Comment by cryptonector | Hacker News Reader

Comment by cryptonector | Hacker News Reader

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> Structs are a part of C semantic.

Uh, no, structs, records, whatever you want to call them, are in many, if not most programming languages. "Structs" is not just "C structs" -- it's just shorthand for "structured data types" (same as in C!).

> Asn.1 is both quite complicated and not very efficient.

Every rich encoding system is complicated. As for efficiency, ASN.1 has many encoding rules, some of which are quite bad (BER/DER/CER, which are the first family of ERs, and so many thing ASN.1 == BER/DER/CER, but that's not the case), and some of which are very efficient (PER, OER). Heck, you can use XML and JSON as ASN.1 encoding rules (XER, JER).

> They could certainly have gone with protobufs or another binary serialisation format but would it really be better than the current choice?

Protocol buffers is a tag-length-value (TLV) encoding, same as BER/DER/CER. Having to have a tag and length for every value encoded is very inefficient, both in terms of encoding size as well as in terms of computation.

The better ASN.1 ERs -PER and OER- are much more akin to XDR and Flat buffers than to protobufs.

> I don’t think the issue they are trying to solve is related to serialisation anyway. Seems to me they are unhappy about the bus part not the message format part.

This definitely seems to be be the case.

It seems you posit taglessness to be a universal crucial merit of any encoding scheme. This is good in an ideal world, heh.

I have had a misfortune to work for 5G which is full of PER-encoded protocols. Dealing with discrepancies in them - incompatible changes in 3GPP standard versions, different vendorsʼ errors, combined with usually low level of developers and managers in a typical corporation - was an utter nightmare.

IETF, in general, provides a good policy combining truly fixed binary protocols when they are unavoidable (IP/TCP/UDP levels) and flexible, often text, protocols where there is no substantial overhead from their use. Their early moves, well, suffered from over-grammaticalization (as RFC822). CBOR is nice here because it combines tagness and compactness. 3-bit basic tag combined with value (if fit) or length, it is commensurable with OER in efficiency but is decodable without scheme - and it is extremely useful in practice.

> Uh, no, structs, records, whatever you want to call them

It's plenty clear from discussion context that OP is talking about C struct but yes, replace C with any languages which suit you. It will still be part of the language semantic and not an IPC specification.

The point is you can't generally use memory layout as an IPC protocol because you generally have no guarantee that it will be the same for all architectures.

If it's IPC, it's the same architecture (mostly; typically there's at most 3 local architectures). The receiver can always make right. If there's hidden remoting going on, the proxies can make things right.

> The receiver can always make right.

Certainly but that’s hardly structs anymore. You are implicitly defining a binary format which is aligned on the sender memory layout then.

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.

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