cereal VS Cap'n Proto

I'd stick with cereal for serialization

Today I'm back to working on Pataro, the roguelike built on libtcod that made up much of my Hacktoberfest efforts. I had been assigned to an issue requesting the addition of serialization and deserialization, but unfortunately ran out of time and wasn't able to finish the former or start the latter. I ran into issues with Cereal, and had a hard time figuring out the structure of the program and how to go about implementing serialization for all the relevant components. At the end of that attempt I mentioned that if I were to try again I'd start by testing out Cereal separately and getting a handle on that before trying to implement it in Pataro - so that's what I'm doing today.

I am once again working on Pataro today, and I've succeeded in clearing up some issues and creating new ones. I've been stuck on an issue where Visual Studio was raising errors in the portion of the code where I call the cereal archive on some types, but was able to clear up that issue by moving the save function definitions out of their respective headers and into the corresponding .cpp files. Examining this repo and its use of cereal again, I was able to get a bit clearer of an idea of how it's implemented, and I included just about every relevant cereal header I could find to try and avoid any issues like the previous one popping up again (with the intention of later removing whichever I can to avoid redundant inclusions).

On the Pataro front, I've started looking at other examples of people using cereal for their games. It seems to be a popular choice for roguelike games like this, so hopefully I can figure out both the syntax problems I'm facing, as well as logical ones like how the program should be structured to have all the necessary data properly serialized and deserialized.

Progress on one front but roadblocks on another. After my post yesterday outlining my plans to add serialization to Pataro I ran into some issues with calling the archive class in cereal wherein the call wouldn't go through due to an incorrect number of arguments. This happened with both vector and size_t data members, and I'm still investigating why.

This is the simplest serialization library I saw. You only need to add one method to your class and you can stream it to desired archive. It supports binary as well as json, XML and others. https://github.com/USCiLab/cereal

Yeah I pretty much only use my own alternate container implementations (from KJ[0]), which avoid these footguns, but the result is everyone complains our project is written in Kenton-Language rather than C++ and there's no Stack Overflow for it and we can't hire engineers who know how to write it... oops.

[0] https://github.com/capnproto/capnproto/blob/v2/kjdoc/tour.md

- may massively reduce the latency involved.

Those sharing Cap'n Proto-encoded data may have particular interest. Cap'n Proto (https://capnproto.org) is fantastic at its core task - in-place serialization with zero-copy - and we wanted to make the IPC (inter-process communication) involving capnp-serialized messages be zero-copy, end-to-end.

That said, we paid equal attention to other varieties of payload; it's not limited to capnp-encoded messages. For example there is painless (<-- I hope!) zero-copy transmission of arbitrary combinations of STL-compliant native C++ data structures.

To help determine whether Flow-IPC is relevant to you we wrote an intro blog post. It works through an example, summarizes the available features, and has some performance results. https://www.linode.com/blog/open-source/flow-ipc-introductio...

Of course there's nothing wrong with going straight to the GitHub link and getting into the README and docs.

Currently Flow-IPC is for Linux. (macOS/ARM64 and Windows support could follow soon, depending on demand/contributions.)

FWIW, my C++ toolkit library, KJ, does the same thing.[0]

But presumably you could still write a condition predicate which looks at things which aren't actually part of the mutex-wrapped structure? Or does is the Rust type system able to enforce that the callback can only consider the mutex-wrapped value and values that are constant over the lifetime of the wait? (You need the latter e.g. if you are waiting for the mutex-wrapped value to compare equal to some local variable...)

[0] https://github.com/capnproto/capnproto/blob/e6ad6f919aeb381b...

The second one is to encode data in such a way that you can read it and operate on it directly from the buffer. You write data in a layout that is the same, or easily transformed as types in memory. To do that you usually need to encode with a known schema, only Sized types to efficiently compute fields locations as offsets in the buffer, and you usually represent pointers as offset into the encode. You can look at capnproto protocol for instance https://capnproto.org/

Worked well for Cap'n Proto (the cerealization protocol)! https://capnproto.org/

With all due respect, you read completely wrong.

* The very first use case for which Cap'n Proto was designed was to be the protocol that Sandstorm.io used to talk between sandbox and supervisor -- an explicitly adversarial security scenario.

* The documentation explicitly calls out how implementations should manage resource exhaustion problems like deep recursion depth (stack overflow risk).

* The implementation has been fuzz-tested multiple ways, including as part of Google's oss-fuzz.

* When there are security bugs, I issue advisories like this:

https://github.com/capnproto/capnproto/tree/v2/security-advi...

* The primary aim of the entire project is to be a Capability-Based Security RPC protocol.

I like how they use capability-based security [0] and use Cap'n Proto protocol. This is another technology that is slow to get broad adoption, but has many things going for when compared to e.g. Protocol Buffers (Cap'n Proto is created by the primary author of Protobuf v2, Kenton Varda).

[0] https://sandstorm.io/how-it-works#capabilities

[1] https://capnproto.org

Related but not Rust-specific: FlatBuffers, Cap'n Proto.