CB.scala

  // sourceList from CL re-written how it is in haskell-conduit now.
  def sourceList[F[_], A](l: => Stream[A])(implicit M: Monad[F]): Source[F, A] = l match {
    case Stream.Empty => Closed[F, A]
    case x #:: xs => Open(sourceHandle(xs), M.point(()), x)
  }

  // sans IO monad:
  def sourceHandle(h: InputStream): Source[Id, Array[Byte]] = {
    val arrayBuf = new Array[Byte](4096)
    val r = h.read(arrayBuf)
    if (r == -1)
      Closed[Id, Array[Byte]]
    else
      Open(sourceHandle(h), ???, arrayBuf take r)
  }

  // With IO monad, ported straight from Haskell
  def sourceHandle[F[_]](h: InputStream)(implicit M: Monad[F]): Source[F, Array[Byte]] = {
    lazy val pull:F[Source[F, Array[Byte]]] = IO{
      val arrayBuf = new Array[Byte](4096)
      val r = h.read(arrayBuf)
      if (r == -1)
        None
      else
        Some(arrayBuf take r)
    }.liftIO map {
      case None => Closed[F, Array[Byte]]
      case Some(bytes) => Open(src, close, bytes)
    }
    val close:F[Unit] = M.point(())
    lazy val src = SourceM(pull, close)
    src
  }