Service class

Base class for a C++ shared-library service accessed through dart:ffi.

A service is a shared library (.so / .dll / .dylib) that exports exactly these five C functions:

void start_service();
void stop_service();
T*   get_next_message();        // T is your message struct; nullptr = empty
void free_message(T*);
void set_message_callback(void (*cb)());  // store cb; call it when a message is ready

Instead of a periodic polling timer, each service registers a NativeCallable with set_message_callback. The C++ worker thread calls the callback whenever a new message is pushed; Dart then drains the entire queue in one shot on the event loop — zero CPU consumption at idle.

Subclassing

Extend Service to bind any additional functions your library exposes:

class ColorService extends Service {
  ColorService(super.libname) {
    getColor = lib
        .lookup<NativeFunction<Uint32 Function(Pointer<BackendMsg>)>>('get_color')
        .asFunction<int Function(Pointer<BackendMsg>)>();
  }

  late final int Function(Pointer<BackendMsg>) getColor;
}

Receiving messages

Use assignJob to register a callback that is invoked for every message:

colorService.assignJob((msg) {
  myNotifier.value = colorService.getColor(msg);
});

freeMessage is called automatically after the job returns.

Lifecycle

Add the service to a ServicePool (which calls startService for you), or subclass StandaloneService to start the service immediately. Call dispose when done.

Implementers

StandaloneService

Constructors

Service(String libname): Creates a Service by opening the shared library at libname, binding the five mandatory C functions, and registering the notification callback.

Properties

freeMessage ↔ void Function(Pointer<BackendMsg>): Bound to the C free_message() function.
getter/setter pair
getNextMessage ↔ Pointer<BackendMsg> Function(): Bound to the C get_next_message() function.
getter/setter pair
hashCode → int: The hash code for this object.
no setterinherited
lib ↔ DynamicLibrary: The opened DynamicLibrary. Available to subclasses for binding additional native functions.
getter/setter pair
libname → String: Path to the shared library, as passed to DynamicLibrary.open.
final
messageController → StreamController<Pointer<BackendMsg>>: Broadcast stream of raw message pointers drained from the C++ queue.
final
messageStream → Stream<Pointer<BackendMsg>>: The broadcast stream fed by messageController.
no setter
runtimeType → Type: A representation of the runtime type of the object.
no setterinherited
startService ↔ void Function(): Bound to the C start_service() function.
getter/setter pair
stopService ↔ void Function(): Bound to the C stop_service() function.
getter/setter pair

Methods

assignJob(void job(Pointer<BackendMsg>)) → void: Registers job as the handler invoked for every message emitted by this service.
dispose() → void: Stops the service and releases the native callback.
noSuchMethod(Invocation invocation) → dynamic: Invoked when a nonexistent method or property is accessed.
inherited
toString() → String: A string representation of this object.
inherited

Operators

operator ==(Object other) → bool: The equality operator.
inherited