SynchronousDispatchStreamController

Synchronous notifier that implements StreamController variant with O(1) broadcast unsubscription (swap-remove) and compact tagged queues (pre-listen/pause) with lazy stack-trace capture and allocation-lean hot paths

• O(1) broadcast unsubscription (swap-remove) with a deferred sweep that avoids modifying the subscriber list mid-notification
• Compact tagged queues for pre-listen and paused delivery ([tag, payload?]) to reduce allocations and branch costs
• Lazy stack-trace capture for errors - a StackTrace is produced only if at least one listener requests it
• Allocation-lean hot paths for data/error/done to minimize overhead in tight event loops

Installation

Add to your pubspec.yaml:

dependencies:
  synchronous_stream: ^1.0.0

Import:

import 'package:synchronous_stream/synchronous_stream.dart';

Quick Start

import 'dart:async';
import 'package:notifier_stream_controller2/notifier_stream_controller2.dart';

Future<void> main() async {
  final controller = SynchronousDispatchStreamController<int>(
    onListen: () => print('onListen'),
    onPause: () => print('onPause'),
    onResume: () => print('onResume'),
    onCancel: () => print('onCancel'),
  );

  // Pre-listen buffering (single)
  controller.add(1);
  controller.add(2);

  final sub = controller.stream.listen(
    (v) => print('data: $v'),
    onError: (e, st) => print('error: $e'),
    onDone: () => print('done'),
  );

  sub.pause(Future<void>.delayed(const Duration(milliseconds: 20)));
  controller.add(3);

  await controller.close();
  await controller.done;
}