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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.Collection;
import java.util.Iterator;
import java.util.Objects;
import java.util.Spliterator;
import java.util.concurrent.atomic.AtomicLongFieldUpdater;
import org.reactivestreams.Subscriber;
import reactor.core.CoreSubscriber;
import reactor.core.Exceptions;
import reactor.core.Fuseable;
import reactor.util.annotation.Nullable;
import reactor.util.function.Tuple2;
/**
* Emits the contents of an Iterable source. Attempt to discard remainder of a source
* in case of error / cancellation, but uses the {@link Spliterator} API to try and detect
* infinite sources (so that said discarding doesn't loop infinitely).
*
* @param the value type
*
* @see Reactive-Streams-Commons
*/
final class FluxIterable extends Flux implements Fuseable, SourceProducer {
/**
* Utility method to check that a given {@link Iterable} can be positively identified as
* finite, which implies forEachRemaining type of iteration can be done to discard unemitted
* values (in case of cancellation or error).
*
* A {@link Collection} is assumed to be finite, and for other iterables the {@link Spliterator}
* {@link Spliterator#SIZED} characteristic is looked for.
*
* @param iterable the {@link Iterable} to check.
* @param
* @return true if the {@link Iterable} can confidently classified as finite, false if not finite/unsure
*/
static boolean checkFinite(Iterable iterable) {
return iterable instanceof Collection || iterable.spliterator().hasCharacteristics(Spliterator.SIZED);
}
final Iterable iterable;
@Nullable
private final Runnable onClose;
FluxIterable(Iterable iterable, @Nullable Runnable onClose) {
this.iterable = Objects.requireNonNull(iterable, "iterable");
this.onClose = onClose;
}
FluxIterable(Iterable iterable) {
this(iterable, null);
}
@Override
public void subscribe(CoreSubscriber actual) {
boolean knownToBeFinite;
Iterator it;
try {
knownToBeFinite = FluxIterable.checkFinite(iterable);
it = iterable.iterator();
}
catch (Throwable e) {
Operators.error(actual, Operators.onOperatorError(e, actual.currentContext()));
return;
}
subscribe(actual, it, knownToBeFinite, onClose);
}
@Override
public Object scanUnsafe(Attr key) {
if (key == Attr.BUFFERED) {
if (iterable instanceof Collection) return ((Collection) iterable).size();
if (iterable instanceof Tuple2) return ((Tuple2) iterable).size();
}
if (key == Attr.RUN_STYLE) {
return Attr.RunStyle.SYNC;
}
return null;
}
/**
* Common method to take an {@link Iterator} as a source of values.
*
* @param s the subscriber to feed this iterator to
* @param it the {@link Iterator} to use as a predictable source of values
*/
static void subscribe(CoreSubscriber s, Iterator it, boolean knownToBeFinite) {
subscribe(s, it, knownToBeFinite, null);
}
/**
* Common method to take an {@link Iterator} as a source of values.
*
* @param s the subscriber to feed this iterator to
* @param it the {@link Iterator} to use as a source of values
* @param onClose close handler to call once we're done with the iterator (provided it
* is not null, this includes when the iteration errors or complete or the subscriber
* is cancelled). Null to ignore.
*/
@SuppressWarnings("unchecked")
static void subscribe(CoreSubscriber s, Iterator it,
boolean knownToBeFinite, @Nullable Runnable onClose) {
//noinspection ConstantConditions
if (it == null) {
Operators.error(s, new NullPointerException("The iterator is null"));
return;
}
boolean b;
try {
b = it.hasNext();
}
catch (Throwable e) {
Operators.error(s, Operators.onOperatorError(e, s.currentContext()));
if (onClose != null) {
try {
onClose.run();
}
catch (Throwable t) {
Operators.onErrorDropped(t, s.currentContext());
}
}
return;
}
if (!b) {
Operators.complete(s);
if (onClose != null) {
try {
onClose.run();
}
catch (Throwable t) {
Operators.onErrorDropped(t, s.currentContext());
}
}
return;
}
if (s instanceof ConditionalSubscriber) {
s.onSubscribe(new IterableSubscriptionConditional<>((ConditionalSubscriber) s,
it, knownToBeFinite, onClose));
}
else {
s.onSubscribe(new IterableSubscription<>(s, it, knownToBeFinite, onClose));
}
}
static final class IterableSubscription
implements InnerProducer, SynchronousSubscription {
final CoreSubscriber actual;
final Iterator iterator;
final boolean knownToBeFinite;
final Runnable onClose;
volatile boolean cancelled;
volatile long requested;
@SuppressWarnings("rawtypes")
static final AtomicLongFieldUpdater REQUESTED =
AtomicLongFieldUpdater.newUpdater(IterableSubscription.class,
"requested");
int state;
/**
* Indicates that the iterator's hasNext returned true before but the value is not
* yet retrieved.
*/
static final int STATE_HAS_NEXT_NO_VALUE = 0;
/**
* Indicates that there is a value available in current.
*/
static final int STATE_HAS_NEXT_HAS_VALUE = 1;
/**
* Indicates that there are no more values available.
*/
static final int STATE_NO_NEXT = 2;
/**
* Indicates that the value has been consumed and a new value should be retrieved.
*/
static final int STATE_CALL_HAS_NEXT = 3;
T current;
Throwable hasNextFailure;
IterableSubscription(CoreSubscriber actual,
Iterator iterator, boolean knownToBeFinite, @Nullable Runnable onClose) {
this.actual = actual;
this.iterator = iterator;
this.knownToBeFinite = knownToBeFinite;
this.onClose = onClose;
}
IterableSubscription(CoreSubscriber actual,
Iterator iterator, boolean knownToBeFinite) {
this(actual, iterator, knownToBeFinite, null);
}
@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);
}
}
}
}
private void onCloseWithDropError() {
if (onClose != null) {
try {
onClose.run();
}
catch (Throwable t) {
Operators.onErrorDropped(t, actual.currentContext());
}
}
}
void slowPath(long n) {
final Iterator a = iterator;
final Subscriber s = actual;
long e = 0L;
for (; ; ) {
while (e != n) {
T t;
try {
t = Objects.requireNonNull(a.next(),
"The iterator returned a null value");
}
catch (Throwable ex) {
s.onError(ex);
onCloseWithDropError();
return;
}
if (cancelled) {
return;
}
s.onNext(t);
if (cancelled) {
return;
}
boolean b;
try {
b = a.hasNext();
}
catch (Throwable ex) {
s.onError(ex);
onCloseWithDropError();
return;
}
if (cancelled) {
return;
}
if (!b) {
s.onComplete();
onCloseWithDropError();
return;
}
e++;
}
n = requested;
if (n == e) {
n = REQUESTED.addAndGet(this, -e);
if (n == 0L) {
return;
}
e = 0L;
}
}
}
void fastPath() {
final Iterator a = iterator;
final Subscriber s = actual;
for (; ; ) {
if (cancelled) {
return;
}
T t;
try {
t = Objects.requireNonNull(a.next(),
"The iterator returned a null value");
}
catch (Exception ex) {
s.onError(ex);
onCloseWithDropError();
return;
}
if (cancelled) {
return;
}
s.onNext(t);
if (cancelled) {
return;
}
boolean b;
try {
b = a.hasNext();
}
catch (Exception ex) {
s.onError(ex);
onCloseWithDropError();
return;
}
if (cancelled) {
return;
}
if (!b) {
s.onComplete();
onCloseWithDropError();
return;
}
}
}
@Override
public void cancel() {
onCloseWithDropError();
cancelled = true;
Operators.onDiscardMultiple(this.iterator, this.knownToBeFinite, actual.currentContext());
}
@Override
public CoreSubscriber actual() {
return actual;
}
@Override
@Nullable
public Object scanUnsafe(Attr key) {
if (key == Attr.CANCELLED) return cancelled;
if (key == Attr.REQUESTED_FROM_DOWNSTREAM) return requested;
if (key == Attr.TERMINATED) return state == STATE_NO_NEXT;
if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC;
return InnerProducer.super.scanUnsafe(key);
}
@Override
public void clear() {
Operators.onDiscardMultiple(this.iterator, this.knownToBeFinite, actual.currentContext());
state = STATE_NO_NEXT;
}
@Override
public boolean isEmpty() {
int s = state;
if (s == STATE_NO_NEXT) {
return true;
}
else if (cancelled && !knownToBeFinite) {
return true; //interrupts poll in discard loops due to cancellation
}
else if (s == STATE_HAS_NEXT_HAS_VALUE || s == STATE_HAS_NEXT_NO_VALUE) {
return false;
}
else {
boolean hasNext;
try {
hasNext = iterator.hasNext();
}
catch (Throwable t) {
//this is a corner case, most Iterators are not expected to throw in hasNext.
//since most calls to isEmpty are in preparation for poll() in fusion, we "defer"
//the exception by pretending queueSub isn't empty, but keeping track of exception
//to be re-thrown by a subsequent call to poll()
state = STATE_HAS_NEXT_NO_VALUE;
hasNextFailure = t;
return false;
}
if (hasNext) {
state = STATE_HAS_NEXT_NO_VALUE;
return false;
}
state = STATE_NO_NEXT;
return true;
}
}
@Override
@Nullable
public T poll() {
if (hasNextFailure != null) {
state = STATE_NO_NEXT;
throw Exceptions.propagate(hasNextFailure);
}
if (!isEmpty()) {
T c;
if (state == STATE_HAS_NEXT_NO_VALUE) {
c = iterator.next();
}
else {
c = current;
current = null;
}
state = STATE_CALL_HAS_NEXT;
if (c == null) {
onCloseWithDropError();
throw new NullPointerException("iterator returned a null value");
}
return c;
}
onCloseWithDropError();
return null;
}
@Override
public int size() {
if (state == STATE_NO_NEXT) {
return 0;
}
return 1;
}
}
static final class IterableSubscriptionConditional
implements InnerProducer, SynchronousSubscription {
final ConditionalSubscriber actual;
final Iterator iterator;
final boolean knownToBeFinite;
final Runnable onClose;
volatile boolean cancelled;
volatile long requested;
@SuppressWarnings("rawtypes")
static final AtomicLongFieldUpdater REQUESTED =
AtomicLongFieldUpdater.newUpdater(IterableSubscriptionConditional.class,
"requested");
int state;
/**
* Indicates that the iterator's hasNext returned true before but the value is not
* yet retrieved.
*/
static final int STATE_HAS_NEXT_NO_VALUE = 0;
/**
* Indicates that there is a value available in current.
*/
static final int STATE_HAS_NEXT_HAS_VALUE = 1;
/**
* Indicates that there are no more values available.
*/
static final int STATE_NO_NEXT = 2;
/**
* Indicates that the value has been consumed and a new value should be retrieved.
*/
static final int STATE_CALL_HAS_NEXT = 3;
T current;
Throwable hasNextFailure;
IterableSubscriptionConditional(ConditionalSubscriber actual,
Iterator iterator, boolean knownToBeFinite, @Nullable Runnable onClose) {
this.actual = actual;
this.iterator = iterator;
this.knownToBeFinite = knownToBeFinite;
this.onClose = onClose;
}
IterableSubscriptionConditional(ConditionalSubscriber actual,
Iterator iterator, boolean knownToBeFinite) {
this(actual, iterator, knownToBeFinite, null);
}
@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);
}
}
}
}
private void onCloseWithDropError() {
if (onClose != null) {
try {
onClose.run();
}
catch (Throwable t) {
Operators.onErrorDropped(t, actual.currentContext());
}
}
}
void slowPath(long n) {
final Iterator a = iterator;
final ConditionalSubscriber s = actual;
long e = 0L;
for (; ; ) {
while (e != n) {
T t;
try {
t = Objects.requireNonNull(a.next(),
"The iterator returned a null value");
}
catch (Throwable ex) {
s.onError(ex);
onCloseWithDropError();
return;
}
if (cancelled) {
return;
}
boolean consumed = s.tryOnNext(t);
if (cancelled) {
return;
}
boolean b;
try {
b = a.hasNext();
}
catch (Throwable ex) {
s.onError(ex);
onCloseWithDropError();
return;
}
if (cancelled) {
return;
}
if (!b) {
s.onComplete();
onCloseWithDropError();
return;
}
if (consumed) {
e++;
}
}
n = requested;
if (n == e) {
n = REQUESTED.addAndGet(this, -e);
if (n == 0L) {
return;
}
e = 0L;
}
}
}
void fastPath() {
final Iterator a = iterator;
final ConditionalSubscriber s = actual;
for (; ; ) {
if (cancelled) {
return;
}
T t;
try {
t = Objects.requireNonNull(a.next(),
"The iterator returned a null value");
}
catch (Exception ex) {
s.onError(ex);
onCloseWithDropError();
return;
}
if (cancelled) {
return;
}
s.tryOnNext(t);
if (cancelled) {
return;
}
boolean b;
try {
b = a.hasNext();
}
catch (Exception ex) {
s.onError(ex);
onCloseWithDropError();
return;
}
if (cancelled) {
return;
}
if (!b) {
s.onComplete();
onCloseWithDropError();
return;
}
}
}
@Override
public void cancel() {
onCloseWithDropError();
cancelled = true;
Operators.onDiscardMultiple(this.iterator, this.knownToBeFinite, actual.currentContext());
}
@Override
public CoreSubscriber actual() {
return actual;
}
@Override
@Nullable
public Object scanUnsafe(Attr key) {
if (key == Attr.CANCELLED) return cancelled;
if (key == Attr.REQUESTED_FROM_DOWNSTREAM) return requested;
if (key == Attr.TERMINATED) return state == STATE_NO_NEXT;
if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC;
return InnerProducer.super.scanUnsafe(key);
}
@Override
public void clear() {
Operators.onDiscardMultiple(this.iterator, this.knownToBeFinite, actual.currentContext());
state = STATE_NO_NEXT;
}
@Override
public boolean isEmpty() {
int s = state;
if (s == STATE_NO_NEXT) {
return true;
}
else if (cancelled && !knownToBeFinite) {
return true; //interrupts poll() during discard loop if cancelled
}
else if (s == STATE_HAS_NEXT_HAS_VALUE || s == STATE_HAS_NEXT_NO_VALUE) {
return false;
}
else {
boolean hasNext;
try {
hasNext = iterator.hasNext();
}
catch (Throwable t) {
//this is a corner case, most Iterators are not expected to throw in hasNext.
//since most calls to isEmpty are in preparation for poll() in fusion, we "defer"
//the exception by pretending queueSub isn't empty, but keeping track of exception
//to be re-thrown by a subsequent call to poll()
state = STATE_HAS_NEXT_NO_VALUE;
hasNextFailure = t;
return false;
}
if (hasNext) {
state = STATE_HAS_NEXT_NO_VALUE;
return false;
}
state = STATE_NO_NEXT;
return true;
}
}
@Override
@Nullable
public T poll() {
if (hasNextFailure != null) {
state = STATE_NO_NEXT;
throw Exceptions.propagate(hasNextFailure);
}
if (!isEmpty()) {
T c;
if (state == STATE_HAS_NEXT_NO_VALUE) {
c = iterator.next();
}
else {
c = current;
current = null;
}
state = STATE_CALL_HAS_NEXT;
return c;
}
onCloseWithDropError();
return null;
}
@Override
public int size() {
if (state == STATE_NO_NEXT) {
return 0;
}
return 1; // no way of knowing without enumerating first
}
}
}