[Bluetooth] Clean up code to extract a UUID from SDP data.

device/bluetooth/bluetooth_device_mac.mm

Index: device/bluetooth/bluetooth_device_mac.mm
diff --git a/device/bluetooth/bluetooth_device_mac.mm b/device/bluetooth/bluetooth_device_mac.mm
index 60574b040c30b88738dc67db2c4a853261a0e803..6ec64992eabad12e14bb848612e6dd02b159a029 100644
--- a/device/bluetooth/bluetooth_device_mac.mm
+++ b/device/bluetooth/bluetooth_device_mac.mm
@@ -11,7 +11,6 @@
 #include "base/sequenced_task_runner.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
-#include "base/strings/stringprintf.h"
 #include "base/strings/sys_string_conversions.h"
 #include "device/bluetooth/bluetooth_profile_mac.h"
 #include "device/bluetooth/bluetooth_socket_mac.h"
@@ -40,10 +39,12 @@
                  outTransmitPowerLevel:(BluetoothHCITransmitPowerLevel*)level;
 @end
 
+namespace device {
 namespace {
 
-void ExtractUuid(IOBluetoothSDPDataElement* service_class_data,
-                 std::string* uuid) {
+// Returns the first (should be, only) UUID contained within the
+// |service_class_data|. Returns an invalid (empty) UUID if none is found.
+BluetoothUUID ExtractUuid(IOBluetoothSDPDataElement* service_class_data) {
   NSArray* inner_elements = [service_class_data getArrayValue];
   IOBluetoothSDPUUID* sdp_uuid = nil;
   for (IOBluetoothSDPDataElement* inner_element in inner_elements) {
@@ -52,21 +53,22 @@ void ExtractUuid(IOBluetoothSDPDataElement* service_class_data,
       break;
     }
   }
-  if (sdp_uuid != nil) {
-    const uint8* uuid_bytes = reinterpret_cast<const uint8*>([sdp_uuid bytes]);
-    *uuid = base::StringPrintf(
-        "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
-        uuid_bytes[0], uuid_bytes[1], uuid_bytes[2], uuid_bytes[3],
-        uuid_bytes[4], uuid_bytes[5], uuid_bytes[6], uuid_bytes[7],
-        uuid_bytes[8], uuid_bytes[9], uuid_bytes[10], uuid_bytes[11],
-        uuid_bytes[12], uuid_bytes[13], uuid_bytes[14], uuid_bytes[15]);
-  }
+
+  if (!sdp_uuid)
+    return BluetoothUUID();
+
+  const uint8* uuid_bytes = reinterpret_cast<const uint8*>([sdp_uuid bytes]);
+  std::string uuid_str = base::HexEncode(uuid_bytes, 16);
+  DCHECK_EQ(uuid_str.size(), 32U);
+  uuid_str.insert(8, "-");
+  uuid_str.insert(13, "-");
+  uuid_str.insert(18, "-");
+  uuid_str.insert(23, "-");
+  return BluetoothUUID(uuid_str);
 }
 
 }  // namespace
 
-namespace device {
-
 BluetoothDeviceMac::BluetoothDeviceMac(IOBluetoothDevice* device)
     : device_([device retain]) {
 }
@@ -157,14 +159,14 @@ bool BluetoothDeviceMac::IsConnecting() const {
 BluetoothDevice::UUIDList BluetoothDeviceMac::GetUUIDs() const {
   UUIDList uuids;
   for (IOBluetoothSDPServiceRecord* service_record in [device_ services]) {
-    const BluetoothSDPServiceAttributeID service_class_id = 1;
     IOBluetoothSDPDataElement* service_class_data =
-        [service_record getAttributeDataElement:service_class_id];
+        [service_record getAttributeDataElement:
+            kBluetoothSDPAttributeIdentifierServiceClassIDList];
     if ([service_class_data getTypeDescriptor] ==
             kBluetoothSDPDataElementTypeDataElementSequence) {
-      std::string uuid_str;
-      ExtractUuid(service_class_data, &uuid_str);
-      uuids.push_back(BluetoothUUID(uuid_str));
+      BluetoothUUID uuid = ExtractUuid(service_class_data);
+      if (uuid.IsValid())
+        uuids.push_back(uuid);
     }
   }
   return uuids;