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/data_fetcher_shared_memory.h"
 #include "content/browser/device_orientation/device_data.h"
 
 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.
 
-class DataFetcherImplAndroid : public DataFetcher {
+class DataFetcherImplAndroid
+    : public DataFetcher, public DataFetcherSharedMemory {
  public:
   // Must be called at startup, before Create().
   static void Init(JNIEnv* env);
 
+  static DataFetcherImplAndroid* instance();
+
   // Factory function. We'll listen for events for the lifetime of this object.
   // Returns NULL on error.
   static DataFetcher* Create();
 
   virtual ~DataFetcherImplAndroid();
 
   // 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:
+  // Implementation of the new API using shared memory.
+
+  virtual bool NeedsPolling() OVERRIDE { return false; }
+  virtual bool FetchDeviceMotionDataIntoBuffer() OVERRIDE;
+  virtual bool StartFetchingDeviceMotionData(
+      DeviceMotionHardwareBuffer* buffer) OVERRIDE;
+  virtual void StopFetchingDeviceMotionData() OVERRIDE;
+
+ protected:

[bulach, 2013/07/04 08:23:36]

why is it protected? styleguide forbids non-private data members..

[timvolodine, 2013/07/04 12:02:52]

I needed a couple of methods to be protected for easier testing (i.e. in
data_fetcher_impl_android_unittest). I've made the data members private now.

   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);
 
   virtual int GetNumberActiveDeviceMotionSensors();
+  void CheckBufferReadyToRead();
 
   // 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 receivedMotionData[3];

[bulach, 2013/07/04 08:23:36]

nit: received_motion_data.
also, I think using the indices to map the type could be done more explicitly,
something like:

enum {
  DATA_ACCELERATION = 0,
  DATA_ACCELERATION_INCLUDING_GRAVITY = 1,
  DATA_ROTATION_RATE = 2,
  DATA_MAX = 3,
};
int received_motioned_data[DATA_MAX];

[timvolodine, 2013/07/04 12:02:52]

Done.

+  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_