[net/dns] Watch configd notifications to detect DnsConfig changes on Mac.

net/dns/notify_watcher_mac.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef NET_DNS_NOTIFY_WATCHER_MAC_H_
+#define NET_DNS_NOTIFY_WATCHER_MAC_H_
+#pragma once
+
+#include "base/callback.h"
+#include "base/message_loop.h"
+
+namespace net {
+
+// Watches for notifications from Libnotify and delivers them to a Callback.
+// After failure the watch is cancelled and will have to be restarted.
+class NotifyWatcherMac : public MessageLoopForIO::Watcher {
+ public:
+  // Called on received notification with true on success and false on error.
+  typedef base::Callback<void(bool succeeded)> CallbackType;
+
+  NotifyWatcherMac();
+
+  // When deleted, automatically cancels.
+  virtual ~NotifyWatcherMac();
+
+  // Registers for notifications for |key|. Returns true if succeeds. If so,
+  // will deliver asynchronous notifications and errors to |callback|.
+  bool Watch(const char* key, const CallbackType& callback);
+
+  // Cancels the watch.
+  void Cancel();
+
+ private:
+  // MessageLoopForIO::Watcher:
+  virtual void OnFileCanReadWithoutBlocking(int fd) OVERRIDE;
+  virtual void OnFileCanWriteWithoutBlocking(int fd) OVERRIDE {}
+
+  int notify_fd_;
+  int notify_token_;
+  CallbackType callback_;
+  MessageLoopForIO::FileDescriptorWatcher watcher_;
+
+  DISALLOW_COPY_AND_ASSIGN(NotifyWatcherMac);
+};
+
+}  // namespace net
+
+#endif  // NET_DNS_NOTIFY_WATCHER_MAC_H_