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.
+    virtual std::unique_ptr<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
+  };
+
+  // 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;
+
+  Packet CreateConnectionRequest();
+  Packet CreateConnectionResponse();
+  Packet CreateConnectionClose(ReasonForClose reason_for_close);
+
+  // Packet size must be greater than 2.

[Tim Song, 2016/06/22 18:41:31]

Why have this limitation as long as its greater than 0? BTW, it should also say
20 instead of 2.

[jingxuy, 2016/06/22 19:07:02]

I originally set it to 2 because there need to be at least 1 byte for header and
1 byte for data. Need the header and then the data byte is making sure sending
data packet doesn't spin forever because it can't send any byte. packet_size_ is
actually also used in sending the original control message, which would have a
field that says maximum packet size, and that has to be at least 20 or the
request will be rejected. So Gustavo and Kyle suggested that you shouldn't be
setting maximum packet size to anything less than 20.

+  void SetDataPacketSize(uint32_t size);
+
+  // Will crash if message is empty.

[Tim Song, 2016/06/22 18:41:32]

Crashing isn't the right thing to do. You should return an empty vector instead.

[jingxuy, 2016/06/22 19:07:02]

It originally returned an empty vector returned on an empty message received.
But Gustavo and Kyle both considered empty message to be an error.

+  std::vector<Packet> EncodeDataMessage(std::string message);
+
+ protected:
+  BluetoothLowEnergyWeavePacketGenerator();
+
+ private:
+  Packet CreateControlPacket(uint16_t size);
+
+  void SetShortField(uint32_t byte_offset, uint16_t val, Packet* packet);
+  void SetPacketTypeBit(PacketType val, Packet* packet);
+  void SetControlCommand(ControlCommand val, Packet* packet);
+  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_