| // Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| library async.single_subscription_transformer; |
| |
| import 'dart:async'; |
| |
| /// A transformer that converts a broadcast stream into a single-subscription |
| /// stream. |
| /// |
| /// This buffers the broadcast stream's events, which means that it starts |
| /// listening to a stream as soon as it's bound. |
| class SingleSubscriptionTransformer<S, T> implements StreamTransformer<S, T> { |
| const SingleSubscriptionTransformer(); |
| |
| Stream<T> bind(Stream<S> stream) { |
| var subscription; |
| var controller = new StreamController(sync: true, |
| onCancel: () => subscription.cancel()); |
| subscription = stream.listen(controller.add, |
| onError: controller.addError, onDone: controller.close); |
| return controller.stream; |
| } |
| } |