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Unified Diff: pkg/watcher/lib/src/directory_watcher/resubscribable.dart

Issue 46843003: Wrap Directory.watch on linux for the watcher package. (Closed) Base URL: https://dart.googlecode.com/svn/branches/bleeding_edge/dart
Patch Set: code review Created 7 years, 1 month ago
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Index: pkg/watcher/lib/src/directory_watcher/resubscribable.dart
diff --git a/pkg/watcher/lib/src/directory_watcher/resubscribable.dart b/pkg/watcher/lib/src/directory_watcher/resubscribable.dart
new file mode 100644
index 0000000000000000000000000000000000000000..daa813a3e35c63bbdf4b4ac0d72b93eefec0d68e
--- /dev/null
+++ b/pkg/watcher/lib/src/directory_watcher/resubscribable.dart
@@ -0,0 +1,79 @@
+// Copyright (c) 2013, 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 watcher.directory_watcher.resubscribable;
+
+import 'dart:async';
+import 'dart:io';
+
+import '../directory_watcher.dart';
+import '../utils.dart';
+import '../watch_event.dart';
+
+typedef ManuallyClosedDirectoryWatcher WatcherFactory();
+
+/// A wrapper for [ManuallyClosedDirectoryWatcher] that encapsulates support for
+/// closing the watcher when it has no subscribers and re-opening it when it's
+/// re-subscribed.
+///
+/// It's simpler to implement watchers without worrying about this behavior.
+/// This class wraps a watcher class which can be written with the simplifying
+/// assumption that it can continue emitting events until an explicit `close`
+/// method is called, at which point it will cease emitting events entirely. The
+/// [ManuallyClosedDirectoryWatcher] interface is used for these watchers.
+///
+/// This would be more cleanly implemented as a function that takes a class and
+/// emits a new class, but Dart doesn't support that sort of thing. Instead it
+/// takes a factory function that produces instances of the inner class.
+abstract class ResubscribableDirectoryWatcher implements DirectoryWatcher {
+ /// The factory function that produces instances of the inner class.
+ final WatcherFactory _factory;
+
+ final String directory;
+
+ Stream<WatchEvent> get events => _eventsController.stream;
+ StreamController<WatchEvent> _eventsController;
+
+ bool get isReady => _readyCompleter.isCompleted;
+
+ Future get ready => _readyCompleter.future;
+ var _readyCompleter = new Completer();
+
+ /// Creates a new [ResubscribableDirectoryWatcher] wrapping the watchers
+ /// emitted by [_factory].
+ ResubscribableDirectoryWatcher(this.directory, this._factory) {
+ var watcher;
+ var subscription;
+
+ _eventsController = new StreamController<WatchEvent>.broadcast(
+ onListen: () {
+ watcher = _factory();
+ subscription = watcher.events.listen(_eventsController.add,
+ onError: _eventsController.addError,
+ onDone: _eventsController.close);
+
+ // It's important that we complete the value of [_readyCompleter] at the
+ // time [onListen] is called, as opposed to the value when [watcher.ready]
+ // fires. A new completer may be created by that time.
+ watcher.ready.then(_readyCompleter.complete);
+ }, onCancel: () {
+ // Cancel the subscription before closing the watcher so that the
+ // watcher's `onDone` event doesn't close [events].
+ subscription.cancel();
+ watcher.close();
+ _readyCompleter = new Completer();
+ }, sync: true);
+ }
+}
+
+/// An interface for watchers with an explicit, manual [close] method.
+///
+/// See [ResubscribableDirectoryWatcher].
+abstract class ManuallyClosedDirectoryWatcher implements DirectoryWatcher {
+ /// Closes the watcher.
+ ///
+ /// Subclasses should close their [events] stream and release any internal
+ /// resources.
+ void close();
+}
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