Add example/example.dart (dart-lang/stream_channel#52)

pkgs/stream_channel/CHANGELOG.md

diff --git a/pkgs/stream_channel/CHANGELOG.md b/pkgs/stream_channel/CHANGELOG.md
index 0d73828..8932188 100644
--- a/pkgs/stream_channel/CHANGELOG.md
+++ b/pkgs/stream_channel/CHANGELOG.md
@@ -1,6 +1,7 @@
 ## 2.1.2-dev
 
 * Require Dart 2.19
+* Add an example.
 
 ## 2.1.1
 

pkgs/stream_channel/example/example.dart

diff --git a/pkgs/stream_channel/example/example.dart b/pkgs/stream_channel/example/example.dart
new file mode 100644
index 0000000..dd16f67
--- /dev/null
+++ b/pkgs/stream_channel/example/example.dart
@@ -0,0 +1,110 @@
+// Copyright (c) 2023, 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 'dart:io';
+import 'dart:isolate';
+
+import 'package:stream_channel/isolate_channel.dart';
+import 'package:stream_channel/stream_channel.dart';
+
+Future<void> main() async {
+  // A StreamChannel<T>, is in simplest terms, a wrapper around a Stream<T> and
+  // a StreamSink<T>. For example, you can create a channel that wraps standard
+  // IO:
+  var stdioChannel = StreamChannel(stdin, stdout);
+  stdioChannel.sink.add('Hello!\n'.codeUnits);
+
+  // Like a Stream<T> can be transformed with a StreamTransformer<T>, a
+  // StreamChannel<T> can be transformed with a StreamChannelTransformer<T>.
+  // For example, we can handle standard input as strings:
+  var stringChannel = stdioChannel
+      .transform(StreamChannelTransformer.fromCodec(utf8))
+      .transformStream(LineSplitter());
+  stringChannel.sink.add('world!\n');
+
+  // You can implement StreamChannel<T> by extending StreamChannelMixin<T>, but
+  // it's much easier to use a StreamChannelController<T>. A controller has two
+  // StreamChannel<T> members: `local` and `foreign`. The creator of a
+  // controller should work with the `local` channel, while the recipient should
+  // work with the `foreign` channel, and usually will not have direct access to
+  // the underlying controller.
+  var ctrl = StreamChannelController<String>();
+  ctrl.local.stream.listen((event) {
+    // Do something useful here...
+  });
+
+  // You can also pipe events from one channel to another.
+  ctrl
+    ..foreign.pipe(stringChannel)
+    ..local.sink.add('Piped!\n');
+  await ctrl.local.sink.close();
+
+  // The StreamChannel<T> interface provides several guarantees, which can be
+  // found here:
+  // https://pub.dev/documentation/stream_channel/latest/stream_channel/StreamChannel-class.html
+  //
+  // By calling `StreamChannel<T>.withGuarantees()`, you can create a
+  // StreamChannel<T> that provides all guarantees.
+  var dummyCtrl0 = StreamChannelController<String>();
+  var guaranteedChannel = StreamChannel.withGuarantees(
+      dummyCtrl0.foreign.stream, dummyCtrl0.foreign.sink);
+
+  // To close a StreamChannel, use `sink.close()`.
+  await guaranteedChannel.sink.close();
+
+  // A MultiChannel<T> multiplexes multiple virtual channels across a single
+  // underlying transport layer. For example, an application listening over
+  // standard I/O can still support multiple clients if it has a mechanism to
+  // separate events from different clients.
+  //
+  // A MultiChannel<T> splits events into numbered channels, which are
+  // instances of VirtualChannel<T>.
+  var dummyCtrl1 = StreamChannelController<String>();
+  var multiChannel = MultiChannel<String>(dummyCtrl1.foreign);
+  var channel1 = multiChannel.virtualChannel();
+  await multiChannel.sink.close();
+
+  // The client/peer should also create its own MultiChannel<T>, connected to
+  // the underlying transport, use the corresponding ID's to handle events in
+  // their respective channels. It is up to you how to communicate channel ID's
+  // across different endpoints.
+  var dummyCtrl2 = StreamChannelController<String>();
+  var multiChannel2 = MultiChannel<String>(dummyCtrl2.foreign);
+  var channel2 = multiChannel2.virtualChannel(channel1.id);
+  await channel2.sink.close();
+  await multiChannel2.sink.close();
+
+  // Multiple instances of a Dart application can communicate easily across
+  // `SendPort`/`ReceivePort` pairs by means of the `IsolateChannel<T>` class.
+  // Typically, one endpoint will create a `ReceivePort`, and call the
+  // `IsolateChannel.connectReceive` constructor. The other endpoint will be
+  // given the corresponding `SendPort`, and then call
+  // `IsolateChannel.connectSend`.
+  var recv = ReceivePort();
+  var recvChannel = IsolateChannel.connectReceive(recv);
+  var sendChannel = IsolateChannel.connectSend(recv.sendPort);
+
+  // You must manually close `IsolateChannel<T>` sinks, however.
+  await recvChannel.sink.close();
+  await sendChannel.sink.close();
+
+  // You can use the `Disconnector` transformer to cause a channel to act as
+  // though the remote end of its transport had disconnected.
+  var disconnector = Disconnector<String>();
+  var disconnectable = stringChannel.transform(disconnector);
+  disconnectable.sink.add('Still connected!');
+  await disconnector.disconnect();
+
+  // Additionally:
+  //   * The `DelegatingStreamController<T>` class can be extended to build a
+  //     basis for wrapping other `StreamChannel<T>` objects.
+  //   * The `jsonDocument` transformer converts events to/from JSON, using
+  //     the `json` codec from `dart:convert`.
+  //   * `package:json_rpc_2` directly builds on top of
+  //     `package:stream_channel`, so any compatible transport can be used to
+  //      create interactive client/server or peer-to-peer applications (i.e.
+  //      language servers, microservices, etc.
+}