Chrome OS uWeave Characteristics Server

components/proximity_auth/ble/bluetooth_low_energy_eid_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_EID_GENERATOR_H_
+#define COMPONENTS_PROXIMITY_AUTH_BLE_BLUETOOTH_LOW_ENERGY_WEAVE_EID_GENERATOR_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <memory>
+
+#include "components/proximity_auth/remote_device.h"
+
+namespace proximity_auth {
+namespace weave {
+
+// Represent a EID generator for a single device. The code client has the

[rkc, 2016/07/27 00:56:34]

What's an EID?

[jingxuy, 2016/07/27 23:31:48]

Done.

+// responsiblity for keeping track of multiple clients
+class BluetoothLowEnergyEidGenerator {
+ public:
+  class Factory {

[Kyle Horimoto, 2016/07/27 17:58:48]

Is there a reason that a Factory is needed for this class?

[jingxuy, 2016/07/27 23:31:48]

I was under the impression that you want to mock out classes in testing process.
Unless we are moving toward a different testing approach for which we can talk
about.

+   public:
+    // TODO(jingxuy): this is just stop compiler from complaining.

[rkc, 2016/07/27 00:56:34]

Complaining about?
Generally when a compiler complains, there is often a good reason.

[jingxuy, 2016/07/27 23:31:48]

I didn't have a .cc file since I intend this class to be not implemented by me.
So it wouldn't let the ad_rotator construct this class.

+    static std::unique_ptr<BluetoothLowEnergyEidGenerator> NewInstance(
+        const RemoteDevice& device) {
+      return std::unique_ptr<BluetoothLowEnergyEidGenerator>(
+          new BluetoothLowEnergyEidGenerator(device));
+    }
+
+    // Exposed for testing.
+    static void SetInstanceForTesting(Factory* factory);
+
+   protected:
+    // Exposed for testing.
+    virtual std::unique_ptr<BluetoothLowEnergyEidGenerator> BuildInstance(
+        const RemoteDevice& device);
+
+   private:
+    static Factory* factory_instance_;
+  };
+
+  typedef uint8_t EidSeed[32];

[rkc, 2016/07/27 00:56:34]

Why 32? Also, make this a constexpr.

[Kyle Horimoto, 2016/07/27 17:58:48]

+1, I'm not sure that seeds are 32 bytes, but even if they are, the seeds will
be abstracted into a BeaconSeed class, so this typedef should not be necessary.

[jingxuy, 2016/07/27 23:31:48]

According to Jeremy it is 256 bits. This typedef is just a place holder. I do
not intend to implement the EID generator at all. 

+
+  // TODO(tether-dev): Make this actually generate EID.
+  // This function should look at the time and get the correct seed out of the
+  // remote device. If this seed is different from the current_seed_, then
+  // re-seed the generator. Otherwise generate based on time and stuff.
+  uint16_t GetEid() { return 42; }

[rkc, 2016/07/27 00:56:34]

Again, why 42?

[Kyle Horimoto, 2016/07/27 17:58:48]

This function should take a list of BeaconSeeds and return a current EID as well
as an adjacent EID if possible.

[Kyle Horimoto, 2016/07/27 17:58:48]

I think she's just returning a fake value and will implement this later. Jing,
please write TODO: implement in this case.

[jingxuy, 2016/07/27 23:31:48]

It has a TODO above the function explaining exactly what there is to do.

[jingxuy, 2016/07/27 23:31:48]

I think our design for the EID generator is different. My design owns a
remote_device. So it should be able to pull the BeasonSeeds out of the
remote_device. One of the main reasons for this difference is that I do not
intend to implement the EID seed generator. Hence I have to abstract away any
EID seed related things including BeaconSeed definition.

[jingxuy, 2016/07/28 22:09:03]

Resolved on offline discussion. Currently will take RemoteDevice. This is an
incomplete interface available for extensions.

+
+ protected:
+  BluetoothLowEnergyEidGenerator(const RemoteDevice& device)

[rkc, 2016/07/27 00:56:34]

Why is this protected?

[jingxuy, 2016/07/27 23:31:48]

Same as the comment in the rotator. It comes with factory implementation. Let me
know what testing injection we are going to use.

+      : device_(device){};
+
+ private:
+  const RemoteDevice& device_;
+
+  EidSeed current_seed_;
+};
+
+}  // namespace weave
+
+}  // namespace proximity_auth
+
+#endif