MessagePack support

[3Hren]

Does anyone need MessagePack support?

I can implement it in https://github.com/3Hren/msgpack-rust as an option.

It's not an issue actually, but it may generate issues if I start to working with it :)

[erickt]

That would be wonderful! If you haven't starting working on it yet, I think I have a partially implemented version I started and didn't finish months ago.

[dswd]

I am working on that. It seems to work pretty well except for enums which are very complicated as each variant can have a different type. How should I publish the code?
Should I make a separate crate or should I create a pull request?
BTW: I also have some macros which allow to serialize structs to tuples and maps without using a compiler plugin.

[3Hren]

Actually I've already have rustc_serialize support in RMP: https://github.com/3Hren/msgpack-rust/blob/master/src/decode.rs#L1754.
Migrating from it to serde doesn't seems like a big problem.

The real challenge - is to how implement zero-copy deserialization into a non-owning structs, which contains &str or &[T] for example. Does serde allows to do that somehow?

Personally I want to make RMP the main Rust MessagePack library.

PR is ok if only serde plans to be the main serialization/deserialization library for Rust (and rustc_serialize is going to be dead, right?). Otherwise the separate crate is the only meaningful option.

[dswd]

My main problem with rmp, mpack and msgpack was that neither of them allowed me to serialize [u8] to msgpack bin. Instead all rustc-serialize based serializers serialize [u8] as a list of single u8 which is very inefficient as half of those bytes require two bytes to serialize.

[3Hren]

Wrong: https://github.com/3Hren/msgpack-rust/blob/master/src/encode.rs#L646

Oops, it's private right now :( I'll make an update ASAP.

UPD: If you have problems with RMP you should definitely create an issue :)
UPD2: Done: v0.4.0. You're welcome.

[dswd]

Yes, you are right. However I did not figure out any way to use that with rustc-serialize.

[3Hren]

With rustc_serialize - you're right, it's impossible. Does serde allows to encode &[u8] directly?

[dswd]

Not exactly but there is a wrapper type Bytes which serializes to bin. I don't think such a wrapper type would be possible with rustc_serialize as it does not expose any way to serialize binary data through its API.

[erickt]

@3Hren and @dswd: I've also hacked up msgpack support in 3Hren/msgpack-rust#26.

[erickt]

This has landed in rmp!

[dswd]

I don't see how this improves on the &[u8] issue. As far as I can see rmp still does not support it. There is no way to serialize something to binary data and you get a type mismatch error if you try to deserialize it.

[3Hren]

Does this help with deserializing: 3Hren/msgpack-rust@380a68b?

[3Hren]

And this should help with serialization: 3Hren/msgpack-rust@6c1f7c1