Receive HTTP file uploads as a stream

I am currently porting an akka-http project to Finagle. One feature I liked about akka-http is that it exposes file uploads as a stream. In Finagle, large files may get written to disk. Furthermore, the interface for accessing the content of file uploads is slightly inconvenient, requiring me to use pattern matching several times:

val r = req.multipart.flatMap(
  _.files.collectFirst {
    case (k, v) if k == "file" => v
  }.flatMap(_.headOption))

val file = r.map match {
  case d: http.exp.Multipart.OnDiskFileUpload   => d.content
  case m: http.exp.Multipart.InMemoryFileUpload =>
    m.content match {
      case Buf.ByteArray.Owned(bytes, _, _) =>
        val f = File.createTempFile("upload", ".tmp")
        val fw = new FileOutputStream(f)
        fw.write(bytes)
        fw.close()
        f
    }
}