It's "structs" when the sender and receiver are using the same architecture, and if they're using the same int/long/pointer sizes then the only work to do is sw

It's "structs" when the sender and receiver are using the same architecture, and if they're using the same int/long/pointer sizes then the only work to do is swabbing and pointer validation / fixups. That's a lot less work than is needed to do just about any encoding like protocol buffers, but it's not far from flat buffers and capnp.