Noissue - Extract the stringHash to allow using in std::unordered_map<>

compiled/StringMap.h

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #pragma once
 
 #include <cstddef>
 
 #include "Map.h"
 #include "String.h"
 
+namespace {
+  size_t stringHash(const String& key)
+  {
+    // FNV-1a hash function
+    size_t result = 2166136261;
+    for (size_t i = 0; i < key.length(); i++)
+      result = (result ^ key[i]) * 16777619;
+    return result;
+  }
+}
+
+struct StringHash
+{
+  size_t operator()(const String& key) const
+  {
+    return stringHash(key);
+  }
+};
+
 namespace StringMap_internal
 {
   template<typename Key,
     class = typename std::enable_if<std::is_base_of<String, Key>::value>::type>
   struct StringSetEntry
   {
     typedef Key key_type;
     typedef const String& key_type_cref;
     typedef size_t size_type;
 
@@ skipping 20 matching lines @@
       return first.is_deleted();
     }
 
     void erase()
     {
       first.erase();
     }
 
     static size_type hash(key_type_cref key)
     {
-      // FNV-1a hash function
-      size_type result = 2166136261;
-      for (String::size_type i = 0; i < key.length(); i++)
-        result = (result ^ key[i]) * 16777619;
-      return result;
+      return stringHash(key);
     }
   };
 
   template<typename Key, typename Value>
   struct StringMapEntry : StringSetEntry<Key>
   {
     typedef StringSetEntry<Key> super;
     typedef Value value_type;
 
     value_type second;
@@ skipping 11 matching lines @@
     }
   };
 }
 
 using StringSet = Set<StringMap_internal::StringSetEntry<DependentString>>;
 
 template<typename Value>
 using StringMap = Map<StringMap_internal::StringMapEntry<DependentString, Value>>;
 template<typename Value>
 using OwnedStringMap = Map<StringMap_internal::StringMapEntry<OwnedString, Value>>;