Read and expose accelerometer values from cros-ec-accel trigger.

chromeos/accelerometer/accelerometer_reader.h

+// Copyright 2014 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 CHROMEOS_ACCELEROMETER_ACCELEROMETER_READER_H_
+#define CHROMEOS_ACCELEROMETER_ACCELEROMETER_READER_H_
+
+#include <vector>
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
+#include "chromeos/chromeos_export.h"
+#include "ui/gfx/geometry/vector3d_f.h"
+
+namespace base {
+class TaskRunner;
+}
+
+namespace chromeos {
+
+// Reads an accelerometer device and reports data back to an
+// AccelerometerDelegate.
+class CHROMEOS_EXPORT AccelerometerReader {
+ public:
+  // Configuration structure for accelerometer device.
+  struct ConfigurationData {

[Daniel Erat, 2014/04/02 18:11:57]

can you just forward-declare this in the header and define it in the .cc file?

(if you additionally wanted to make it private, you could probably make the
functions that use it be private static members.)

[flackr, 2014/04/02 18:52:55]

Unfortunately I don't think I can forward the typedef and the RefCountedData
template needs the full type.

+    ConfigurationData();
+    ~ConfigurationData();
+
+    // Scale of accelerometers (i.e. raw value * 1.0f / scale = G's).
+    unsigned int base_scale;
+    unsigned int lid_scale;
+
+    // Index of each accelerometer axis in data stream.
+    std::vector<unsigned int> index;
+  };
+  typedef base::RefCountedData<ConfigurationData> Configuration;
+  typedef base::RefCountedData<char[12]> Reading;

[Daniel Erat, 2014/04/02 18:11:57]

can you turn this '12' into a constant in the .cc file?

[flackr, 2014/04/02 18:52:55]

Same for this. I could move the definition of the axes into the .h as well so
that this is only defined once or change this to be a vector<char> /
vector<int16> to avoid this constant here.

[flackr, 2014/04/02 18:57:42]

Or define the length in this .h and assert that the length matches the number of
axes * data size in the .cc.

+
+  // An interface to receive data from the AccelerometerReader.
+  class Delegate {
+   public:
+    virtual void HandleAccelerometerReading(const gfx::Vector3dF& base,
+                                            const gfx::Vector3dF& lid) = 0;
+  };
+
+  AccelerometerReader(base::TaskRunner* blocking_task_runner,
+                      Delegate* delegate);
+  ~AccelerometerReader();
+
+ private:
+  // Dispatched when initialization is complete. If |success|, |configuration|
+  // provides the details of the detected accelerometer.
+  void OnInitialized(scoped_refptr<Configuration> configuration, bool success);
+
+  // Triggers an asynchronous read from the accelerometer, signalling
+  // OnDataRead with the result.
+  void TriggerRead();
+
+  // If |success|, converts the raw reading to a pair of Vector3dF
+  // values and notifies the |delegate_| with the new readings.
+  // Triggers another read from the accelerometer at the current sampling rate.
+  void OnDataRead(scoped_refptr<Reading> reading, bool success);
+
+  // The task runner to use for blocking tasks.
+  scoped_refptr<base::TaskRunner> task_runner_;
+
+  // A weak pointer to the delegate to send accelerometer readings to.
+  Delegate* delegate_;
+
+  // The accelerometer configuration.
+  scoped_refptr<Configuration> configuration_;
+
+  base::WeakPtrFactory<AccelerometerReader> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(AccelerometerReader);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROMEOS_ACCELEROMETER_ACCELEROMETER_READER_H_