Function emit_dotdot 

pub fn emit_dotdot(
    file: &FileObject,
    sink: &mut dyn DirentSink,
) -> Result<(), Errno>

If the offset is less than 2, emits . and .. entries for the specified file.

The offset will always be at least 2 after this function returns successfully. It’s often necessary to subtract 2 from the offset in subsequent logic.