Implement Android shared memory data fetcher for Device Motion.

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/data_fetcher.h"
 #include "content/browser/device_orientation/device_data.h"
+#include "content/common/device_motion_hardware_buffer.h"
+
+template<typename T> struct DefaultSingletonTraits;

[bulach, 2013/07/10 16:59:41]

nit: LeakySingletonTraits

[timvolodine, 2013/07/11 14:31:34]

apparently this needs to be DefaultSingletonTraits, cannot get it to compile
otherwise.

 
 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): Move this class implementation to
+// data_fetcher_shared_memory_android.cc, once Device Orientation switches to
+// shared memory implementation.
 class DataFetcherImplAndroid : public DataFetcher {
  public:
   // Must be called at startup, before Create().
-  static void Init(JNIEnv* env);
+  static void Register(JNIEnv* env);
 
   // Factory function. We'll listen for events for the lifetime of this object.
   // Returns NULL on error.
   static DataFetcher* Create();
 
-  virtual ~DataFetcherImplAndroid();
+  // Needs to be thread-safe, because accessed from a thread in provider_impl.cc

[bulach, 2013/07/10 16:59:41]

nit: s/a thread/different threads/

[timvolodine, 2013/07/11 14:31:34]

Done.

+  // and device_motion_provider.cc.
+  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);
 
   // Implementation of DataFetcher.
   virtual const DeviceData* GetDeviceData(DeviceData::Type type) OVERRIDE;
 
- private:
-  DataFetcherImplAndroid();
-  const Orientation* GetOrientation();
-
   // Wrappers for JNI methods.
   // TODO(timvolodine): move the DeviceData::Type enum to the service class
   // once it is implemented.
-  bool Start(DeviceData::Type event_type, int rate_in_milliseconds);
-  void Stop(DeviceData::Type event_type);
+  virtual bool Start(DeviceData::Type event_type, int rate_in_milliseconds);
+  virtual void Stop(DeviceData::Type event_type);
+
+  // Shared memory related methods.
+  virtual bool NeedsPolling();
+  virtual bool FetchDeviceMotionDataIntoBuffer();
+  virtual bool StartFetchingDeviceMotionData(
+      DeviceMotionHardwareBuffer* buffer);
+  virtual void StopFetchingDeviceMotionData();
+
+ protected:
+  DataFetcherImplAndroid();
+  virtual ~DataFetcherImplAndroid();
+
+  const Orientation* GetOrientation();
 
   virtual int GetNumberActiveDeviceMotionSensors();
+  void CheckBufferReadyToRead();
+  void SetBufferReadyStatus(bool ready);
+  void ClearInternalBuffers();
 
+ private:
+  friend struct DefaultSingletonTraits<DataFetcherImplAndroid>;
+
+  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_