chromeos/accelerometer/accelerometer_reader.h

   1 // Copyright 2014 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 CHROMEOS_ACCELEROMETER_ACCELEROMETER_READER_H_
   6 #define CHROMEOS_ACCELEROMETER_ACCELEROMETER_READER_H_
   7
   8 #include "base/memory/ref_counted.h"
   9 #include "base/memory/weak_ptr.h"
  10 #include "base/observer_list_threadsafe.h"
  11 #include "chromeos/accelerometer/accelerometer_types.h"
  12 #include "chromeos/chromeos_export.h"
  13
  14 template <typename T>
  15 struct DefaultSingletonTraits;
  16
  17 namespace base {
  18 class TaskRunner;
  19 }
  20
  21 namespace chromeos {
  22
  23 // Reads an accelerometer device and reports data back to an
  24 // AccelerometerDelegate.
  25 class CHROMEOS_EXPORT AccelerometerReader {
  26  public:
  27   // The time to wait between reading the accelerometer.
  28   static const int kDelayBetweenReadsMs;
  29
  30   // Configuration structure for accelerometer device.
  31   struct ConfigurationData {
  32     ConfigurationData();
  33     ~ConfigurationData();
  34
  35     // Number of accelerometers on device.
  36     size_t count;
  37
  38     // Length of accelerometer updates.
  39     size_t length;
  40
  41     // Which accelerometers are present on device.
  42     bool has[ACCELEROMETER_SOURCE_COUNT];
  43
  44     // Scale of accelerometers (i.e. raw value * scale = m/s^2).
  45     float scale[ACCELEROMETER_SOURCE_COUNT][3];
  46
  47     // Index of each accelerometer axis in data stream.
  48     int index[ACCELEROMETER_SOURCE_COUNT][3];
  49   };
  50   typedef base::RefCountedData<ConfigurationData> Configuration;
  51   typedef base::RefCountedData<char[12]> Reading;
  52
  53   // An interface to receive data from the AccelerometerReader.
  54   class Observer {
  55    public:
  56     virtual void OnAccelerometerUpdated(
  57         scoped_refptr<const AccelerometerUpdate> update) = 0;
  58
  59    protected:
  60     virtual ~Observer() {}
  61   };
  62
  63   static AccelerometerReader* GetInstance();
  64
  65   void Initialize(scoped_refptr<base::TaskRunner> blocking_task_runner);
  66
  67   // Add/Remove observers.
  68   void AddObserver(Observer* observer);
  69   void RemoveObserver(Observer* observer);
  70
  71  protected:
  72   AccelerometerReader();
  73   virtual ~AccelerometerReader();
  74
  75  private:
  76   friend struct DefaultSingletonTraits<AccelerometerReader>;
  77
  78   // Dispatched when initialization is complete. If |success|, |configuration|
  79   // provides the details of the detected accelerometer.
  80   void OnInitialized(scoped_refptr<Configuration> configuration, bool success);
  81
  82   // Triggers an asynchronous read from the accelerometer, signalling
  83   // OnDataRead with the result.
  84   void TriggerRead();
  85
  86   // If |success|, converts the raw reading to an AccelerometerUpdate
  87   // message and notifies the |delegate_| with the new readings.
  88   // Triggers another read from the accelerometer at the current sampling rate.
  89   void OnDataRead(scoped_refptr<Reading> reading, bool success);
  90
  91   // The task runner to use for blocking tasks.
  92   scoped_refptr<base::TaskRunner> task_runner_;
  93
  94   // The last seen accelerometer data.
  95   scoped_refptr<AccelerometerUpdate> update_;
  96
  97   // The accelerometer configuration.
  98   scoped_refptr<Configuration> configuration_;
  99
 100   scoped_refptr<ObserverListThreadSafe<Observer>> observers_;
 101
 102   base::WeakPtrFactory<AccelerometerReader> weak_factory_;
 103
 104   DISALLOW_COPY_AND_ASSIGN(AccelerometerReader);
 105 };
 106
 107 }  // namespace chromeos
 108
 109 #endif  // CHROMEOS_ACCELEROMETER_ACCELEROMETER_READER_H_