| 1 | | | import 'dart:async'; |
| 2 | | | |
| 3 | | | import '../../exceptions/squadron_error.dart'; |
| 4 | | | import '../../exceptions/squadron_exception.dart'; |
| 5 | | | |
| 6 | | | class ForwardStreamController<T> { |
| 7 | | 10 | ForwardStreamController( |
| 8 | | | {void Function()? onListen, FutureOr<void> Function()? onCancel}) { |
| 9 | | 20 | _controller = StreamController( |
| 10 | | | onListen: onListen, |
| 11 | | 10 | onPause: _pause, |
| 12 | | 10 | onResume: _resume, |
| 13 | | | onCancel: onCancel, |
| 14 | | | ); |
| 15 | | | } |
| 16 | | | |
| 17 | | | late final StreamController<T> _controller; |
| 18 | | | |
| 19 | | 30 | Stream<T> get stream => _controller.stream; |
| 20 | | | |
| 21 | | 30 | Future<void> get done => _controller.done; |
| 22 | | | |
| 23 | | | var _closed = false; |
| 24 | | 40 | bool get isClosed => _closed || _controller.isClosed; |
| 25 | | | |
| 26 | | | StreamSubscription<T>? _sub; |
| 27 | | | |
| 28 | | 20 | StreamSubscription<T>? get subscription => _sub; |
| 29 | | | |
| 30 | | 10 | void add(T data) { |
| 31 | | 30 | if (!isClosed) _controller.add(data); |
| 32 | | | } |
| 33 | | | |
| 34 | | 7 | void addError(SquadronException ex) { |
| 35 | | 21 | if (!isClosed) _controller.addError(ex); |
| 36 | | | } |
| 37 | | | |
| 38 | | 10 | Future<void> close() async { |
| 39 | | 10 | _closed = true; |
| 40 | | 20 | await _sub?.cancel(); |
| 41 | | 10 | _sub = null; |
| 42 | | 20 | _controller.close(); |
| 43 | | | } |
| 44 | | | |
| 45 | | | int _pauses = 0; |
| 46 | | | |
| 47 | | 1 | void _pause() { |
| 48 | | | // per Dart documentation https://api.dart.dev/dart-async/StreamSubscription/pause.html |
| 49 | | | // If the subscription is paused more than once, an equal number of resumes |
| 50 | | | // must be performed to resume the stream |
| 51 | | 2 | _pauses++; |
| 52 | | | } |
| 53 | | | |
| 54 | | 1 | void _resume() { |
| 55 | | 2 | if (_pauses > 0) { |
| 56 | | | // per Dart documentation https://api.dart.dev/dart-async/StreamSubscription/pause.html |
| 57 | | | // If the subscription is paused more than once, an equal number of resumes |
| 58 | | | // must be performed to resume the stream |
| 59 | | 2 | _pauses--; |
| 60 | | | } else { |
| 61 | | | // per Dart documentation https://api.dart.dev/dart-async/StreamSubscription/resume.html |
| 62 | | | // It is safe to resume even when the subscription is not paused, and the |
| 63 | | | // resume will have no effect. |
| 64 | | | } |
| 65 | | | } |
| 66 | | | |
| 67 | | 10 | void attachSubscription(StreamSubscription<T> sub) { |
| 68 | | 10 | if (_sub != null) { |
| 69 | | 0 | throw SquadronErrorImpl.create( |
| 70 | | | 'Invalid state: a subscription is already attached'); |
| 71 | | | } |
| 72 | | 10 | _sub = sub; |
| 73 | | | // pass pending pause events on to the subscription |
| 74 | | 20 | while (_pauses > 0) { |
| 75 | | 2 | _pauses--; |
| 76 | | 1 | sub.pause(); |
| 77 | | | } |
| 78 | | | // have the subscription handle pause/resume events from now on |
| 79 | | 30 | _controller.onPause = sub.pause; |
| 80 | | 30 | _controller.onResume = sub.resume; |
| 81 | | | // have the subscription handle the cancel event if the controller doesn't |
| 82 | | | // handle it already |
| 83 | | 30 | _controller.onCancel ??= sub.cancel; |
| 84 | | | } |
| 85 | | | } |