Support shelf 0.7.0.

lib/src/util/stream_channel.dart

-// Copyright (c) 2015, 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';
-
-/// An abstract class representing a two-way communication channel.
-///
-/// Subclasses can mix in [StreamChannelMixin] to get default implementations of
-/// the various instance methods.
-abstract class StreamChannel<T> {
-  /// The stream that emits values from the other endpoint.
-  Stream<T> get stream;
-
-  /// The sink for sending values to the other endpoint.
-  StreamSink<T> get sink;
-
-  /// Creates a new [StreamChannel] that communicates over [stream] and [sink].
-  factory StreamChannel(Stream<T> stream, StreamSink<T> sink) =>
-      new _StreamChannel<T>(stream, sink);
-
-  /// Connects [this] to [other], so that any values emitted by either are sent
-  /// directly to the other.
-  void pipe(StreamChannel<T> other);
-}
-
-/// An implementation of [StreamChannel] that simply takes a stream and a sink
-/// as parameters.
-///
-/// This is distinct from [StreamChannel] so that it can use
-/// [StreamChannelMixin].
-class _StreamChannel<T> extends StreamChannelMixin<T> {
-  final Stream<T> stream;
-  final StreamSink<T> sink;
-
-  _StreamChannel(this.stream, this.sink);
-}
-
-/// A mixin that implements the instance methods of [StreamChannel] in terms of
-/// [stream] and [sink].
-abstract class StreamChannelMixin<T> implements StreamChannel<T> {
-  void pipe(StreamChannel<T> other) {
-    stream.pipe(other.sink);
-    other.stream.pipe(sink);
-  }
-}