/*
* 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.atomic.
AtomicReferenceFieldUpdater;
import java.util.function.
Consumer;
import reactor.core.
Disposable;
import reactor.core.
Disposables;
import reactor.util.annotation.
Nullable;
/**
* Utility methods to work with {@link Disposable} atomically.
*
* @author Simon Baslé
* @author David Karnok
*/
final class
OperatorDisposables {
/**
* A singleton {@link Disposable} that represents a disposed instance. Should not be
* leaked to clients.
*/
//NOTE: There is a private similar DISPOSED singleton in DefaultDisposable as well
static final
Disposable DISPOSED =
Disposables.
disposed();
/**
* Atomically set the field to a {@link Disposable} and dispose the old content.
*
* @param updater the target field updater
* @param holder the target instance holding the field
* @param newValue the new Disposable to set
* @return true if successful, false if the field contains the {@link #DISPOSED} instance.
*/
public static <T> boolean
set(
AtomicReferenceFieldUpdater<T,
Disposable>
updater, T
holder, @
Nullable Disposable newValue) {
for (;;) {
Disposable current =
updater.
get(
holder);
if (
current ==
DISPOSED) {
if (
newValue != null) {
newValue.
dispose();
}
return false;
}
if (
updater.
compareAndSet(
holder,
current,
newValue)) {
if (
current != null) {
current.
dispose();
}
return true;
}
}
}
/**
* Atomically set the field to the given non-null {@link Disposable} and return true,
* or return false if the field is non-null.
* If the target field contains the common {@link #DISPOSED} instance, the supplied disposable
* is disposed. If the field contains other non-null {@link Disposable}, an {@link IllegalStateException}
* is signalled to the {@code errorCallback}.
*
* @param updater the target field updater
* @param holder the target instance holding the field
* @param newValue the new Disposable to set, not null
* @return true if the operation succeeded, false
*/
public static <T> boolean
setOnce(
AtomicReferenceFieldUpdater<T,
Disposable>
updater, T
holder,
Disposable newValue,
Consumer<
RuntimeException>
errorCallback) {
Objects.
requireNonNull(
newValue, "newValue is null");
if (!
updater.
compareAndSet(
holder, null,
newValue)) {
newValue.
dispose();
if (
updater.
get(
holder) !=
DISPOSED) {
errorCallback.
accept(new
IllegalStateException("Disposable already pushed"));
}
return false;
}
return true;
}
/**
* Atomically replace the {@link Disposable} in the field with the given new Disposable
* but do not dispose the old one.
*
* @param updater the target field updater
* @param holder the target instance holding the field
* @param newValue the new Disposable to set, null allowed
* @return true if the operation succeeded, false if the target field contained
* the common {@link #DISPOSED} instance and the given disposable is not null but is disposed.
*/
public static <T> boolean
replace(
AtomicReferenceFieldUpdater<T,
Disposable>
updater, T
holder, @
Nullable Disposable newValue) {
for (;;) {
Disposable current =
updater.
get(
holder);
if (
current ==
DISPOSED) {
if (
newValue != null) {
newValue.
dispose();
}
return false;
}
if (
updater.
compareAndSet(
holder,
current,
newValue)) {
return true;
}
}
}
/**
* Atomically dispose the {@link Disposable} in the field if not already disposed.
*
* @param updater the target field updater
* @param holder the target instance holding the field
* @return true if the {@link Disposable} held by the field was properly disposed
*/
public static <T> boolean
dispose(
AtomicReferenceFieldUpdater<T,
Disposable>
updater, T
holder) {
Disposable current =
updater.
get(
holder);
Disposable d =
DISPOSED;
if (
current !=
d) {
current =
updater.
getAndSet(
holder,
d);
if (
current !=
d) {
if (
current != null) {
current.
dispose();
}
return true;
}
}
return false;
}
/**
* Verify that current is null and next is not null, otherwise signal a
* {@link NullPointerException} to the {@code errorCallback} and return false.
*
* @param current the current {@link Disposable}, expected to be null
* @param next the next {@link Disposable}, expected to be non-null
* @return true if the validation succeeded
*/
public static boolean
validate(@
Nullable Disposable current,
Disposable next,
Consumer<
RuntimeException>
errorCallback) {
//noinspection ConstantConditions
if (
next == null) {
errorCallback.
accept(new
NullPointerException("next is null"));
return false;
}
if (
current != null) {
next.
dispose();
errorCallback.
accept(new
IllegalStateException("Disposable already pushed"));
return false;
}
return true;
}
/**
* Atomically try to set the given {@link Disposable} on the field if it is null or
* disposes it if the field contains {@link #DISPOSED}.
*
* @param updater the target field updater
* @param holder the target instance holding the field
* @param newValue the disposable to set
* @return true if successful, false otherwise
*/
public static <T> boolean
trySet(
AtomicReferenceFieldUpdater<T,
Disposable>
updater, T
holder,
Disposable newValue) {
if (!
updater.
compareAndSet(
holder, null,
newValue)) {
if (
updater.
get(
holder) ==
DISPOSED) {
newValue.
dispose();
}
return false;
}
return true;
}
/**
* Check if the given {@link Disposable} is the singleton {@link #DISPOSED}.
*
* @param d the disposable to check
* @return true if d is {@link #DISPOSED}
*/
public static boolean
isDisposed(
Disposable d) {
return
d ==
DISPOSED;
}
}