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Comment by dim13 | Hacker News Reader

Grandfather of Protobuf is ASN.1

Very much so. Pretty much all of these protocols are simplifications of asn1 and in some cases (like protobuf) there are a handful of things that got lost because the wire formats didn’t have them as they didn’t need them. A schema indicator being the single biggest flaw in protobuf.

Why is the lack of a schema indicator the biggest flaw of protobuf?

If you parse a serialized protobuf byte array without having a .proto file, you have no way to dustinguish a byte string field from a nested message field. Thus you have no way to know how deep your parser should go.

Semi-related, one of the `imessage-exporter` contributors provided a great write-up on reverse engineering the handwritten and digital touch message protobufs [0]. The reconstructed proto files are [1] [2].

[0]: https://github.com/trymoose/handwriting2svg/blob/0eb56cf4582...

[1]: https://github.com/ReagentX/imessage-exporter/blob/beeb853b2...

[2]: https://github.com/ReagentX/imessage-exporter/blob/beeb853b2...

It makes it impossible to write a general purpose dissector that takes captured messages or bytes and figure out how to parse it.

All they needed was a varint at the head of any marshaled from to at least provide some scoping clue.

One usually has two grandfathers, so it still works out.

The telco industry, including GSM and its successors, uses ASN.1 widely.

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