FD_OPEN
if ((fd->sc_flags & FD_OPEN) != 0 &&
fd->sc_flags |= FD_OPEN;
fd->sc_flags &= ~FD_OPEN;
if ((fd->sc_flags & FD_OPEN) != 0 &&
fd->sc_flags |= FD_OPEN;
fd->sc_flags &= ~FD_OPEN;