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package eu.mulk.fibers
import monix.eval.Task
import monix.execution.Ack.{Continue, Stop}
import monix.execution.cancelables.MultiAssignmentCancelable
import monix.execution.{Cancelable, Scheduler}
import monix.reactive.{Observable, OverflowStrategy}
import scala.concurrent.{ExecutionContext, Future}
import scala.util.Try
import scala.util.continuations.{reset, shift}
import scala.util.control.NonFatal
/**
* Fiber-related functionality.
*/
object Fiber extends FiberConversions with FiberTypes {
sealed trait Effect[-Out] { type Result }
private[this] object Effect {
case object Finish extends Effect[Any] {
override type Result = Nothing
}
case class AwaitTask[T](task: Task[T], scheduler: Scheduler)
extends Effect[Any] {
override type Result = Try[T]
}
case class AwaitFuture[T](future: Future[T],
executionContext: ExecutionContext)
extends Effect[Any] {
override type Result = Try[T]
}
case class Fail(throwable: Throwable) extends Effect[Any] {
override type Result = Nothing
}
case class Emit[-T](returnValue: T) extends Effect[T] {
override type Result = Unit
}
case object GetFiberVar extends Effect[Any] {
override type Result = Any
}
case class PutFiberVar(value: Any) extends Effect[Any] {
override type Result = Unit
}
}
private[this] final class FiberState {
var fiberVar: Any = _
}
private[this] def perform[Out](
effect: Effect[Out]): effect.Result @fiber[Out] = {
val result = shift { (k: Any ⇒ Any) ⇒
(effect, k)
}
result.asInstanceOf[effect.Result]
}
/**
* Runs and awaits the completion of a [[monix.eval.Task]].
*
* Returns either a [[scala.util.Success]] or [[scala.util.Failure]] depending on
* the result of the [[scala.concurrent.Future]]. If you prefer raising an exception
* instead, consider destructuring the return value:
*
* val Success(x) = await(...)
*
* The supplied [[Scheduler]] is used to run the continuation of the fiber.
*/
def await[T, Out](task: Task[T])(
implicit scheduler: Scheduler): Try[T] @fiber[Out] =
perform(Effect.AwaitTask(task, scheduler))
/**
* Awaits the completion of a [[scala.concurrent.Future]].
*
* Returns either a [[scala.util.Success]] or [[scala.util.Failure]] depending on
* the result of the [[scala.concurrent.Future]]. If you prefer raising an exception
* instead, consider destructuring the return value:
*
* val Success(x) = await(...)
*/
def await[T, Out](fut: Future[T])(
implicit ec: ExecutionContext): Try[T] @fiber[Out] =
perform(Effect.AwaitFuture(fut, ec))
/**
* Emits a value to the output [[monix.reactive.Observable]].
*/
def emit[Out](x: Out): Unit @fiber[Out] =
perform(Effect.Emit(x))
/**
* Replaces the current fiber-local state variable.
*
* This can be used like a thread-local variable, but for fibers.
*
* @see [[getFiberVar]]
*/
def putFiberVar[Out](x: Any): Unit @fiber[Out] =
perform(Effect.PutFiberVar(x))
/**
* Gets the current fiber-local state variable.
*
* The fiber-local state must have been set with [[putFiberVar]] before.
*
* @see [[putFiberVar]]
*/
def getFiberVar[Out]: Any @fiber[Out] =
perform(Effect.GetFiberVar)
/**
* Runs a fiber.
*
* @tparam Out the type of objects [[Fiber.emit]]ted by the fiber.
* @return a [[monix.reactive.Observable]] producing the objects
* [[Fiber.emit]]ted by the fiber.
*/
def run[Out](thunk: ⇒ Unit @fiber[Out]): Observable[Out] = {
val state = new FiberState
monix.reactive.Observable.create[Out](OverflowStrategy.Unbounded) { out ⇒
val cancelable = MultiAssignmentCancelable()
def handle(init: (Effect[Out], Any ⇒ Any)): Unit = {
var more = init
var done = false
cancelable := Cancelable { () ⇒
out.onComplete()
done = true
}
while (!done) {
try {
val (effect, continue) = more
effect match {
case Effect.AwaitTask(task, scheduler) ⇒
task.asyncBoundary.runOnComplete({ result ⇒
val k = continue(result)
handle(k.asInstanceOf[(Effect[Out], Any ⇒ Any)])
})(scheduler)
done = true
case Effect.AwaitFuture(task, executionContext) ⇒
task.onComplete({ result ⇒
val k = continue(result)
handle(k.asInstanceOf[(Effect[Out], Any ⇒ Any)])
})(executionContext)
done = true
case Effect.GetFiberVar ⇒
more = continue(state.fiberVar)
.asInstanceOf[(Effect[Out], Any ⇒ Any)]
case Effect.PutFiberVar(value) ⇒
state.fiberVar = value
more = continue(()).asInstanceOf[(Effect[Out], Any ⇒ Any)]
case Effect.Emit(returnValue) ⇒
out.onNext(returnValue.asInstanceOf[Out]) match {
case _: Continue ⇒
more = continue(()).asInstanceOf[(Effect[Out], Any ⇒ Any)]
case _: Stop ⇒
cancelable.cancel()
}
case Effect.Fail(throwable) ⇒
out.onError(throwable)
done = true
case Effect.Finish ⇒
out.onComplete()
done = true
}
} catch {
case NonFatal(err) ⇒
out.onError(err)
done = true
}
}
}
try {
val (effect, continue): (Effect[Out], Any ⇒ Any) = reset {
thunk
(Effect.Finish, (_: Any) ⇒ ???)
}
handle(effect, continue)
} catch {
case NonFatal(err) ⇒
out.onError(err)
}
cancelable
}
}
}
|
