SystemMonitor refactoring: move power state monitor into a separate class called PowerMonitor

base/power_state_manager.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 BASE_POWER_STATE_MANAGMER_H_
+#define BASE_POWER_STATE_MANAGMER_H_
+
+#include "base/base_export.h"
+#include "base/basictypes.h"
+
+// Windows HiRes timers drain the battery faster so we need to know the battery
+// status.  This isn't true for other platforms.
+#if defined(OS_WIN)
+#define ENABLE_BATTERY_MONITORING 1
+#else
+#undef ENABLE_BATTERY_MONITORING
+#endif  // !OS_WIN
+
+#include "base/observer_list_threadsafe.h"
+#if defined(ENABLE_BATTERY_MONITORING)
+#include "base/timer.h"
+#endif  // defined(ENABLE_BATTERY_MONITORING)
+
+#if defined(OS_IOS)
+#include <objc/runtime.h>
+#endif  // OS_IOS
+
+namespace base {
+
+class BASE_EXPORT PowerStateManager {
+ public:
+  // Normalized list of power events.
+  enum PowerEvent {
+    POWER_STATE_EVENT,  // The Power status of the system has changed.
+    SUSPEND_EVENT,      // The system is being suspended.
+    RESUME_EVENT        // The system is being resumed.
+  };
+
+  // Callbacks will be called on the thread which creates the SystemMonitor.
+  // During the callback, Add/RemoveObserver will block until the callbacks
+  // are finished. Observers should implement quick callback functions; if
+  // lengthy operations are needed, the observer should take care to invoke
+  // the operation on an appropriate thread.
+  class BASE_EXPORT PowerObserver {
+   public:
+    // Notification of a change in power status of the computer, such
+    // as from switching between battery and A/C power.
+    virtual void OnPowerStateChange(bool on_battery_power) {}
+
+    // Notification that the system is suspending.
+    virtual void OnSuspend() {}
+
+    // Notification that the system is resuming.
+    virtual void OnResume() {}
+
+   protected:
+    virtual ~PowerObserver() {}
+  };
+
+  PowerStateManager();
+  ~PowerStateManager();
+
+  void AddPowerObserver(PowerObserver* observer);
+  void RemovePowerObserver(PowerObserver* observer);
+
+  // Handle the power event and notify its observers with the specific state.
+  void HandlePowerEvent(PowerEvent event_id);
+
+  // Is the computer currently on battery power. Can be called on any thread.
+  bool BatteryPower() const {
+    // Using a lock here is not necessary for just a bool.
+    return battery_in_use_;
+  }
+
+  // Return the single instance in the application wide.
+  static PowerStateManager* Get();
+
+#if defined(OS_MACOSX)
+  // Allocate system resources needed by the PowerStateManager class.
+  //
+  // This function must be called before instantiating an instance of the class
+  // and before the Sandbox is initialized.
+#if !defined(OS_IOS)
+  static void AllocateSystemIOPorts();
+#else
+  static void AllocateSystemIOPorts() {}
+#endif  // OS_IOS
+#endif  // OS_MACOSX
+
+ private:
+#if defined(OS_MACOSX)
+  void PlatformInit();
+  void PlatformDestroy();
+#endif
+
+  // Platform-specific method to check whether the system is currently
+  // running on battery power.  Returns true if running on batteries,
+  // false otherwise.
+  bool IsBatteryPower();
+
+  // Checks the battery status and notifies observers if the battery
+  // status has changed.
+  void BatteryCheck();
+
+  void NotifyPowerStateChange();
+  void NotifySuspend();
+  void NotifyResume();
+
+#if defined(OS_IOS)
+  // Holds pointers to system event notification observers.
+  std::vector<id> notification_observers_;
+#endif
+
+#if defined(ENABLE_BATTERY_MONITORING)
+    base::OneShotTimer<SystemMonitor> delayed_battery_check_;
+#endif
+  scoped_refptr<ObserverListThreadSafe<PowerObserver> > power_observer_list_;
+  bool battery_in_use_;
+  bool suspended_;
+
+  DISALLOW_COPY_AND_ASSIGN(PowerStateManager);
+};
+
+}  // namespace base
+
+#endif  // BASE_POWER_STATE_MANAGMER_H_