base/power_monitor/power_monitor_source.h

   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/basictypes.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_