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1 // Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file | 1 // Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file |
2 // for details. All rights reserved. Use of this source code is governed by a | 2 // for details. All rights reserved. Use of this source code is governed by a |
3 // BSD-style license that can be found in the LICENSE file. | 3 // BSD-style license that can be found in the LICENSE file. |
4 | 4 |
5 library async.stream_sink_completer; | 5 library async.stream_sink_completer; |
6 | 6 |
7 import 'dart:async'; | 7 import 'dart:async'; |
8 | 8 |
| 9 import 'null_stream_sink.dart'; |
| 10 |
9 /// A [sink] where the destination is provided later. | 11 /// A [sink] where the destination is provided later. |
10 /// | 12 /// |
11 /// The [sink] is a normal sink that you can add events to to immediately, but | 13 /// The [sink] is a normal sink that you can add events to to immediately, but |
12 /// until [setDestinationSink] is called, the events will be buffered. | 14 /// until [setDestinationSink] is called, the events will be buffered. |
13 /// | 15 /// |
14 /// The same effect can be achieved by using a [StreamController] and adding it | 16 /// The same effect can be achieved by using a [StreamController] and adding it |
15 /// to the sink using [Sink.addStream] when the destination sink is ready. This | 17 /// to the sink using [Sink.addStream] when the destination sink is ready. This |
16 /// class attempts to shortcut some of the overhead when possible. For example, | 18 /// class attempts to shortcut some of the overhead when possible. For example, |
17 /// if the [sink] only has events added after the destination sink has been set, | 19 /// if the [sink] only has events added after the destination sink has been set, |
18 /// those events are added directly to the sink. | 20 /// those events are added directly to the sink. |
19 class StreamSinkCompleter<T> { | 21 class StreamSinkCompleter<T> { |
20 /// The sink for this completer. | 22 /// The sink for this completer. |
21 /// | 23 /// |
22 /// When a destination sink is provided, events that have been passed to the | 24 /// When a destination sink is provided, events that have been passed to the |
23 /// sink will be forwarded to the destination. | 25 /// sink will be forwarded to the destination. |
24 /// | 26 /// |
25 /// Events can be added to the sink either before or after a destination sink | 27 /// Events can be added to the sink either before or after a destination sink |
26 /// is set. | 28 /// is set. |
27 final StreamSink<T> sink = new _CompleterSink<T>(); | 29 final StreamSink<T> sink = new _CompleterSink<T>(); |
28 | 30 |
29 /// Returns [sink] typed as a [_CompleterSink]. | 31 /// Returns [sink] typed as a [_CompleterSink]. |
30 _CompleterSink<T> get _sink => sink; | 32 _CompleterSink<T> get _sink => sink; |
31 | 33 |
| 34 /// Convert a `Future<StreamSink>` to a `StreamSink`. |
| 35 /// |
| 36 /// This creates a sink using a sink completer, and sets the destination sink |
| 37 /// to the result of the future when the future completes. |
| 38 /// |
| 39 /// If the future completes with an error, the returned sink will instead |
| 40 /// be closed. Its [Sink.done] future will contain the error. |
| 41 static StreamSink fromFuture(Future<StreamSink> sinkFuture) { |
| 42 var completer = new StreamSinkCompleter(); |
| 43 sinkFuture.then(completer.setDestinationSink, |
| 44 onError: completer.setError); |
| 45 return completer.sink; |
| 46 } |
| 47 |
32 /// Sets a sink as the destination for events from the [StreamSinkCompleter]'s | 48 /// Sets a sink as the destination for events from the [StreamSinkCompleter]'s |
33 /// [sink]. | 49 /// [sink]. |
34 /// | 50 /// |
35 /// The completer's [sink] will act exactly as [destinationSink]. | 51 /// The completer's [sink] will act exactly as [destinationSink]. |
36 /// | 52 /// |
37 /// If the destination sink is set before events are added to [sink], further | 53 /// If the destination sink is set before events are added to [sink], further |
38 /// events are forwarded directly to [destinationSink]. | 54 /// events are forwarded directly to [destinationSink]. |
39 /// | 55 /// |
40 /// If events are added to [sink] before setting the destination sink, they're | 56 /// If events are added to [sink] before setting the destination sink, they're |
41 /// buffered until the destination is available. | 57 /// buffered until the destination is available. |
42 /// | 58 /// |
43 /// A destination sink may be set at most once. | 59 /// A destination sink may be set at most once. |
| 60 /// |
| 61 /// Either of [setDestinationSink] or [setError] may be called at most once. |
| 62 /// Trying to call either of them again will fail. |
44 void setDestinationSink(StreamSink<T> destinationSink) { | 63 void setDestinationSink(StreamSink<T> destinationSink) { |
45 if (_sink._destinationSink != null) { | 64 if (_sink._destinationSink != null) { |
46 throw new StateError("Destination sink already set"); | 65 throw new StateError("Destination sink already set"); |
47 } | 66 } |
48 _sink._setDestinationSink(destinationSink); | 67 _sink._setDestinationSink(destinationSink); |
49 } | 68 } |
| 69 |
| 70 /// Completes this to a closed sink whose [Sink.done] future emits [error]. |
| 71 /// |
| 72 /// This is useful when the process of loading the sink fails. |
| 73 /// |
| 74 /// Either of [setDestinationSink] or [setError] may be called at most once. |
| 75 /// Trying to call either of them again will fail. |
| 76 void setError(error, [StackTrace stackTrace]) { |
| 77 setDestinationSink(new NullStreamSink.error(error, stackTrace)); |
| 78 } |
50 } | 79 } |
51 | 80 |
52 /// [StreamSink] completed by [StreamSinkCompleter]. | 81 /// [StreamSink] completed by [StreamSinkCompleter]. |
53 class _CompleterSink<T> implements StreamSink<T> { | 82 class _CompleterSink<T> implements StreamSink<T> { |
54 /// Controller for an intermediate sink. | 83 /// Controller for an intermediate sink. |
55 /// | 84 /// |
56 /// Created if the user adds events to this sink before the destination sink | 85 /// Created if the user adds events to this sink before the destination sink |
57 /// is set. | 86 /// is set. |
58 StreamController<T> _controller; | 87 StreamController<T> _controller; |
59 | 88 |
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142 .catchError((_) {}); | 171 .catchError((_) {}); |
143 } | 172 } |
144 | 173 |
145 // If the user has already asked when the sink is done, connect the sink's | 174 // If the user has already asked when the sink is done, connect the sink's |
146 // done callback to that completer. | 175 // done callback to that completer. |
147 if (_doneCompleter != null) { | 176 if (_doneCompleter != null) { |
148 _doneCompleter.complete(sink.done); | 177 _doneCompleter.complete(sink.done); |
149 } | 178 } |
150 } | 179 } |
151 } | 180 } |
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