/*
* 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.atomic.
AtomicLongFieldUpdater;
import java.util.function.
BiFunction;
import java.util.function.
Consumer;
import reactor.core.
CoreSubscriber;
import reactor.core.
Exceptions;
import reactor.core.
Fuseable;
import reactor.util.annotation.
Nullable;
import reactor.util.context.
Context;
/**
* Generate signals one-by-one via a function callback.
* <p>
* <p>
* The {@code stateSupplier} may return {@code null} but your {@code stateConsumer} should be prepared to
* handle it.
*
* @param <T> the value type emitted
* @param <S> the custom state per subscriber
* @see <a href="https://github.com/reactor/reactive-streams-commons">https://github.com/reactor/reactive-streams-commons</a>
*/
final class
FluxGenerate<T, S>
extends
Flux<T> implements
Fuseable,
SourceProducer<T> {
static final
Callable EMPTY_CALLABLE = () -> null;
final
Callable<S>
stateSupplier;
final
BiFunction<S,
SynchronousSink<T>, S>
generator;
final
Consumer<? super S>
stateConsumer;
@
SuppressWarnings("unchecked")
FluxGenerate(
Consumer<
SynchronousSink<T>>
generator) {
this(
EMPTY_CALLABLE, (
state,
sink) -> {
generator.
accept(
sink);
return null;
});
}
FluxGenerate(
Callable<S>
stateSupplier,
BiFunction<S,
SynchronousSink<T>, S>
generator) {
this(
stateSupplier,
generator,
s -> {
});
}
FluxGenerate(
Callable<S>
stateSupplier,
BiFunction<S,
SynchronousSink<T>, S>
generator,
Consumer<? super S>
stateConsumer) {
this.
stateSupplier =
Objects.
requireNonNull(
stateSupplier, "stateSupplier");
this.
generator =
Objects.
requireNonNull(
generator, "generator");
this.
stateConsumer =
Objects.
requireNonNull(
stateConsumer, "stateConsumer");
}
@
Override
public void
subscribe(
CoreSubscriber<? super T>
actual) {
S
state;
try {
state =
stateSupplier.
call();
} catch (
Throwable e) {
Operators.
error(
actual,
Operators.
onOperatorError(
e,
actual.
currentContext()));
return;
}
actual.
onSubscribe(new
GenerateSubscription<>(
actual,
state,
generator,
stateConsumer));
}
@
Override
public
Object scanUnsafe(
Attr key) {
return null; //no particular key to be represented, still useful in hooks
}
static final class
GenerateSubscription<T, S>
implements
QueueSubscription<T>,
InnerProducer<T>,
SynchronousSink<T> {
final
CoreSubscriber<? super T>
actual;
final
BiFunction<S,
SynchronousSink<T>, S>
generator;
final
Consumer<? super S>
stateConsumer;
volatile boolean
cancelled;
S
state;
boolean
terminate;
boolean
hasValue;
boolean
outputFused;
T
generatedValue;
Throwable generatedError;
volatile long
requested;
@
SuppressWarnings("rawtypes")
static final
AtomicLongFieldUpdater<
GenerateSubscription>
REQUESTED =
AtomicLongFieldUpdater.
newUpdater(
GenerateSubscription.class, "requested");
GenerateSubscription(
CoreSubscriber<? super T>
actual, S
state,
BiFunction<S,
SynchronousSink<T>, S>
generator,
Consumer<? super
S>
stateConsumer) {
this.
actual =
actual;
this.
state =
state;
this.
generator =
generator;
this.
stateConsumer =
stateConsumer;
}
@
Override
public
Context currentContext() {
return
actual.
currentContext();
}
@
Override
@
Nullable
public
Object scanUnsafe(
Attr key) {
if (
key ==
Attr.
TERMINATED) return
terminate;
if (
key ==
Attr.
REQUESTED_FROM_DOWNSTREAM) return
requested;
if (
key ==
Attr.
CANCELLED) return
cancelled;
if (
key ==
Attr.
ERROR) return
generatedError;
return
InnerProducer.super.scanUnsafe(
key);
}
@
Override
public
CoreSubscriber<? super T>
actual() {
return
actual;
}
@
Override
public void
next(T
t) {
if (
terminate) {
Operators.
onNextDropped(
t,
actual.
currentContext());
return;
}
if (
hasValue) {
error(new
IllegalStateException("More than one call to onNext"));
return;
}
//noinspection ConstantConditions
if (
t == null) {
error(new
NullPointerException("The generator produced a null value"));
return;
}
hasValue = true;
if (
outputFused) {
generatedValue =
t;
} else {
actual.
onNext(
t);
}
}
@
Override
public void
error(
Throwable e) {
if (
terminate) {
return;
}
terminate = true;
if (
outputFused) {
generatedError =
e;
} else {
actual.
onError(
e);
}
}
@
Override
public void
complete() {
if (
terminate) {
return;
}
terminate = true;
if (!
outputFused) {
actual.
onComplete();
}
}
@
Override
public void
request(long
n) {
if (
Operators.
validate(
n)) {
if (
Operators.
addCap(
REQUESTED, this,
n) == 0) {
if (
n ==
Long.
MAX_VALUE) {
fastPath();
} else {
slowPath(
n);
}
}
}
}
void
fastPath() {
S
s =
state;
final
BiFunction<S,
SynchronousSink<T>, S>
g =
generator;
for (; ; ) {
if (
cancelled) {
cleanup(
s);
return;
}
try {
s =
g.
apply(
s, this);
} catch (
Throwable e) {
cleanup(
s);
actual.
onError(
Operators.
onOperatorError(
e,
actual.
currentContext()));
return;
}
if (
terminate ||
cancelled) {
cleanup(
s);
return;
}
if (!
hasValue) {
cleanup(
s);
actual.
onError(new
IllegalStateException("The generator didn't call any of the " +
"SynchronousSink method"));
return;
}
hasValue = false;
}
}
void
slowPath(long
n) {
S
s =
state;
long
e = 0L;
final
BiFunction<S,
SynchronousSink<T>, S>
g =
generator;
for (; ; ) {
while (
e !=
n) {
if (
cancelled) {
cleanup(
s);
return;
}
try {
s =
g.
apply(
s, this);
} catch (
Throwable ex) {
cleanup(
s);
actual.
onError(
ex);
return;
}
if (
terminate ||
cancelled) {
cleanup(
s);
return;
}
if (!
hasValue) {
cleanup(
s);
actual.
onError(new
IllegalStateException("The generator didn't call any of the " +
"SynchronousSink method"));
return;
}
e++;
hasValue = false;
}
n =
requested;
if (
n ==
e) {
state =
s;
n =
REQUESTED.
addAndGet(this, -
e);
if (
n == 0L) {
return;
}
}
}
}
@
Override
public void
cancel() {
if (!
cancelled) {
cancelled = true;
if (
REQUESTED.
getAndIncrement(this) == 0) {
cleanup(
state);
}
}
}
void
cleanup(S
s) {
try {
state = null;
stateConsumer.
accept(
s);
} catch (
Throwable e) {
Operators.
onErrorDropped(
e,
actual.
currentContext());
}
}
@
Override
public int
requestFusion(int
requestedMode) {
if ((
requestedMode &
Fuseable.
SYNC) != 0 && (
requestedMode &
Fuseable.
THREAD_BARRIER) == 0) {
outputFused = true;
return
Fuseable.
SYNC;
}
return
Fuseable.
NONE;
}
@
Override
@
Nullable
public T
poll() {
S
s =
state;
if (
terminate) {
cleanup(
s);
Throwable e =
generatedError;
if (
e != null) {
generatedError = null;
Exceptions.
bubble(
e);
}
return null;
}
try {
s =
generator.
apply(
s, this);
} catch (final
Throwable ex) {
cleanup(
s);
throw
ex;
}
if (!
hasValue) {
cleanup(
s);
if (!
terminate) {
throw new
IllegalStateException("The generator didn't call any of the " + "FluxGenerateOutput method");
}
Throwable e =
generatedError;
if (
e != null) {
generatedError = null;
throw
Exceptions.
bubble(
e);
}
return null;
}
T
v =
generatedValue;
generatedValue = null;
hasValue = false;
state =
s;
return
v;
}
@
Override
public boolean
isEmpty() {
return
terminate;
}
@
Override
public int
size() {
return
isEmpty() ? 0 : -1;
}
@
Override
public void
clear() {
generatedError = null;
generatedValue = null;
}
}
}