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Avoid boxing in ScopedResource.State internals #3140

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Avoid boxing in ScopedResource.State internals #3140

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36 changes: 19 additions & 17 deletions core/shared/src/main/scala/fs2/internal/ScopedResource.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -108,15 +108,17 @@ private[internal] object ScopedResource {
*/
private[this] final case class State[+F[_]](
open: Boolean,
finalizer: Option[Resource.ExitCase => F[Either[Throwable, Unit]]],
finalizer: Resource.ExitCase => F[
Either[Throwable, Unit]
], // or null which is used as an Optional type to avoid boxing
leases: Int
) {
/* The `isFinished` predicate indicates that the finalizer can be run at the present state:
which happens IF it is closed, AND there are no acquired leases pending to be released. */
@inline def isFinished: Boolean = !open && leases == 0
}

private[this] val initial = State(open = true, finalizer = None, leases = 0)
private[this] val initial = State(open = true, finalizer = null, leases = 0)

def create[F[_]](implicit F: Compiler.Target[F]): F[ScopedResource[F]] =
for {
Expand All @@ -129,17 +131,20 @@ private[internal] object ScopedResource {
private[this] val pru: F[Either[Throwable, Unit]] =
(Right(()): Either[Throwable, Unit]).pure[F]

private[this] val prtrue: F[Either[Throwable, Boolean]] =
F.pure(Right(true))

def release(ec: Resource.ExitCase): F[Either[Throwable, Unit]] =
state
.modify { s =>
if (s.leases != 0)
// do not allow to run finalizer if there are leases open
(s.copy(open = false), None)
(s.copy(open = false), null)
else
// reset finalizer to None, will be run, it available, otherwise the acquire will take care of it
(s.copy(open = false, finalizer = None), s.finalizer)
// reset finalizer to null, will be run, it available, otherwise the acquire will take care of it
(s.copy(open = false, finalizer = null), s.finalizer)
}
.flatMap(finalizer => finalizer.map(_(ec)).getOrElse(pru))
.flatMap(finalizer => if (finalizer ne null) finalizer(ec) else pru)

def acquired(finalizer: Resource.ExitCase => F[Unit]): F[Either[Throwable, Boolean]] =
state.modify { s =>
Expand All @@ -149,10 +154,7 @@ private[internal] object ScopedResource {
else {
val attemptFinalizer = (ec: Resource.ExitCase) => finalizer(ec).attempt
// either state is open, or leases are present, either release or `Lease#cancel` will run the finalizer
s.copy(finalizer = Some(attemptFinalizer)) -> (Right(true): Either[
Throwable,
Boolean
]).pure[F]
s.copy(finalizer = attemptFinalizer) -> prtrue
}
}.flatten

Expand All @@ -171,17 +173,17 @@ private[internal] object ScopedResource {
val now = s.copy(leases = s.leases - 1)
now -> now
}
.flatMap { now =>
if (now.isFinished)
.flatMap {
case now if now.isFinished =>
state.modify { s =>
// Scope is closed and this is last lease, assure finalizer is removed from the state and run
// previous finalizer shall be always present at this point, this shall invoke it
s.copy(finalizer = None) -> (s.finalizer match {
case Some(ff) => ff(Resource.ExitCase.Succeeded)
case None => pru
})
s.copy(finalizer = null) ->
(if (s.finalizer ne null)
s.finalizer(Resource.ExitCase.Succeeded)
else pru)
}.flatten
else
case _ =>
pru
}
}
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