diff options
Diffstat (limited to 'src')
-rw-r--r-- | src/library/scala/concurrent/ExecutionContext.scala | 8 | ||||
-rw-r--r-- | src/library/scala/concurrent/impl/Promise.scala | 12 |
2 files changed, 17 insertions, 3 deletions
diff --git a/src/library/scala/concurrent/ExecutionContext.scala b/src/library/scala/concurrent/ExecutionContext.scala index 8081bb32da..ac462ac9d2 100644 --- a/src/library/scala/concurrent/ExecutionContext.scala +++ b/src/library/scala/concurrent/ExecutionContext.scala @@ -12,6 +12,7 @@ package scala.concurrent import java.util.concurrent.{ ExecutorService, Executor } import scala.concurrent.util.Duration import scala.annotation.implicitNotFound +import scala.util.Try /** * An `ExecutionContext` is an abstraction over an entity that can execute program logic. @@ -27,6 +28,13 @@ trait ExecutionContext { */ def reportFailure(t: Throwable): Unit + /** Prepares for the execution of callback `f`. Returns the prepared + * execution context which should be used to schedule the execution + * of the task associated with `f`. + */ + def prepare[T, U](f: Try[T] => U): ExecutionContext = + this + } /** diff --git a/src/library/scala/concurrent/impl/Promise.scala b/src/library/scala/concurrent/impl/Promise.scala index fab6b55c52..9f30529dc8 100644 --- a/src/library/scala/concurrent/impl/Promise.scala +++ b/src/library/scala/concurrent/impl/Promise.scala @@ -22,7 +22,9 @@ private[concurrent] trait Promise[T] extends scala.concurrent.Promise[T] with sc def future: this.type = this } -private class CallbackRunnable[T](val executor: ExecutionContext, val onComplete: (Try[T]) => Any) extends Runnable with OnCompleteRunnable { +/* Precondition: `executor` is prepared, i.e., `executor` has been returned from invocation of `prepare` on some other `ExecutionContext`. + */ +private class CallbackRunnable[T](val executor: ExecutionContext, val onComplete: Try[T] => Any) extends Runnable with OnCompleteRunnable { // must be filled in before running it var value: Try[T] = null @@ -34,6 +36,8 @@ private class CallbackRunnable[T](val executor: ExecutionContext, val onComplete def executeWithValue(v: Try[T]): Unit = { require(value eq null) // can't complete it twice value = v + // Note that we cannot prepare the ExecutionContext at this point, since we might + // already be running on a different thread! executor.execute(this) } } @@ -125,7 +129,8 @@ private[concurrent] object Promise { } def onComplete[U](func: Try[T] => U)(implicit executor: ExecutionContext): Unit = { - val runnable = new CallbackRunnable[T](executor, func) + val preparedEC = executor.prepare(func) + val runnable = new CallbackRunnable[T](preparedEC, func) @tailrec //Tries to add the callback, if already completed, it dispatches the callback to be executed def dispatchOrAddCallback(): Unit = @@ -151,7 +156,8 @@ private[concurrent] object Promise { def onComplete[U](func: Try[T] => U)(implicit executor: ExecutionContext): Unit = { val completedAs = value.get - (new CallbackRunnable(executor, func)).executeWithValue(completedAs) + val preparedEC = executor.prepare(func) + (new CallbackRunnable(preparedEC, func)).executeWithValue(completedAs) } def ready(atMost: Duration)(implicit permit: CanAwait): this.type = this |