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| 1 // Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file |
| 2 // for details. All rights reserved. Use of this source code is governed by a |
| 3 // BSD-style license that can be found in the LICENSE file. |
| 4 |
| 5 library barback.utils.stream_pool; |
| 6 |
| 7 import 'dart:async'; |
| 8 |
| 9 /// A pool of streams whose events are unified and emitted through a central |
| 10 /// stream. |
| 11 class StreamPool<T> { |
| 12 /// The stream through which all events from streams in the pool are emitted. |
| 13 Stream<T> get stream => _controller.stream; |
| 14 final StreamController<T> _controller; |
| 15 |
| 16 /// Subscriptions to the streams that make up the pool. |
| 17 final _subscriptions = new Map<Stream<T>, StreamSubscription<T>>(); |
| 18 |
| 19 /// Creates a new stream pool that only supports a single subscriber. |
| 20 /// |
| 21 /// Any events from broadcast streams in the pool will be buffered until a |
| 22 /// listener is subscribed. |
| 23 StreamPool() |
| 24 // Create the controller as sync so that any sync input streams will be |
| 25 // forwarded synchronously. Async input streams will have their asynchrony |
| 26 // preserved, since _controller.add will be called asynchronously. |
| 27 : _controller = new StreamController<T>(sync: true); |
| 28 |
| 29 /// Creates a new stream pool where [stream] can be listened to more than |
| 30 /// once. |
| 31 /// |
| 32 /// Any events from buffered streams in the pool will be emitted immediately, |
| 33 /// regardless of whether [stream] has any subscribers. |
| 34 StreamPool.broadcast() |
| 35 // Create the controller as sync so that any sync input streams will be |
| 36 // forwarded synchronously. Async input streams will have their asynchrony |
| 37 // preserved, since _controller.add will be called asynchronously. |
| 38 : _controller = new StreamController<T>.broadcast(sync: true); |
| 39 |
| 40 /// Adds [stream] as a member of this pool. |
| 41 /// |
| 42 /// Any events from [stream] will be emitted through [this.stream]. If |
| 43 /// [stream] is sync, they'll be emitted synchronously; if [stream] is async, |
| 44 /// they'll be emitted asynchronously. |
| 45 void add(Stream<T> stream) { |
| 46 if (_subscriptions.containsKey(stream)) return; |
| 47 _subscriptions[stream] = stream.listen(_controller.add, |
| 48 onError: _controller.addError, |
| 49 onDone: () => remove(stream)); |
| 50 } |
| 51 |
| 52 /// Removes [stream] as a member of this pool. |
| 53 void remove(Stream<T> stream) { |
| 54 var subscription = _subscriptions.remove(stream); |
| 55 if (subscription != null) subscription.cancel(); |
| 56 } |
| 57 |
| 58 /// Removes all streams from this pool and closes [stream]. |
| 59 void close() { |
| 60 for (var subscription in _subscriptions.values) { |
| 61 subscription.cancel(); |
| 62 } |
| 63 _subscriptions.clear(); |
| 64 _controller.close(); |
| 65 } |
| 66 } |
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