Function enc_16lsd 

unsafe fn enc_16lsd<const OFFSET: usize>(buf: &mut [MaybeUninit<u8>], n: u64)

Encodes the 16 least-significant decimals of n into buf[OFFSET .. OFFSET + 16 ].

Safety

n must be below 1e16, and buf must be at least OFFSET + 16 bytes long.