/**
* Copyright (C) 2009-2011 Typesafe Inc. <http://www.typesafe.com>
*/
package scala.concurrent
//import akka.AkkaException (replaced with Exception)
//import akka.event.Logging.Error (removed all logging)
import scala.util.{ Timeout, Duration }
import scala.Option
//import akka.japi.{ Procedure, Function ⇒ JFunc, Option ⇒ JOption } (commented methods)
import java.util.concurrent.{ ConcurrentLinkedQueue, TimeUnit, Callable }
import java.util.concurrent.TimeUnit.{ NANOSECONDS ⇒ NANOS, MILLISECONDS ⇒ MILLIS }
import java.lang.{ Iterable ⇒ JIterable }
import java.util.{ LinkedList ⇒ JLinkedList }
import scala.annotation.tailrec
import scala.collection.mutable.Stack
//import akka.util.Switch (commented method)
import java.{ lang ⇒ jl }
import java.util.concurrent.atomic.{ AtomicReferenceFieldUpdater, AtomicInteger, AtomicBoolean }
import scala.collection.mutable.Builder
import scala.collection.generic.CanBuildFrom
/** The trait that represents futures.
*
* @define futureTimeout
* The timeout of the future is:
* - if this future was obtained from a task (i.e. by calling `task.future`), the timeout associated with that task
* - if this future was obtained from a promise (i.e. by calling `promise.future`), the timeout associated with that promise
*
* @define multipleCallbacks
* Multiple callbacks may be registered; there is no guarantee that they will be
* executed in a particular order.
*
* @define caughtThrowables
* The future may contain a throwable object and this means that the future failed.
* Futures obtained through combinators have the same exception as the future they were obtained from.
* The following throwable objects are not contained in the future:
* - Error - errors are not contained within futures
* - scala.util.control.ControlThrowable - not contained within futures
* - InterruptedException - not contained within futures
*
* Instead, the future is completed with a ExecutionException with one of the exceptions above
* as the cause.
*
* @define forComprehensionExamples
* Example:
*
* {{{
* val f = future { 5 }
* val g = future { 3 }
* val h = for {
* x: Int <- f // returns Future(5)
* y: Int <- g // returns Future(5)
* } yield x + y
* }}}
*
* is translated to:
*
* {{{
* f flatMap { (x: Int) => g map { (y: Int) => x + y } }
* }}}
*/
trait Future[+T] extends Blockable[T] {
self =>
/* Callbacks */
/** When this future is completed successfully (i.e. with a value),
* apply the provided function to the value.
*
* If the future has already been completed with a value,
* this will either be applied immediately or be scheduled asynchronously.
*
* Will not be called in case of an exception (this includes the FutureTimeoutException).
*
* $multipleCallbacks
*/
def onSuccess[U](func: T => U): this.type = onComplete {
case Left(t) => // do nothing
case Right(v) => func(v)
}
/** When this future is completed with a failure (i.e. with a throwable),
* apply the provided callback to the throwable.
*
* $caughtThrowables
*
* If the future has already been completed with a failure,
* this will either be applied immediately or be scheduled asynchronously.
*
* Will not be called in case that the future is completed with a value.
*
* Will be called if the future is completed with a FutureTimeoutException.
*
* $multipleCallbacks
*/
def onFailure[U](callback: PartialFunction[Throwable, U]): this.type = onComplete {
case Left(t) if t.isInstanceOf[FutureTimeoutException] || isFutureThrowable(t) => if (callback.isDefinedAt(t)) callback(t)
case Right(v) => // do nothing
}
/** When this future times out, apply the provided function.
*
* If the future has already timed out,
* this will either be applied immediately or be scheduled asynchronously.
*
* $multipleCallbacks
*/
def onTimeout[U](callback: FutureTimeoutException => U): this.type = onComplete {
case Left(te: FutureTimeoutException) => callback(te)
case Right(v) => // do nothing
}
/** When this future is completed, either through an exception, a timeout, or a value,
* apply the provided function.
*
* If the future has already been completed,
* this will either be applied immediately or be scheduled asynchronously.
*
* $multipleCallbacks
*/
def onComplete[U](func: Either[Throwable, T] => U): this.type
/* Miscellaneous */
/** The execution context of the future.
*/
def executionContext: ExecutionContext
/** Creates a new promise.
*/
def newPromise[S]: Promise[S] = executionContext promise
/** Tests whether this `Future`'s timeout has expired.
*
* $futureTimeout
*
* Note that an expired Future may still contain a value, or it may be
* completed with a value.
*/
def isTimedout: Boolean
/* Projections */
/** Returns a failed projection of this future.
*
* The failed projection is a future holding a value of type `Throwable`.
*
* It is completed with a value which is the throwable of the original future
* in case the original future is failed.
*
* It is failed with a `NoSuchElementException` if the original future is completed successfully.
*
* Blocking on this future returns a value if the original future is completed with an exception
* and throws a corresponding exception if the original future fails.
*/
def failed: Future[Throwable] = new Future[Throwable] {
def executionContext = self.executionContext
def onComplete[U](func: Either[Throwable, Throwable] => U) = {
self.onComplete {
case Left(t) => func(Right(t))
case Right(v) => func(Left(noSuchElem(v))) // do nothing
}
this
}
def isTimedout = self.isTimedout
def block()(implicit canblock: CanBlock) = try {
val res = self.block()
throw noSuchElem(res)
} catch {
case t: Throwable => t
}
private def noSuchElem(v: T) =
new NoSuchElementException("Future.failed not completed with a throwable. Instead completed with: " + v)
}
/** A timed out projection of this future.
*
* The timed out projection is a future holding a value of type `FutureTimeoutException`.
*
* It is completed with a value which is a `FutureTimeoutException` of the original future
* in case the original future is timed out.
*
* It is failed with a `NoSuchElementException` if the original future is completed successfully.
* It is failed with the original exception otherwise.
*
* Blocking on this future returns a value only if the original future timed out, and a
* corresponding exception otherwise.
*/
def timedout: Future[FutureTimeoutException] = new Future[FutureTimeoutException] {
def executionContext = self.executionContext
def onComplete[U](func: Either[Throwable, FutureTimeoutException] => U) = {
self.onComplete {
case Left(te: FutureTimeoutException) => func(Right(te))
case Left(t) => func(Left(noSuchElemThrowable(t)))
case Right(v) => func(Left(noSuchElemValue(v)))
}
this
}
def isTimedout = self.isTimedout
def block()(implicit canblock: CanBlock) = try {
val res = self.block()
throw noSuchElemValue(res)
} catch {
case ft: FutureTimeoutException =>
ft
case t: Throwable =>
throw noSuchElemThrowable(t)
}
private def noSuchElemValue(v: T) =
new NoSuchElementException("Future.timedout didn't time out. Instead completed with: " + v)
private def noSuchElemThrowable(v: Throwable) =
new NoSuchElementException("Future.timedout didn't time out. Instead failed with: " + v)
}
/* Monadic operations */
/** Creates a new future that will handle any matching throwable that this
* future might contain. If there is no match, or if this future contains
* a valid result then the new future will contain the same.
*
* Example:
*
* {{{
* future (6 / 0) recover { case e: ArithmeticException ⇒ 0 } // result: 0
* future (6 / 0) recover { case e: NotFoundException ⇒ 0 } // result: exception
* future (6 / 2) recover { case e: ArithmeticException ⇒ 0 } // result: 3
* }}}
*/
def recover[U >: T](pf: PartialFunction[Throwable, U]): Future[U] = {
val p = newPromise[U]
onComplete {
case Left(t) => if (pf isDefinedAt t) p fulfill pf(t) else p break t
case Right(v) => p fulfill v
}
p.future
}
/** Asynchronously processes the value in the future once the value becomes available.
*
* Will not be called if the future times out or fails.
*
* This method typically registers an `onSuccess` callback.
*/
def foreach[U](f: T => U): Unit = onSuccess(f)
/** Creates a new future by applying a function to the successful result of
* this future. If this future is completed with an exception then the new
* future will also contain this exception.
*
* $forComprehensionExample
*/
def map[S](f: T => S): Future[S] = {
val p = newPromise[S]
onComplete {
case Left(t) => p break t
case Right(v) => p fulfill f(v)
}
p.future
}
/** Creates a new future by applying a function to the successful result of
* this future, and returns the result of the function as the new future.
* If this future is completed with an exception then the new future will
* also contain this exception.
*
* $forComprehensionExample
*/
def flatMap[S](f: T => Future[S]): Future[S] = {
val p = newPromise[S]
onComplete {
case Left(t) => p break t
case Right(v) => f(v) onComplete {
case Left(t) => p break t
case Right(v) => p fulfill v
}
}
p.future
}
/** Creates a new future by filtering the value of the current future with a predicate.
*
* If the current future contains a value which satisfies the predicate, the new future will also hold that value.
* Otherwise, the resulting future will fail with a `NoSuchElementException`.
*
* If the current future fails or times out, the resulting future also fails or times out, respectively.
*
* Example:
* {{{
* val f = future { 5 }
* val g = g filter { _ % 2 == 1 }
* val h = f filter { _ % 2 == 0 }
* block on g // evaluates to 5
* block on h // throw a NoSuchElementException
* }}}
*/
def filter(pred: T => Boolean): Future[T] = {
val p = newPromise[T]
onComplete {
case Left(t) => p break t
case Right(v) => if (pred(v)) p fulfill v else p break new NoSuchElementException("Future.filter predicate is not satisfied by: " + v)
}
p.future
}
}
object Future {
def all[T,Coll[_] <: Traversable[_]](fs: Coll[Future[T]])(implicit cbf: CanBuildFrom[Coll[Future[T]],T,Coll[T]]): Future[Coll[T]] = {
val builder = cbf(fs)
val p: Promise[Coll[T]] = executionContext.promise[Coll[T]]
if (fs.size == 1) fs.head onComplete {
case Left(t) => p break t
case Right(v) => builder += v
p fulfill builder.result
} else {
val restFutures = all(fs.tail)
fs.head onComplete {
case Left(t) => p break t
case Right(v) => builder += v
restFuture onComplete {
case Left(t) => p break t
case Right(vs) => for (v <- vs) builder += v
p fulfill builder.result
}
}
}
p.future
}
}
