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/*
* Copyright (c) 2016-2021 VMware Inc. or its affiliates, All Rights Reserved.
*
* 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
*
* https://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 reactor.core.publisher;
import java.util.Objects;
import java.util.concurrent.Callable;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import reactor.core.CoreSubscriber;
import reactor.core.Disposable;
import reactor.core.Fuseable;
import reactor.core.Scannable;
import reactor.core.scheduler.Scheduler;
import reactor.util.annotation.Nullable;
/**
* Executes a Callable and emits its value on the given Scheduler.
*
* @param the value type
* @see https://github.com/reactor/reactive-streams-commons
*/
final class FluxSubscribeOnCallable extends Flux implements Fuseable, Scannable {
final Callable callable;
final Scheduler scheduler;
FluxSubscribeOnCallable(Callable callable, Scheduler scheduler) {
this.callable = Objects.requireNonNull(callable, "callable");
this.scheduler = Objects.requireNonNull(scheduler, "scheduler");
}
@Override
public void subscribe(CoreSubscriber actual) {
CallableSubscribeOnSubscription parent =
new CallableSubscribeOnSubscription<>(actual, callable, scheduler);
actual.onSubscribe(parent);
try {
Disposable f = scheduler.schedule(parent);
parent.setMainFuture(f);
}
catch (RejectedExecutionException ree) {
if(parent.state != CallableSubscribeOnSubscription.HAS_CANCELLED) {
actual.onError(Operators.onRejectedExecution(ree, actual.currentContext()));
}
}
}
@Override
public Object scanUnsafe(Attr key) {
if (key == Attr.RUN_ON) return scheduler;
if (key == Attr.RUN_STYLE) return Attr.RunStyle.ASYNC;
return null;
}
static final class CallableSubscribeOnSubscription
implements QueueSubscription, InnerProducer, Runnable {
final CoreSubscriber actual;
final Callable callable;
final Scheduler scheduler;
volatile int state;
@SuppressWarnings("rawtypes")
static final AtomicIntegerFieldUpdater STATE =
AtomicIntegerFieldUpdater.newUpdater(CallableSubscribeOnSubscription.class,
"state");
T value;
static final int NO_REQUEST_HAS_VALUE = 1;
static final int HAS_REQUEST_NO_VALUE = 2;
static final int HAS_REQUEST_HAS_VALUE = 3;
static final int HAS_CANCELLED = 4;
int fusionState;
static final int NO_VALUE = 1;
static final int HAS_VALUE = 2;
static final int COMPLETE = 3;
volatile Disposable mainFuture;
@SuppressWarnings("rawtypes")
static final AtomicReferenceFieldUpdater
MAIN_FUTURE = AtomicReferenceFieldUpdater.newUpdater(
CallableSubscribeOnSubscription.class,
Disposable.class,
"mainFuture");
volatile Disposable requestFuture;
@SuppressWarnings("rawtypes")
static final AtomicReferenceFieldUpdater
REQUEST_FUTURE = AtomicReferenceFieldUpdater.newUpdater(
CallableSubscribeOnSubscription.class,
Disposable.class,
"requestFuture");
CallableSubscribeOnSubscription(CoreSubscriber actual,
Callable callable,
Scheduler scheduler) {
this.actual = actual;
this.callable = callable;
this.scheduler = scheduler;
}
@Override
public CoreSubscriber actual() {
return actual;
}
@Override
@Nullable
public Object scanUnsafe(Attr key) {
if (key == Attr.CANCELLED) return state == HAS_CANCELLED;
if (key == Attr.BUFFERED) return value != null ? 1 : 0;
if (key == Attr.RUN_ON) return scheduler;
if (key == Attr.RUN_STYLE) return Attr.RunStyle.ASYNC;
return InnerProducer.super.scanUnsafe(key);
}
@Override
public void cancel() {
state = HAS_CANCELLED;
fusionState = COMPLETE;
Disposable a = mainFuture;
if (a != OperatorDisposables.DISPOSED) {
a = MAIN_FUTURE.getAndSet(this, OperatorDisposables.DISPOSED);
if (a != null && a != OperatorDisposables.DISPOSED) {
a.dispose();
}
}
a = requestFuture;
if (a != OperatorDisposables.DISPOSED) {
a = REQUEST_FUTURE.getAndSet(this, OperatorDisposables.DISPOSED);
if (a != null && a != OperatorDisposables.DISPOSED) {
a.dispose();
}
}
}
@Override
public void clear() {
value = null;
fusionState = COMPLETE;
}
@Override
public boolean isEmpty() {
return fusionState == COMPLETE;
}
@Override
@Nullable
public T poll() {
if (fusionState == HAS_VALUE) {
fusionState = COMPLETE;
return value;
}
return null;
}
@Override
public int requestFusion(int requestedMode) {
if ((requestedMode & ASYNC) != 0 && (requestedMode & THREAD_BARRIER) == 0) {
fusionState = NO_VALUE;
return ASYNC;
}
return NONE;
}
@Override
public int size() {
return isEmpty() ? 0 : 1;
}
void setMainFuture(Disposable c) {
for (; ; ) {
Disposable a = mainFuture;
if (a == OperatorDisposables.DISPOSED) {
c.dispose();
return;
}
if (MAIN_FUTURE.compareAndSet(this, a, c)) {
return;
}
}
}
void setRequestFuture(Disposable c) {
for (; ; ) {
Disposable a = requestFuture;
if (a == OperatorDisposables.DISPOSED) {
c.dispose();
return;
}
if (REQUEST_FUTURE.compareAndSet(this, a, c)) {
return;
}
}
}
@Override
public void run() {
T v;
try {
v = callable.call();
}
catch (Throwable ex) {
actual.onError(Operators.onOperatorError(this, ex,
actual.currentContext()));
return;
}
if (v == null) {
fusionState = COMPLETE;
actual.onComplete();
return;
}
for (; ; ) {
int s = state;
if (s == HAS_CANCELLED || s == HAS_REQUEST_HAS_VALUE || s == NO_REQUEST_HAS_VALUE) {
return;
}
if (s == HAS_REQUEST_NO_VALUE) {
if (fusionState == NO_VALUE) {
this.value = v;
this.fusionState = HAS_VALUE;
}
actual.onNext(v);
if (state != HAS_CANCELLED) {
actual.onComplete();
}
return;
}
this.value = v;
if (STATE.compareAndSet(this, s, NO_REQUEST_HAS_VALUE)) {
return;
}
}
}
@Override
public void request(long n) {
if (Operators.validate(n)) {
for (; ; ) {
int s = state;
if (s == HAS_CANCELLED || s == HAS_REQUEST_NO_VALUE || s == HAS_REQUEST_HAS_VALUE) {
return;
}
if (s == NO_REQUEST_HAS_VALUE) {
if (STATE.compareAndSet(this, s, HAS_REQUEST_HAS_VALUE)) {
try {
Disposable f = scheduler.schedule(this::emitValue);
setRequestFuture(f);
}
catch (RejectedExecutionException ree) {
actual.onError(Operators.onRejectedExecution(ree,
actual.currentContext()));
}
}
return;
}
if (STATE.compareAndSet(this, s, HAS_REQUEST_NO_VALUE)) {
return;
}
}
}
}
void emitValue() {
if (fusionState == NO_VALUE) {
this.fusionState = HAS_VALUE;
}
T v = value;
clear();
if (v != null) {
actual.onNext(v);
}
if (state != HAS_CANCELLED) {
actual.onComplete();
}
}
}
}
