Refactors GetDeviceIdentifier()

base/ios/device_util.mm

 // Copyright (c) 2012 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.
 
 #include "base/ios/device_util.h"
 
 #include <CommonCrypto/CommonDigest.h>
 #import <UIKit/UIKit.h>
 
 #include <ifaddrs.h>
@@ skipping 139 matching lines @@
 
   NSString* client_id = [defaults stringForKey:kClientIdPreferenceKey];
 
   if (!client_id || ![last_seen_hardware isEqualToString:current_hardware]) {
     client_id = GenerateClientId();
     [defaults setObject:client_id forKey:kClientIdPreferenceKey];
     [defaults setObject:current_hardware forKey:kHardwareTypePreferenceKey];
     [defaults synchronize];
   }
 
-  NSData* hash_data = [[NSString stringWithFormat:@"%@%s", client_id,
-      salt ? salt : kDefaultSalt] dataUsingEncoding:NSUTF8StringEncoding];
+  return GetSaltedString([client_id UTF8String], salt ? salt : kDefaultSalt);
+}
+
+std::string GetSaltedString(const std::string& in_string,
+                            const std::string& salt) {
+  DCHECK(in_string.length());
+  DCHECK(salt.length());
+  NSData* hash_data =
+      [[NSString stringWithFormat:@"%s%s", in_string.c_str(), salt.c_str()]
+          dataUsingEncoding:NSUTF8StringEncoding];
 
   unsigned char hash[CC_SHA256_DIGEST_LENGTH];
   CC_SHA256([hash_data bytes], [hash_data length], hash);
   CFUUIDBytes* uuid_bytes = reinterpret_cast<CFUUIDBytes*>(hash);
 
   base::ScopedCFTypeRef<CFUUIDRef> uuid_object(
       CFUUIDCreateFromUUIDBytes(kCFAllocatorDefault, *uuid_bytes));
   base::ScopedCFTypeRef<CFStringRef> device_id(
       CFUUIDCreateString(kCFAllocatorDefault, uuid_object));
   return base::SysCFStringRefToUTF8(device_id);
 }
 
 }  // namespace device_util
 }  // namespace ios