util: split platform-specific NetworkMonitor backends into separate files

In preparation for a major overhaul of the rtnetlink implementation.

Change-Id: Iab660ab4bceb0f06db01a31f264cdfe0b7cdf077
Refs: #3353
diff --git a/src/util/detail/network-monitor-impl-osx.hpp b/src/util/detail/network-monitor-impl-osx.hpp
new file mode 100644
index 0000000..4015a78
--- /dev/null
+++ b/src/util/detail/network-monitor-impl-osx.hpp
@@ -0,0 +1,67 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2016 Regents of the University of California.
+ *
+ * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
+ *
+ * ndn-cxx library is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-cxx library is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
+ *
+ * You should have received copies of the GNU General Public License and GNU Lesser
+ * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
+ */
+
+#ifndef NDN_UTIL_NETWORK_MONITOR_IMPL_OSX_HPP
+#define NDN_UTIL_NETWORK_MONITOR_IMPL_OSX_HPP
+
+#include "../network-monitor.hpp"
+
+#include "../scheduler.hpp"
+#include "../scheduler-scoped-event-id.hpp"
+
+#include <CoreFoundation/CoreFoundation.h>
+#include <SystemConfiguration/SystemConfiguration.h>
+
+namespace ndn {
+namespace util {
+
+class NetworkMonitor::Impl
+{
+public:
+  Impl(NetworkMonitor& nm, boost::asio::io_service& io);
+
+  ~Impl();
+
+  static void
+  afterNotificationCenterEvent(CFNotificationCenterRef center,
+                               void *observer,
+                               CFStringRef name,
+                               const void *object,
+                               CFDictionaryRef userInfo);
+
+private:
+  void
+  scheduleCfLoop();
+
+  void
+  pollCfLoop();
+
+private:
+  NetworkMonitor& m_nm;
+
+  Scheduler m_scheduler;
+  scheduler::ScopedEventId m_cfLoopEvent;
+};
+
+} // namespace util
+} // namespace ndn
+
+#endif // NDN_UTIL_NETWORK_MONITOR_IMPL_OSX_HPP