dart_monty_ffi 0.8.3

Native FFI backend for dart_monty, pure Dart bindings for Monty — a restricted sandboxed Python interpreter built in Rust.

dart_monty_ffi

Part of dart_monty — pure Dart bindings for Monty, a restricted, sandboxed Python interpreter built in Rust.

Live Demo | GitHub | Monty

This package is co-designed by human and AI — nearly all code is AI-generated.

Pure Dart native FFI implementation of dart_monty. Wraps the Rust libdart_monty_native shared library via dart:ffi, providing synchronous bindings to the Monty sandboxed Python interpreter.

This package has no Flutter dependency and can be used in CLI tools, server-side Dart, or any Dart project.

• Most users should import dart_monty instead — it selects the native or web backend at compile time via conditional imports.
• Direct usage is for projects that need explicit control over the backend (e.g. custom bindings, testing).

Architecture

Dart -> NativeBindingsFfi (dart:ffi)
  -> DynamicLibrary.open(libdart_monty_native)
    -> 17 extern "C" functions (Rust)

Key Classes

Class	Description
NativeBindings	Abstract interface over the 17 native C functions
NativeBindingsFfi	Concrete FFI implementation with pointer lifecycle management
MontyFfi	MontyPlatform implementation using NativeBindings
MontyNative	Isolate-based wrapper — runs FFI calls off the main thread
NativeIsolateBindings	Abstract interface for the Isolate bridge
NativeIsolateBindingsImpl	Concrete Isolate bridge implementation
NativeLibraryLoader	Platform-aware library path resolution

MontyNative and the Isolate bridge classes were moved here from dart_monty_native in 0.7.0, making the Isolate bridge usable without Flutter (CLI tools, server-side Dart).

Cancellation

cancel() sets an atomic flag in the Monty bytecode loop via FFI, causing the interpreter to abort cooperatively. terminate() adds a 5-second timeout with zombie tracking for stuck FFI calls.

Usage

import 'package:dart_monty_ffi/dart_monty_ffi.dart';
import 'package:dart_monty_platform_interface/dart_monty_platform_interface.dart';

Future<void> main() async {
  final monty = MontyFfi();

  // Simple execution
  final result = await monty.run('2 + 2');
  print(result.value); // 4

  // External function dispatch — Python pauses when it calls fetch().
  var progress = await monty.start(
    'fetch("https://example.com")',
    externalFunctions: ['fetch'],
  );
  if (progress is MontyPending) {
    // Your app handles the call (HTTP, DB, etc.) and feeds the
    // return value back to Python. Here we just return a mock result.
    progress = await monty.resume({'status': 'ok'});
  }
  final complete = progress as MontyComplete;
  print(complete.result.value); // {status: ok}

  await monty.dispose();
}

See the main dart_monty repository for full documentation.