Oilpan: Allowing hashing of RawPtr.

Source/wtf/HashTraits.h

 /*
  * Copyright (C) 2005, 2006, 2007, 2008, 2011, 2012 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 68 matching lines @@
         typedef T EmptyValueType;
 
         static T emptyValue() { return T(); }
 
         // Type for functions that do not take ownership, such as contains.
         typedef const T& PeekInType;
         typedef T* IteratorGetType;
         typedef const T* IteratorConstGetType;
         typedef T& IteratorReferenceType;
         typedef const T& IteratorConstReferenceType;
-        static IteratorConstGetType getToConstGetConversion(const T* x) { return x; }

[tkent, 2014/03/03 10:19:57]

Why do you remove this line?

[Mads Ager (chromium), 2014/03/03 10:20:50]

Because it is unused in the code base. :)

[tkent, 2014/03/03 10:23:43]

I see.  I don't think we should include this change in this CL because it's
unrelated.

[Mads Ager (chromium), 2014/03/03 10:30:35]

It seems to me that removing dead code is always a good idea. I'm cutting it out
in this change so I don't have to put it in for new code when I know that it is
dead anyway. :)

         static IteratorReferenceType getToReferenceConversion(IteratorGetType x) { return *x; }
         static IteratorConstReferenceType getToReferenceConstConversion(IteratorConstGetType x) { return *x; }
         // Type for functions that take ownership, such as add.
         // The store function either not be called or called once to store something passed in.
         // The value passed to the store function will be PassInType.
         typedef const T& PassInType;
         static void store(const T& value, T& storage) { storage = value; }
 
         // Type for return value of functions that transfer ownership, such as take.
         typedef T PassOutType;
@@ skipping 84 matching lines @@
 
         typedef PassRefPtr<P> PassOutType;
         static PassOutType passOut(RefPtr<P>& value) { return value.release(); }
         static PassOutType passOut(std::nullptr_t) { return nullptr; }
 
         typedef P* PeekOutType;
         static PeekOutType peek(const RefPtr<P>& value) { return value.get(); }
         static PeekOutType peek(std::nullptr_t) { return 0; }
     };
 
+    template<typename T> struct HashTraits<RawPtr<T> > : SimpleClassHashTraits<RawPtr<T> > {
+        static const bool needsDestruction = false;
+        typedef T* PeekInType;
+        typedef T* PassInType;
+        typedef RawPtr<T>* IteratorGetType;
+        typedef const RawPtr<T>* IteratorConstGetType;
+        typedef RawPtr<T>& IteratorReferenceType;
+        typedef T* const IteratorConstReferenceType;

[Mikhail, 2014/03/03 10:25:56]

could I ask why 'IteratorReferenceType' and 'IteratorConstReferenceType' are
declared in so different way?

[Mads Ager (chromium), 2014/03/03 10:29:00]

Yes, there is no reason for the extra indirection for the const reference type.
A raw pointer is usable exactly as a raw pointer and for the const version we
can cut out the indirection safely which is better for performance.

+        static IteratorReferenceType getToReferenceConversion(IteratorGetType x) { return *x; }
+        static IteratorConstReferenceType getToReferenceConstConversion(IteratorConstGetType x) { return x->get(); }
+        typedef T* PeekOutType;
+        typedef T* PassOutType;
+
+        template<typename U>
+        static void store(const U& value, RawPtr<T>& storage) { storage = value; }
+
+        static PeekOutType peek(const RawPtr<T>& value) { return value; }
+        static PassOutType passOut(const RawPtr<T>& value) { return value; }
+    };
+
     template<> struct HashTraits<String> : SimpleClassHashTraits<String> {
         static const bool hasIsEmptyValueFunction = true;
         static bool isEmptyValue(const String&);
     };
 
     // This struct template is an implementation detail of the isHashTraitsEmptyValue function,
     // which selects either the emptyValue function or the isEmptyValue function to check for empty values.
     template<typename Traits, bool hasEmptyValueFunction> struct HashTraitsEmptyValueChecker;
     template<typename Traits> struct HashTraitsEmptyValueChecker<Traits, true> {
         template<typename T> static bool isEmptyValue(const T& value) { return Traits::isEmptyValue(value); }
@@ skipping 85 matching lines @@
     };
 
 } // namespace WTF
 
 using WTF::HashTraits;
 using WTF::PairHashTraits;
 using WTF::NullableHashTraits;
 using WTF::SimpleClassHashTraits;
 
 #endif // WTF_HashTraits_h