErrors && !errors.isEmpty()) {
if (errors.size() == 1) {
child.onError(errors.poll());
} else {
child.onError(new CompositeException(errors));
}
} else {
child.onCompleted();
}
}
}
static final class SourceSubscriber extends Subscriber {
final RxRingBuffer queue;
final MergeProducer parent;
volatile boolean done;
public SourceSubscriber(MergeProducer parent) {
queue = RxRingBuffer.getSpscInstance();
this.parent = parent;
}
@Override
public void onStart() {
add(queue);
request(RxRingBuffer.SIZE);
}
public void requestMore(long n) {
request(n);
}
@Override
public void onNext(T t) {
try {
queue.onNext(parent.nl.next(t));
} catch (MissingBackpressureException mbe) {
try {
onError(mbe);
} finally {
unsubscribe();
}
return;
} catch (IllegalStateException ex) {
if (!isUnsubscribed()) {
try {
onError(ex);
} finally {
unsubscribe();
}
}
return;
}
parent.emit();
}
@Override
public void onError(Throwable e) {
done = true;
parent.error(e);
}
@Override
public void onCompleted() {
done = true;
parent.emit();
}
}
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