rx.internal.producers.ProducerArbiter Maven / Gradle / Ivy
/**
* Copyright 2015 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.internal.producers;
import rx.*;
/**
* Producer that allows changing an underlying producer atomically and correctly resume with the accumulated
* requests.
*/
public final class ProducerArbiter implements Producer {
long requested;
Producer currentProducer;
boolean emitting;
long missedRequested;
long missedProduced;
Producer missedProducer;
static final Producer NULL_PRODUCER = new Producer() {
@Override
public void request(long n) {
}
};
@Override
public void request(long n) {
if (n < 0) {
throw new IllegalArgumentException("n >= 0 required");
}
if (n == 0) {
return;
}
synchronized (this) {
if (emitting) {
missedRequested += n;
return;
}
emitting = true;
}
boolean skipFinal = false;
try {
long r = requested;
long u = r + n;
if (u < 0) {
u = Long.MAX_VALUE;
}
requested = u;
Producer p = currentProducer;
if (p != null) {
p.request(n);
}
emitLoop();
skipFinal = true;
} finally {
if (!skipFinal) {
synchronized (this) {
emitting = false;
}
}
}
}
public void produced(long n) {
if (n <= 0) {
throw new IllegalArgumentException("n > 0 required");
}
synchronized (this) {
if (emitting) {
missedProduced += n;
return;
}
emitting = true;
}
boolean skipFinal = false;
try {
long r = requested;
if (r != Long.MAX_VALUE) {
long u = r - n;
if (u < 0) {
throw new IllegalStateException("more items arrived than were requested");
}
requested = u;
}
emitLoop();
skipFinal = true;
} finally {
if (!skipFinal) {
synchronized (this) {
emitting = false;
}
}
}
}
public void setProducer(Producer newProducer) {
synchronized (this) {
if (emitting) {
missedProducer = newProducer == null ? NULL_PRODUCER : newProducer;
return;
}
emitting = true;
}
boolean skipFinal = false;
try {
currentProducer = newProducer;
if (newProducer != null) {
newProducer.request(requested);
}
emitLoop();
skipFinal = true;
} finally {
if (!skipFinal) {
synchronized (this) {
emitting = false;
}
}
}
}
public void emitLoop() {
for (;;) {
long localRequested;
long localProduced;
Producer localProducer;
synchronized (this) {
localRequested = missedRequested;
localProduced = missedProduced;
localProducer = missedProducer;
if (localRequested == 0L
&& localProduced == 0L
&& localProducer == null) {
emitting = false;
return;
}
missedRequested = 0L;
missedProduced = 0L;
missedProducer = null;
}
long r = requested;
if (r != Long.MAX_VALUE) {
long u = r + localRequested;
if (u < 0 || u == Long.MAX_VALUE) {
r = Long.MAX_VALUE;
requested = r;
} else {
long v = u - localProduced;
if (v < 0) {
throw new IllegalStateException("more produced than requested");
}
r = v;
requested = v;
}
}
if (localProducer != null) {
if (localProducer == NULL_PRODUCER) {
currentProducer = null;
} else {
currentProducer = localProducer;
localProducer.request(r);
}
} else {
Producer p = currentProducer;
if (p != null && localRequested != 0L) {
p.request(localRequested);
}
}
}
}
}