Add a mDNS package

pkg/mdns/lib/src/lookup_resolver.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.
+
+library mdns.src.lookup_resolver;
+
+import 'dart:async';
+import 'dart:collection';
+
+import 'package:mdns/src/packet.dart';
+
+class PendingRequest extends LinkedListEntry {
+  final String hostname;
+  final Completer completer;
+  PendingRequest(this.hostname, this.completer);
+}
+
+/// Class for keeping track of pending lookups and process incoming
+/// query responses.
+///
+/// Currently the responses are no cached.
+class LookupResolver {
+  LinkedList pendingRequests = new LinkedList();
+
+  Future addPendingRequest(String hostname, Duration timeout) {
+    var completer = new Completer();
+    var request = new PendingRequest(hostname, completer);
+    pendingRequests.add(request);
+    return completer.future.timeout(timeout, onTimeout: () {
+      request.unlink();
+      return null;
+    });
+  }
+
+  void handleResponse(List<DecodeResult> response) {
+    for (var r in response) {
+      pendingRequests
+          .where((pendingRequest) => pendingRequest.hostname == r.name)
+          .forEach((pendingRequest) {
+                pendingRequest.completer.complete(r.address);
+                pendingRequest.unlink();
+              });
+          }
+  }
+}
+