| // 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; |
| |
| // ------------------------------------------------------------------- |
| // Core Stream types |
| // ------------------------------------------------------------------- |
| |
| /** |
| * A source of asynchronous data events. |
| * |
| * A Stream provides a sequence of events. Each event is either a data event or |
| * an error event, representing the result of a single computation. When the |
| * Stream is exhausted, it may send a single "done" event. |
| * |
| * You can [listen] on a stream to receive the events it sends. When you listen, |
| * you receive a [StreamSubscription] object that can be used to stop listening, |
| * or to temporarily pause events from the stream. |
| * |
| * When an event is fired, the listeners at that time are informed. |
| * If a listener is added or removed while an event is being fired, the change |
| * will only take effect after the event is completely fired. |
| * |
| * Streams always respect "pause" requests. If necessary they need to buffer |
| * their input, but often, and preferably, they can simply request their input |
| * to pause too. |
| * |
| * There are two kinds of streams: The normal "single-subscription" streams and |
| * "broadcast" streams. |
| * |
| * A single-subscription stream allows only a single listener at a time. |
| * It holds back events until it gets a listener, and it may exhaust |
| * itself when the listener is unsubscribed, even if the stream wasn't done. |
| * |
| * Single-subscription streams are generally used for streaming parts of |
| * contiguous data like file I/O. |
| * |
| * A broadcast stream allows any number of listeners, and it fires |
| * its events when they are ready, whether there are listeners or not. |
| * |
| * Broadcast streams are used for independent events/observers. |
| * |
| * The default implementation of [isBroadcast] returns false. |
| * A broadcast stream inheriting from [Stream] must override [isBroadcast] |
| * to return [:true:]. |
| */ |
| abstract class Stream<T> { |
| Stream(); |
| |
| /** |
| * Creates a new single-subscription stream from the future. |
| * |
| * When the future completes, the stream will fire one event, either |
| * data or error, and then close with a done-event. |
| */ |
| factory Stream.fromFuture(Future<T> future) { |
| _StreamImpl<T> stream = new _SingleStreamImpl<T>(); |
| future.then((value) { |
| stream._add(value); |
| stream._close(); |
| }, |
| onError: (error) { |
| stream._signalError(error); |
| stream._close(); |
| }); |
| return stream; |
| } |
| |
| /** |
| * Creates a single-subscription stream that gets its data from [data]. |
| */ |
| factory Stream.fromIterable(Iterable<T> data) { |
| _PendingEvents iterableEvents = new _IterablePendingEvents<T>(data); |
| return new _GeneratedSingleStreamImpl<T>(iterableEvents); |
| } |
| |
| /** |
| * Whether the stream is a broadcast stream. |
| */ |
| bool get isBroadcast => false; |
| |
| /** |
| * Returns a multi-subscription stream that produces the same events as this. |
| * |
| * If this stream is single-subscription, return a new stream that allows |
| * multiple subscribers. It will subscribe to this stream when its first |
| * subscriber is added, and unsubscribe again when the last subscription is |
| * cancelled. |
| * |
| * If this stream is already a broadcast stream, it is returned unmodified. |
| */ |
| Stream<T> asBroadcastStream() { |
| if (isBroadcast) return this; |
| return new _SingleStreamMultiplexer<T>(this); |
| } |
| |
| /** |
| * Add a subscription to this stream. |
| * |
| * On each data event from this stream, the subscribers [onData] handler |
| * is called. If [onData] is null, nothing happens. |
| * |
| * On errors from this stream, the [onError] handler is given a |
| * [AsyncError] object describing the error. |
| * |
| * If this stream closes, the [onDone] handler is called. |
| * |
| * If [unsubscribeOnError] is true, the subscription is ended when |
| * the first error is reported. The default is false. |
| */ |
| StreamSubscription<T> listen(void onData(T event), |
| { void onError(AsyncError error), |
| void onDone(), |
| bool unsubscribeOnError}); |
| |
| /** |
| * Creates a new stream from this stream that discards some data events. |
| * |
| * The new stream sends the same error and done events as this stream, |
| * but it only sends the data events that satisfy the [test]. |
| */ |
| Stream<T> where(bool test(T event)) { |
| return new _WhereStream<T>(this, test); |
| } |
| |
| /** |
| * Create a new stream that converts each element of this stream |
| * to a new value using the [convert] function. |
| */ |
| Stream map(convert(T event)) { |
| return new _MapStream<T, dynamic>(this, convert); |
| } |
| |
| /** |
| * Deprecated alias for [map]. |
| * |
| * @deprecated |
| */ |
| Stream mappedBy(f(T element)) => map(f); |
| |
| /** |
| * Create a wrapper Stream that intercepts some errors from this stream. |
| * |
| * If this stream sends an error that matches [test], then it is intercepted |
| * by the [handle] function. |
| * |
| * An [AsyncError] [:e:] is matched by a test function if [:test(e):] returns |
| * true. If [test] is omitted, every error is considered matching. |
| * |
| * If the error is intercepted, the [handle] function can decide what to do |
| * with it. It can throw if it wants to raise a new (or the same) error, |
| * or simply return to make the stream forget the error. |
| * |
| * If you need to transform an error into a data event, use the more generic |
| * [Stream.transformEvent] to handle the event by writing a data event to |
| * the output sink |
| */ |
| Stream<T> handleError(void handle(AsyncError error), { bool test(error) }) { |
| return new _HandleErrorStream<T>(this, handle, test); |
| } |
| |
| /** |
| * Create a new stream from this stream that converts each element |
| * into zero or more events. |
| * |
| * Each incoming event is converted to an [Iterable] of new events, |
| * and each of these new events are then sent by the returned stream |
| * in order. |
| */ |
| Stream expand(Iterable convert(T value)) { |
| return new _ExpandStream<T, dynamic>(this, convert); |
| } |
| |
| /** |
| * Bind this stream as the input of the provided [StreamConsumer]. |
| */ |
| Future pipe(StreamConsumer<T, dynamic> streamConsumer) { |
| return streamConsumer.consume(this); |
| } |
| |
| /** |
| * Chain this stream as the input of the provided [StreamTransformer]. |
| * |
| * Returns the result of [:streamTransformer.bind:] itself. |
| */ |
| Stream transform(StreamTransformer<T, dynamic> streamTransformer) { |
| return streamTransformer.bind(this); |
| } |
| |
| /** Reduces a sequence of values by repeatedly applying [combine]. */ |
| Future reduce(var initialValue, combine(var previous, T element)) { |
| _FutureImpl result = new _FutureImpl(); |
| var value = initialValue; |
| StreamSubscription subscription; |
| subscription = this.listen( |
| // TODO(ahe): Restore type when feature is implemented in dart2js |
| // checked mode. http://dartbug.com/7733 |
| (/*T*/ element) { |
| _runUserCode( |
| () => combine(value, element), |
| (result) { value = result; }, |
| _cancelAndError(subscription, result) |
| ); |
| }, |
| onError: (AsyncError e) { |
| result._setError(e); |
| }, |
| onDone: () { |
| result._setValue(value); |
| }, |
| unsubscribeOnError: true); |
| return result; |
| } |
| |
| // Deprecated method, previously called 'pipe', retained for compatibility. |
| Future pipeInto(Sink<T> sink, |
| {void onError(AsyncError error), |
| bool unsubscribeOnError}) { |
| _FutureImpl<T> result = new _FutureImpl<T>(); |
| this.listen( |
| sink.add, |
| onError: onError, |
| onDone: () { |
| sink.close(); |
| result._setValue(null); |
| }, |
| unsubscribeOnError: unsubscribeOnError); |
| return result; |
| } |
| |
| |
| /** |
| * Check whether [match] occurs in the elements provided by this stream. |
| * |
| * Completes the [Future] when the answer is known. |
| * If this stream reports an error, the [Future] will report that error. |
| */ |
| Future<bool> contains(T match) { |
| _FutureImpl<bool> future = new _FutureImpl<bool>(); |
| StreamSubscription subscription; |
| subscription = this.listen( |
| // TODO(ahe): Restore type when feature is implemented in dart2js |
| // checked mode. http://dartbug.com/7733 |
| (/*T*/ element) { |
| _runUserCode( |
| () => (element == match), |
| (bool isMatch) { |
| if (isMatch) { |
| subscription.cancel(); |
| future._setValue(true); |
| } |
| }, |
| _cancelAndError(subscription, future) |
| ); |
| }, |
| onError: future._setError, |
| onDone: () { |
| future._setValue(false); |
| }, |
| unsubscribeOnError: true); |
| return future; |
| } |
| |
| /** |
| * Check whether [test] accepts all elements provided by this stream. |
| * |
| * Completes the [Future] when the answer is known. |
| * If this stream reports an error, the [Future] will report that error. |
| */ |
| Future<bool> every(bool test(T element)) { |
| _FutureImpl<bool> future = new _FutureImpl<bool>(); |
| StreamSubscription subscription; |
| subscription = this.listen( |
| // TODO(ahe): Restore type when feature is implemented in dart2js |
| // checked mode. http://dartbug.com/7733 |
| (/*T*/ element) { |
| _runUserCode( |
| () => test(element), |
| (bool isMatch) { |
| if (!isMatch) { |
| subscription.cancel(); |
| future._setValue(false); |
| } |
| }, |
| _cancelAndError(subscription, future) |
| ); |
| }, |
| onError: future._setError, |
| onDone: () { |
| future._setValue(true); |
| }, |
| unsubscribeOnError: true); |
| return future; |
| } |
| |
| /** |
| * Check whether [test] accepts any element provided by this stream. |
| * |
| * Completes the [Future] when the answer is known. |
| * If this stream reports an error, the [Future] will report that error. |
| */ |
| Future<bool> any(bool test(T element)) { |
| _FutureImpl<bool> future = new _FutureImpl<bool>(); |
| StreamSubscription subscription; |
| subscription = this.listen( |
| // TODO(ahe): Restore type when feature is implemented in dart2js |
| // checked mode. http://dartbug.com/7733 |
| (/*T*/ element) { |
| _runUserCode( |
| () => test(element), |
| (bool isMatch) { |
| if (isMatch) { |
| subscription.cancel(); |
| future._setValue(true); |
| } |
| }, |
| _cancelAndError(subscription, future) |
| ); |
| }, |
| onError: future._setError, |
| onDone: () { |
| future._setValue(false); |
| }, |
| unsubscribeOnError: true); |
| return future; |
| } |
| |
| |
| /** Counts the elements in the stream. */ |
| Future<int> get length { |
| _FutureImpl<int> future = new _FutureImpl<int>(); |
| int count = 0; |
| this.listen( |
| (_) { count++; }, |
| onError: future._setError, |
| onDone: () { |
| future._setValue(count); |
| }, |
| unsubscribeOnError: true); |
| return future; |
| } |
| |
| /** |
| * Finds the least element in the stream. |
| * |
| * If the stream is empty, the result is [:null:]. |
| * Otherwise the result is a value from the stream that is not greater |
| * than any other value from the stream (according to [compare], which must |
| * be a [Comparator]). |
| * |
| * If [compare] is omitted, it defaults to [Comparable.compare]. |
| */ |
| Future<T> min([int compare(T a, T b)]) { |
| if (compare == null) { |
| var defaultCompare = Comparable.compare; |
| compare = defaultCompare; |
| } |
| _FutureImpl<T> future = new _FutureImpl<T>(); |
| StreamSubscription subscription; |
| T min = null; |
| subscription = this.listen( |
| // TODO(ahe): Restore type when feature is implemented in dart2js |
| // checked mode. http://dartbug.com/7733 |
| (/*T*/ value) { |
| min = value; |
| subscription.onData((T value) { |
| _runUserCode( |
| () => compare(min, value) > 0, |
| (bool foundSmaller) { |
| if (foundSmaller) { |
| min = value; |
| } |
| }, |
| _cancelAndError(subscription, future) |
| ); |
| }); |
| }, |
| onError: future._setError, |
| onDone: () { |
| future._setValue(min); |
| }, |
| unsubscribeOnError: true |
| ); |
| return future; |
| } |
| |
| /** |
| * Finds the largest element in the stream. |
| * |
| * If the stream is empty, the result is [:null:]. |
| * Otherwise the result is an value from the stream that is not smaller |
| * than any other value from the stream (according to [compare], which must |
| * be a [Comparator]). |
| * |
| * If [compare] is omitted, it defaults to [Comparable.compare]. |
| */ |
| Future<T> max([int compare(T a, T b)]) { |
| if (compare == null) { |
| var defaultCompare = Comparable.compare; |
| compare = defaultCompare; |
| } |
| _FutureImpl<T> future = new _FutureImpl<T>(); |
| StreamSubscription subscription; |
| T max = null; |
| subscription = this.listen( |
| // TODO(ahe): Restore type when feature is implemented in dart2js |
| // checked mode. http://dartbug.com/7733 |
| (/*T*/ value) { |
| max = value; |
| subscription.onData((T value) { |
| _runUserCode( |
| () => compare(max, value) < 0, |
| (bool foundGreater) { |
| if (foundGreater) { |
| max = value; |
| } |
| }, |
| _cancelAndError(subscription, future) |
| ); |
| }); |
| }, |
| onError: future._setError, |
| onDone: () { |
| future._setValue(max); |
| }, |
| unsubscribeOnError: true |
| ); |
| return future; |
| } |
| |
| /** Reports whether this stream contains any elements. */ |
| Future<bool> get isEmpty { |
| _FutureImpl<bool> future = new _FutureImpl<bool>(); |
| StreamSubscription subscription; |
| subscription = this.listen( |
| (_) { |
| subscription.cancel(); |
| future._setValue(false); |
| }, |
| onError: future._setError, |
| onDone: () { |
| future._setValue(true); |
| }, |
| unsubscribeOnError: true); |
| return future; |
| } |
| |
| /** Collect the data of this stream in a [List]. */ |
| Future<List<T>> toList() { |
| List<T> result = <T>[]; |
| _FutureImpl<List<T>> future = new _FutureImpl<List<T>>(); |
| this.listen( |
| // TODO(ahe): Restore type when feature is implemented in dart2js |
| // checked mode. http://dartbug.com/7733 |
| (/*T*/ data) { |
| result.add(data); |
| }, |
| onError: future._setError, |
| onDone: () { |
| future._setValue(result); |
| }, |
| unsubscribeOnError: true); |
| return future; |
| } |
| |
| /** Collect the data of this stream in a [Set]. */ |
| Future<Set<T>> toSet() { |
| Set<T> result = new Set<T>(); |
| _FutureImpl<Set<T>> future = new _FutureImpl<Set<T>>(); |
| this.listen( |
| // TODO(ahe): Restore type when feature is implemented in dart2js |
| // checked mode. http://dartbug.com/7733 |
| (/*T*/ data) { |
| result.add(data); |
| }, |
| onError: future._setError, |
| onDone: () { |
| future._setValue(result); |
| }, |
| unsubscribeOnError: true); |
| return future; |
| } |
| |
| /** |
| * Provide at most the first [n] values of this stream. |
| * |
| * Forwards the first [n] data events of this stream, and all error |
| * events, to the returned stream, and ends with a done event. |
| * |
| * If this stream produces fewer than [count] values before it's done, |
| * so will the returned stream. |
| */ |
| Stream<T> take(int count) { |
| return new _TakeStream(this, count); |
| } |
| |
| /** |
| * Forwards data events while [test] is successful. |
| * |
| * The returned stream provides the same events as this stream as long |
| * as [test] returns [:true:] for the event data. The stream is done |
| * when either this stream is done, or when this stream first provides |
| * a value that [test] doesn't accept. |
| */ |
| Stream<T> takeWhile(bool test(T value)) { |
| return new _TakeWhileStream(this, test); |
| } |
| |
| /** |
| * Skips the first [count] data events from this stream. |
| */ |
| Stream<T> skip(int count) { |
| return new _SkipStream(this, count); |
| } |
| |
| /** |
| * Skip data events from this stream while they are matched by [test]. |
| * |
| * Error and done events are provided by the returned stream unmodified. |
| * |
| * Starting with the first data event where [test] returns true for the |
| * event data, the returned stream will have the same events as this stream. |
| */ |
| Stream<T> skipWhile(bool test(T value)) { |
| return new _SkipWhileStream(this, test); |
| } |
| |
| /** |
| * Skip data events if they are equal to the previous data event. |
| * |
| * The returned stream provides the same events as this stream, except |
| * that it never provides two consequtive data events that are equal. |
| * |
| * Equality is determined by the provided [equals] method. If that is |
| * omitted, the '==' operator on the last provided data element is used. |
| */ |
| Stream<T> distinct([bool equals(T previous, T next)]) { |
| return new _DistinctStream(this, equals); |
| } |
| |
| /** |
| * Returns the first element. |
| * |
| * If [this] is empty throws a [StateError]. Otherwise this method is |
| * equivalent to [:this.elementAt(0):] |
| */ |
| Future<T> get first { |
| _FutureImpl<T> future = new _FutureImpl<T>(); |
| StreamSubscription subscription; |
| subscription = this.listen( |
| // TODO(ahe): Restore type when feature is implemented in dart2js |
| // checked mode. http://dartbug.com/7733 |
| (/*T*/ value) { |
| future._setValue(value); |
| subscription.cancel(); |
| return; |
| }, |
| onError: future._setError, |
| onDone: () { |
| future._setError(new AsyncError(new StateError("No elements"))); |
| }, |
| unsubscribeOnError: true); |
| return future; |
| } |
| |
| /** |
| * Returns the last element. |
| * |
| * If [this] is empty throws a [StateError]. |
| */ |
| Future<T> get last { |
| _FutureImpl<T> future = new _FutureImpl<T>(); |
| T result = null; |
| bool foundResult = false; |
| StreamSubscription subscription; |
| subscription = this.listen( |
| // TODO(ahe): Restore type when feature is implemented in dart2js |
| // checked mode. http://dartbug.com/7733 |
| (/*T*/ value) { |
| foundResult = true; |
| result = value; |
| }, |
| onError: future._setError, |
| onDone: () { |
| if (foundResult) { |
| future._setValue(result); |
| return; |
| } |
| future._setError(new AsyncError(new StateError("No elements"))); |
| }, |
| unsubscribeOnError: true); |
| return future; |
| } |
| |
| /** |
| * Returns the single element. |
| * |
| * If [this] is empty or has more than one element throws a [StateError]. |
| */ |
| Future<T> get single { |
| _FutureImpl<T> future = new _FutureImpl<T>(); |
| T result = null; |
| bool foundResult = false; |
| StreamSubscription subscription; |
| subscription = this.listen( |
| // TODO(ahe): Restore type when feature is implemented in dart2js |
| // checked mode. http://dartbug.com/7733 |
| (/*T*/ value) { |
| if (foundResult) { |
| // This is the second element we get. |
| Error error = new StateError("More than one element"); |
| future._setError(new AsyncError(error)); |
| subscription.cancel(); |
| return; |
| } |
| foundResult = true; |
| result = value; |
| }, |
| onError: future._setError, |
| onDone: () { |
| if (foundResult) { |
| future._setValue(result); |
| return; |
| } |
| future._setError(new AsyncError(new StateError("No elements"))); |
| }, |
| unsubscribeOnError: true); |
| return future; |
| } |
| |
| /** |
| * Find the first element of this stream matching [test]. |
| * |
| * Returns a future that is filled with the first element of this stream |
| * that [test] returns true for. |
| * |
| * If no such element is found before this stream is done, and a |
| * [defaultValue] function is provided, the result of calling [defaultValue] |
| * becomes the value of the future. |
| * |
| * If an error occurs, or if this stream ends without finding a match and |
| * with no [defaultValue] function provided, the future will receive an |
| * error. |
| */ |
| Future<T> firstMatching(bool test(T value), {T defaultValue()}) { |
| _FutureImpl<T> future = new _FutureImpl<T>(); |
| StreamSubscription subscription; |
| subscription = this.listen( |
| // TODO(ahe): Restore type when feature is implemented in dart2js |
| // checked mode. http://dartbug.com/7733 |
| (/*T*/ value) { |
| _runUserCode( |
| () => test(value), |
| (bool isMatch) { |
| if (isMatch) { |
| subscription.cancel(); |
| future._setValue(value); |
| } |
| }, |
| _cancelAndError(subscription, future) |
| ); |
| }, |
| onError: future._setError, |
| onDone: () { |
| if (defaultValue != null) { |
| _runUserCode(defaultValue, future._setValue, future._setError); |
| return; |
| } |
| future._setError( |
| new AsyncError(new StateError("firstMatch ended without match"))); |
| }, |
| unsubscribeOnError: true); |
| return future; |
| } |
| |
| /** |
| * Finds the last element in this stream matching [test]. |
| * |
| * As [firstMatching], except that the last matching element is found. |
| * That means that the result cannot be provided before this stream |
| * is done. |
| */ |
| Future<T> lastMatching(bool test(T value), {T defaultValue()}) { |
| _FutureImpl<T> future = new _FutureImpl<T>(); |
| T result = null; |
| bool foundResult = false; |
| StreamSubscription subscription; |
| subscription = this.listen( |
| // TODO(ahe): Restore type when feature is implemented in dart2js |
| // checked mode. http://dartbug.com/7733 |
| (/*T*/ value) { |
| _runUserCode( |
| () => true == test(value), |
| (bool isMatch) { |
| if (isMatch) { |
| foundResult = true; |
| result = value; |
| } |
| }, |
| _cancelAndError(subscription, future) |
| ); |
| }, |
| onError: future._setError, |
| onDone: () { |
| if (foundResult) { |
| future._setValue(result); |
| return; |
| } |
| if (defaultValue != null) { |
| _runUserCode(defaultValue, future._setValue, future._setError); |
| return; |
| } |
| future._setError( |
| new AsyncError(new StateError("lastMatch ended without match"))); |
| }, |
| unsubscribeOnError: true); |
| return future; |
| } |
| |
| /** |
| * Finds the single element in this stream matching [test]. |
| * |
| * Like [lastMatch], except that it is an error if more than one |
| * matching element occurs in the stream. |
| */ |
| Future<T> singleMatching(bool test(T value)) { |
| _FutureImpl<T> future = new _FutureImpl<T>(); |
| T result = null; |
| bool foundResult = false; |
| StreamSubscription subscription; |
| subscription = this.listen( |
| // TODO(ahe): Restore type when feature is implemented in dart2js |
| // checked mode. http://dartbug.com/7733 |
| (/*T*/ value) { |
| _runUserCode( |
| () => true == test(value), |
| (bool isMatch) { |
| if (isMatch) { |
| if (foundResult) { |
| subscription.cancel(); |
| future._setError(new AsyncError( |
| new StateError('Multiple matches for "single"'))); |
| return; |
| } |
| foundResult = true; |
| result = value; |
| } |
| }, |
| _cancelAndError(subscription, future) |
| ); |
| }, |
| onError: future._setError, |
| onDone: () { |
| if (foundResult) { |
| future._setValue(result); |
| return; |
| } |
| future._setError( |
| new AsyncError(new StateError("single ended without match"))); |
| }, |
| unsubscribeOnError: true); |
| return future; |
| } |
| |
| /** |
| * Returns the value of the [index]th data event of this stream. |
| * |
| * If an error event occurs, the future will end with this error. |
| * |
| * If this stream provides fewer than [index] elements before closing, |
| * an error is reported. |
| */ |
| Future<T> elementAt(int index) { |
| if (index is! int || index < 0) throw new ArgumentError(index); |
| _FutureImpl<T> future = new _FutureImpl<T>(); |
| StreamSubscription subscription; |
| subscription = this.listen( |
| // TODO(ahe): Restore type when feature is implemented in dart2js |
| // checked mode. http://dartbug.com/7733 |
| (/*T*/ value) { |
| if (index == 0) { |
| future._setValue(value); |
| subscription.cancel(); |
| return; |
| } |
| index -= 1; |
| }, |
| onError: future._setError, |
| onDone: () { |
| future._setError(new AsyncError( |
| new StateError("Not enough elements for elementAt"))); |
| }, |
| unsubscribeOnError: true); |
| return future; |
| } |
| } |
| |
| /** |
| * A control object for the subscription on a [Stream]. |
| * |
| * When you subscribe on a [Stream] using [Stream.listen], |
| * a [StreamSubscription] object is returned. This object |
| * is used to later unsubscribe again, or to temporarily pause |
| * the stream's events. |
| */ |
| abstract class StreamSubscription<T> { |
| /** |
| * Cancels this subscription. It will no longer receive events. |
| * |
| * If an event is currently firing, this unsubscription will only |
| * take effect after all subscribers have received the current event. |
| */ |
| void cancel(); |
| |
| /** Set or override the data event handler of this subscription. */ |
| void onData(void handleData(T data)); |
| |
| /** Set or override the error event handler of this subscription. */ |
| void onError(void handleError(AsyncError error)); |
| |
| /** Set or override the done event handler of this subscription. */ |
| void onDone(void handleDone()); |
| |
| /** |
| * Request that the stream pauses events until further notice. |
| * |
| * If [resumeSignal] is provided, the stream will undo the pause |
| * when the future completes. If the future completes with an error, |
| * it will not be handled! |
| * |
| * A call to [resume] will also undo a pause. |
| * |
| * If the subscription is paused more than once, an equal number |
| * of resumes must be performed to resume the stream. |
| */ |
| void pause([Future resumeSignal]); |
| |
| /** |
| * Resume after a pause. |
| */ |
| void resume(); |
| } |
| |
| |
| /** |
| * An interface that abstracts sending events into a [Stream]. |
| */ |
| abstract class StreamSink<T> implements Sink<T> { |
| void add(T event); |
| /** Signal an async error to the receivers of this sink's values. */ |
| void signalError(AsyncError errorEvent); |
| void close(); |
| } |
| |
| /** [Stream] wrapper that only exposes the [Stream] interface. */ |
| class StreamView<T> extends Stream<T> { |
| Stream<T> _stream; |
| |
| StreamView(this._stream); |
| |
| bool get isBroadcast => _stream.isBroadcast; |
| |
| Stream<T> asBroadcastStream() => _stream.asBroadcastStream(); |
| |
| StreamSubscription<T> listen(void onData(T value), |
| { void onError(AsyncError error), |
| void onDone(), |
| bool unsubscribeOnError }) { |
| return _stream.listen(onData, onError: onError, onDone: onDone, |
| unsubscribeOnError: unsubscribeOnError); |
| } |
| } |
| |
| /** |
| * [StreamSink] wrapper that only exposes the [StreamSink] interface. |
| */ |
| class StreamSinkView<T> implements StreamSink<T> { |
| final StreamSink<T> _sink; |
| |
| StreamSinkView(this._sink); |
| |
| void add(T value) { _sink.add(value); } |
| void signalError(AsyncError error) { _sink.signalError(error); } |
| void close() { _sink.close(); } |
| } |
| |
| |
| /** |
| * The target of a [Stream.pipe] call. |
| * |
| * The [Stream.pipe] call will pass itself to this object, and then return |
| * the resulting [Future]. The pipe should complete the future when it's |
| * done. |
| */ |
| abstract class StreamConsumer<S, T> { |
| Future<T> consume(Stream<S> stream); |
| } |
| |
| |
| /** |
| * The target of a [Stream.transform] call. |
| * |
| * The [Stream.transform] call will pass itself to this object and then return |
| * the resulting stream. |
| */ |
| abstract class StreamTransformer<S, T> { |
| /** |
| * Create a [StreamTransformer] that delegates events to the given functions. |
| * |
| * This is actually a [StreamEventTransformer] where the event handling is |
| * performed by the function arguments. |
| * If an argument is omitted, it acts as the corresponding default method from |
| * [StreamEventTransformer]. |
| * |
| * Example use: |
| * |
| * stringStream.transform(new StreamTransformer<String, String>( |
| * handleData: (Strung value, StreamSink<String> sink) { |
| * sink.add(value); |
| * sink.add(value); // Duplicate the incoming events. |
| * })); |
| * |
| */ |
| factory StreamTransformer({ |
| void handleData(S data, StreamSink<T> sink), |
| void handleError(AsyncError error, StreamSink<T> sink), |
| void handleDone(StreamSink<T> sink)}) { |
| return new _StreamTransformerImpl<S, T>(handleData, |
| handleError, |
| handleDone); |
| } |
| |
| Stream<T> bind(Stream<S> stream); |
| } |
| |
| |
| /** |
| * Base class for transformers that modifies stream events. |
| * |
| * A [StreamEventTransformer] transforms incoming Stream |
| * events of one kind into outgoing events of (possibly) another kind. |
| * |
| * Subscribing on the stream returned by [bind] is the same as subscribing on |
| * the source stream, except that events are passed through the [transformer] |
| * before being emitted. The transformer may generate any number and |
| * types of events for each incoming event. Pauses on the returned |
| * subscription are forwarded to this stream. |
| * |
| * An example that duplicates all data events: |
| * |
| * class DoubleTransformer<T> extends StreamEventTransformerBase<T, T> { |
| * void handleData(T data, StreamSink<T> sink) { |
| * sink.add(value); |
| * sink.add(value); |
| * } |
| * } |
| * someTypeStream.transform(new DoubleTransformer<Type>()); |
| * |
| * The default implementations of the "handle" methods forward |
| * the events unmodified. If using the default [handleData] the generic type [T] |
| * needs to be assignable to [S]. |
| */ |
| abstract class StreamEventTransformer<S, T> implements StreamTransformer<S, T> { |
| const StreamEventTransformer(); |
| |
| Stream<T> bind(Stream<S> source) { |
| return new EventTransformStream<S, T>(source, this); |
| } |
| |
| /** |
| * Act on incoming data event. |
| * |
| * The method may generate any number of events on the sink, but should |
| * not throw. |
| */ |
| void handleData(S event, StreamSink<T> sink) { |
| var data = event; |
| sink.add(data); |
| } |
| |
| /** |
| * Act on incoming error event. |
| * |
| * The method may generate any number of events on the sink, but should |
| * not throw. |
| */ |
| void handleError(AsyncError error, StreamSink<T> sink) { |
| sink.signalError(error); |
| } |
| |
| /** |
| * Act on incoming done event. |
| * |
| * The method may generate any number of events on the sink, but should |
| * not throw. |
| */ |
| void handleDone(StreamSink<T> sink){ |
| sink.close(); |
| } |
| } |
| |
| |
| /** |
| * Stream that transforms another stream by intercepting and replacing events. |
| * |
| * This [Stream] is a transformation of a source stream. Listening on this |
| * stream is the same as listening on the source stream, except that events |
| * are intercepted and modified by a [StreamEventTransformer] before becoming |
| * events on this stream. |
| */ |
| class EventTransformStream<S, T> extends Stream<T> { |
| final Stream<S> _source; |
| final StreamEventTransformer _transformer; |
| EventTransformStream(Stream<S> source, |
| StreamEventTransformer<S, T> transformer) |
| : _source = source, _transformer = transformer; |
| |
| StreamSubscription<T> listen(void onData(T data), |
| { void onError(AsyncError error), |
| void onDone(), |
| bool unsubscribeOnError }) { |
| return new _EventTransformStreamSubscription(_source, _transformer, |
| onData, onError, onDone, |
| unsubscribeOnError); |
| } |
| } |
| |
| class _EventTransformStreamSubscription<S, T> |
| extends _BaseStreamSubscription<T> |
| implements _StreamOutputSink<T> { |
| /** The transformer used to transform events. */ |
| final StreamEventTransformer<S, T> _transformer; |
| /** Whether to unsubscribe when emitting an error. */ |
| final bool _unsubscribeOnError; |
| /** Source of incoming events. */ |
| StreamSubscription<S> _subscription; |
| /** Cached StreamSink wrapper for this class. */ |
| StreamSink<T> _sink; |
| |
| _EventTransformStreamSubscription(Stream<S> source, |
| this._transformer, |
| void onData(T data), |
| void onError(AsyncError error), |
| void onDone(), |
| this._unsubscribeOnError) |
| : super(onData, onError, onDone) { |
| _sink = new _StreamOutputSinkWrapper<T>(this); |
| _subscription = source.listen(_handleData, |
| onError: _handleError, |
| onDone: _handleDone); |
| } |
| |
| void pause([Future pauseSignal]) { |
| if (_subscription != null) _subscription.pause(pauseSignal); |
| } |
| |
| void resume() { |
| if (_subscription != null) _subscription.resume(); |
| } |
| |
| void cancel() { |
| if (_subscription != null) { |
| _subscription.cancel(); |
| _subscription = null; |
| } |
| } |
| |
| void _handleData(S data) { |
| try { |
| _transformer.handleData(data, _sink); |
| } catch (e, s) { |
| _sendError(_asyncError(e, s)); |
| } |
| } |
| |
| void _handleError(AsyncError error) { |
| try { |
| _transformer.handleError(error, _sink); |
| } catch (e, s) { |
| _sendError(_asyncError(e, s, error)); |
| } |
| } |
| |
| void _handleDone() { |
| try { |
| _transformer.handleDone(_sink); |
| } catch (e, s) { |
| _sendError(_asyncError(e, s)); |
| } |
| } |
| |
| // StreamOutputSink interface. |
| void _sendData(T data) { |
| _onData(data); |
| } |
| |
| void _sendError(AsyncError error) { |
| _onError(error); |
| if (_unsubscribeOnError) { |
| cancel(); |
| } |
| } |
| |
| void _sendDone() { |
| // It's ok to cancel even if we have been unsubscribed already. |
| cancel(); |
| _onDone(); |
| } |
| } |
| |
| class _StreamOutputSinkWrapper<T> implements StreamSink<T> { |
| _StreamOutputSink _sink; |
| _StreamOutputSinkWrapper(this._sink); |
| |
| void add(T data) => _sink._sendData(data); |
| void signalError(AsyncError error) => _sink._sendError(error); |
| void close() => _sink._sendDone(); |
| } |