Run coding system auto-detection manually?

[Kai Großjohann]

Suppose I have a buffer and hit C-x C-s.  Then Emacs figures out a
coding system to use, possibly based on the filename.

But I would like to use write-region to write the buffer contents to
another file, but I would like this call to use the same coding
system that Emacs would have used for C-x C-s.

How do I do that?

kai

PS: Background info: In the write-region handler, Tramp first writes
    the region to a local temp file and then transfers this temp file to
    the remote host via scp (say).  So the write-region handler needs
    to use the right coding system when writing the temp file.
-- 
A large number of young women don't trust men with beards.  (BFBS Radio)