dart-bridge

In-process Dart ↔ Python byte transport — the C library powering serious_python's Dart-to-Python FFI bridge and (transitively) Flet's socket-free transport on flet build outputs.

This repository publishes pre-built native binaries consumed by the serious_python_* Flutter plugins. End users don't typically interact with this repo directly — they depend on serious_python (or flet) and get the bridge transparently.

What's in here

• src/dart_bridge.c — single C source containing both the Dart-callable surface (DartBridge_InitDartApiDL, DartBridge_EnqueueMessage(port, ...)) and the Python built-in module (PyInit_dart_bridge, set_enqueue_handler_func(port, callable), send_bytes(port, payload)). Statically linked together — no dlsym/dlopen plumbing needed because both halves share the keyed handler list trivially. The 64-bit Dart native port doubles as the channel key in both directions, so multiple PythonBridge instances (UI channel + logging channel + ...) coexist without colliding.
• src/serious_python_run.c — Python lifecycle: Py_Initialize, PyRun_SimpleFile / PyRun_SimpleString, env / sys.argv setup, worker- thread execution. Lifted from the platform-specific implementations in serious_python_{darwin,linux,windows,android}. Exposes serious_python_run(config) (sync or async via Dart port), serious_python_register_extension(name, init) (additional inittab entries beyond dart_bridge), serious_python_request_stop(), serious_python_finalize().
• src/dart_api/ — Dart SDK headers (vendored from the Dart SDK).

Released binaries

Every tagged release attaches the following artifacts:

Platform	Artifact
Linux x86_64	libdart_bridge-linux-x86_64.so
Linux aarch64	libdart_bridge-linux-aarch64.so
Windows x86_64 (Release CRT)	dart_bridge-windows-x86_64.dll
Windows x86_64 (Debug CRT)	dart_bridge_d-windows-x86_64.dll
Android arm64-v8a / armeabi-v7a / x86_64	libdart_bridge-android-<abi>-py<ver>.so
Apple (iOS device + iOS sim + macOS)	dart_bridge-apple.xcframework.zip

abi3 (Py_LIMITED_API=0x030c0000) makes one binary work for any CPython 3.12+ on Linux/Windows/Apple. Android is the exception: python-build- standalone ships libpython3.so as a GNU linker script that resolves to libpython3.<ver>.so, so the resulting DT_NEEDED entry is version- specific and we publish a binary per (abi × python_version).

armeabi-v7a is only published for Python 3.12 — CPython dropped 32-bit Android in 3.13+ (PEP 738).

Download URL pattern:

https://github.com/flet-dev/dart-bridge/releases/download/v<ver>/<artifact>

Local build

# Linux (uses system Python headers)
cmake -B build -S . -DCMAKE_BUILD_TYPE=Release
cmake --build build

# Apple xcframework
./apple/build_xcframework.sh

For Windows / Android cross-builds, see scripts/build_windows.ps1 and scripts/build_android.sh — they handle the toolchain setup CI uses.

Versioning

Plain semver, decoupled from CPython. The bridge is abi3-stable across all 3.12+ Pythons; one binary per (platform × arch) covers every supported runtime. serious_python pins to a specific dart-bridge version via its plugin build scripts.

License

MIT — see LICENSE.