Extend the mDNS package with a native extension used on Mac OS

pkg/mdns/lib/src/native_extension_client.dart

+// Copyright (c) 2015, the Fletch 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.md file.
+
+library mdns.src.native_extension_client;
+
+import 'dart:async';
+import 'dart:io';
+import 'dart:isolate';
+
+import 'package:mdns/mdns.dart';
+import 'package:mdns/src/lookup_resolver.dart';
+import 'package:mdns/src/packet.dart';
+
+import "dart-ext:../native/mdns_extension_lib";
+
+// Requests Ids. This should be aligned with the C code.
+enum RequestType {
+  echoRequest,  // 0
+  lookupRequest,  // 1
+}
+
+// Implementation of mDNS client using a native extension.
+class NativeExtensionMDnsClient implements MDnsClient {
+  bool _starting = false;
+  bool _started = false;
+  SendPort _service;
+  ReceivePort _incoming;
+  final LookupResolver _resolver = new LookupResolver();
+
+  /// Start the mDNS client.
+  Future start() async {

[ricow1, 2015/10/30 10:28:33]

this does not return a future

[Søren Gjesse, 2015/10/30 12:13:16]

It is "async", so it does.

+    if (_started && _starting) {
+      throw new StateError('mDNS client already started');
+    }
+    _starting = true;
+
+    _service = servicePort();
+    _incoming = new ReceivePort();
+    _incoming.listen(_handleIncoming);
+
+    _starting = false;
+    _started = true;
+  }
+
+  void stop() {
+    if (!_started) return;
+    if (_starting) {
+      throw new StateError('Cannot stop mDNS client wile it is starting');
+    }
+
+    _incoming.close();
+
+    _started = false;
+  }
+
+  Future<InternetAddress> lookup(
+      String hostname, {Duration timeout: const Duration(seconds: 5)}) {
+    if (!_started) {
+      throw new StateError('mDNS client is not started');
+    }
+
+    // Add the pending request before sending the query.
+    var future = _resolver.addPendingRequest(hostname, timeout);
+
+    // Send the request.
+    _service.send([_incoming.sendPort,
+                   RequestType.lookupRequest.index,
+                   hostname]);
+
+    return future;
+  }
+
+  // Process incoming datagrams.
+  _handleIncoming(response) {
+    if (response is List && response.length == 2) {

[ricow1, 2015/10/30 10:28:33]

should we do something different if we get a non working response? log it
somewhere? Also, maybe add a comment with a description of the structure

[Søren Gjesse, 2015/10/30 12:13:16]

Added a print for errors for now.

Documented the response.

+      if (response[0] is String &&
+          response[1] is List && response[1].length == 4) {
+        response = new DecodeResult(response[0],
+                                    new InternetAddress(response[1].join('.')));
+        _resolver.handleResponse([response]);
+      }
+    }
+  }
+}
+
+Future nativeExtensionEchoTest(dynamic message) async {
+  SendPort service = servicePort();
+  ReceivePort port = new ReceivePort();
+  try {
+    service.send([port.sendPort, RequestType.echoRequest.index, message]);
+    return await port.first;
+  } finally {
+    port.close();
+  }
+}
+
+SendPort servicePort() native 'MDnsExtension_ServicePort';