Sometimes I just hate Apple for their API policies.
Today I've needed libquarantine for properly handling of "com.apple.quarantine" xattr within archives (both for compressing and extracting). I've got to know that content of this xattr is handled separately when packing/unpacking into/from AppleDouble format (after some hours of searching for modern version of copyfile.c). This process involves using of <quarantine.h> API with qtn_XXX functions set (qtn_xattr_name, qtn_file_alloc, qtn_file_init_with_data etc), which are unfortunately absolutely closed. Why? No ideas, since this functions are used by many Apple-baked tools, including patched open-source ones.
As a result - Files manager won't handle such quarantine flags properly, as it expected to be. Amen.