Postcard Bindgen

Postcard Bindgen generates code for other languages to serialize and deserialize postcard byte format. This facilitates communication between, for example, a microcontroller and a mobile app using the postcard crate.

Structs and enums can be annotated with PostcardBindings to generate code. The generated code can be exported as an npm package for JavaScript or a pip package for Python.

Supported Languages

• 🌐 JavaScript (>= ES2021)
• 🐍 Python (>= 3.9)

Usage

:warning: Use rust nightly to run the crate that generates the bindings. This crate depends on genco, which uses a nightly feature.

Annotate structs and enums with Serialize/Deserialize from the serde crate and the PostcardBindings macro from this crate.

The process has two steps:

1. Annotate structs and enums in a library crate.
2. Import the annotated structs and enums in a binary crate, add the generation logic, and run the binary crate to generate the npm package.

Enable the generating feature if postcard-bindgen is added as a dependency in the generation binary crate.

Example

This example shows how to generate an npm package. The struct Test and the generation logic are in the same Rust file.

#[derive(Serialize, PostcardBindings)]
struct Test {
    name: u8,
    other: u16,
}

fn main() {
    javascript::build_package(
        std::env::current_dir().unwrap().as_path(),
        PackageInfo {
            name: "generation-test".into(),
            version: "0.1.0".try_into().unwrap(),
        },
        javascript::GenerationSettings::enable_all(),
        generate_bindings!(Test),
    )
    .unwrap();
}

The following code can now be used to serialize an object in JavaScript.

import { serialize } from "generation-test";

const test = {
    name: "test",
    other: 23
}

const bytes = serialize("Test", test)

Type mappings

struct UnitStruct;

{}

class UnitStruct:
    pass

t = UnitStruct()

struct TupleStruct(u8, u16, u32);

[123, 1234, 12345]

class TupleStruct(tuple[u8]):
    ...

t = TupleStruct(123, 1234, 12345)

struct Struct {
    a: u8,
    b: u16
};

{
    a: 123,
    b: 1234
}

@dataclass
class Struct
    a: u8
    b: u16

t = Struct(a = 123, b = 1234)

enum Enum {
    A,
    B(u8),
    C {
        a: u8
    }
};

{
    tag: "A",
},
{
    tag: "B",
    value: 123
},
{
    tag: "C",
    value: {
        a: 123
    }
}

class Enum:
    pass

class Enum_A(Enum):
    pass

class Enum_B(Enum, tuple[u8]):
    ...

@dataclass
class Enum_C(Enum)
    a: u8

a = Enum_A()
b = Enum_B(23)
c = Enum_C(a = 23)

struct OptionTuple(Option<u8>);

struct OptionStruct {
    a: Option<u8>
}

// OptionTuple(Some(123))
[123]
// OptionTuple(None)
[undefined]

// OptionStruct { a: Some(123) }
{
    a: 123
}
// OptionStruct { a: None }
{}
// or
{
    a: undefined
}

# OptionTuple(Some(123))
OptionTuple(123)
# OptionTuple(None)
OptionTuple(None)

# OptionStruct { a: Some(123) }
OptionStruct(a = 123)
# OptionStruct { a: None }
OptionStruct(a = None)

let map_string_key = HashMap::<String, u8>::new();

let map_any_key = HashMap::<u16, u8>::new();

// map_string_key
{
    key: value
}

// map_any_key
new Map()

# map_string_key
: Dict[str, u8] = {
    key: value
}

# map_any_key
: Dict[u16, u8] = {
    key: value
}

License

Licensed under either of Apache License, Version 2.0 or MIT license at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in Postcard Bindgen by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions