WTF HashSet: Implement move semantics for values.

third_party/WebKit/Source/wtf/HashSet.h

 /*
  * Copyright (C) 2005, 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 75 matching lines @@
     // An alternate version of find() that finds the object by hashing and
     // comparing with some other type, to avoid the cost of type
     // conversion. HashTranslator must have the following function members:
     //   static unsigned hash(const T&);
     //   static bool equal(const ValueType&, const T&);
     template <typename HashTranslator, typename T> iterator find(const T&) const;
     template <typename HashTranslator, typename T> bool contains(const T&) const;
 
     // The return value is a pair of an iterator to the new value's location,
     // and a bool that is true if an new entry was added.
-    AddResult add(ValuePassInType);
+    template <typename IncomingValueType>
+    AddResult add(IncomingValueType&&);
 
     // An alternate version of add() that finds the object by hashing and
     // comparing with some other type, to avoid the cost of type conversion if
     // the object is already in the table. HashTranslator must have the
     // following function members:
     //   static unsigned hash(const T&);
     //   static bool equal(const ValueType&, const T&);
-    //   static translate(ValueType&, const T&, unsigned hashCode);
-    template <typename HashTranslator, typename T> AddResult add(const T&);
+    //   static translate(ValueType&, T&&, unsigned hashCode);
+    template <typename HashTranslator, typename T> AddResult addWithTranslator(T&&);
 
     void remove(ValuePeekInType);
     void remove(iterator);
     void clear();
     template <typename Collection>
     void removeAll(const Collection& toBeRemoved) { WTF::removeAll(*this, toBeRemoved); }
 
     ValuePassOutType take(iterator);
     ValuePassOutType take(ValuePeekInType);
     ValuePassOutType takeAny();
 
     template <typename VisitorDispatcher>
     void trace(VisitorDispatcher visitor) { m_impl.trace(visitor); }
 
 private:
     HashTableType m_impl;
 };
 
 struct IdentityExtractor {
     STATIC_ONLY(IdentityExtractor);
     template <typename T>
     static const T& extract(const T& t) { return t; }
 };
 
 template <typename Translator>
 struct HashSetTranslatorAdapter {
     STATIC_ONLY(HashSetTranslatorAdapter);
     template <typename T> static unsigned hash(const T& key) { return Translator::hash(key); }
     template <typename T, typename U> static bool equal(const T& a, const U& b) { return Translator::equal(a, b); }
-    template <typename T, typename U> static void translate(T& location, const U& key, const U&, unsigned hashCode)
+    template <typename T, typename U, typename V> static void translate(T& location, U&& key, const V&, unsigned hashCode)
     {
-        Translator::translate(location, key, hashCode);
+        Translator::translate(location, std::forward<U>(key), hashCode);
     }
 };
 
 template <typename T, typename U, typename V, typename W>
 inline unsigned HashSet<T, U, V, W>::size() const
 {
     return m_impl.size();
 }
 
 template <typename T, typename U, typename V, typename W>
@@ skipping 41 matching lines @@
 }
 
 template <typename Value, typename HashFunctions, typename Traits, typename Allocator>
 template <typename HashTranslator, typename T>
 inline bool HashSet<Value, HashFunctions, Traits, Allocator>::contains(const T& value) const
 {
     return m_impl.template contains<HashSetTranslatorAdapter<HashTranslator>>(value);
 }
 
 template <typename T, typename U, typename V, typename W>
-inline typename HashSet<T, U, V, W>::AddResult HashSet<T, U, V, W>::add(ValuePassInType value)
+template <typename IncomingValueType>
+inline typename HashSet<T, U, V, W>::AddResult HashSet<T, U, V, W>::add(IncomingValueType&& value)
 {
-    return m_impl.add(value);
+    return m_impl.add(std::forward<IncomingValueType>(value));
 }
 
 template <typename Value, typename HashFunctions, typename Traits, typename Allocator>
 template <typename HashTranslator, typename T>
 inline typename HashSet<Value, HashFunctions, Traits, Allocator>::AddResult
-HashSet<Value, HashFunctions, Traits, Allocator>::add(const T& value)
+HashSet<Value, HashFunctions, Traits, Allocator>::addWithTranslator(T&& value)
 {
-    return m_impl.template addPassingHashCode<HashSetTranslatorAdapter<HashTranslator>>(value, value);
+    // Forward only the first argument, because the second argument isn't actually used in HashSetTranslatorAdapter.
+    return m_impl.template addPassingHashCode<HashSetTranslatorAdapter<HashTranslator>>(std::forward<T>(value), value);
 }
 
 template <typename T, typename U, typename V, typename W>
 inline void HashSet<T, U, V, W>::remove(iterator it)
 {
     m_impl.remove(it.m_impl);
 }
 
 template <typename T, typename U, typename V, typename W>
 inline void HashSet<T, U, V, W>::remove(ValuePeekInType value)
@@ skipping 53 matching lines @@
 struct NeedsTracing<HashSet<T, U, V>> {
     static const bool value = false;
 };
 #endif
 
 } // namespace WTF
 
 using WTF::HashSet;
 
 #endif // WTF_HashSet_h