Weave Packet Generator

components/proximity_auth/ble/bluetooth_low_energy_weave_packet_generator.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 COMPONENTS_PROXIMITY_AUTH_BLE_BLUETOOTH_LOW_ENERGY_WEAVE_PACKET_GENERATOR_H_
+#define COMPONENTS_PROXIMITY_AUTH_BLE_BLUETOOTH_LOW_ENERGY_WEAVE_PACKET_GENERATOR_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <memory>
+#include <string>
+#include <vector>
+
+namespace proximity_auth {
+// Generates the messages sent using the uWeave protocol.
+class BluetoothLowEnergyWeavePacketGenerator {
+ public:
+  class Factory {
+   public:
+    static std::unique_ptr<BluetoothLowEnergyWeavePacketGenerator>
+    NewInstance();
+
+    // Exposed for testing.
+    static void SetInstanceForTesting(Factory* factory);
+
+   protected:
+    // Exposed for testing.
+    BluetoothLowEnergyWeavePacketGenerator* BuildInstance();
+
+   private:
+    static Factory* factory_instance_;
+  };
+
+  // Determine whether a packet is a control packet or a data packet.
+  enum PacketType { DATA = 0x00, CONTROL = 0x01 };
+
+  // Identify the action intended by the control packet.
+  enum ControlCommand {
+    CONNECTION_REQUEST = 0x00,
+    CONNECTION_RESPONSE = 0x01,
+    CONNECTION_CLOSE = 0x02
+  };

[sacomoto, 2016/06/13 16:05:19]

Why PacketType and ControlCommand are public? 

[jingxuy, 2016/06/17 00:56:45]

It's part of a todo in the receiver. the commonalities b/t generator and
receiver will be moved to a separate class

[sacomoto, 2016/06/17 15:38:04]

Ok, that makes sense.

[jingxuy, 2016/06/17 18:59:00]

Done.

+
+  // Sent with the ConnectionClose control packet.
+  // Identify why the client/server wished to close the connection.
+  enum ReasonForClose {
+    CLOSE_WITHOUT_ERROR = 0x00,
+    UNKNOWN_ERROR = 0x01,
+    NO_COMMON_VERSION_SUPPORTED = 0x02,
+    RECEIVED_PACKET_OUT_OF_SEQUENCE = 0x03,
+    APPLICATION_ERROR = 0x80
+  };
+
+  typedef std::vector<uint8_t> Packet;
+
+  std::unique_ptr<Packet> CreateConnectionRequest();
+  std::unique_ptr<Packet> CreateConnectionResponse();

[sacomoto, 2016/06/13 16:05:19]

This method should receive the chosen protocol version as a parameter. Without
parsing the connection request packet, I don't see how this class could decide
the right version to use.

The connection request packet contains a min and max protocol version supported
by the client. After receiving that packet, the server should reply with a
connection response packet containing the maximum version supported by _both_
the server and the client. 

[jingxuy, 2016/06/17 00:56:45]

Initially the protocol version is a parameter, but Kyle suggested that since
there is only 1 version right now, it's okay to leave it off. Since if there is
another version, the class will undergo significant enough changes that
supporting versions that it's not necessary right now to support versions that
don't exist.

[sacomoto, 2016/06/17 15:38:04]

Ok, that makes sense.

[jingxuy, 2016/06/17 18:59:00]

Done.

+  std::unique_ptr<Packet> CreateConnectionClose(
+      ReasonForClose reason_for_close);
+
+  void SetDataPacketSize(uint32_t size);
+
+  std::unique_ptr<std::vector<Packet>> EncodeDataMessage(std::string message);
+
+ protected:
+  BluetoothLowEnergyWeavePacketGenerator();
+
+ private:
+  Packet* CreateControlPacket();
+
+  void SetShortField(Packet* packet, uint32_t byte_offset, uint16_t val);
+  void SetPacketTypeBit(Packet* packet, PacketType val);
+  void SetControlCommand(Packet* packet, ControlCommand val);
+  void SetPacketCounter(Packet* packet);
+  void SetDataFirstBit(Packet* packet);
+  void SetDataLastBit(Packet* packet);
+
+  // The default data packet length is 20 unless SetDataPacketLength() is called
+  // and specified otherwise.
+  uint32_t packet_size_;
+
+  // Counter for the number of packets sent, starting at 0.
+  uint32_t packet_number_;
+};
+
+}  // namespace proximity_auth
+
+#endif  // COMPONENTS_PROXIMITY_AUTH_BLE_BLUETOOTH_LOW_ENERGY_WEAVE_PACKET_GENERATOR_H_