How to serialize a 3rd party container?

[magras]

There is a way to deserialize a 3rd party container like that:

#[binread]
struct S {
  #[br(temp)]
  len: u8,
  #[br(parse_with = binrw::helpers::count(len as usize))]
  container: arrayvec::ArrayVec<u8, 255>,
}

But how to serialize this container? Is it possible only with custom #[writer]?

[csnover]

Hi, and thanks for your question! If the third-party container can be converted to a slice, then it can be written by e.g. #[bw(map = |c| &c[..])], which will then use binrw’s built-in write implementation for slices.

[magras]

@csnover, thank you, it works perfectly with arrayvec.
For others, I find #[bw(map = AsRef::as_ref)] to be slightly more readable, but it's a matter of personal preference.

While I don't need it at the moment, I'm still curious if there's an attribute that can take IntoIterator or similar trait for non-contiguous containers like VecDeque.

[csnover]

I'm still curious if there's an attribute that can take IntoIterator or similar trait for non-contiguous containers like VecDeque.

Right now there isn’t anything within binrw like that, but only for historical reasons (binrw started life as a read-only library). It’s definitely something that is desired, though! It just requires a community contribution. I think right now there is only a tracking ticket for the specific issue of handling write-indirection, at #4. It would be fine to open an enhancement request, or, author some write-versions of the existing helpers and submit a PR. :-)

[magras]

I'm not entirely sure if I'm qualified to write library code in rust. I've had some troubles without generic specialization when dealing with conflicts between IntoIterator and concrete container types. However, if I manage to develop a working solution, I'd be happy to contribute it.