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      1 // Copyright 2013 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef BASE_POWER_MONITOR_POWER_MONITOR_SOURCE_H_
      6 #define BASE_POWER_MONITOR_POWER_MONITOR_SOURCE_H_
      7 
      8 #include "base/base_export.h"
      9 #include "base/macros.h"
     10 #include "base/memory/ref_counted.h"
     11 #include "base/observer_list_threadsafe.h"
     12 #include "base/synchronization/lock.h"
     13 
     14 namespace base {
     15 
     16 class PowerMonitor;
     17 
     18 // Communicates power state changes to the power monitor.
     19 class BASE_EXPORT PowerMonitorSource {
     20  public:
     21   PowerMonitorSource();
     22   virtual ~PowerMonitorSource();
     23 
     24   // Normalized list of power events.
     25   enum PowerEvent {
     26     POWER_STATE_EVENT,  // The Power status of the system has changed.
     27     SUSPEND_EVENT,      // The system is being suspended.
     28     RESUME_EVENT        // The system is being resumed.
     29   };
     30 
     31   // Is the computer currently on battery power. Can be called on any thread.
     32   bool IsOnBatteryPower();
     33 
     34  protected:
     35   friend class PowerMonitorTest;
     36 
     37   // Friend function that is allowed to access the protected ProcessPowerEvent.
     38   friend void ProcessPowerEventHelper(PowerEvent);
     39 
     40   // Get the process-wide PowerMonitorSource (if not present, returns NULL).
     41   static PowerMonitorSource* Get();
     42 
     43   // ProcessPowerEvent should only be called from a single thread, most likely
     44   // the UI thread or, in child processes, the IO thread.
     45   static void ProcessPowerEvent(PowerEvent event_id);
     46 
     47   // Platform-specific method to check whether the system is currently
     48   // running on battery power.  Returns true if running on batteries,
     49   // false otherwise.
     50   virtual bool IsOnBatteryPowerImpl() = 0;
     51 
     52  private:
     53   bool on_battery_power_;
     54   bool suspended_;
     55 
     56   // This lock guards access to on_battery_power_, to ensure that
     57   // IsOnBatteryPower can be called from any thread.
     58   Lock battery_lock_;
     59 
     60   DISALLOW_COPY_AND_ASSIGN(PowerMonitorSource);
     61 };
     62 
     63 }  // namespace base
     64 
     65 #endif  // BASE_POWER_MONITOR_POWER_MONITOR_SOURCE_H_
     66