Playframework BodyParsers multipartParser (source: https://github.com/playframework/playframework/blob/92078f9cc751a5c19117dede18c7ca63aca73347/framework/src/play/src/main/scala/play/api/mvc/ContentTypes.scala#L615)

BodyParsersMultipartParser.scala

def multipartParser[A](partHandler: Map[String, String] => Iteratee[Array[Byte], A]):
    BodyParser[Seq[A]] = parse.using { request =>

  val maybeBoundary = for {
    mt <- request.mediaType
    (_, value) <- mt.parameters.find(_._1.equalsIgnoreCase("boundary"))
    boundary <- value
  } yield ("\r\n--" + boundary).getBytes("utf-8")

  maybeBoundary.map { boundary =>

    BodyParser { request =>

      // implementation with some iteratee fu

    }

  }.getOrElse(parse.error(createBadResult("Missing boundary header")(request)))

}