serde_rustler 0.0.2

Serializer and Deserializer traits for Rustler NIFs
Documentation

serde_rustler

Crates.io Documentation MIT license

serde_rustler provides a Serde Serializer and Deserializer for Rustler types, so you can easily serialize and deserialize native Rust types directly to and from native Elixir terms within your NIFs.

Installation

Install from Crates.io:

[dependencies]
serde_rustler = "0.0.2"

API Overview

Below is an example of how you might use serde_rustler within a rust NIF:

#[macro_use]
extern crate rustler;

use rustler::{Env, error::Error as NifError, NifResult, Term};
use serde::{Serialize, Deserialize};
use serde_rustler::{from_term, to_term};

rustler_export_nifs! {
    "Elixir.SerdeNif",
    [("readme", 1, readme)],
    None
}

// NOTE: to serialize to the correct Elixir record, you MUST tell serde to
// rename the variants to the full Elixir record module atom.
#[derive(Debug, Serialize, Deserialize)]
enum AnimalType {
    #[serde(rename = "Elixir.SerdeNif.AnimalType.Cat")]
    Cat(String),
    #[serde(rename = "Elixir.SerdeNif.AnimalType.Dog")]
    Dog(String),
}

// NOTE: to serialize to an actual Elixir struct (rather than a just map with
// a :__struct__ key), you MUST tell serde to rename the struct to the full
// Elixir struct module atom.
#[derive(Debug, Serialize, Deserialize)]
#[serde(rename = "Elixir.SerdeNif.Animal")]
struct Animal {
    #[serde(rename = "type")]
    _type: AnimalType,
    name: String,
    age: u8,
    owner: Option<String>,
}

fn readme<'a>(env: Env<'a>, args: &[Term<'a>]) -> NifResult<Term<'a>> {
    let animal: Animal = from_term(args[0]).or(Err(NifError::BadArg))?;

    println!("serialized animal: {:?}", animal);

    to_term(env, animal).or(Err(NifError::BadArg))
}

Corresponding Elixir code (code structure, imports, aliases and requires simplified or omitted for brevity):

defmodule SerdeNif do
  use Rustler, otp_app: :serde_nif

  def readme(_term), do: :erlang.nif_error(:nif_not_loaded)

  defmodule Animal do
    @type t :: %Animal{
      type: Cat.t() | Dog.t(),
      name: bitstring,
      age: pos_integer,
      owner: nil | bitstring
    }
    defstruct type: Cat.record(), name: "", age: 0, owner: nil

    @doc "Deserializes term as a Rust `Animal` struct, then serializes it back into an Elixir `Animal` struct. Should return true."
    def test() do
      animal = %Animal{
        type: Animal.Cat.record(),
        name: "Garfield",
        age: 41,
      }

      SerdeNif.readme(animal) == animal
    end
  end

  defmodule AnimalType.Cat do
    require Record
    @type t {__MODULE__, String.t()}
    Record.defrecord(:record, __MODULE__, breed: "tabby")
  end

  defmodule AnimalType.Dog do
    require Record
    @type t {__MODULE__, String.t()}
    Record.defrecord(:record, :Dog, breed: "mutt")
  end
end

Conversion Table

Type Name Serde (Rust) Values Elixir Terms (default behaviour)
bool true or false true or false
1 number i8, i16, i32, i64, u8, u16, u32, u64, f32, f64 (TODO: i128 and u128) number
1 char "" bitstring
string "" bitstring
2 byte array &[u8] or Vec<u8> <<_::_*8>>
option Some(T) or None T or :nil
unit None :nil
unit struct struct Unit :nil
3 unit variant E::A in enum UnitVariant { A } :A
3 newtype struct struct Millimeters(u8) {:Millimeters, u8}
3 newtype variant E::N in enum E { N(u8) } {:N, u8}
newtype variant (any Ok and Err tagged enum) enum R<T, E> { Ok(T), Err(E) } {:ok, T} or {:error, E}
seq Vec<T> [T]
tuple (u8,) {u8,}
3 tuple struct struct Rgb(u8, u8, u8) {:Rgb, u8, u8, u8}
3 tuple variant E::T in enum E { T(u8, u8) } {:T, u8, u8}
1 map HashMap<K, V> %{}
3 struct struct Rgb { r: u8, g: u8, b: u8 } %Rgb{ r: byte, g: byte, b: byte }
3 struct variant E::S in enum E { Rgb { r: u8, g: u8, b: u8 } } %Rgb{ r: byte, g: byte, b: byte }

1: API still being decided / implemented.

2: Requires specifying a specific serialize implementation, such as serde_bytes.

3: When serializing unknown input to terms, atoms will not be created and will instead be replaced with Elixir bitstrings. Therefore "records" will be tuples ({bitstring, ...}) and "structs" will be maps containing %{:__struct__ => bitstring}. The unfortunate consequence of this is that deserialize_any will lack the necessary information needed deserialize many terms without type hints, such as structs, enums and enum variants, and tuples. (Feedback on how best to solve this is very welcome here).

TODO

  • finalize behaviour around chars, charlists, iolists, map keys
  • still getting used to Rust, so may need to improve error handling nnd ergnomoics around API
  • support for i128 and u128
  • more extensive (i.e. possible addition of smoke, property-based) testing
  • benchmarking

Changelog

Version Change Summary
v0.0.2 cleanup, better deserialize_any support
v0.0.1 initial release

Contributing

  1. Fork it https://github.com/your_username/serde_rustler/fork
  2. Create your feature branch (git checkout -b feature/fooBar)
  3. Commit your changes (git commit -am 'Add some fooBar')
  4. Push to the branch (git push origin feature/fooBar)
  5. Create a new Pull Request

Maintainers

License

MIT