| // Copyright (c) 2016, 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. |
| |
| import 'dart:async'; |
| import 'dart:convert'; |
| |
| import 'package:async/async.dart'; |
| |
| import '../stream_channel.dart'; |
| |
| /// A [StreamChannelTransformer] transforms the events being passed to and |
| /// emitted by a [StreamChannel]. |
| /// |
| /// This works on the same principle as [StreamTransformer] and |
| /// [StreamSinkTransformer]. Each transformer defines a [bind] method that takes |
| /// in the original [StreamChannel] and returns the transformed version. |
| /// |
| /// Transformers must be able to have `bind` called multiple times. |
| class StreamChannelTransformer<S, T> { |
| /// The transformer to use on the channel's stream. |
| final StreamTransformer _streamTransformer; |
| |
| /// The transformer to use on the channel's sink. |
| final StreamSinkTransformer _sinkTransformer; |
| |
| /// Creates a [StreamChannelTransformer] from existing stream and sink |
| /// transformers. |
| const StreamChannelTransformer( |
| this._streamTransformer, this._sinkTransformer); |
| |
| /// Creates a [StreamChannelTransformer] from a codec's encoder and decoder. |
| /// |
| /// All input to the inner channel's sink is encoded using [Codec.encoder], |
| /// and all output from its stream is decoded using [Codec.decoder]. |
| StreamChannelTransformer.fromCodec(Codec<S, T> codec) |
| : this( |
| codec.decoder, |
| new StreamSinkTransformer.fromStreamTransformer(codec.encoder)); |
| |
| /// Transforms the events sent to and emitted by [channel]. |
| /// |
| /// Creates a new channel. When events are passed to the returned channel's |
| /// sink, the transformer will transform them and pass the transformed |
| /// versions to `channel.sink`. When events are emitted from the |
| /// `channel.straem`, the transformer will transform them and pass the |
| /// transformed versions to the returned channel's stream. |
| StreamChannel<S> bind(StreamChannel<T> channel) => |
| new StreamChannel<S>( |
| channel.stream.transform(_streamTransformer), |
| _sinkTransformer.bind(channel.sink)); |
| } |