content/browser/device_orientation/data_fetcher_impl_android.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 CHROME_BROWSER_DEVICE_ORIENTATION_DATA_FETCHER_IMPL_ANDROID_H_
#define CHROME_BROWSER_DEVICE_ORIENTATION_DATA_FETCHER_IMPL_ANDROID_H_

#include "base/android/scoped_java_ref.h"
#include "base/memory/scoped_ptr.h"
#include "base/synchronization/lock.h"
#include "content/browser/device_orientation/device_data.h"
#include "content/common/content_export.h"
#include "content/common/device_motion_hardware_buffer.h"

template<typename T> struct DefaultSingletonTraits;

namespace content {
class Orientation;

// Android implementation of DeviceOrientation API.

// Android's SensorManager has a push API, whereas Chrome wants to pull data.
// To fit them together, we store incoming sensor events in a 1-element buffer.
// SensorManager calls SetOrientation() which pushes a new value (discarding the
// previous value if any). Chrome calls GetDeviceData() which reads the most
// recent value. Repeated calls to GetDeviceData() will return the same value.

// TODO(timvolodine): Simplify this class and remove GetDeviceData() method,
// once Device Orientation switches to shared memory implementation.
// Also rename this class to SensorManagerAndroid.
class CONTENT_EXPORT DataFetcherImplAndroid {
 public:
  // Must be called at startup, before GetInstance().
  static bool Register(JNIEnv* env);

  // Needs to be thread-safe, because accessed from different threads.
  static DataFetcherImplAndroid* GetInstance();

  // Called from Java via JNI.
  void GotOrientation(JNIEnv*, jobject,
                      double alpha, double beta, double gamma);
  void GotAcceleration(JNIEnv*, jobject,
                       double x, double y, double z);
  void GotAccelerationIncludingGravity(JNIEnv*, jobject,
                                       double x, double y, double z);
  void GotRotationRate(JNIEnv*, jobject,
                       double alpha, double beta, double gamma);

  const DeviceData* GetDeviceData(DeviceData::Type type);

  virtual bool Start(DeviceData::Type event_type);
  virtual void Stop(DeviceData::Type event_type);

  // Shared memory related methods.
  bool StartFetchingDeviceMotionData(DeviceMotionHardwareBuffer* buffer);
  void StopFetchingDeviceMotionData();

 protected:
  DataFetcherImplAndroid();
  virtual ~DataFetcherImplAndroid();

  virtual int GetNumberActiveDeviceMotionSensors();

 private:
  friend struct DefaultSingletonTraits<DataFetcherImplAndroid>;

  const Orientation* GetOrientation();

  void CheckBufferReadyToRead();
  void SetBufferReadyStatus(bool ready);
  void ClearInternalBuffers();

  enum {
    RECEIVED_MOTION_DATA_ACCELERATION = 0,
    RECEIVED_MOTION_DATA_ACCELERATION_INCL_GRAVITY = 1,
    RECEIVED_MOTION_DATA_ROTATION_RATE = 2,
    RECEIVED_MOTION_DATA_MAX = 3,
  };
  // Value returned by GetDeviceData.
  scoped_refptr<Orientation> current_orientation_;

  // 1-element buffer, written by GotOrientation, read by GetDeviceData.
  base::Lock next_orientation_lock_;
  scoped_refptr<Orientation> next_orientation_;

  // The Java provider of orientation info.
  base::android::ScopedJavaGlobalRef<jobject> device_orientation_;
  int number_active_device_motion_sensors_;
  int received_motion_data_[RECEIVED_MOTION_DATA_MAX];
  DeviceMotionHardwareBuffer* device_motion_buffer_;
  bool is_buffer_ready_;

  DISALLOW_COPY_AND_ASSIGN(DataFetcherImplAndroid);
};

}  // namespace content

#endif  // CHROME_BROWSER_DEVICE_ORIENTATION_DATA_FETCHER_IMPL_ANDROID_H_