monix.execution.atomic.AtomicAny.scala Maven / Gradle / Ivy
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/*
* Copyright (c) 2014-2019 by The Monix Project Developers.
* See the project homepage at: https://monix.io
*
* 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 monix.execution.atomic
/** Atomic references wrapping `AnyRef` values.
*
* @tparam A is forced to be an `AnyRef` because the equality test is
* by reference and not by value.
*/
final class AtomicAny[A <: AnyRef] private[atomic] (initialValue: A) extends Atomic[A] {
private[this] var ref = initialValue
def getAndSet(update: A): A = {
val current = ref
ref = update
current
}
def compareAndSet(expect: A, update: A): Boolean = {
if (ref eq expect) {
ref = update
true
} else
false
}
def set(update: A): Unit = {
ref = update
}
def get(): A = ref
}
/** @define createDesc Constructs an [[AtomicAny]] reference, allowing
* for fine-tuning of the created instance.
*
* A [[PaddingStrategy]] can be provided in order to counter
* the "false sharing" problem.
*
* Note that for ''Scala.js'' we aren't applying any padding,
* as it doesn't make much sense, since Javascript execution
* is single threaded, but this builder is provided for
* syntax compatibility anyway across the JVM and Javascript
* and we never know how Javascript engines will evolve.
*/
object AtomicAny {
/** Builds an [[AtomicAny]] reference.
*
* @param initialValue is the initial value with which to initialize the atomic
*/
def apply[A <: AnyRef](initialValue: A): AtomicAny[A] =
new AtomicAny(initialValue)
/** $createDesc
*
* @param initialValue is the initial value with which to initialize the atomic
* @param padding is the [[PaddingStrategy]] to apply
*/
def withPadding[A <: AnyRef](initialValue: A, padding: PaddingStrategy): AtomicAny[A] =
new AtomicAny(initialValue)
/** $createDesc
*
* Also this builder on top Java 8 also allows for turning off the
* Java 8 intrinsics, thus forcing usage of CAS-loops for
* `getAndSet` and for `getAndAdd`.
*
* @param initialValue is the initial value with which to initialize the atomic
* @param padding is the [[PaddingStrategy]] to apply
* @param allowPlatformIntrinsics is a boolean parameter that specifies whether
* the instance is allowed to use the Java 8 optimized operations
* for `getAndSet` and for `getAndAdd`
*/
def create[A <: AnyRef](initialValue: A, padding: PaddingStrategy, allowPlatformIntrinsics: Boolean): AtomicAny[A] =
new AtomicAny(initialValue)
/** $createDesc
*
* This builder guarantees to construct a safe atomic reference that
* does not make use of `sun.misc.Unsafe`. On top of platforms that
* don't support it, notably some versions of Android or on top of
* the upcoming Java 9, this might be desirable.
*
* NOTE that explicit usage of this builder is not usually necessary
* because [[create]] can auto-detect whether the underlying platform
* supports `sun.misc.Unsafe` and if it does, then its usage is
* recommended, because the "safe" atomic instances have overhead.
*
* @param initialValue is the initial value with which to initialize the atomic
* @param padding is the [[PaddingStrategy]] to apply
*/
def safe[A <: AnyRef](initialValue: A, padding: PaddingStrategy): AtomicAny[A] =
new AtomicAny(initialValue)
}