Add Lock to std #3542
Add Lock to std #3542
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| abstract class Lock[F[_]] { | ||
| def shared: Resource[F, Unit] | ||
| def exclusive: Resource[F, Unit] | ||
| } |
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I suspect we should have an implementation here as well, apart from just HotSwap. People are almost certainly going to try to do Lock[IO].flatMap(lock => ...) and wonder why it doesn't work. :-D
| @@ -51,7 +51,7 @@ import cats.syntax.all._ | |||
| * | |||
| * Ported from https://github.com/typelevel/fs2. | |||
| */ | |||
| sealed trait Hotswap[F[_], R] { | |||
| sealed trait Hotswap[F[_], R] extends Lock[F] { | |||
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I'm not sure Hotswap should extend Lock – it seems more like an implementation detail of Hotswap.
| abstract class Lock[F[_]] { | ||
| def shared: Resource[F, Unit] | ||
| def exclusive: Resource[F, Unit] | ||
| } |
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We may want to consider adding some other APIs here. For example:
def tryShared: Resource[F, Boolean]
def tryExclusive: Resource[F, Boolean]Also should check Chris's lib for inspiration.
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Understood ! I'm working on that !
| def apply[F[_]: Concurrent](maxShared: Long): F[Lock[F]] = | ||
| Semaphore[F](maxShared).map { semaphore => | ||
| new Lock[F] { | ||
| override def shared: Resource[F, Unit] = semaphore.permit | ||
| override def exclusive: Resource[F, Unit] = | ||
| Resource.makeFull((poll: Poll[F]) => poll(semaphore.acquireN(maxShared)))(_ => | ||
| semaphore.releaseN(maxShared)) | ||
| } | ||
| } |
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We should add a test for this implementation. For example to verify that the exclusive lock is indeed exclusive.
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Definitely should be tested. It occurred to me the other day that I just didn't catch that; thanks for being on it, Arman. :-)
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Not sure this is enough for folks that want traditional locking. Like its an approach, but locks are decently diverse. |
Resolves #3535