/*
* Copyright (c) 2011-2017 Pivotal Software Inc, 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
*
* 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 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 <T> the value type
* @see <a href="https://github.com/reactor/reactive-streams-commons">https://github.com/reactor/reactive-streams-commons</a>
*/
final class
FluxSubscribeOnCallable<T> extends
Flux<T> implements
Fuseable,
Scannable {
final
Callable<? extends T>
callable;
final
Scheduler scheduler;
FluxSubscribeOnCallable(
Callable<? extends T>
callable,
Scheduler scheduler) {
this.
callable =
Objects.
requireNonNull(
callable, "callable");
this.
scheduler =
Objects.
requireNonNull(
scheduler, "scheduler");
}
@
Override
public void
subscribe(
CoreSubscriber<? super T>
actual) {
CallableSubscribeOnSubscription<T>
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;
return null;
}
static final class
CallableSubscribeOnSubscription<T>
implements
QueueSubscription<T>,
InnerProducer<T>,
Runnable {
final
CoreSubscriber<? super T>
actual;
final
Callable<? extends T>
callable;
final
Scheduler scheduler;
volatile int
state;
@
SuppressWarnings("rawtypes")
static final
AtomicIntegerFieldUpdater<
CallableSubscribeOnSubscription>
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<
CallableSubscribeOnSubscription,
Disposable>
MAIN_FUTURE =
AtomicReferenceFieldUpdater.
newUpdater(
CallableSubscribeOnSubscription.class,
Disposable.class,
"mainFuture");
volatile
Disposable requestFuture;
@
SuppressWarnings("rawtypes")
static final
AtomicReferenceFieldUpdater<
CallableSubscribeOnSubscription,
Disposable>
REQUEST_FUTURE =
AtomicReferenceFieldUpdater.
newUpdater(
CallableSubscribeOnSubscription.class,
Disposable.class,
"requestFuture");
CallableSubscribeOnSubscription(
CoreSubscriber<? super T>
actual,
Callable<? extends T>
callable,
Scheduler scheduler) {
this.
actual =
actual;
this.
callable =
callable;
this.
scheduler =
scheduler;
}
@
Override
public
CoreSubscriber<? super T>
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;
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();
}
}
}
}