serialize::json is encouraging allocating intermediate buffers

[steveklabnik]

Issue by huonw
Tuesday Jul 01, 2014 at 23:58 GMT

For earlier discussion, see rust-lang/rust#15317

This issue was labelled with: A-libs in the Rust repository

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The Encodable/Decodable interface is designed to avoid having to allocate everything to intermediate buffers, but json is encouraging going via String. serialize::json has the top level encode function returning a String, and all the examples use encode directly, there's no demonstration of the good direct-to-Writer API.

That is, something like

println!("{}", json::encode(&x))

can be written a little like

encodable.encode(&mut json::Encoder::new(&mut io::stdout()))

If that is deemed too ugly, I think we should work on fixing the ergonomics of the good version, rather than just leaping straight to the -> String ones (e.g. json::encode(&mut io::stdout(), &x) would be nice, and work with json::encode(&mut some_file, &x), json::encode(&mut some_tcp_stream, &x), etc.).

cc @aturon

[oli-obk]

For decoding the entire source iterator is consumed, everything is converted to Json objects, and then decoded to the final type, dropping the Json objects.

[alexcrichton]

I'm going to close this now that this crate is deprecated in favor of serde. We're discontinuing feature development in rustc-serialize but will still continue to merge bug fixes if they arise.