spray contentType filtering directive

WithContentTypeDirective.scala

import spray.http._
import shapeless.HNil
import spray.util.pimpSeq

def withContentType(ctStr: String): Directive0 = {
    def isContentType(h: HttpHeader) = h match {
      case HttpHeaders.`Content-Type`(ContentType(MediaType(mt), _))  ⇒ Some(mt)
      case _                                                          ⇒ None
    }
    extract(_.request.headers.mapFind(isContentType(_))).flatMap[HNil] {
      case Some(curr) if curr == ctStr ⇒ pass
      case x                           ⇒ reject(ContentTypeRejection(ctStr))
    } & cancelAllRejections(ofType[ContentTypeRejection])
}

case class ContentTypeRejection(ctype: String) extends Rejection


/**
 * usage example: 
 path("") {
    authUser { user ⇒
      post {
        parameters((
          'fileType.as[String],
          'fileName.as[String]?
        )) { (fileType: String, fileName: Option[String]) ⇒
          withContentType("application/octet-stream") {
            import eu.be3d.api.marshaller.OctetStreamUnmarshaller.OctetStreamUnmarshaller
            entity(as[Array[Byte]]) { bytes ⇒
              doSomethingWith(bytes)
            }
          } ~
          withContentType("application/x-data-url") {
            import eu.be3d.api.marshaller.DataUrlUnmarshallers.DataUrlUnmarshaller
            entity(as[DataUrlFile]) { contents ⇒
              doSomethingWith(contents)
            }
          }
        }
      }
    }
  }
*/