Coding system question

Is it possible to set buffer-file-coding-system-for-read to a coding system such that: 1. Loading a file, modifying it, and saving it does not change its EOL type. 2. Line breaks are auto-detected (and displayed without control charatcers etc). ? I find that 'no-coding satisfies 1 but I have to live with ^M's, and that every other coding system I try uses a particular, fixed, eol type for write. I expected 'undecided to be the answer, but this strips CR's from CRLF encoded files on write. FWIW: XEmacs 21.5 (beta9) "brussels sprouts" [Lucid] (i686-pc-cygwin) of Thu Sep 26 2002 on PASTON CYGWIN_NT-5.0 PASTON 1.3.12(0.54/3/2) 2002-07-06 02:16 i686 unknown Thanks, - Phil