Bluetooth low energy connection.

components/proximity_auth/ble/bluetooth_low_energy_connection.h

+// Copyright 2015 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 COMPONENTS_PROXIMITY_AUTH_BLUETOOTH_LOW_ENERGY_CONNECTION_H
+#define COMPONENTS_PROXIMITY_AUTH_BLUETOOTH_LOW_ENERGY_CONNECTION_H
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "components/proximity_auth/ble/fake_wire_message.h"
+#include "components/proximity_auth/connection.h"
+#include "device/bluetooth/bluetooth_adapter.h"
+#include "device/bluetooth/bluetooth_device.h"
+#include "device/bluetooth/bluetooth_gatt_characteristic.h"
+#include "device/bluetooth/bluetooth_gatt_notify_session.h"
+#include "device/bluetooth/bluetooth_uuid.h"
+
+namespace proximity_auth {
+
+// Represents a connection with a remote device over Bluetooth low energy. The
+// connection is a persistent bidirectional channel for sending and receiving
+// wire messages. The remote device is the peripheral mode and the service
+// contains two characteristics: one to send data and another to receive it.
+class BluetoothLowEnergyConnection : public Connection,
+                                     public device::BluetoothAdapter::Observer {
+ public:
+  enum class ControlSignal : uint32 {
+    kInviteToConnectSignal = 0,
+    kInvitationResponseSignal = 1,
+    kSendSignal = 2,
+    kDisconnectSignal = 3,
+  };
+
+  // Constructs a Bluetooth low energy connection to the service with

[Tim Song, 2015/05/12 03:02:47]

I think an diagram would be much more descriptive of the flow:

 Discover ReaderCharacteristic          Discover WriterCharacteristic
             |                                         |
    Start Notify Session                               |
             |                                         |
              ---------------- && ---------------------
                                |
                                |
                                |
           Write InviteToConnect to WriterCharacteristic
                                |
                                |
                                |
         Read InvitationResponse from ReaderCharacteristic
                                |
                                |
                                |
               Proximity Auth Connection Established

[sacomoto, 2015/05/12 07:23:19]

Done.

+  // |remote_service_uuid| on the |remote_device|. The GATT connection with
+  // |remote_device| must be already established and |adapter| already
+  // initialized.
+  //
+  // The connection is complete when:
+  // (i) |to_peripheral_char_| and |from_peripheral_char_| were found;
+  // (ii) |notify_session_| was set for |from_peripheral_char_|;
+  // (iii) A kInviteToConnectSignal was sent;
+  // (iv) kInvitationResponseSignal was received.
+  //
+  // Conditions (i) and (ii) can happen in any order, but an invite to connect
+  // signal is sent only when (i) and (ii) are satisfied.
+  BluetoothLowEnergyConnection(
+      const RemoteDevice& remote_device,
+      scoped_refptr<device::BluetoothAdapter> adapter,
+      const device::BluetoothUUID remote_service_uuid,
+      const device::BluetoothUUID to_peripheral_char_uuid,
+      const device::BluetoothUUID from_peripheral_char_uuid,
+      scoped_ptr<device::BluetoothGattConnection> gatt_connection);
+
+  ~BluetoothLowEnergyConnection();
+
+  // proximity_auth::Connection
+  void Connect() override;
+  void Disconnect() override;
+
+ protected:
+  // proximity_auth::Connection
+  void SendMessageImpl(scoped_ptr<WireMessage> message) override;
+  scoped_ptr<WireMessage> DeserializeWireMessage(
+      bool* is_incomplete_message) override;
+
+  // device::BluetoothAdapter::Observer
+  void DeviceRemoved(device::BluetoothAdapter* adapter,
+                     device::BluetoothDevice* device) override;
+  void GattDiscoveryCompleteForService(
+      device::BluetoothAdapter* adapter,
+      device::BluetoothGattService* service) override;
+  void GattCharacteristicAdded(
+      device::BluetoothAdapter* adapter,
+      device::BluetoothGattCharacteristic* characteristic) override;
+  void GattCharacteristicValueChanged(
+      device::BluetoothAdapter* adapter,
+      device::BluetoothGattCharacteristic* characteristic,
+      const std::vector<uint8>& value) override;
+
+ private:
+  struct RemoteCharacteristic {
+    device::BluetoothUUID uuid;
+    std::string id;
+  };
+
+  // Sends an invite to connect signal to the peripheral if the connection
+  // is ready. That is, satisfying the conditions:
+  // (i) |to_peripheral_char_| and |from_peripheral_char_| were found;
+  // (ii) |notify_session_| was set for |from_peripheral_char_|.
+  //
+  // The asynchronous events that can casue these conditions to be
+  // satisfied are:
+  // (i) a new characteristic is discovered (HandleCharacteristicUpdate);
+  // (ii) a new notify session is started (OnNotifySessionStarted).
+  void SendInviteToConnectSignal();
+
+  // Called when there is an error writing to the remote characteristic
+  // |to_peripheral_char_|.
+  void OnWriteRemoteCharacteristicError(
+      device::BluetoothGattService::GattErrorCode error);
+
+  // Handles the discovery of a new characteristic.
+  void HandleCharacteristicUpdate(
+      device::BluetoothGattCharacteristic* characteristic);
+
+  // This function verifies if the connection is complete and updates
+  // the status accordingly. The only asynchronous event
+  // that can cause the connection to be completed is receiving a
+  // kInvitationResponseSignal (GattCharateristcValueChanged).
+  void CompleteConnection();
+
+  // Starts a notify session for |from_peripheral_char_|.
+  void StartNotifySession();
+
+  // Called when there is an error starting a notification session for
+  // |from_peripheral_char_| characteristic.
+  void OnNotifySessionError(device::BluetoothGattService::GattErrorCode);
+
+  // Called when a notification session is successfully started for
+  // |from_peripheral_char_| characteristic.
+  void OnNotifySessionStarted(
+      scoped_ptr<device::BluetoothGattNotifySession> notify_session);
+
+  // Stops |notify_session_|.
+  void StopNotifySession();
+
+  // Updates the value of |to_peripheral_char_| and
+  // |from_peripheral_char_|
+  // when |characteristic| was found.
+  void UpdateCharacteristicsStatus(
+      device::BluetoothGattCharacteristic* characteristic);
+
+  // Returns the Bluetooth address of the remote device.
+  const std::string& GetRemoteDeviceAddress();
+
+  // Returns the device corresponding to |remote_device_address_|.
+  device::BluetoothDevice* GetRemoteDevice();
+
+  // Returns the service corresponding to |remote_service_uuid_| in the current
+  // device.
+  device::BluetoothGattService* GetRemoteService();
+
+  // Returns the characteristic corresponding to |identifier| in the current
+  // service.
+  device::BluetoothGattCharacteristic* GetGattCharacteristic(
+      const std::string& identifier);
+
+  // Convert the first 4 bytes from a byte vector to a uint32.
+  uint32 ToUint32(const std::vector<uint8>& bytes);
+
+  // Convert an uint32 to a byte array.
+  const std::string ToString(const uint32 value);
+
+  // The Bluetooth adapter over which the Bluetooth connection will be made.
+  scoped_refptr<device::BluetoothAdapter> adapter_;
+
+  // The uuid of the service it looks for to establish a GattConnection.
+  const device::BluetoothUUID remote_service_uuid_;

[Tim Song, 2015/05/12 03:02:47]

You can put |remote_service_uuid_| and |remote_service_id_| in a
RemoteCharacteristic struct as well, but you should probably change the name.

[sacomoto, 2015/05/12 07:23:19]

Done.

[Tim Song, 2015/05/13 02:36:56]

I don't see this change.

+
+  // The identifier of the service corresponding to |remote_service_uuid_|.
+  std::string remote_service_id_;
+
+  // Characteristic used to send data to the remote device.
+  RemoteCharacteristic to_peripheral_char_;
+
+  // Characteristic used to receive data from the remote device.
+  RemoteCharacteristic from_peripheral_char_;
+
+  // The GATT connection with the remote device.
+  scoped_ptr<device::BluetoothGattConnection> connection_;
+
+  // Indicates if there is a pending notification session. Used to ensure there
+  // is only one pending notify session.
+  bool notify_session_pending_;
+
+  // The notify session for |from_peripheral_char|.
+  scoped_ptr<device::BluetoothGattNotifySession> notify_session_;
+
+  // Indicates if there pending response to a invite to connect signal.
+  bool connect_signal_response_pending_;
+
+  base::WeakPtrFactory<BluetoothLowEnergyConnection> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(BluetoothLowEnergyConnection);
+};
+
+}  // namespace proximity_auth
+
+#endif  // COMPONENTS_PROXIMITY_AUTH_BLUETOOTH_LOW_ENERGY_CONNECTION_H