sink.write(boundaryByteString)
      sink.write(CRLF)

      if (headers != null) {
        for (h in 0 until headers.size) {
          sink.writeUtf8(headers.name(h))
            .write(COLONSPACE)
            .writeUtf8(headers.value(h))
            .write(CRLF)
        }
      }

      val contentType = body.contentType()
      if (contentType != null) {
        sink.writeUtf8("Content-Type: ")