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* Copyright (C) 2005, 2006, 2008 Apple Inc. All rights reserved.
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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* You should have received a copy of the GNU Library General Public License
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* along with this library; see the file COPYING.LIB. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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* Boston, MA 02110-1301, USA.
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#ifndef WTF_HashFunctions_h
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#define WTF_HashFunctions_h
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#include <wtf/RefPtr.h>
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template<size_t size> struct IntTypes;
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template<> struct IntTypes<1> { typedef int8_t SignedType; typedef uint8_t UnsignedType; };
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template<> struct IntTypes<2> { typedef int16_t SignedType; typedef uint16_t UnsignedType; };
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template<> struct IntTypes<4> { typedef int32_t SignedType; typedef uint32_t UnsignedType; };
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template<> struct IntTypes<8> { typedef int64_t SignedType; typedef uint64_t UnsignedType; };
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// integer hash function
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// Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
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inline unsigned intHash(uint8_t key8)
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// Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
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inline unsigned intHash(uint16_t key16)
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// Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
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inline unsigned intHash(uint32_t key)
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// Thomas Wang's 64 bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
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inline unsigned intHash(uint64_t key)
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return static_cast<unsigned>(key);
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// Compound integer hash method: http://opendatastructures.org/versions/edition-0.1d/ods-java/node33.html#SECTION00832000000000000000
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inline unsigned pairIntHash(unsigned key1, unsigned key2)
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unsigned shortRandom1 = 277951225; // A random 32-bit value.
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unsigned shortRandom2 = 95187966; // A random 32-bit value.
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uint64_t longRandom = 19248658165952622LL; // A random 64-bit value.
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uint64_t product = longRandom * (shortRandom1 * key1 + shortRandom2 * key2);
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unsigned highBits = static_cast<unsigned>(product >> (sizeof(uint64_t) - sizeof(unsigned)));
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template<typename T> struct IntHash {
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static unsigned hash(T key) { return intHash(static_cast<typename IntTypes<sizeof(T)>::UnsignedType>(key)); }
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static bool equal(T a, T b) { return a == b; }
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static const bool safeToCompareToEmptyOrDeleted = true;
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template<typename T> struct FloatHash {
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typedef typename IntTypes<sizeof(T)>::UnsignedType Bits;
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static unsigned hash(T key)
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return intHash(bitwise_cast<Bits>(key));
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static bool equal(T a, T b)
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return bitwise_cast<Bits>(a) == bitwise_cast<Bits>(b);
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static const bool safeToCompareToEmptyOrDeleted = true;
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// pointer identity hash function
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template<typename T> struct PtrHash {
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static unsigned hash(T key)
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#pragma warning(push)
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#pragma warning(disable: 4244) // work around what seems to be a bug in MSVC's conversion warnings
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return IntHash<uintptr_t>::hash(reinterpret_cast<uintptr_t>(key));
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static bool equal(T a, T b) { return a == b; }
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static const bool safeToCompareToEmptyOrDeleted = true;
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template<typename P> struct PtrHash<RefPtr<P> > : PtrHash<P*> {
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using PtrHash<P*>::hash;
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static unsigned hash(const RefPtr<P>& key) { return hash(key.get()); }
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using PtrHash<P*>::equal;
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static bool equal(const RefPtr<P>& a, const RefPtr<P>& b) { return a == b; }
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static bool equal(P* a, const RefPtr<P>& b) { return a == b; }
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static bool equal(const RefPtr<P>& a, P* b) { return a == b; }
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// default hash function for each type
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template<typename T> struct DefaultHash;
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template<typename T, typename U> struct PairHash {
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static unsigned hash(const std::pair<T, U>& p)
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return pairIntHash(DefaultHash<T>::Hash::hash(p.first), DefaultHash<U>::Hash::hash(p.second));
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static bool equal(const std::pair<T, U>& a, const std::pair<T, U>& b)
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return DefaultHash<T>::Hash::equal(a.first, b.first) && DefaultHash<U>::Hash::equal(a.second, b.second);
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static const bool safeToCompareToEmptyOrDeleted = DefaultHash<T>::Hash::safeToCompareToEmptyOrDeleted
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&& DefaultHash<U>::Hash::safeToCompareToEmptyOrDeleted;
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template<typename T, typename U> struct IntPairHash {
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static unsigned hash(const std::pair<T, U>& p) { return pairIntHash(p.first, p.second); }
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static bool equal(const std::pair<T, U>& a, const std::pair<T, U>& b) { return PairHash<T, T>::equal(a, b); }
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static const bool safeToCompareToEmptyOrDeleted = PairHash<T, U>::safeToCompareToEmptyOrDeleted;
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// make IntHash the default hash function for many integer types
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template<> struct DefaultHash<short> { typedef IntHash<unsigned> Hash; };
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template<> struct DefaultHash<unsigned short> { typedef IntHash<unsigned> Hash; };
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template<> struct DefaultHash<int> { typedef IntHash<unsigned> Hash; };
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template<> struct DefaultHash<unsigned> { typedef IntHash<unsigned> Hash; };
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template<> struct DefaultHash<long> { typedef IntHash<unsigned long> Hash; };
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template<> struct DefaultHash<unsigned long> { typedef IntHash<unsigned long> Hash; };
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template<> struct DefaultHash<long long> { typedef IntHash<unsigned long long> Hash; };
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template<> struct DefaultHash<unsigned long long> { typedef IntHash<unsigned long long> Hash; };
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#if !COMPILER(MSVC) || defined(_NATIVE_WCHAR_T_DEFINED)
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template<> struct DefaultHash<wchar_t> { typedef IntHash<wchar_t> Hash; };
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template<> struct DefaultHash<float> { typedef FloatHash<float> Hash; };
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template<> struct DefaultHash<double> { typedef FloatHash<double> Hash; };
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// make PtrHash the default hash function for pointer types that don't specialize
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template<typename P> struct DefaultHash<P*> { typedef PtrHash<P*> Hash; };
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template<typename P> struct DefaultHash<RefPtr<P> > { typedef PtrHash<RefPtr<P> > Hash; };
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// make IntPairHash the default hash function for pairs of (at most) 32-bit integers.
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template<> struct DefaultHash<std::pair<short, short> > { typedef IntPairHash<short, short> Hash; };
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template<> struct DefaultHash<std::pair<short, unsigned short> > { typedef IntPairHash<short, unsigned short> Hash; };
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template<> struct DefaultHash<std::pair<short, int> > { typedef IntPairHash<short, int> Hash; };
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template<> struct DefaultHash<std::pair<short, unsigned> > { typedef IntPairHash<short, unsigned> Hash; };
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template<> struct DefaultHash<std::pair<unsigned short, short> > { typedef IntPairHash<unsigned short, short> Hash; };
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template<> struct DefaultHash<std::pair<unsigned short, unsigned short> > { typedef IntPairHash<unsigned short, unsigned short> Hash; };
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template<> struct DefaultHash<std::pair<unsigned short, int> > { typedef IntPairHash<unsigned short, int> Hash; };
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template<> struct DefaultHash<std::pair<unsigned short, unsigned> > { typedef IntPairHash<unsigned short, unsigned> Hash; };
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template<> struct DefaultHash<std::pair<int, short> > { typedef IntPairHash<int, short> Hash; };
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template<> struct DefaultHash<std::pair<int, unsigned short> > { typedef IntPairHash<int, unsigned short> Hash; };
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template<> struct DefaultHash<std::pair<int, int> > { typedef IntPairHash<int, int> Hash; };
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template<> struct DefaultHash<std::pair<int, unsigned> > { typedef IntPairHash<unsigned, unsigned> Hash; };
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template<> struct DefaultHash<std::pair<unsigned, short> > { typedef IntPairHash<unsigned, short> Hash; };
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template<> struct DefaultHash<std::pair<unsigned, unsigned short> > { typedef IntPairHash<unsigned, unsigned short> Hash; };
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template<> struct DefaultHash<std::pair<unsigned, int> > { typedef IntPairHash<unsigned, int> Hash; };
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template<> struct DefaultHash<std::pair<unsigned, unsigned> > { typedef IntPairHash<unsigned, unsigned> Hash; };
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// make PairHash the default hash function for pairs of arbitrary values.
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template<typename T, typename U> struct DefaultHash<std::pair<T, U> > { typedef PairHash<T, U> Hash; };
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using WTF::DefaultHash;
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#endif // WTF_HashFunctions_h