Packages

abstract class MVar[A] extends AnyRef

A mutable location, that is either empty or contains a value of type A.

It has 2 fundamental atomic operations:

  • put which fills the var if empty, or blocks (asynchronously) until the var is empty again
  • take which empties the var if full, returning the contained value, or blocks (asynchronously) otherwise until there is a value to pull

The MVar is appropriate for building synchronization primitives and performing simple inter-thread communications. If it helps, it's similar with a BlockingQueue(capacity = 1), except that it doesn't block any threads, all waiting being done asynchronously by means of Task.

Given its asynchronous, non-blocking nature, it can be used on top of Javascript as well.

Inspired by Control.Concurrent.MVar from Haskell and by scalaz.concurrent.MVar.

Source
MVar.scala
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Instance Constructors

  1. new MVar()

Abstract Value Members

  1. abstract def put(a: A): Task[Unit]

    Fills the MVar if it is empty, or blocks (asynchronously) if the MVar is full, until the given value is next in line to be consumed on take.

    Fills the MVar if it is empty, or blocks (asynchronously) if the MVar is full, until the given value is next in line to be consumed on take.

    This operation is atomic. *

    returns

    a task that on evaluation will complete when the put operation succeeds in filling the MVar, with the given value being next in line to be consumed

  2. abstract def read: Task[A]

    Tries reading the current value, or blocks (asynchronously) until there is a value available, at which point the operation resorts to a take followed by a put.

    Tries reading the current value, or blocks (asynchronously) until there is a value available, at which point the operation resorts to a take followed by a put.

    This read operation is equivalent to:

    for (a <- v.take; _ <- v.put(a)) yield a

    This operation is not atomic. Being equivalent with a take followed by a put, in order to ensure that no race conditions happen, additional synchronization is necessary. See TaskSemaphore for a possible solution.

    returns

    a task that on evaluation will be completed after a value has been read

  3. abstract def take: Task[A]

    Empties the MVar if full, returning the contained value, or blocks (asynchronously) until a value is available.

    Empties the MVar if full, returning the contained value, or blocks (asynchronously) until a value is available.

    This operation is atomic.

    returns

    a task that on evaluation will be completed after a value was retrieved

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