pub const POSTAMBLE_SIZE: usize = 24;Expand description
Postamble size in v3: first_footer_offset(8) + total_length(8) + end_magic(8) = 24.
The total_length field was added in v3 to make the postamble
self-locating from any byte position inside a message — see
plans/WIRE_FORMAT.md §7 and §9.2.