[sensors] Introduce Generic Sensor API interfaces

device/sensors/platform_sensor.h

+// 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.
+
+#ifndef DEVICE_SENSORS_PLATFORM_SENSOR_H_
+#define DEVICE_SENSORS_PLATFORM_SENSOR_H_
+
+#include <list>
+#include <map>
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
+#include "mojo/public/cpp/system/buffer.h"
+
+namespace device {
+
+class PlatformSensorProvider;
+class PlatformSensorConfiguration;
+
+// Note: this enum must be in sync with mojo enum SensorType that is defined
+// in public/interfaces/sensor.mojom.
+enum class SensorType : int32_t {
+  FIRST = 1,
+  AMBIENT_LIGHT = FIRST,
+  PROXIMITY,
+  ACCELEROMETER,
+  GYROSCOPE,
+  PRESSURE,
+  LAST = PRESSURE,
+};
+
+// Note: this enum must be in sync with mojo enum ReportingMode that is defined
+// in public/interfaces/sensor.mojom.
+enum class ReportingMode : int32_t {
+  ON_CHANGE,
+  CONTINUOUS,
+};
+
+// Base class for the sensors provided by the platform. Concrete instances of
+// this class are created by platform specific PlatformSensorProvider.
+class PlatformSensor : public base::RefCountedThreadSafe<PlatformSensor> {
+ public:
+  // The interface that must be implemented by PlatformSensor clients.
+  class Client {
+   public:
+    virtual void OnSensorReadingChanged() {}
+    virtual void OnSensorError() {}
+
+   protected:
+    virtual ~Client() {}
+  };
+
+  virtual ReportingMode GetReportingMode() = 0;
+
+  SensorType GetType() const;
+
+  bool StartListening(Client* client,
+                      const PlatformSensorConfiguration& config);
+  bool StopListening(Client* client, const PlatformSensorConfiguration& config);
+
+  void AddClient(Client*);
+  void RemoveClient(Client*);
+
+ protected:
+  virtual ~PlatformSensor();
+  PlatformSensor(SensorType type,
+                 mojo::ScopedSharedBufferMapping mapping,
+                 PlatformSensorProvider* provider);
+
+  using ConfigMap = std::map<Client*, std::list<PlatformSensorConfiguration>>;
+
+  virtual bool UpdateSensor(const ConfigMap& configurations) = 0;
+  virtual bool CheckSensorConfiguration(
+      const PlatformSensorConfiguration& configuration) = 0;
+
+  void NotifySensorReadingChanged();
+  void NotifySensorError();
+
+  mojo::ScopedSharedBufferMapping shared_buffer_mapping_;
+
+ private:
+  friend class base::RefCountedThreadSafe<PlatformSensor>;
+
+  SensorType type_;
+  base::ObserverList<Client, true> clients_;
+  ConfigMap config_map_;
+  PlatformSensorProvider* provider_;
+  base::WeakPtrFactory<PlatformSensor> weak_factory_;
+  DISALLOW_COPY_AND_ASSIGN(PlatformSensor);
+};
+
+}  // namespace device
+
+#endif  // DEVICE_SENSORS_PLATFORM_SENSOR_H_