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      1 /*
      2  * Copyright (C) 2005, 2006, 2008 Apple Inc. All rights reserved.
      3  *
      4  * This library is free software; you can redistribute it and/or
      5  * modify it under the terms of the GNU Library General Public
      6  * License as published by the Free Software Foundation; either
      7  * version 2 of the License, or (at your option) any later version.
      8  *
      9  * This library is distributed in the hope that it will be useful,
     10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
     11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     12  * Library General Public License for more details.
     13  *
     14  * You should have received a copy of the GNU Library General Public License
     15  * along with this library; see the file COPYING.LIB.  If not, write to
     16  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
     17  * Boston, MA 02110-1301, USA.
     18  *
     19  */
     20 
     21 #ifndef WTF_HashFunctions_h
     22 #define WTF_HashFunctions_h
     23 
     24 #include "wtf/RefPtr.h"
     25 #include <stdint.h>
     26 
     27 namespace WTF {
     28 
     29     template<size_t size> struct IntTypes;
     30     template<> struct IntTypes<1> { typedef int8_t SignedType; typedef uint8_t UnsignedType; };
     31     template<> struct IntTypes<2> { typedef int16_t SignedType; typedef uint16_t UnsignedType; };
     32     template<> struct IntTypes<4> { typedef int32_t SignedType; typedef uint32_t UnsignedType; };
     33     template<> struct IntTypes<8> { typedef int64_t SignedType; typedef uint64_t UnsignedType; };
     34 
     35     // integer hash function
     36 
     37     // Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
     38     inline unsigned intHash(uint8_t key8)
     39     {
     40         unsigned key = key8;
     41         key += ~(key << 15);
     42         key ^= (key >> 10);
     43         key += (key << 3);
     44         key ^= (key >> 6);
     45         key += ~(key << 11);
     46         key ^= (key >> 16);
     47         return key;
     48     }
     49 
     50     // Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
     51     inline unsigned intHash(uint16_t key16)
     52     {
     53         unsigned key = key16;
     54         key += ~(key << 15);
     55         key ^= (key >> 10);
     56         key += (key << 3);
     57         key ^= (key >> 6);
     58         key += ~(key << 11);
     59         key ^= (key >> 16);
     60         return key;
     61     }
     62 
     63     // Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
     64     inline unsigned intHash(uint32_t key)
     65     {
     66         key += ~(key << 15);
     67         key ^= (key >> 10);
     68         key += (key << 3);
     69         key ^= (key >> 6);
     70         key += ~(key << 11);
     71         key ^= (key >> 16);
     72         return key;
     73     }
     74 
     75     // Thomas Wang's 64 bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
     76     inline unsigned intHash(uint64_t key)
     77     {
     78         key += ~(key << 32);
     79         key ^= (key >> 22);
     80         key += ~(key << 13);
     81         key ^= (key >> 8);
     82         key += (key << 3);
     83         key ^= (key >> 15);
     84         key += ~(key << 27);
     85         key ^= (key >> 31);
     86         return static_cast<unsigned>(key);
     87     }
     88 
     89     // Compound integer hash method: http://opendatastructures.org/versions/edition-0.1d/ods-java/node33.html#SECTION00832000000000000000
     90     inline unsigned pairIntHash(unsigned key1, unsigned key2)
     91     {
     92         unsigned shortRandom1 = 277951225; // A random 32-bit value.
     93         unsigned shortRandom2 = 95187966; // A random 32-bit value.
     94         uint64_t longRandom = 19248658165952622LL; // A random 64-bit value.
     95 
     96         uint64_t product = longRandom * (shortRandom1 * key1 + shortRandom2 * key2);
     97         unsigned highBits = static_cast<unsigned>(product >> (sizeof(uint64_t) - sizeof(unsigned)));
     98         return highBits;
     99     }
    100 
    101     template<typename T> struct IntHash {
    102         static unsigned hash(T key) { return intHash(static_cast<typename IntTypes<sizeof(T)>::UnsignedType>(key)); }
    103         static bool equal(T a, T b) { return a == b; }
    104         static const bool safeToCompareToEmptyOrDeleted = true;
    105     };
    106 
    107     template<typename T> struct FloatHash {
    108         typedef typename IntTypes<sizeof(T)>::UnsignedType Bits;
    109         static unsigned hash(T key)
    110         {
    111             return intHash(bitwise_cast<Bits>(key));
    112         }
    113         static bool equal(T a, T b)
    114         {
    115             return bitwise_cast<Bits>(a) == bitwise_cast<Bits>(b);
    116         }
    117         static const bool safeToCompareToEmptyOrDeleted = true;
    118     };
    119 
    120     // pointer identity hash function
    121 
    122     template<typename T> struct PtrHash {
    123         static unsigned hash(T key)
    124         {
    125 #if COMPILER(MSVC)
    126 #pragma warning(push)
    127 #pragma warning(disable: 4244) // work around what seems to be a bug in MSVC's conversion warnings
    128 #endif
    129             return IntHash<uintptr_t>::hash(reinterpret_cast<uintptr_t>(key));
    130 #if COMPILER(MSVC)
    131 #pragma warning(pop)
    132 #endif
    133         }
    134         static bool equal(T a, T b) { return a == b; }
    135         static const bool safeToCompareToEmptyOrDeleted = true;
    136     };
    137     template<typename P> struct PtrHash<RefPtr<P> > : PtrHash<P*> {
    138         using PtrHash<P*>::hash;
    139         static unsigned hash(const RefPtr<P>& key) { return hash(key.get()); }
    140         using PtrHash<P*>::equal;
    141         static bool equal(const RefPtr<P>& a, const RefPtr<P>& b) { return a == b; }
    142         static bool equal(P* a, const RefPtr<P>& b) { return a == b; }
    143         static bool equal(const RefPtr<P>& a, P* b) { return a == b; }
    144     };
    145 
    146     // default hash function for each type
    147 
    148     template<typename T> struct DefaultHash;
    149 
    150     template<typename T, typename U> struct PairHash {
    151         static unsigned hash(const std::pair<T, U>& p)
    152         {
    153             return pairIntHash(DefaultHash<T>::Hash::hash(p.first), DefaultHash<U>::Hash::hash(p.second));
    154         }
    155         static bool equal(const std::pair<T, U>& a, const std::pair<T, U>& b)
    156         {
    157             return DefaultHash<T>::Hash::equal(a.first, b.first) && DefaultHash<U>::Hash::equal(a.second, b.second);
    158         }
    159         static const bool safeToCompareToEmptyOrDeleted = DefaultHash<T>::Hash::safeToCompareToEmptyOrDeleted
    160                                                             && DefaultHash<U>::Hash::safeToCompareToEmptyOrDeleted;
    161     };
    162 
    163     template<typename T, typename U> struct IntPairHash {
    164         static unsigned hash(const std::pair<T, U>& p) { return pairIntHash(p.first, p.second); }
    165         static bool equal(const std::pair<T, U>& a, const std::pair<T, U>& b) { return PairHash<T, T>::equal(a, b); }
    166         static const bool safeToCompareToEmptyOrDeleted = PairHash<T, U>::safeToCompareToEmptyOrDeleted;
    167     };
    168 
    169     // make IntHash the default hash function for many integer types
    170 
    171     template<> struct DefaultHash<short> { typedef IntHash<unsigned> Hash; };
    172     template<> struct DefaultHash<unsigned short> { typedef IntHash<unsigned> Hash; };
    173     template<> struct DefaultHash<int> { typedef IntHash<unsigned> Hash; };
    174     template<> struct DefaultHash<unsigned> { typedef IntHash<unsigned> Hash; };
    175     template<> struct DefaultHash<long> { typedef IntHash<unsigned long> Hash; };
    176     template<> struct DefaultHash<unsigned long> { typedef IntHash<unsigned long> Hash; };
    177     template<> struct DefaultHash<long long> { typedef IntHash<unsigned long long> Hash; };
    178     template<> struct DefaultHash<unsigned long long> { typedef IntHash<unsigned long long> Hash; };
    179 
    180 #if !COMPILER(MSVC) || defined(_NATIVE_WCHAR_T_DEFINED)
    181     template<> struct DefaultHash<wchar_t> { typedef IntHash<wchar_t> Hash; };
    182 #endif
    183 
    184     template<> struct DefaultHash<float> { typedef FloatHash<float> Hash; };
    185     template<> struct DefaultHash<double> { typedef FloatHash<double> Hash; };
    186 
    187     // make PtrHash the default hash function for pointer types that don't specialize
    188 
    189     template<typename P> struct DefaultHash<P*> { typedef PtrHash<P*> Hash; };
    190     template<typename P> struct DefaultHash<RefPtr<P> > { typedef PtrHash<RefPtr<P> > Hash; };
    191 
    192     // make IntPairHash the default hash function for pairs of (at most) 32-bit integers.
    193 
    194     template<> struct DefaultHash<std::pair<short, short> > { typedef IntPairHash<short, short> Hash; };
    195     template<> struct DefaultHash<std::pair<short, unsigned short> > { typedef IntPairHash<short, unsigned short> Hash; };
    196     template<> struct DefaultHash<std::pair<short, int> > { typedef IntPairHash<short, int> Hash; };
    197     template<> struct DefaultHash<std::pair<short, unsigned> > { typedef IntPairHash<short, unsigned> Hash; };
    198     template<> struct DefaultHash<std::pair<unsigned short, short> > { typedef IntPairHash<unsigned short, short> Hash; };
    199     template<> struct DefaultHash<std::pair<unsigned short, unsigned short> > { typedef IntPairHash<unsigned short, unsigned short> Hash; };
    200     template<> struct DefaultHash<std::pair<unsigned short, int> > { typedef IntPairHash<unsigned short, int> Hash; };
    201     template<> struct DefaultHash<std::pair<unsigned short, unsigned> > { typedef IntPairHash<unsigned short, unsigned> Hash; };
    202     template<> struct DefaultHash<std::pair<int, short> > { typedef IntPairHash<int, short> Hash; };
    203     template<> struct DefaultHash<std::pair<int, unsigned short> > { typedef IntPairHash<int, unsigned short> Hash; };
    204     template<> struct DefaultHash<std::pair<int, int> > { typedef IntPairHash<int, int> Hash; };
    205     template<> struct DefaultHash<std::pair<int, unsigned> > { typedef IntPairHash<unsigned, unsigned> Hash; };
    206     template<> struct DefaultHash<std::pair<unsigned, short> > { typedef IntPairHash<unsigned, short> Hash; };
    207     template<> struct DefaultHash<std::pair<unsigned, unsigned short> > { typedef IntPairHash<unsigned, unsigned short> Hash; };
    208     template<> struct DefaultHash<std::pair<unsigned, int> > { typedef IntPairHash<unsigned, int> Hash; };
    209     template<> struct DefaultHash<std::pair<unsigned, unsigned> > { typedef IntPairHash<unsigned, unsigned> Hash; };
    210 
    211     // make PairHash the default hash function for pairs of arbitrary values.
    212 
    213     template<typename T, typename U> struct DefaultHash<std::pair<T, U> > { typedef PairHash<T, U> Hash; };
    214 
    215 } // namespace WTF
    216 
    217 using WTF::DefaultHash;
    218 using WTF::IntHash;
    219 using WTF::PtrHash;
    220 
    221 #endif // WTF_HashFunctions_h
    222