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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 watcher.directory_watcher.resubscribable; |
| 6 |
| 7 import 'dart:async'; |
| 8 import 'dart:io'; |
| 9 |
| 10 import '../directory_watcher.dart'; |
| 11 import '../utils.dart'; |
| 12 import '../watch_event.dart'; |
| 13 |
| 14 typedef ManuallyClosedDirectoryWatcher WatcherFactory(); |
| 15 |
| 16 /// A wrapper for [ManuallyClosedDirectoryWatcher] that encapsulates support for |
| 17 /// closing the watcher when it has no subscribers and re-opening it when it's |
| 18 /// re-subscribed. |
| 19 /// |
| 20 /// It's simpler to implement watchers without worrying about this behavior. |
| 21 /// This class wraps a watcher class which can be written with the simplifying |
| 22 /// assumption that it can continue emitting events until an explicit `close` |
| 23 /// method is called, at which point it will cease emitting events entirely. The |
| 24 /// [ManuallyClosedDirectoryWatcher] interface is used for these watchers. |
| 25 /// |
| 26 /// This would be more cleanly implemented as a function that takes a class and |
| 27 /// emits a new class, but Dart doesn't support that sort of thing. Instead it |
| 28 /// takes a factory function that produces instances of the inner class. |
| 29 abstract class ResubscribableDirectoryWatcher implements DirectoryWatcher { |
| 30 /// The factory function that produces instances of the inner class. |
| 31 final WatcherFactory _factory; |
| 32 |
| 33 final String directory; |
| 34 |
| 35 Stream<WatchEvent> get events => _eventsController.stream; |
| 36 StreamController<WatchEvent> _eventsController; |
| 37 |
| 38 bool get isReady => _readyCompleter.isCompleted; |
| 39 |
| 40 Future get ready => _readyCompleter.future; |
| 41 var _readyCompleter = new Completer(); |
| 42 |
| 43 /// Creates a new [ResubscribableDirectoryWatcher] wrapping the watchers |
| 44 /// emitted by [_factory]. |
| 45 ResubscribableDirectoryWatcher(this.directory, this._factory) { |
| 46 var watcher; |
| 47 var subscription; |
| 48 |
| 49 _eventsController = new StreamController<WatchEvent>.broadcast( |
| 50 onListen: () { |
| 51 watcher = _factory(); |
| 52 subscription = watcher.events.listen(_eventsController.add, |
| 53 onError: _eventsController.addError, |
| 54 onDone: _eventsController.close); |
| 55 |
| 56 // It's important that we complete the value of [_readyCompleter] at the |
| 57 // time [onListen] is called, as opposed to the value when [watcher.ready] |
| 58 // fires. A new completer may be created by that time. |
| 59 watcher.ready.then(_readyCompleter.complete); |
| 60 }, onCancel: () { |
| 61 // Cancel the subscription before closing the watcher so that the |
| 62 // watcher's `onDone` event doesn't close [events]. |
| 63 subscription.cancel(); |
| 64 watcher.close(); |
| 65 _readyCompleter = new Completer(); |
| 66 }, sync: true); |
| 67 } |
| 68 } |
| 69 |
| 70 /// An interface for watchers with an explicit, manual [close] method. |
| 71 /// |
| 72 /// See [ResubscribableDirectoryWatcher]. |
| 73 abstract class ManuallyClosedDirectoryWatcher implements DirectoryWatcher { |
| 74 /// Closes the watcher. |
| 75 /// |
| 76 /// Subclasses should close their [events] stream and release any internal |
| 77 /// resources. |
| 78 void close(); |
| 79 } |
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