Streaming

StreamFixedLength.scala

 val route = path("download") {
    get {
      optionalHeaderValueByName("Range") {
        case None =>
          // there must always be range
          complete(StatusCodes.RequestedRangeNotSatisfiable)
        case Some(range) =>
          val file = new File("movie.mp4")
          val fileSize = file.length()
          val rng = range.split("=")(1).split("-")
          val start = rng(0).toInt
          val end = if (rng.length > 1) {
            //there is end range
            rng(1).toLong
          } else {
            fileSize - 1
          }

          respondWithHeaders(List(
            RawHeader("Content-Range", s"bytes ${start}-${end}/${fileSize}"),
            RawHeader("Accept-Ranges", s"bytes")
          )) {
            complete {
              val chunkSize = 1024 * 1000 * 4 // read 4MB of data = 4,096,000 Bytes 
              val raf = new RandomAccessFile(file, "r")
              val dataArray = Array.ofDim[Byte](chunkSize)
              raf.seek(start) // start readinng from `start` position
              val bytesRead = raf.read(dataArray, 0, chunkSize)
              val readChunk = dataArray.take(bytesRead)
              HttpResponse(StatusCodes.PartialContent,
                entity = HttpEntity(MediaTypes.`video/mp4`, readChunk))
            }
          }
      }
    }
  }