[sensors] Introduce Generic Sensor API interfaces

device/sensors/platform_sensor.cc

+// Copyright 2016 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 "device/sensors/platform_sensor.h"
+
+#include <utility>
+
+#include "device/sensors/platform_sensor_configuration.h"
+#include "device/sensors/platform_sensor_provider.h"
+
+namespace device {
+
+namespace {
+// Maximum allowed frequency is capped to 60Hz, if client requests higher
+// sensor polling frequency, StartListening would return error.
+bool IsAllowedFrequency(const PlatformSensorConfiguration& config) {
+  return config.frequency() <= 60.0 && config.frequency() > 0.0;

[dcheng, 2016/07/14 02:50:27]

As mentioned in the other CL, can we move this check to the StructTraits for
reading in this configuration? It's better if we don't need to remember to call
this outside of the bindings layer.

+}
+}
+
+PlatformSensor::PlatformSensor(SensorType type,
+                               mojo::ScopedSharedBufferMapping mapping,
+                               PlatformSensorProvider* provider)
+    : shared_buffer_mapping_(std::move(mapping)),
+      type_(type),
+      provider_(provider),
+      weak_factory_(this) {}
+
+PlatformSensor::~PlatformSensor() {
+  provider_->RemoveSensor(GetType());
+}
+
+SensorType PlatformSensor::GetType() const {
+  return type_;
+}
+
+bool PlatformSensor::StartListening(Client* client,
+                                    const PlatformSensorConfiguration& config) {
+  DCHECK(clients_.HasObserver(client));
+  if (!CheckSensorConfiguration(config) || !IsAllowedFrequency(config))
+    return false;
+
+  auto& config_list = config_map_[client];
+  config_list.push_back(config);
+
+  if (UpdateSensor(config_map_))
+    return true;
+
+  auto iterator = std::find(config_list.begin(), config_list.end(), config);
+  if (iterator != config_list.end())
+    config_list.erase(iterator);
+  return false;
+}
+
+bool PlatformSensor::StopListening(Client* client,
+                                   const PlatformSensorConfiguration& config) {
+  DCHECK(clients_.HasObserver(client));
+  auto client_entry = config_map_.find(client);
+  if (client_entry == config_map_.end())
+    return false;
+
+  auto& config_list = client_entry->second;
+  auto config_entry = std::find(config_list.begin(), config_list.end(), config);
+  if (config_entry == config_list.end())
+    return false;
+
+  config_list.erase(config_entry);
+
+  return UpdateSensor(config_map_);
+}
+
+void PlatformSensor::AddClient(Client* client) {
+  DCHECK(client);
+  clients_.AddObserver(client);
+}
+
+void PlatformSensor::RemoveClient(Client* client) {
+  DCHECK(client);
+  clients_.RemoveObserver(client);
+  auto client_entry = config_map_.find(client);
+  if (client_entry != config_map_.end()) {
+    config_map_.erase(client_entry);
+    UpdateSensor(config_map_);
+  }
+}
+
+void PlatformSensor::NotifySensorReadingChanged() {
+  FOR_EACH_OBSERVER(Client, clients_, OnSensorReadingChanged());
+}
+
+void PlatformSensor::NotifySensorError() {
+  FOR_EACH_OBSERVER(Client, clients_, OnSensorError());
+}
+
+}  // namespace device