c indentation - replace spaces with tabs

[Micha Feigin]

Is it possible to make emacs automatically replace every 8 consecutive
spaces with a tab? (this can actually be done in indentation time
instead of write time if I menage to get the indentations right).
I am looking to get the same functionality gotten in vim for:
set ts=8
set sw=4
For example, when a line is indented 12 spaces it would be replaced with
[tab]4*[space]