This doesn't answer your question directly, but it might be good enough.
If you know the native line ending convention for the platform you're on, you can look on the left side of the Emacs mode line. If the file uses a non-native convention, you should see a notation like
(Unix). If there's no notation, then that implies the native convention. From that, you can figure out what each line ends in.
So, for example, if you're running Emacs on a Unix system, and you open a file with DOS line endings, you should see
(DOS) in the lower left of the screen.
If the line ending convention in the file is inconsistently applied, then you'll see stray