Mac: implement orientation/motion shared memory data fetcher.

content/browser/device_orientation/data_fetcher_shared_memory_mac.cc

+// Copyright 2013 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.
+
+#include "data_fetcher_shared_memory.h"
+
+#include "base/logging.h"
+#include "third_party/sudden_motion_sensor/sudden_motion_sensor_mac.h"
+
+namespace {
+
+void FetchMotion(SuddenMotionSensor* sensor,
+    content::DeviceMotionHardwareBuffer* buffer) {
+  DCHECK(buffer);
+
+  float axis_value[3];
+  if (!sensor->ReadSensorValues(axis_value))
+    return;
+
+  buffer->seqlock.WriteBegin();
+  buffer->data.accelerationIncludingGravityX = axis_value[0];
+  buffer->data.hasAccelerationIncludingGravityX = true;
+  buffer->data.accelerationIncludingGravityY = axis_value[1];
+  buffer->data.hasAccelerationIncludingGravityY = true;
+  buffer->data.accelerationIncludingGravityZ = axis_value[2];
+  buffer->data.hasAccelerationIncludingGravityZ = true;
+  buffer->data.allAvailableSensorsAreActive = true;
+  buffer->seqlock.WriteEnd();
+}
+
+void FetchOrientation(SuddenMotionSensor* sensor,
+    content::DeviceOrientationHardwareBuffer* buffer) {
+  DCHECK(buffer);
+
+  // Retrieve per-axis calibrated values.
+  float axis_value[3];
+  if (!sensor->ReadSensorValues(axis_value))
+    return;
+
+  // Transform the accelerometer values to W3C draft angles.
+  //
+  // Accelerometer values are just dot products of the sensor axes
+  // by the gravity vector 'g' with the result for the z axis inverted.
+  //
+  // To understand this transformation calculate the 3rd row of the z-x-y
+  // Euler angles rotation matrix (because of the 'g' vector, only 3rd row
+  // affects to the result). Note that z-x-y matrix means R = Ry * Rx * Rz.
+  // Then, assume alpha = 0 and you get this:
+  //
+  // x_acc = sin(gamma)
+  // y_acc = - cos(gamma) * sin(beta)
+  // z_acc = cos(beta) * cos(gamma)
+  //
+  // After that the rest is just a bit of trigonometry.
+  //
+  // Also note that alpha can't be provided but it's assumed to be always zero.
+  // This is necessary in order to provide enough information to solve
+  // the equations.
+  //
+  const double kRad2deg = 180.0 / M_PI;
+  double beta = kRad2deg * atan2(-axis_value[1], axis_value[2]);
+  double gamma = kRad2deg * asin(axis_value[0]);
+
+  // TODO(aousterh): should absolute_ be set to false here?
+  // See crbug.com/136010.
+
+  // Make sure that the interval boundaries comply with the specification. At
+  // this point, beta is [-180, 180] and gamma is [-90, 90], but the spec has
+  // the upper bound open on both.
+  if (beta == 180.0)
+    beta = -180;  // -180 == 180 (upside-down)
+  if (gamma == 90.0)
+    gamma = nextafter(90, 0);
+
+  // At this point, DCHECKing is paranoia. Never hurts.
+  DCHECK_GE(beta, -180.0);
+  DCHECK_LT(beta,  180.0);
+  DCHECK_GE(gamma, -90.0);
+  DCHECK_LT(gamma,  90.0);
+
+  buffer->seqlock.WriteBegin();
+  buffer->data.beta = beta;
+  buffer->data.hasBeta = true;
+  buffer->data.gamma = gamma;
+  buffer->data.hasGamma = true;
+  buffer->data.allAvailableSensorsAreActive = true;
+  buffer->seqlock.WriteEnd();
+}
+
+}  // namespace
+
+namespace content {
+
+DataFetcherSharedMemory::DataFetcherSharedMemory() {
+}
+
+DataFetcherSharedMemory::~DataFetcherSharedMemory() {
+}
+
+void DataFetcherSharedMemory::Fetch(unsigned consumer_bitmask) {
+  DCHECK(base::MessageLoop::current() == GetPollingMessageLoop());
+  DCHECK(sudden_motion_sensor_);
+
+  if (consumer_bitmask & CONSUMER_TYPE_ORIENTATION)
+    FetchOrientation(sudden_motion_sensor_.get(), orientation_buffer_);
+  else if (consumer_bitmask & CONSUMER_TYPE_MOTION)
+    FetchMotion(sudden_motion_sensor_.get(), motion_buffer_);
+
+  NOTREACHED();
+}
+
+bool DataFetcherSharedMemory::IsPolling() const {
+  return true;
+}
+
+bool DataFetcherSharedMemory::Start(ConsumerType consumer_type) {
+  DCHECK(base::MessageLoop::current() == GetPollingMessageLoop());
+  switch (consumer_type) {
+    case CONSUMER_TYPE_MOTION:
+      if (void* buffer = InitSharedMemoryBuffer(consumer_type,
+          sizeof(DeviceMotionHardwareBuffer))) {
+        motion_buffer_ = static_cast<DeviceMotionHardwareBuffer*>(buffer);
+        if (!sudden_motion_sensor_)
+          sudden_motion_sensor_.reset(SuddenMotionSensor::Create());
+        return true;
+      }
+    case CONSUMER_TYPE_ORIENTATION:
+      if (void* buffer = InitSharedMemoryBuffer(consumer_type,
+          sizeof(DeviceOrientationHardwareBuffer))) {
+        orientation_buffer_ =
+            static_cast<DeviceOrientationHardwareBuffer*>(buffer);
+        if (!sudden_motion_sensor_)
+          sudden_motion_sensor_.reset(SuddenMotionSensor::Create());
+        return true;
+      }
+    default:
+      NOTREACHED();
+  }
+  return false;
+}
+
+bool DataFetcherSharedMemory::Stop(ConsumerType consumer_type) {
+  DCHECK(base::MessageLoop::current() == GetPollingMessageLoop());
+  switch (consumer_type) {
+    case CONSUMER_TYPE_MOTION:
+      motion_buffer_->seqlock.WriteBegin();
+      motion_buffer_->data.allAvailableSensorsAreActive = false;
+      motion_buffer_->seqlock.WriteEnd();
+      motion_buffer_ = NULL;
+      return true;
+    case CONSUMER_TYPE_ORIENTATION:
+      orientation_buffer_->seqlock.WriteBegin();
+      orientation_buffer_->data.allAvailableSensorsAreActive = false;
+      orientation_buffer_->seqlock.WriteEnd();
+      orientation_buffer_ = NULL;
+      return true;
+    default:
+      NOTREACHED();
+  }
+  return false;
+}
+
+}  // namespace content