BluetoothAdapterMac::LowEnergyDeviceUpdated() Implemented

device/bluetooth/bluetooth_adapter_mac.mm

Index: device/bluetooth/bluetooth_adapter_mac.mm
diff --git a/device/bluetooth/bluetooth_adapter_mac.mm b/device/bluetooth/bluetooth_adapter_mac.mm
index cf33939b61c4902c156f616a9e554e1fbabc6469..cc65ddf8fbe124f4cf932947948b454cfca5acd2 100644
--- a/device/bluetooth/bluetooth_adapter_mac.mm
+++ b/device/bluetooth/bluetooth_adapter_mac.mm
@@ -402,11 +402,39 @@ void BluetoothAdapterMac::ClassicDeviceAdded(IOBluetoothDevice* device) {
                     DeviceAdded(this, devices_[device_address]));
 }
 
-// TODO(krstnmnlsn): Implement method. http://crbug.com/496987.
 void BluetoothAdapterMac::LowEnergyDeviceUpdated(
     CBPeripheral* peripheral,
     NSDictionary* advertisementData,
     int rssi) {
+  std::string device_address =
+      BluetoothLowEnergyDeviceMac::GetPeripheralHashAddress(peripheral);
+  BluetoothDevice*& device_reference = devices_[device_address];

[armansito, 2015/07/15 18:14:42]

Please add a comment here explaining why you're using a reference to a pointer
and why it's OK to use the std::map [] operator before checking if the element
doesn't exist (since the operator will create the map entry if it doesn't
exist). Just explain the assignment done below.

[krstnmnlsn, 2015/07/15 20:38:14]

Done.

+

[armansito, 2015/07/15 18:14:42]

Remove extra space here.

[krstnmnlsn, 2015/07/15 20:38:14]

Done.

+  if (!device_reference) {
+    // A new device has been found.
+    device_reference =
+        new BluetoothLowEnergyDeviceMac(peripheral, advertisementData, rssi);
+    FOR_EACH_OBSERVER(BluetoothAdapter::Observer, observers_,
+                      DeviceAdded(this, device_reference));
+    return;
+  }
+
+  if (static_cast<BluetoothLowEnergyDeviceMac*>(device_reference)
+          ->GetIdentifier() !=
+      BluetoothLowEnergyDeviceMac::GetPeripheralIdentifier(peripheral)) {
+    // Collision, two identifiers map to the same hash address.  With a 48 bit
+    // hash the probability of this occuring with 10,000 devices
+    // simultaneously present is 1e-6 (see
+    // https://en.wikipedia.org/wiki/Birthday_problem#Probability_table).  We
+    // ignore the second device by returning.
+    return;
+  }
+
+  // A device has an update.
+  static_cast<BluetoothLowEnergyDeviceMac*>(device_reference)
+      ->Update(peripheral, advertisementData, rssi);
+  FOR_EACH_OBSERVER(BluetoothAdapter::Observer, observers_,
+                    DeviceChanged(this, device_reference));
 }
 
 void BluetoothAdapterMac::RemoveTimedOutDevices() {