Create network change notifier.

webrtc/base/networkmonitor.h

Index: webrtc/base/networkmonitor.h
diff --git a/webrtc/base/networkmonitor.h b/webrtc/base/networkmonitor.h
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+/*
+ *  Copyright 2015 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_BASE_NETWORKMONITOR_H_
+#define WEBRTC_BASE_NETWORKMONITOR_H_
+
+#include "webrtc/base/logging.h"
+#include "webrtc/base/scoped_ptr.h"
+#include "webrtc/base/sigslot.h"
+#include "webrtc/base/thread.h"
+
+namespace rtc {
+/*
+ * Receives network-change events via |OnNetworksChanged| and signals the
+ * networks changed event.
+ *
+ * Threading consideration:
+ * It is expected that all upstream operations (from native to Java) are
+ * performed from the worker thread. This includes creating, starting and
+ * stopping the monitor. This avoids the potential race condition when creating
+ * the singleton Java NetworkMonitor class. Downstream operations can be from
+ * any thread, but this class will forward all the downstream operations onto
+ * the worker thread.
+ *
+ * Memory consideration:
+ * NetworkMonitor is owned by the caller (NetworkManager). The global network
+ * monitor factory is owned by the factory itself but needs to be released from
+ * the factory creator.
+ */
+// Generic network monitor interface. It starts and stops monitoring network
+// changes, and fires the SignalNetworksChanged event when networks change.
+class NetworkMonitorInterface {
+ public:
+  NetworkMonitorInterface();
+  virtual ~NetworkMonitorInterface();
+
+  sigslot::signal0<> SignalNetworksChanged;
+
+  virtual void Start() = 0;
+  virtual void Stop() = 0;
+
+  // Implementations should call this method on the base when networks change,
+  // and the base will fire SignalNetworksChanged on the right thread.
+  virtual void OnNetworksChanged() = 0;
+};
+
+class NetworkMonitorBase : public NetworkMonitorInterface,
+                           public MessageHandler,
+                           public sigslot::has_slots<> {
+ public:
+  NetworkMonitorBase();
+  ~NetworkMonitorBase() override;
+
+  void OnNetworksChanged() override;
+
+  void OnMessage(Message* msg) override;
+
+ private:
+  Thread* thread_;
+};
+
+/*
+ * NetworkMonitorFactory creates NetworkMonitors.
+ */
+class NetworkMonitorFactory {
+ public:
+  // This is not thread-safe; it should be called once (or once per audio/video
+  // call) during the call initialization.
+  static void SetFactory(NetworkMonitorFactory* factory);
+
+  static void ReleaseFactory(NetworkMonitorFactory* factory);
+  static NetworkMonitorFactory* GetFactory();
+
+  virtual NetworkMonitorInterface* CreateNetworkMonitor() = 0;
+
+  virtual ~NetworkMonitorFactory();
+
+ protected:
+  NetworkMonitorFactory();
+};
+
+}  // namespace rtc
+
+#endif  // WEBRTC_BASE_NETWORKMONITOR_H_