Bindings to dart FFI.

Crate version corresponds to Dart SDK release

• Build your rust code as cdylib lib

• When building for mobile device, you need to build with correct target (i.e. for android-arm64 your rust target must be aarch64-linux-android)

• Place rust library into android/app/src/main/jniLibs accordingly to your target (i.e. for android-arm64 you need to place it inside arm64-v8a)

• Build flutter application;

• Refer to Dart application for next steps. Flutter embeds your library inside APK so you can refer to it by just library full name.

• Dart FFI provides API to load C shared libraries: ffi.DynamicLibrary.open(<path to shared library>);

• Once library successfully loaded, returned object can be used to lookup function pointers.

Given following rust function:

#[no_mangle]
pub unsafe extern "C" fn handle(rd: *const c_char) -> i8 {
    //Do something
    return 0;
}

You can access its pointer in following way

import 'dart:ffi' as ffi;
// External package https://pub.dev/packages/ffi
import 'package:ffi/ffi.dart' as ffiUtils;

typedef NativeFunctionT = ffi.Int8 Function(ffi.Pointer<ffiUtils.Utf8>);
typedef DartFunctionT = int Function(ffi.Pointer<ffiUtils.Utf8>);

final d = ffi.DynamicLibrary.open("my_shared_lib_name.so");
final DartFunctionT sendDataToRust = d.lookupFunction<RustRxNativeFunc, RustRxDartFunc>("handle");

/// Use function to send string data which internally converts it to C compatible char buffer.
void sendNative(DartFunctionT sendDataToRust, String d) {
    final data = d.toNativeUtf8();
    sendDataToRust(data);
    ffiUtils.calloc.free(data);
}

1. Update version in Cargo.toml to be equal to desired version of SDK

2. Run cargo build --features download-sources,build-bindings

3. Optionally run rustfmt src/lib.rs to make it pretty

4. Commit and publish