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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 | |
3 // BSD-style license that can be found in the LICENSE file. | |
4 | |
5 import 'dart:async'; | |
6 | |
7 import 'package:async/async.dart'; | |
8 | |
9 import '../stream_channel.dart'; | |
10 | |
11 /// A [channel] where the source and destination are provided later. | |
12 /// | |
13 /// The [channel] is a normal channel that can be listened to and that events | |
14 /// can be added to immediately, but until [setChannel] is called it won't emit | |
15 /// any events and all events added to it will be buffered. | |
16 class StreamChannelCompleter<T> { | |
17 /// The completer for this channel's stream. | |
18 final _streamCompleter = new StreamCompleter<T>(); | |
19 | |
20 /// The completer for this channel's sink. | |
21 final _sinkCompleter = new StreamSinkCompleter<T>(); | |
22 | |
23 /// The channel for this completer. | |
24 StreamChannel<T> get channel => _channel; | |
25 StreamChannel<T> _channel; | |
26 | |
27 /// Whether [setChannel] has been called. | |
28 bool _set = false; | |
Bob Nystrom
2016/01/26 19:00:18
Instead of a separate field, can you just do:
_st
nweiz
2016/01/26 23:24:57
No, the point of a completer is that the object it
| |
29 | |
30 /// Convert a `Future<StreamChannel>` to a `StreamChannel`. | |
31 /// | |
32 /// This creates a channel using a channel completer, and sets the source | |
33 /// channel to the result of the future when the future completes. | |
34 /// | |
35 /// If the future completes with an error, the returned channel's stream will | |
36 /// instead contain just that error. The sink will silently discard all | |
37 /// events. | |
38 static StreamChannel fromFuture(Future<StreamChannel> channelFuture) { | |
39 var completer = new StreamChannelCompleter(); | |
40 channelFuture.then(completer.setChannel, onError: completer.setError); | |
41 return completer.channel; | |
42 } | |
43 | |
44 StreamChannelCompleter() { | |
45 _channel = new StreamChannel<T>( | |
46 _streamCompleter.stream, _sinkCompleter.sink); | |
47 } | |
48 | |
49 /// Set a channel as the source and destination for [channel]. | |
50 /// | |
51 /// A channel may be set at most once. | |
52 /// | |
53 /// Either [setChannel] or [setError] may be called at most once. Trying to | |
54 /// call any of them again will fail. | |
Bob Nystrom
2016/01/26 19:00:18
"any" -> "either".
nweiz
2016/01/26 23:24:57
Done.
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55 void setChannel(StreamChannel<T> channel) { | |
56 if (_set) throw new StateError("The channel has already been set."); | |
57 _set = true; | |
58 | |
59 _streamCompleter.setSourceStream(channel.stream); | |
60 _sinkCompleter.setDestinationSink(channel.sink); | |
61 } | |
62 | |
63 /// Indicates that there was an error connecting the channel. | |
64 /// | |
65 /// This makes the stream emit [error] and close. It makes the sink discard | |
66 /// all its events. | |
67 /// | |
68 /// Either [setChannel] or [setError] may be called at most once. Trying to | |
69 /// call any of them again will fail. | |
Bob Nystrom
2016/01/26 19:00:18
Ditto.
nweiz
2016/01/26 23:24:57
Done.
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70 void setError(error, [StackTrace stackTrace]) { | |
71 if (_set) throw new StateError("The channel has already been set."); | |
72 _set = true; | |
73 | |
74 _streamCompleter.setError(error, stackTrace); | |
75 _sinkCompleter.setDestinationSink(new NullStreamSink()); | |
76 } | |
77 } | |
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