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Unified Diff: sdk/lib/async/stream_impl.dart

Issue 17490002: Make asBroadcastStream take two callbacks. (Closed) Base URL: https://dart.googlecode.com/svn/branches/bleeding_edge/dart
Patch Set: Reintroduce zone. Created 7 years, 6 months ago
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Index: sdk/lib/async/stream_impl.dart
diff --git a/sdk/lib/async/stream_impl.dart b/sdk/lib/async/stream_impl.dart
index 85aa0833b6f0233cf7399ffb256e21aee5261169..40cc3da63e5ec550249be0dcce588766a272a4a9 100644
--- a/sdk/lib/async/stream_impl.dart
+++ b/sdk/lib/async/stream_impl.dart
@@ -696,13 +696,47 @@ class _BroadcastLinkedList {
}
}
+typedef void _broadcastCallback(StreamSubscription subscription);
+
+/**
+ * Dummy subscription that will never receive any events.
+ */
+class _DummyStreamSubscription<T> implements StreamSubscription<T> {
+ int _pauseCounter = 0;
+
+ void onData(void handleData(T data)) {}
+ void onError(void handleError(Object data)) {}
+ void onDone(void handleDone()) {}
+
+ void pause([Future resumeSignal]) {
+ _pauseCounter++;
+ if (resumeSignal != null) resumeSignal.then((_) { resume(); });
+ }
+ void resume() {
+ if (_pauseCounter > 0) _pauseCounter--;
+ }
+ void cancel() {}
+ bool get isPaused => _pauseCounter > 0;
+
+ Future asFuture([futureValue]) => new _FutureImpl();
+}
+
class _AsBroadcastStream<T> extends Stream<T> {
final Stream<T> _source;
+ final _broadcastCallback _onListenHandler;
+ final _broadcastCallback _onCancelHandler;
+ final _Zone _zone;
+
_AsBroadcastStreamController<T> _controller;
StreamSubscription<T> _subscription;
- _AsBroadcastStream(this._source) {
- _controller = new _AsBroadcastStreamController<T>(null, _onCancel);
+ _AsBroadcastStream(this._source,
+ this._onListenHandler,
+ this._onCancelHandler)
+ : _zone = _Zone.current {
+ _controller = new _AsBroadcastStreamController<T>(_onListen, _onCancel);
+ // Keep zone alive until we are done doing callbacks.
+ _zone.expectCallback();
}
bool get isBroadcast => true;
@@ -712,7 +746,9 @@ class _AsBroadcastStream<T> extends Stream<T> {
void onDone(),
bool cancelOnError}) {
if (_controller == null) {
- throw new StateError("Source stream has been closed.");
+ // Return a dummy subscription backed by nothing, since
+ // it won't ever receive any events.
+ return new _DummyStreamSubscription<T>();
}
if (_subscription == null) {
_subscription = _source.listen(_controller.add,
@@ -724,14 +760,102 @@ class _AsBroadcastStream<T> extends Stream<T> {
}
void _onCancel() {
+ bool shutdown = (_controller == null) || _controller.isClosed;
+ if (_onCancelHandler != null) {
+ _zone.executePeriodicCallbackGuarded(
+ () => _onCancelHandler(new _BroadcastSubscriptionWrapper(this)));
+ }
+ if (shutdown) {
+ if (_subscription != null) {
+ _subscription.cancel();
+ _subscription = null;
+ }
+ _zone.cancelCallbackExpectation();
+ }
+ }
+
+ void _onListen() {
+ if (_onListenHandler != null) {
+ _zone.executePeriodicCallbackGuarded(
+ () => _onListenHandler(new _BroadcastSubscriptionWrapper(this)));
+ }
+ }
+
+ // Methods called from _BroadcastSubscriptionWrapper.
+ void _cancelSubscription() {
+ if (_subscription == null) return;
// Called by [_controller] when it has no subscribers left.
StreamSubscription subscription = _subscription;
_subscription = null;
+ if (_controller._isEmpty) {
+ _zone.cancelCallbackExpectation();
+ }
_controller = null; // Marks the stream as no longer listenable.
subscription.cancel();
}
+
+ void _pauseSubscription(Future resumeSignal) {
+ if (_subscription == null) return;
+ _subscription.pause(resumeSignal);
+ }
+
+ void _resumeSubscription() {
+ if (_subscription == null) return;
+ _subscription.resume();
+ }
+
+ bool get _isSubscriptionPaused {
+ if (_subscription == null) return false;
+ return _subscription.isPaused;
+ }
+}
+
+/**
+ * Wrapper for subscription that disallows changing handlers.
+ */
+class _BroadcastSubscriptionWrapper<T> implements StreamSubscription<T> {
+ final _AsBroadcastStream _stream;
+
+ _BroadcastSubscriptionWrapper(this._stream);
+
+ void onData(void handleData(T data)) {
+ throw new UnsupportedError(
+ "Cannot change handlers of asBroadcastStream source subscription.");
+ }
+
+ void onError(void handleError(Object data)) {
+ throw new UnsupportedError(
+ "Cannot change handlers of asBroadcastStream source subscription.");
+ }
+
+ void onDone(void handleDone()) {
+ throw new UnsupportedError(
+ "Cannot change handlers of asBroadcastStream source subscription.");
+ }
+
+ void pause([Future resumeSignal]) {
+ _stream._pauseSubscription(resumeSignal);
+ }
+
+ void resume() {
+ _stream._resumeSubscription();
+ }
+
+ void cancel() {
+ _stream._cancelSubscription();
+ }
+
+ bool get isPaused {
+ return _stream._isSubscriptionPaused;
+ }
+
+ Future asFuture([var futureValue]) {
+ throw new UnsupportedError(
+ "Cannot change handlers of asBroadcastStream source subscription.");
+ }
}
+
/**
* Simple implementation of [StreamIterator].
*/
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