Remove duplicate code, add helper functions and constants

Change-Id: Ib8702e2ce9918b47a608f6eb6fd2af7fd4dd1d0d
Reviewed-on: https://gerrit.libreoffice.org/23727Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: jan iversen <jani@documentfoundation.org>