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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 import 'dart:convert'; | |
7 | |
8 import 'package:async/async.dart'; | |
9 | |
10 import '../stream_channel.dart'; | |
11 | |
12 /// A [StreamChannelTransformer] transforms the events being passed to and | |
13 /// emitted by a [StreamChannel]. | |
14 /// | |
15 /// This works on the same principle as [StreamTransformer] and | |
16 /// [StreamSinkTransformer]. Each transformer defines a [bind] method that takes | |
17 /// in the original [StreamChannel] and returns the transformed version. | |
18 /// | |
19 /// Transformers must be able to have `bind` called used multiple times. | |
Bob Nystrom
2016/01/27 19:30:41
Remove "used".
nweiz
2016/01/27 23:23:49
Done.
| |
20 class StreamChannelTransformer<S, T> { | |
21 /// The transformer to use on the channel's stream. | |
22 final StreamTransformer _streamTransformer; | |
23 | |
24 /// The transformer to use on the channel's sink. | |
25 final StreamSinkTransformer _sinkTransformer; | |
26 | |
27 /// Creates a [StreamChannelTransformer] from existing stream and sink | |
28 /// transformers. | |
29 const StreamChannelTransformer( | |
30 this._streamTransformer, this._sinkTransformer); | |
31 | |
32 /// Creates a [StreamChannelTransformer] from a codec's encoder and decoder. | |
33 /// | |
34 /// All input to the inner channel's sink is encoded using [Codec.encoder], | |
35 /// and all output from its stream is decoded using [Codec.decoder]. | |
36 StreamChannelTransformer.fromCodec(Codec<S, T> codec) | |
37 : this( | |
38 codec.decoder, | |
39 new StreamSinkTransformer.fromStreamTransformer(codec.encoder)); | |
40 | |
41 /// Transforms the events sent to and emitted by [channel]. | |
42 /// | |
43 /// Creates a new channel. When events are passed to the returned channel's | |
44 /// sink, the transformer will transform them and pass the transformed | |
45 /// versions to `channel.sink`. When events are emitted from the | |
46 /// `channel.straem`, the transformer will transform them and pass the | |
47 /// transformed versions to the returned channel's stream. | |
48 StreamChannel<S> bind(StreamChannel<T> channel) => | |
49 new StreamChannel<S>( | |
50 channel.stream.transform(_streamTransformer), | |
51 _sinkTransformer.bind(channel.sink)); | |
52 } | |
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