boltffi_cli-0.2.0 is not a library.

BoltFFI

A high-performance multi-language bindings generator for Rust. Up to 1,000x faster than UniFFI. Up to 450x faster than wasm-bindgen.

Quick links: User Guide | Tutorial | Getting Started

Performance

vs UniFFI (Swift/Kotlin)

Benchmark	BoltFFI	UniFFI	Speedup
noop	<1 ns	1,416 ns	>1000x
echo_i32	<1 ns	1,416 ns	>1000x
counter_increment (1k calls)	1,083 ns	1,388,895 ns	1,282x
generate_locations (1k structs)	4,167 ns	1,276,333 ns	306x
generate_locations (10k structs)	62,542 ns	12,817,000 ns	205x

vs wasm-bindgen (WASM)

Benchmark	BoltFFI	wasm-bindgen	Speedup
1k particles	29,886 ns	13,532,530 ns	453x
100 particles	3,117 ns	748,287 ns	240x
1k locations	21,931 ns	4,037,879 ns	184x
1k trades	42,015 ns	5,781,767 ns	138x
100 locations	2,199 ns	283,753 ns	129x

Full benchmark code: benchmarks

Why BoltFFI?

Serialization-based FFI is slow. UniFFI serializes every value to a byte buffer. wasm-bindgen materializes every struct as a JavaScript object. That overhead shows up even when you're making tens or hundreds of FFI calls per second.

BoltFFI uses zero-copy where possible. Primitives pass as raw values. Structs with primitive fields pass as pointers to memory both sides can read directly. WASM uses a wire buffer format that avoids per-field allocation. Only strings and collections go through encoding.

What it does

Mark your Rust types with #[data] and functions with #[export]:

use boltffi::*;

#[data]
pub struct Point {
    pub x: f64,
    pub y: f64,
}

#[export]
pub fn distance(a: Point, b: Point) -> f64 {
    let dx = b.x - a.x;
    let dy = b.y - a.y;
    (dx * dx + dy * dy).sqrt()
}

Run boltffi pack:

boltffi pack apple
# Produces: ./dist/apple/YourCrate.xcframework + Package.swift

boltffi pack android
# Produces: ./dist/android/jniLibs/*.so + Kotlin bindings

boltffi pack wasm
# Produces: ./dist/wasm/pkg/*.wasm + TypeScript bindings + npm package

Use it from Swift, Kotlin, or TypeScript:

let d = distance(a: Point(x: 0, y: 0), b: Point(x: 3, y: 4)) // 5.0

val d = distance(a = Point(x = 0.0, y = 0.0), b = Point(x = 3.0, y = 4.0)) // 5.0

import { distance } from 'your-crate';
const d = distance({ x: 0, y: 0 }, { x: 3, y: 4 }); // 5.0

The generated bindings use each language's idioms. Swift gets async/await. Kotlin gets coroutines. TypeScript gets Promises. Errors become native exceptions.

Supported languages

Language	Status
Swift	Full support
Kotlin	Full support
WASM/TypeScript	Full support
Python	Planned
C#	Planned
Ruby	Planned

Want another language? Open an issue.

Installation

cargo install boltffi_cli

Add to your Cargo.toml:

[dependencies]
boltffi = "0.1"

[lib]
crate-type = ["staticlib", "cdylib"]

Documentation

Alternative tools

Other tools that solve similar problems:

UniFFI - Mozilla's binding generator, uses serialization-based approach
Diplomat - Focused on C/C++ interop
cxx - Safe C++/Rust interop

Contributing

Contributions are warmly welcomed 🙌

License

BOLTFFI is released under the MIT license. See LICENSE for more information.

boltffi_cli 0.2.0