def add_data_to_hash(data, filename, hasher):
    """Contribute `filename`'s data to the `hasher`.

    `hasher` is a `coverage.misc.Hasher` instance to be updated with
    the file's data.  It should only get the results data, not the run
    data.

    """
    if data.has_arcs():
        hasher.update(sorted(data.arcs(filename) or []))
    else:
        hasher.update(sorted(data.lines(filename) or []))
    hasher.update(data.file_tracer(filename))
