def read()

in util-core/src/main/scala/com/twitter/io/FutureReader.scala [23:61]
33 lines of code
11 McCabe index (conditional complexity)

  def read(): Future[Option[A]] = {
    val (updatedState, result) = synchronized {
      val result = state match {
        case State.Idle =>
          fa.transform {
            case Throw(t) =>
              state = State.Failed(t)
              Future.exception(t)
            case Return(v) =>
              state = State.Read
              Future.value(Some(v))
          }
        case State.Read =>
          state = State.FullyRead
          Future.None
        case State.Failed(_) =>
          // closep is guaranteed to be an exception, flatMap
          // should never be triggered but return the exception
          closep.flatMap(_ => Future.None)
        case State.FullyRead =>
          Future.None
        case State.Discarded =>
          Future.exception(new ReaderDiscardedException)
      }
      (state, result)
    }

    updatedState match {
      case State.Failed(t) =>
        // use `updateIfEmpty` instead of `update` here because we don't want to throw
        // `ImmutableResult` exception when reading from a failed `FutureReader` multiple times
        closep.updateIfEmpty(Throw(t))
      case State.FullyRead =>
        closep.updateIfEmpty(StreamTermination.FullyRead.Return)
      case _ =>
    }

    result
  }