Function sanitize_stem 

pub fn sanitize_stem(name: &str) -> String

Reduces a network name to a single safe filename stem. The name comes from input content, so an unsanitized value like ../../etc/x or /abs/x used in out_dir.join(...) would write outside out_dir. Keeps ASCII alphanumerics, -, _, and .; every other character (path separators included) becomes _. Leading dots are stripped so the result is never ., .., or a hidden file; trailing dots are trimmed and Windows reserved device names get a leading _, both invalid as Windows filenames; the length is capped at 120 bytes; and an empty result falls back to case.

A name the sanitizer had to change carries a hash of the original, so two distinct names that would sanitize identically (a/b and a_b, say) cannot silently overwrite each other’s files in a multi case export. A name that already ends in the suffix shape is hashed too, so a case can never be named to impersonate another case’s disambiguated stem: the suffixed and unsuffixed name spaces stay disjoint. Any other safe name passes through unchanged.