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// 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;
// -------------------------------------------------------------------
// Controller for creating and adding events to a stream.
// -------------------------------------------------------------------
/**
* Type of a stream controller's `onListen`, `onPause` and `onResume` callbacks.
*/
typedef void ControllerCallback();
/**
* Type of stream controller `onCancel` callbacks.
*
* The callback may return either `void` or a future.
*/
typedef ControllerCancelCallback();
/**
* A controller with the stream it controls.
*
* This controller allows sending data, error and done events on
* its [stream].
* This class can be used to create a simple stream that others
* can listen on, and to push events to that stream.
*
* It's possible to check whether the stream is paused or not, and whether
* it has subscribers or not, as well as getting a callback when either of
* these change.
*
* If the stream starts or stops having listeners (first listener subscribing,
* last listener unsubscribing), the `onSubscriptionStateChange` callback
* is notified as soon as possible. If the subscription stat changes during
* an event firing or a callback being executed, the change will not be reported
* until the current event or callback has finished.
* If the pause state has also changed during an event or callback, only the
* subscription state callback is notified.
*
* If the subscriber state has not changed, but the pause state has, the
* `onPauseStateChange` callback is notified as soon as possible, after firing
* a current event or completing another callback. This happens if the stream
* is not paused, and a listener pauses it, or if the stream has been resumed
* from pause and has no pending events. If the listeners resume a paused stream
* while it still has queued events, the controller will still consider the
* stream paused until all queued events have been dispatched.
*
* Whether to invoke a callback depends only on the state before and after
* a stream action, for example firing an event. If the state changes multiple
* times during the action, and then ends up in the same state as before, no
* callback is performed.
*
* If listeners are added after the stream has completed (sent a "done" event),
* the listeners will be sent a "done" event eventually, but they won't affect
* the stream at all, and won't trigger callbacks. From the controller's point
* of view, the stream is completely inert when has completed.
*/
abstract class StreamController<T> implements StreamSink<T> {
/** The stream that this controller is controlling. */
Stream<T> get stream;
/**
* A controller with a [stream] that supports only one single subscriber.
*
* If [sync] is true, the returned stream controller is a
* [SynchronousStreamController], and must be used with the care
* and attention necessary to not break the [Stream] contract.
* See [Completer.sync] for some explanations on when a synchronous
* dispatching can be used.
* If in doubt, keep the controller non-sync.
*
* A Stream should be inert until a subscriber starts listening on it (using
* the [onListen] callback to start producing events). Streams should not
* leak resources (like websockets) when no user ever listens on the stream.
*
* The controller buffers all incoming events until a subscriber is
* registered, but this feature should only be used in rare circumstances.
*
* The [onPause] function is called when the stream becomes
* paused. [onResume] is called when the stream resumed.
*
* The [onListen] callback is called when the stream
* receives its listener and [onCancel] when the listener ends
* its subscription. If [onCancel] needs to perform an asynchronous operation,
* [onCancel] should return a future that completes when the cancel operation
* is done.
*
* If the stream is canceled before the controller needs new data the
* [onResume] call might not be executed.
*/
factory StreamController(
{void onListen(),
void onPause(),
void onResume(),
onCancel(),
bool sync: false}) {
return sync
? new _SyncStreamController<T>(onListen, onPause, onResume, onCancel)
: new _AsyncStreamController<T>(onListen, onPause, onResume, onCancel);
}
/**
* A controller where [stream] can be listened to more than once.
*
* The [Stream] returned by [stream] is a broadcast stream.
* It can be listened to more than once.
*
* A Stream should be inert until a subscriber starts listening on it (using
* the [onListen] callback to start producing events). Streams should not
* leak resources (like websockets) when no user ever listens on the stream.
*
* Broadcast streams do not buffer events when there is no listener.
*
* The controller distributes any events to all currently subscribed
* listeners at the time when [add], [addError] or [close] is called.
* It is not allowed to call `add`, `addError`, or `close` before a previous
* call has returned. The controller does not have any internal queue of
* events, and if there are no listeners at the time the event is added,
* it will just be dropped, or, if it is an error, be reported as uncaught.
*
* Each listener subscription is handled independently,
* and if one pauses, only the pausing listener is affected.
* A paused listener will buffer events internally until unpaused or canceled.
*
* If [sync] is true, events may be fired directly by the stream's
* subscriptions during an [add], [addError] or [close] call.
* The returned stream controller is a [SynchronousStreamController],
* and must be used with the care and attention necessary to not break
* the [Stream] contract.
* See [Completer.sync] for some explanations on when a synchronous
* dispatching can be used.
* If in doubt, keep the controller non-sync.
*
* If [sync] is false, the event will always be fired at a later time,
* after the code adding the event has completed.
* In that case, no guarantees are given with regard to when
* multiple listeners get the events, except that each listener will get
* all events in the correct order. Each subscription handles the events
* individually.
* If two events are sent on an async controller with two listeners,
* one of the listeners may get both events
* before the other listener gets any.
* A listener must be subscribed both when the event is initiated
* (that is, when [add] is called)
* and when the event is later delivered,
* in order to receive the event.
*
* The [onListen] callback is called when the first listener is subscribed,
* and the [onCancel] is called when there are no longer any active listeners.
* If a listener is added again later, after the [onCancel] was called,
* the [onListen] will be called again.
*/
factory StreamController.broadcast(
{void onListen(), void onCancel(), bool sync: false}) {
return sync
? new _SyncBroadcastStreamController<T>(onListen, onCancel)
: new _AsyncBroadcastStreamController<T>(onListen, onCancel);
}
/**
* The callback which is called when the stream is listened to.
*
* May be set to `null`, in which case no callback will happen.
*/
ControllerCallback get onListen;
void set onListen(void onListenHandler());
/**
* The callback which is called when the stream is paused.
*
* May be set to `null`, in which case no callback will happen.
*
* Pause related callbacks are not supported on broadcast stream controllers.
*/
ControllerCallback get onPause;
void set onPause(void onPauseHandler());
/**
* The callback which is called when the stream is resumed.
*
* May be set to `null`, in which case no callback will happen.
*
* Pause related callbacks are not supported on broadcast stream controllers.
*/
ControllerCallback get onResume;
void set onResume(void onResumeHandler());
/**
* The callback which is called when the stream is canceled.
*
* May be set to `null`, in which case no callback will happen.
*/
ControllerCancelCallback get onCancel;
void set onCancel(onCancelHandler());
/**
* Returns a view of this object that only exposes the [StreamSink] interface.
*/
StreamSink<T> get sink;
/**
* Whether the stream controller is closed for adding more events.
*
* The controller becomes closed by calling the [close] method.
* New events cannot be added, by calling [add] or [addError],
* to a closed controller.
*
* If the controller is closed,
* the "done" event might not have been delivered yet,
* but it has been scheduled, and it is too late to add more events.
*/
bool get isClosed;
/**
* Whether the subscription would need to buffer events.
*
* This is the case if the controller's stream has a listener and it is
* paused, or if it has not received a listener yet. In that case, the
* controller is considered paused as well.
*
* A broadcast stream controller is never considered paused. It always
* forwards its events to all uncanceled subscriptions, if any,
* and let the subscriptions handle their own pausing and buffering.
*/
bool get isPaused;
/** Whether there is a subscriber on the [Stream]. */
bool get hasListener;
/**
* Send or enqueue an error event.
*
* If [error] is `null`, it is replaced by a [NullThrownError].
*/
void addError(Object error, [StackTrace stackTrace]);
/**
* Receives events from [source] and puts them into this controller's stream.
*
* Returns a future which completes when the source stream is done.
*
* Events must not be added directly to this controller using [add],
* [addError], [close] or [addStream], until the returned future
* is complete.
*
* Data and error events are forwarded to this controller's stream. A done
* event on the source will end the `addStream` operation and complete the
* returned future.
*
* If [cancelOnError] is true, only the first error on [source] is
* forwarded to the controller's stream, and the `addStream` ends
* after this. If [cancelOnError] is false, all errors are forwarded
* and only a done event will end the `addStream`.
*/
Future addStream(Stream<T> source, {bool cancelOnError: true});
}
/**
* A stream controller that delivers its events synchronously.
*
* A synchronous stream controller is intended for cases where
* an already asynchronous event triggers an event on a stream.
*
* Instead of adding the event to the stream in a later microtask,
* causing extra latency, the event is instead fired immediately by the
* synchronous stream controller, as if the stream event was
* the current event or microtask.
*
* The synchronous stream controller can be used to break the contract
* on [Stream], and it must be used carefully to avoid doing so.
*
* The only advantage to using a [SynchronousStreamController] over a
* normal [StreamController] is the improved latency.
* Only use the synchronous version if the improvement is significant,
* and if its use is safe. Otherwise just use a normal stream controller,
* which will always have the correct behavior for a [Stream], and won't
* accidentally break other code.
*
* Adding events to a synchronous controller should only happen as the
* very last part of a the handling of the original event.
* At that point, adding an event to the stream is equivalent to
* returning to the event loop and adding the event in the next microtask.
*
* Each listener callback will be run as if it was a top-level event
* or microtask. This means that if it throws, the error will be reported as
* uncaught as soon as possible.
* This is one reason to add the event as the last thing in the original event
* handler - any action done after adding the event will delay the report of
* errors in the event listener callbacks.
*
* If an event is added in a setting that isn't known to be another event,
* it may cause the stream's listener to get that event before the listener
* is ready to handle it. We promise that after calling [Stream.listen],
* you won't get any events until the code doing the listen has completed.
* Calling [add] in response to a function call of unknown origin may break
* that promise.
*
* An [onListen] callback from the controller is *not* an asynchronous event,
* and adding events to the controller in the `onListen` callback is always
* wrong. The events will be delivered before the listener has even received
* the subscription yet.
*
* The synchronous broadcast stream controller also has a restrictions that a
* normal stream controller does not:
* The [add], [addError], [close] and [addStream] methods *must not* be
* called while an event is being delivered.
* That is, if a callback on a subscription on the controller's stream causes
* a call to any of the functions above, the call will fail.
* A broadcast stream may have more than one listener, and if an
* event is added synchronously while another is being also in the process
* of being added, the latter event might reach some listeners before
* the former. To prevent that, an event cannot be added while a previous
* event is being fired.
* This guarantees that an event is fully delivered when the
* first [add], [addError] or [close] returns,
* and further events will be delivered in the correct order.
*
* This still only guarantees that the event is delivered to the subscription.
* If the subscription is paused, the actual callback may still happen later,
* and the event will instead be buffered by the subscription.
* Barring pausing, and the following buffered events that haven't been
* delivered yet, callbacks will be called synchronously when an event is added.
*
* Adding an event to a synchronous non-broadcast stream controller while
* another event is in progress may cause the second event to be delayed
* and not be delivered synchronously, and until that event is delivered,
* the controller will not act synchronously.
*/
abstract class SynchronousStreamController<T> implements StreamController<T> {
/**
* Adds event to the controller's stream.
*
* As [StreamController.add], but must not be called while an event is
* being added by [add], [addError] or [close].
*/
void add(T data);
/**
* Adds error to the controller's stream.
*
* As [StreamController.addError], but must not be called while an event is
* being added by [add], [addError] or [close].
*/
void addError(Object error, [StackTrace stackTrace]);
/**
* Closes the controller's stream.
*
* As [StreamController.close], but must not be called while an event is
* being added by [add], [addError] or [close].
*/
Future close();
}
abstract class _StreamControllerLifecycle<T> {
StreamSubscription<T> _subscribe(
void onData(T data), Function onError, void onDone(), bool cancelOnError);
void _recordPause(StreamSubscription<T> subscription) {}
void _recordResume(StreamSubscription<T> subscription) {}
Future _recordCancel(StreamSubscription<T> subscription) => null;
}
/**
* Default implementation of [StreamController].
*
* Controls a stream that only supports a single controller.
*/
abstract class _StreamController<T>
implements
StreamController<T>,
_StreamControllerLifecycle<T>,
_EventSink<T>,
_EventDispatch<T> {
// The states are bit-flags. More than one can be set at a time.
//
// The "subscription state" goes through the states:
// initial -> subscribed -> canceled.
// These are mutually exclusive.
// The "closed" state records whether the [close] method has been called
// on the controller. This can be done at any time. If done before
// subscription, the done event is queued. If done after cancel, the done
// event is ignored (just as any other event after a cancel).
/** The controller is in its initial state with no subscription. */
static const int _STATE_INITIAL = 0;
/** The controller has a subscription, but hasn't been closed or canceled. */
static const int _STATE_SUBSCRIBED = 1;
/** The subscription is canceled. */
static const int _STATE_CANCELED = 2;
/** Mask for the subscription state. */
static const int _STATE_SUBSCRIPTION_MASK = 3;
// The following state relate to the controller, not the subscription.
// If closed, adding more events is not allowed.
// If executing an [addStream], new events are not allowed either, but will
// be added by the stream.
/**
* The controller is closed due to calling [close].
*
* When the stream is closed, you can neither add new events nor add new
* listeners.
*/
static const int _STATE_CLOSED = 4;
/**
* The controller is in the middle of an [addStream] operation.
*
* While adding events from a stream, no new events can be added directly
* on the controller.
*/
static const int _STATE_ADDSTREAM = 8;
/**
* Field containing different data depending on the current subscription
* state.
*
* If [_state] is [_STATE_INITIAL], the field may contain a [_PendingEvents]
* for events added to the controller before a subscription.
*
* While [_state] is [_STATE_SUBSCRIBED], the field contains the subscription.
*
* When [_state] is [_STATE_CANCELED] the field is currently not used.
*/
var _varData;
/** Current state of the controller. */
int _state = _STATE_INITIAL;
/**
* Future completed when the stream sends its last event.
*
* This is also the future returned by [close].
*/
// TODO(lrn): Could this be stored in the varData field too, if it's not
// accessed until the call to "close"? Then we need to special case if it's
// accessed earlier, or if close is called before subscribing.
_Future _doneFuture;
ControllerCallback onListen;
ControllerCallback onPause;
ControllerCallback onResume;
ControllerCancelCallback onCancel;
_StreamController(this.onListen, this.onPause, this.onResume, this.onCancel);
// Return a new stream every time. The streams are equal, but not identical.
Stream<T> get stream => new _ControllerStream<T>(this);
/**
* Returns a view of this object that only exposes the [StreamSink] interface.
*/
StreamSink<T> get sink => new _StreamSinkWrapper<T>(this);
/**
* Whether a listener has existed and been canceled.
*
* After this, adding more events will be ignored.
*/
bool get _isCanceled => (_state & _STATE_CANCELED) != 0;
/** Whether there is an active listener. */
bool get hasListener => (_state & _STATE_SUBSCRIBED) != 0;
/** Whether there has not been a listener yet. */
bool get _isInitialState =>
(_state & _STATE_SUBSCRIPTION_MASK) == _STATE_INITIAL;
bool get isClosed => (_state & _STATE_CLOSED) != 0;
bool get isPaused =>
hasListener ? _subscription._isInputPaused : !_isCanceled;
bool get _isAddingStream => (_state & _STATE_ADDSTREAM) != 0;
/** New events may not be added after close, or during addStream. */
bool get _mayAddEvent => (_state < _STATE_CLOSED);
// Returns the pending events.
// Pending events are events added before a subscription exists.
// They are added to the subscription when it is created.
// Pending events, if any, are kept in the _varData field until the
// stream is listened to.
// While adding a stream, pending events are moved into the
// state object to allow the state object to use the _varData field.
_PendingEvents<T> get _pendingEvents {
assert(_isInitialState);
if (!_isAddingStream) {
return _varData as Object/*=_PendingEvents<T>*/;
}
_StreamControllerAddStreamState<T> state =
_varData as Object/*=_StreamControllerAddStreamState<T>*/;
return state.varData as Object/*=_PendingEvents<T>*/;
}
// Returns the pending events, and creates the object if necessary.
_StreamImplEvents<T> _ensurePendingEvents() {
assert(_isInitialState);
if (!_isAddingStream) {
if (_varData == null) _varData = new _StreamImplEvents<T>();
return _varData as Object/*=_StreamImplEvents<T>*/;
}
_StreamControllerAddStreamState<T> state =
_varData as Object/*=_StreamControllerAddStreamState<T>*/;
if (state.varData == null) state.varData = new _StreamImplEvents<T>();
return state.varData as Object/*=_StreamImplEvents<T>*/;
}
// Get the current subscription.
// If we are adding a stream, the subscription is moved into the state
// object to allow the state object to use the _varData field.
_ControllerSubscription<T> get _subscription {
assert(hasListener);
if (_isAddingStream) {
_StreamControllerAddStreamState<T> addState =
_varData as Object/*=_StreamControllerAddStreamState<T>*/;
return addState.varData as Object/*=_ControllerSubscription<T>*/;
}
return _varData as Object/*=_ControllerSubscription<T>*/;
}
/**
* Creates an error describing why an event cannot be added.
*
* The reason, and therefore the error message, depends on the current state.
*/
Error _badEventState() {
if (isClosed) {
return new StateError("Cannot add event after closing");
}
assert(_isAddingStream);
return new StateError("Cannot add event while adding a stream");
}
// StreamSink interface.
Future addStream(Stream<T> source, {bool cancelOnError: true}) {
if (!_mayAddEvent) throw _badEventState();
if (_isCanceled) return new _Future.immediate(null);
_StreamControllerAddStreamState<T> addState =
new _StreamControllerAddStreamState<T>(
this, _varData, source, cancelOnError);
_varData = addState;
_state |= _STATE_ADDSTREAM;
return addState.addStreamFuture;
}
/**
* Returns a future that is completed when the stream is done
* processing events.
*
* This happens either when the done event has been sent, or if the
* subscriber of a single-subscription stream is cancelled.
*/
Future get done => _ensureDoneFuture();
Future _ensureDoneFuture() {
if (_doneFuture == null) {
_doneFuture = _isCanceled ? Future._nullFuture : new _Future();
}
return _doneFuture;
}
/**
* Send or enqueue a data event.
*/
void add(T value) {
if (!_mayAddEvent) throw _badEventState();
_add(value);
}
/**
* Send or enqueue an error event.
*/
void addError(Object error, [StackTrace stackTrace]) {
if (!_mayAddEvent) throw _badEventState();
error = _nonNullError(error);
AsyncError replacement = Zone.current.errorCallback(error, stackTrace);
if (replacement != null) {
error = _nonNullError(replacement.error);
stackTrace = replacement.stackTrace;
}
_addError(error, stackTrace);
}
/**
* Closes this controller and sends a done event on the stream.
*
* The first time a controller is closed, a "done" event is added to its
* stream.
*
* You are allowed to close the controller more than once, but only the first
* call has any effect.
*
* After closing, no further events may be added using [add], [addError]
* or [addStream].
*
* The returned future is completed when the done event has been delivered.
*/
Future close() {
if (isClosed) {
return _ensureDoneFuture();
}
if (!_mayAddEvent) throw _badEventState();
_closeUnchecked();
return _ensureDoneFuture();
}
void _closeUnchecked() {
_state |= _STATE_CLOSED;
if (hasListener) {
_sendDone();
} else if (_isInitialState) {
_ensurePendingEvents().add(const _DelayedDone());
}
}
// EventSink interface. Used by the [addStream] events.
// Add data event, used both by the [addStream] events and by [add].
void _add(T value) {
if (hasListener) {
_sendData(value);
} else if (_isInitialState) {
_ensurePendingEvents().add(new _DelayedData<T>(value));
}
}
void _addError(Object error, StackTrace stackTrace) {
if (hasListener) {
_sendError(error, stackTrace);
} else if (_isInitialState) {
_ensurePendingEvents().add(new _DelayedError(error, stackTrace));
}
}
void _close() {
// End of addStream stream.
assert(_isAddingStream);
_StreamControllerAddStreamState<T> addState =
_varData as Object/*=_StreamControllerAddStreamState<T>*/;
_varData = addState.varData;
_state &= ~_STATE_ADDSTREAM;
addState.complete();
}
// _StreamControllerLifeCycle interface
StreamSubscription<T> _subscribe(void onData(T data), Function onError,
void onDone(), bool cancelOnError) {
if (!_isInitialState) {
throw new StateError("Stream has already been listened to.");
}
_ControllerSubscription<T> subscription = new _ControllerSubscription<T>(
this, onData, onError, onDone, cancelOnError);
_PendingEvents<T> pendingEvents = _pendingEvents;
_state |= _STATE_SUBSCRIBED;
if (_isAddingStream) {
_StreamControllerAddStreamState<T> addState =
_varData as Object/*=_StreamControllerAddStreamState<T>*/;
addState.varData = subscription;
addState.resume();
} else {
_varData = subscription;
}
subscription._setPendingEvents(pendingEvents);
subscription._guardCallback(() {
_runGuarded(onListen);
});
return subscription;
}
Future _recordCancel(StreamSubscription<T> subscription) {
// When we cancel, we first cancel any stream being added,
// Then we call `onCancel`, and finally the _doneFuture is completed.
// If either of addStream's cancel or `onCancel` returns a future,
// we wait for it before continuing.
// Any error during this process ends up in the returned future.
// If more errors happen, we act as if it happens inside nested try/finallys
// or whenComplete calls, and only the last error ends up in the
// returned future.
Future result;
if (_isAddingStream) {
_StreamControllerAddStreamState<T> addState =
_varData as Object/*=_StreamControllerAddStreamState<T>*/;
result = addState.cancel();
}
_varData = null;
_state =
(_state & ~(_STATE_SUBSCRIBED | _STATE_ADDSTREAM)) | _STATE_CANCELED;
if (onCancel != null) {
if (result == null) {
// Only introduce a future if one is needed.
// If _onCancel returns null, no future is needed.
try {
result = onCancel();
} catch (e, s) {
// Return the error in the returned future.
// Complete it asynchronously, so there is time for a listener
// to handle the error.
result = new _Future().._asyncCompleteError(e, s);
}
} else {
// Simpler case when we already know that we will return a future.
result = result.whenComplete(onCancel);
}
}
void complete() {
if (_doneFuture != null && _doneFuture._mayComplete) {
_doneFuture._asyncComplete(null);
}
}
if (result != null) {
result = result.whenComplete(complete);
} else {
complete();
}
return result;
}
void _recordPause(StreamSubscription<T> subscription) {
if (_isAddingStream) {
_StreamControllerAddStreamState<T> addState =
_varData as Object/*=_StreamControllerAddStreamState<T>*/;
addState.pause();
}
_runGuarded(onPause);
}
void _recordResume(StreamSubscription<T> subscription) {
if (_isAddingStream) {
_StreamControllerAddStreamState<T> addState =
_varData as Object/*=_StreamControllerAddStreamState<T>*/;
addState.resume();
}
_runGuarded(onResume);
}
}
abstract class _SyncStreamControllerDispatch<T>
implements _StreamController<T>, SynchronousStreamController<T> {
int get _state;
void set _state(int state);
void _sendData(T data) {
_subscription._add(data);
}
void _sendError(Object error, StackTrace stackTrace) {
_subscription._addError(error, stackTrace);
}
void _sendDone() {
_subscription._close();
}
}
abstract class _AsyncStreamControllerDispatch<T>
implements _StreamController<T> {
void _sendData(T data) {
_subscription._addPending(new _DelayedData<T>(data));
}
void _sendError(Object error, StackTrace stackTrace) {
_subscription._addPending(new _DelayedError(error, stackTrace));
}
void _sendDone() {
_subscription._addPending(const _DelayedDone());
}
}
// TODO(lrn): Use common superclass for callback-controllers when VM supports
// constructors in mixin superclasses.
class _AsyncStreamController<T> = _StreamController<T>
with _AsyncStreamControllerDispatch<T>;
class _SyncStreamController<T> = _StreamController<T>
with _SyncStreamControllerDispatch<T>;
typedef _NotificationHandler();
void _runGuarded(_NotificationHandler notificationHandler) {
if (notificationHandler == null) return;
try {
notificationHandler();
} catch (e, s) {
Zone.current.handleUncaughtError<Object>(e, s);
}
}
class _ControllerStream<T> extends _StreamImpl<T> {
_StreamControllerLifecycle<T> _controller;
_ControllerStream(this._controller);
StreamSubscription<T> _createSubscription(void onData(T data),
Function onError, void onDone(), bool cancelOnError) =>
_controller._subscribe(onData, onError, onDone, cancelOnError);
// Override == and hashCode so that new streams returned by the same
// controller are considered equal. The controller returns a new stream
// each time it's queried, but doesn't have to cache the result.
int get hashCode => _controller.hashCode ^ 0x35323532;
bool operator ==(Object other) {
if (identical(this, other)) return true;
if (other is! _ControllerStream) return false;
_ControllerStream otherStream = other;
return identical(otherStream._controller, this._controller);
}
}
class _ControllerSubscription<T> extends _BufferingStreamSubscription<T> {
final _StreamControllerLifecycle<T> _controller;
_ControllerSubscription(this._controller, void onData(T data),
Function onError, void onDone(), bool cancelOnError)
: super(onData, onError, onDone, cancelOnError);
Future _onCancel() {
return _controller._recordCancel(this);
}
void _onPause() {
_controller._recordPause(this);
}
void _onResume() {
_controller._recordResume(this);
}
}
/** A class that exposes only the [StreamSink] interface of an object. */
class _StreamSinkWrapper<T> implements StreamSink<T> {
final StreamController _target;
_StreamSinkWrapper(this._target);
void add(T data) {
_target.add(data);
}
void addError(Object error, [StackTrace stackTrace]) {
_target.addError(error, stackTrace);
}
Future close() => _target.close();
Future addStream(Stream<T> source, {bool cancelOnError: true}) =>
_target.addStream(source, cancelOnError: cancelOnError);
Future get done => _target.done;
}
/**
* Object containing the state used to handle [StreamController.addStream].
*/
class _AddStreamState<T> {
// [_Future] returned by call to addStream.
final _Future addStreamFuture;
// Subscription on stream argument to addStream.
final StreamSubscription addSubscription;
_AddStreamState(_EventSink<T> controller, Stream source, bool cancelOnError)
: addStreamFuture = new _Future(),
addSubscription = source.listen(controller._add,
onError: cancelOnError
? makeErrorHandler(controller)
: controller._addError,
onDone: controller._close,
cancelOnError: cancelOnError);
static makeErrorHandler(_EventSink controller) => (e, StackTrace s) {
controller._addError(e, s);
controller._close();
};
void pause() {
addSubscription.pause();
}
void resume() {
addSubscription.resume();
}
/**
* Stop adding the stream.
*
* Complete the future returned by `StreamController.addStream` when
* the cancel is complete.
*
* Return a future if the cancel takes time, otherwise return `null`.
*/
Future cancel() {
var cancel = addSubscription.cancel();
if (cancel == null) {
addStreamFuture._asyncComplete(null);
return null;
}
return cancel.whenComplete(() {
addStreamFuture._asyncComplete(null);
});
}
void complete() {
addStreamFuture._asyncComplete(null);
}
}
class _StreamControllerAddStreamState<T> extends _AddStreamState<T> {
// The subscription or pending data of a _StreamController.
// Stored here because we reuse the `_varData` field in the _StreamController
// to store this state object.
var varData;
_StreamControllerAddStreamState(_StreamController<T> controller, this.varData,
Stream source, bool cancelOnError)
: super(controller, source, cancelOnError) {
if (controller.isPaused) {
addSubscription.pause();
}
}
}