rx.subjects.PublishSubject Maven / Gradle / Ivy
/**
* Copyright 2014 Netflix, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package rx.subjects;
import java.util.*;
import java.util.concurrent.atomic.*;
import rx.*;
import rx.Observer;
import rx.exceptions.*;
import rx.internal.operators.BackpressureUtils;
/**
* Subject that, once an {@link Observer} has subscribed, emits all subsequently observed items to the
* subscriber.
*
* 
*
* Example usage:
*
*
{@code
PublishSubject
*
* @param
* the type of items observed and emitted by the Subject
*/
public final class PublishSubject extends Subject {
final PublishSubjectState state;
/**
* Creates and returns a new {@code PublishSubject}.
*
* @param the value type
* @return the new {@code PublishSubject}
*/
public static PublishSubject create() {
return new PublishSubject(new PublishSubjectState());
}
protected PublishSubject(PublishSubjectState state) {
super(state);
this.state = state;
}
@Override
public void onNext(T v) {
state.onNext(v);
}
@Override
public void onError(Throwable e) {
state.onError(e);
}
@Override
public void onCompleted() {
state.onCompleted();
}
@Override
public boolean hasObservers() {
return state.get().length != 0;
}
/**
* Check if the Subject has terminated with an exception.
* @return true if the subject has received a throwable through {@code onError}.
* @since 1.2
*/
public boolean hasThrowable() {
return state.get() == PublishSubjectState.TERMINATED && state.error != null;
}
/**
* Check if the Subject has terminated normally.
* @return true if the subject completed normally via {@code onCompleted}
* @since 1.2
*/
public boolean hasCompleted() {
return state.get() == PublishSubjectState.TERMINATED && state.error == null;
}
/**
* Returns the Throwable that terminated the Subject.
* @return the Throwable that terminated the Subject or {@code null} if the
* subject hasn't terminated yet or it terminated normally.
* @since 1.2
*/
public Throwable getThrowable() {
if (state.get() == PublishSubjectState.TERMINATED) {
return state.error;
}
return null;
}
static final class PublishSubjectState
extends AtomicReference[]>
implements OnSubscribe, Observer {
/** */
private static final long serialVersionUID = -7568940796666027140L;
@SuppressWarnings("rawtypes")
static final PublishSubjectProducer[] EMPTY = new PublishSubjectProducer[0];
@SuppressWarnings("rawtypes")
static final PublishSubjectProducer[] TERMINATED = new PublishSubjectProducer[0];
Throwable error;
@SuppressWarnings("unchecked")
public PublishSubjectState() {
lazySet(EMPTY);
}
@Override
public void call(Subscriber t) {
PublishSubjectProducer pp = new PublishSubjectProducer(this, t);
t.add(pp);
t.setProducer(pp);
if (add(pp)) {
if (pp.isUnsubscribed()) {
remove(pp);
}
} else {
Throwable ex = error;
if (ex != null) {
t.onError(ex);
} else {
t.onCompleted();
}
}
}
boolean add(PublishSubjectProducer inner) {
for (;;) {
PublishSubjectProducer[] curr = get();
if (curr == TERMINATED) {
return false;
}
int n = curr.length;
@SuppressWarnings("unchecked")
PublishSubjectProducer[] next = new PublishSubjectProducer[n + 1];
System.arraycopy(curr, 0, next, 0, n);
next[n] = inner;
if (compareAndSet(curr, next)) {
return true;
}
}
}
@SuppressWarnings("unchecked")
void remove(PublishSubjectProducer inner) {
for (;;) {
PublishSubjectProducer[] curr = get();
if (curr == TERMINATED || curr == EMPTY) {
return;
}
int n = curr.length;
int j = -1;
for (int i = 0; i < n; i++) {
if (curr[i] == inner) {
j = i;
break;
}
}
if (j < 0) {
return;
}
PublishSubjectProducer[] next;
if (n == 1) {
next = EMPTY;
} else {
next = new PublishSubjectProducer[n - 1];
System.arraycopy(curr, 0, next, 0, j);
System.arraycopy(curr, j + 1, next, j, n - j - 1);
}
if (compareAndSet(curr, next)) {
return;
}
}
}
@Override
public void onNext(T t) {
for (PublishSubjectProducer pp : get()) {
pp.onNext(t);
}
}
@SuppressWarnings("unchecked")
@Override
public void onError(Throwable e) {
error = e;
List errors = null;
for (PublishSubjectProducer pp : getAndSet(TERMINATED)) {
try {
pp.onError(e);
} catch (Throwable ex) {
if (errors == null) {
errors = new ArrayList(1);
}
errors.add(ex);
}
}
Exceptions.throwIfAny(errors);
}
@SuppressWarnings("unchecked")
@Override
public void onCompleted() {
for (PublishSubjectProducer pp : getAndSet(TERMINATED)) {
pp.onCompleted();
}
}
}
static final class PublishSubjectProducer
extends AtomicLong
implements Producer, Subscription, Observer {
/** */
private static final long serialVersionUID = 6451806817170721536L;
final PublishSubjectState parent;
final Subscriber actual;
long produced;
public PublishSubjectProducer(PublishSubjectState parent, Subscriber actual) {
this.parent = parent;
this.actual = actual;
}
@Override
public void request(long n) {
if (BackpressureUtils.validate(n)) {
for (;;) {
long r = get();
if (r == Long.MIN_VALUE) {
return;
}
long u = BackpressureUtils.addCap(r, n);
if (compareAndSet(r, u)) {
return;
}
}
}
}
@Override
public boolean isUnsubscribed() {
return get() == Long.MIN_VALUE;
}
@Override
public void unsubscribe() {
if (getAndSet(Long.MIN_VALUE) != Long.MIN_VALUE) {
parent.remove(this);
}
}
@Override
public void onNext(T t) {
long r = get();
if (r != Long.MIN_VALUE) {
long p = produced;
if (r != p) {
produced = p + 1;
actual.onNext(t);
} else {
unsubscribe();
actual.onError(new MissingBackpressureException("PublishSubject: could not emit value due to lack of requests"));
}
}
}
@Override
public void onError(Throwable e) {
if (get() != Long.MIN_VALUE) {
actual.onError(e);
}
}
@Override
public void onCompleted() {
if (get() != Long.MIN_VALUE) {
actual.onCompleted();
}
}
}
}
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