Revert "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 {
-    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 responses.
-  _handleIncoming(response) {
-    // Right not the only response we can get is the response to a
-    // lookupRequest where the response looks like this:
-    //
-    //  response[0]: hostname (String)
-    //  response[1]: IPv4 address (Uint8List)
-    if (response is List && response.length == 2) {
-      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]);
-      } else {
-        // TODO(sgjesse): Improve the error handling.
-        print('mDNS Response not understood');
-      }
-    }
-  }
-}
-
-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';