Revert "Make StreamController be a StreamSink, not just an EventSink."

sdk/lib/async/broadcast_stream_controller.dart

-// Copyright (c) 2012, 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.
-
-part of dart.async;
-
-class _BroadcastStream<T> extends _StreamImpl<T> {
-  _BroadcastStreamController _controller;
-
-  _BroadcastStream(this._controller);
-
-  bool get isBroadcast => true;
-
-  StreamSubscription<T> _createSubscription(
-      void onData(T data),
-      void onError(Object error),
-      void onDone(),
-      bool cancelOnError) =>
-    _controller._subscribe(onData, onError, onDone, cancelOnError);
-}
-
-abstract class _BroadcastSubscriptionLink {
-  _BroadcastSubscriptionLink _next;
-  _BroadcastSubscriptionLink _previous;
-}
-
-class _BroadcastSubscription<T> extends _ControllerSubscription<T>
-                                implements _BroadcastSubscriptionLink {
-  static const int _STATE_EVENT_ID = 1;
-  static const int _STATE_FIRING = 2;
-  static const int _STATE_REMOVE_AFTER_FIRING = 4;
-  // TODO(lrn): Use the _state field on _ControllerSubscription to
-  // also store this state. Requires that the subscription implementation
-  // does not assume that it's use of the state integer is the only use.
-  int _eventState;
-
-  _BroadcastSubscriptionLink _next;
-  _BroadcastSubscriptionLink _previous;
-
-  _BroadcastSubscription(_StreamControllerLifecycle controller,
-                         void onData(T data),
-                         void onError(Object error),
-                         void onDone(),
-                         bool cancelOnError)
-      : super(controller, onData, onError, onDone, cancelOnError) {
-    _next = _previous = this;
-  }
-
-  _BroadcastStreamController get _controller => super._controller;
-
-  bool _expectsEvent(int eventId) =>
-      (_eventState & _STATE_EVENT_ID) == eventId;
-
-
-  void _toggleEventId() {
-    _eventState ^= _STATE_EVENT_ID;
-  }
-
-  bool get _isFiring => (_eventState & _STATE_FIRING) != 0;
-
-  bool _setRemoveAfterFiring() {
-    assert(_isFiring);
-    _eventState |= _STATE_REMOVE_AFTER_FIRING;
-  }
-
-  bool get _removeAfterFiring =>
-      (_eventState & _STATE_REMOVE_AFTER_FIRING) != 0;
-
-  // The controller._recordPause doesn't do anything for a broadcast controller,
-  // so we don't bother calling it.
-  void _onPause() { }
-
-  // The controller._recordResume doesn't do anything for a broadcast
-  // controller, so we don't bother calling it.
-  void _onResume() { }
-
-  // _onCancel is inherited.
-}
-
-
-abstract class _BroadcastStreamController<T>
-    implements StreamController<T>,
-               _StreamControllerLifecycle<T>,
-               _BroadcastSubscriptionLink,
-               _EventSink<T>,
-               _EventDispatch<T> {
-  static const int _STATE_INITIAL = 0;
-  static const int _STATE_EVENT_ID = 1;
-  static const int _STATE_FIRING = 2;
-  static const int _STATE_CLOSED = 4;
-  static const int _STATE_ADDSTREAM = 8;
-
-  final _NotificationHandler _onListen;
-  final _NotificationHandler _onCancel;
-
-  // State of the controller.
-  int _state;
-
-  // Double-linked list of active listeners.
-  _BroadcastSubscriptionLink _next;
-  _BroadcastSubscriptionLink _previous;
-
-  // Extra state used during an [addStream] call.
-  _AddStreamState<T> _addStreamState;
-
-  /**
-   * Future returned by [close] and [done].
-   *
-   * The future is completed whenever the done event has been sent to all
-   * relevant listeners.
-   * The relevant listeners are the ones that were listening when [close] was
-   * called. When all of these have been canceled (sending the done event makes
-   * them cancel, but they can also be canceled before sending the event),
-   * this future completes.
-   *
-   * Any attempt to listen after calling [close] will throw, so there won't
-   * be any further listeners.
-   */
-  _FutureImpl _doneFuture;
-
-  _BroadcastStreamController(this._onListen, this._onCancel)
-      : _state = _STATE_INITIAL {
-    _next = _previous = this;
-  }
-
-  // StreamController interface.
-
-  Stream<T> get stream => new _BroadcastStream<T>(this);
-
-  StreamSink<T> get sink => new _StreamSinkWrapper<T>(this);
-
-  bool get isClosed => (_state & _STATE_CLOSED) != 0;
-
-  /**
-   * A broadcast controller is never paused.
-   *
-   * Each receiving stream may be paused individually, and they handle their
-   * own buffering.
-   */
-  bool get isPaused => false;
-
-  /** Whether there are currently one or more subscribers. */
-  bool get hasListener => !_isEmpty;
-
-  /** Whether an event is being fired (sent to some, but not all, listeners). */
-  bool get _isFiring => (_state & _STATE_FIRING) != 0;
-
-  bool get _isAddingStream => (_state & _STATE_ADDSTREAM) != 0;
-
-  bool get _mayAddEvent => (_state < _STATE_CLOSED);
-
-  _FutureImpl _ensureDoneFuture() {
-    if (_doneFuture != null) return _doneFuture;
-    return _doneFuture = new _FutureImpl();
-  }
-
-  // Linked list helpers
-
-  bool get _isEmpty => identical(_next, this);
-
-  /** Adds subscription to linked list of active listeners. */
-  void _addListener(_BroadcastSubscription<T> subscription) {
-    assert(identical(subscription._next, subscription));
-    // Insert in linked list just before `this`.
-    subscription._previous = _previous;
-    subscription._next = this;
-    this._previous._next = subscription;
-    this._previous = subscription;
-    subscription._eventState = (_state & _STATE_EVENT_ID);
-  }
-
-  void _removeListener(_BroadcastSubscription<T> subscription) {
-    assert(identical(subscription._controller, this));
-    assert(!identical(subscription._next, subscription));
-    _BroadcastSubscriptionLink previous = subscription._previous;
-    _BroadcastSubscriptionLink next = subscription._next;
-    previous._next = next;
-    next._previous = previous;
-    subscription._next = subscription._previous = subscription;
-  }
-
-  // _StreamControllerLifecycle interface.
-
-  StreamSubscription<T> _subscribe(void onData(T data),
-                                   void onError(Object error),
-                                   void onDone(),
-                                   bool cancelOnError) {
-    if (isClosed) {
-      throw new StateError("Subscribing to closed stream");
-    }
-    StreamSubscription subscription = new _BroadcastSubscription<T>(
-        this, onData, onError, onDone, cancelOnError);
-    _addListener(subscription);
-    if (identical(_next, _previous)) {
-      // Only one listener, so it must be the first listener.
-      _runGuarded(_onListen);
-    }
-    return subscription;
-  }
-
-  void _recordCancel(_BroadcastSubscription<T> subscription) {
-    // If already removed by the stream, don't remove it again.
-    if (identical(subscription._next, subscription)) return;
-    assert(!identical(subscription._next, subscription));
-    if (subscription._isFiring) {
-      subscription._setRemoveAfterFiring();
-    } else {
-      assert(!identical(subscription._next, subscription));
-      _removeListener(subscription);
-      // If we are currently firing an event, the empty-check is performed at
-      // the end of the listener loop instead of here.
-      if (!_isFiring && _isEmpty) {
-        _callOnCancel();
-      }
-    }
-  }
-
-  void _recordPause(StreamSubscription<T> subscription) {}
-  void _recordResume(StreamSubscription<T> subscription) {}
-
-  // EventSink interface.
-
-  Error _addEventError() {
-    if (isClosed) {
-      return new StateError("Cannot add new events after calling close");
-    }
-    assert(_isAddingStream);
-    return new StateError("Cannot add new events while doing an addStream");
-  }
-
-  void add(T data) {
-    if (!_mayAddEvent) throw _addEventError();
-    _sendData(data);
-  }
-
-  void addError(Object error, [Object stackTrace]) {
-    if (!_mayAddEvent) throw _addEventError();
-    if (stackTrace != null) _attachStackTrace(error, stackTrace);
-    _sendError(error);
-  }
-
-  Future close() {
-    if (isClosed) {
-      assert(_doneFuture != null);
-      return _doneFuture;
-    }
-    if (!_mayAddEvent) throw _addEventError();
-    _state |= _STATE_CLOSED;
-    Future doneFuture = _ensureDoneFuture();
-    _sendDone();
-    return doneFuture;
-  }
-
-  Future get done => _ensureDoneFuture();
-
-  Future addStream(Stream<T> stream) {
-    if (!_mayAddEvent) throw _addEventError();
-    _state |= _STATE_ADDSTREAM;
-    _addStreamState = new _AddStreamState(this, stream);
-    return _addStreamState.addStreamFuture;
-  }
-
-  // _EventSink interface, called from AddStreamState.
-  void _add(T data) {
-    _sendData(data);
-  }
-
-  void _addError(Object error) {
-    assert(_isAddingStream);
-    _sendError(error);
-  }
-
-  void _close() {
-    assert(_isAddingStream);
-    _AddStreamState addState = _addStreamState;
-    _addStreamState = null;
-    _state &= ~_STATE_ADDSTREAM;
-    addState.complete();
-  }
-
-  // Event handling.
-  void _forEachListener(
-      void action(_BufferingStreamSubscription<T> subscription)) {
-    if (_isFiring) {
-      throw new StateError(
-          "Cannot fire new event. Controller is already firing an event");
-    }
-    if (_isEmpty) return;
-
-    // Get event id of this event.
-    int id = (_state & _STATE_EVENT_ID);
-    // Start firing (set the _STATE_FIRING bit). We don't do [_onCancel]
-    // callbacks while firing, and we prevent reentrancy of this function.
-    //
-    // Set [_state]'s event id to the next event's id.
-    // Any listeners added while firing this event will expect the next event,
-    // not this one, and won't get notified.
-    _state ^= _STATE_EVENT_ID | _STATE_FIRING;
-    _BroadcastSubscriptionLink link = _next;
-    while (!identical(link, this)) {
-      _BroadcastSubscription<T> subscription = link;
-      if (subscription._expectsEvent(id)) {
-        subscription._eventState |= _BroadcastSubscription._STATE_FIRING;
-        action(subscription);
-        subscription._toggleEventId();
-        link = subscription._next;
-        if (subscription._removeAfterFiring) {
-          _removeListener(subscription);
-        }
-        subscription._eventState &= ~_BroadcastSubscription._STATE_FIRING;
-      } else {
-        link = subscription._next;
-      }
-    }
-    _state &= ~_STATE_FIRING;
-
-    if (_isEmpty) {
-      _callOnCancel();
-    }
-  }
-
-  void _callOnCancel() {
-    assert(_isEmpty);
-    if (isClosed && _doneFuture._mayComplete) {
-      // When closed, _doneFuture is not null.
-      _doneFuture._asyncSetValue(null);
-    }
-    _runGuarded(_onCancel);
-  }
-}
-
-class _SyncBroadcastStreamController<T> extends _BroadcastStreamController<T> {
-  _SyncBroadcastStreamController(void onListen(), void onCancel())
-      : super(onListen, onCancel);
-
-  // EventDispatch interface.
-
-  void _sendData(T data) {
-    if (_isEmpty) return;
-    _forEachListener((_BufferingStreamSubscription<T> subscription) {
-      subscription._add(data);
-    });
-  }
-
-  void _sendError(Object error) {
-    if (_isEmpty) return;
-    _forEachListener((_BufferingStreamSubscription<T> subscription) {
-      subscription._addError(error);
-    });
-  }
-
-  void _sendDone() {
-    if (!_isEmpty) {
-      _forEachListener((_BroadcastSubscription<T> subscription) {
-        subscription._close();
-      });
-    } else {
-      assert(_doneFuture != null);
-      assert(_doneFuture._mayComplete);
-      _doneFuture._asyncSetValue(null);
-    }
-  }
-}
-
-class _AsyncBroadcastStreamController<T> extends _BroadcastStreamController<T> {
-  _AsyncBroadcastStreamController(void onListen(), void onCancel())
-      : super(onListen, onCancel);
-
-  // EventDispatch interface.
-
-  void _sendData(T data) {
-    for (_BroadcastSubscriptionLink link = _next;
-         !identical(link, this);
-         link = link._next) {
-      _BroadcastSubscription<T> subscription = link;
-      subscription._addPending(new _DelayedData(data));
-    }
-  }
-
-  void _sendError(Object error) {
-    for (_BroadcastSubscriptionLink link = _next;
-         !identical(link, this);
-         link = link._next) {
-      _BroadcastSubscription<T> subscription = link;
-      subscription._addPending(new _DelayedError(error));
-    }
-  }
-
-  void _sendDone() {
-    if (!_isEmpty) {
-      for (_BroadcastSubscriptionLink link = _next;
-           !identical(link, this);
-           link = link._next) {
-        _BroadcastSubscription<T> subscription = link;
-        subscription._addPending(const _DelayedDone());
-      }
-    } else {
-      assert(_doneFuture != null);
-      assert(_doneFuture._mayComplete);
-      _doneFuture._asyncSetValue(null);
-    }
-  }
-}
-
-/**
- * Stream controller that is used by [Stream.asBroadcastStream].
- *
- * This stream controller allows incoming events while it is firing
- * other events. This is handled by delaying the events until the
- * current event is done firing, and then fire the pending events.
- *
- * This class extends [_SyncBroadcastStreamController]. Events of
- * an "asBroadcastStream" stream are always initiated by events
- * on another stream, and it is fine to forward them synchronously.
- */
-class _AsBroadcastStreamController<T>
-    extends _SyncBroadcastStreamController<T>
-    implements _EventDispatch<T> {
-  _StreamImplEvents _pending;
-
-  _AsBroadcastStreamController(void onListen(), void onCancel())
-      : super(onListen, onCancel);
-
-  bool get _hasPending => _pending != null && ! _pending.isEmpty;
-
-  void _addPendingEvent(_DelayedEvent event) {
-    if (_pending == null) {
-      _pending = new _StreamImplEvents();
-    }
-    _pending.add(event);
-  }
-
-  void add(T data) {
-    if (!isClosed && _isFiring) {
-      _addPendingEvent(new _DelayedData<T>(data));
-      return;
-    }
-    super.add(data);
-    while (_hasPending) {
-      _pending.handleNext(this);
-    }
-  }
-
-  void addError(Object error, [StackTrace stackTrace]) {
-    if (!isClosed && _isFiring) {
-      _addPendingEvent(new _DelayedError(error));
-      return;
-    }
-    super.addError(error, stackTrace);
-    while (_hasPending) {
-      _pending.handleNext(this);
-    }
-  }
-
-  void close() {
-    if (!isClosed && _isFiring) {
-      _addPendingEvent(const _DelayedDone());
-      _state |= _STATE_CLOSED;
-      return;
-    }
-    super.close();
-    assert(!_hasPending);
-  }
-
-  void _callOnCancel() {
-    if (_hasPending) {
-      _pending.clear();
-      _pending = null;
-    }
-    super._callOnCancel();
-  }
-}
-
-// A subscription that never receives any events.
-// It can simulate pauses, but otherwise does nothing.
-class _DoneSubscription<T> implements StreamSubscription<T> {
-  int _pauseCount = 0;
-  void onData(void handleData(T data)) {}
-  void onError(void handleErrr(Object error)) {}
-  void onDone(void handleDone()) {}
-  void pause([Future resumeSignal]) {
-    if (resumeSignal != null) resumeSignal.then(_resume);
-    _pauseCount++;
-  }
-  void resume() { _resume(null); }
-  void _resume(_) {
-    if (_pauseCount > 0) _pauseCount--;
-  }
-  void cancel() {}
-  bool get isPaused => _pauseCount > 0;
-  Future asFuture(Object value) => new _FutureImpl();
-}