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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 "wtf/StdLibExtras.h"
     26 #include <stdint.h>
     27 
     28 namespace WTF {
     29 
     30     template<size_t size> struct IntTypes;
     31     template<> struct IntTypes<1> { typedef int8_t SignedType; typedef uint8_t UnsignedType; };
     32     template<> struct IntTypes<2> { typedef int16_t SignedType; typedef uint16_t UnsignedType; };
     33     template<> struct IntTypes<4> { typedef int32_t SignedType; typedef uint32_t UnsignedType; };
     34     template<> struct IntTypes<8> { typedef int64_t SignedType; typedef uint64_t UnsignedType; };
     35 
     36     // integer hash function
     37 
     38     // Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
     39     inline unsigned intHash(uint8_t key8)
     40     {
     41         unsigned key = key8;
     42         key += ~(key << 15);
     43         key ^= (key >> 10);
     44         key += (key << 3);
     45         key ^= (key >> 6);
     46         key += ~(key << 11);
     47         key ^= (key >> 16);
     48         return key;
     49     }
     50 
     51     // Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
     52     inline unsigned intHash(uint16_t key16)
     53     {
     54         unsigned key = key16;
     55         key += ~(key << 15);
     56         key ^= (key >> 10);
     57         key += (key << 3);
     58         key ^= (key >> 6);
     59         key += ~(key << 11);
     60         key ^= (key >> 16);
     61         return key;
     62     }
     63 
     64     // Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
     65     inline unsigned intHash(uint32_t key)
     66     {
     67         key += ~(key << 15);
     68         key ^= (key >> 10);
     69         key += (key << 3);
     70         key ^= (key >> 6);
     71         key += ~(key << 11);
     72         key ^= (key >> 16);
     73         return key;
     74     }
     75 
     76     // Thomas Wang's 64 bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
     77     inline unsigned intHash(uint64_t key)
     78     {
     79         key += ~(key << 32);
     80         key ^= (key >> 22);
     81         key += ~(key << 13);
     82         key ^= (key >> 8);
     83         key += (key << 3);
     84         key ^= (key >> 15);
     85         key += ~(key << 27);
     86         key ^= (key >> 31);
     87         return static_cast<unsigned>(key);
     88     }
     89 
     90     // Compound integer hash method: http://opendatastructures.org/versions/edition-0.1d/ods-java/node33.html#SECTION00832000000000000000
     91     inline unsigned pairIntHash(unsigned key1, unsigned key2)
     92     {
     93         unsigned shortRandom1 = 277951225; // A random 32-bit value.
     94         unsigned shortRandom2 = 95187966; // A random 32-bit value.
     95         uint64_t longRandom = 19248658165952622LL; // A random 64-bit value.
     96 
     97         uint64_t product = longRandom * (shortRandom1 * key1 + shortRandom2 * key2);
     98         unsigned highBits = static_cast<unsigned>(product >> (sizeof(uint64_t) - sizeof(unsigned)));
     99         return highBits;
    100     }
    101 
    102     template<typename T> struct IntHash {
    103         static unsigned hash(T key) { return intHash(static_cast<typename IntTypes<sizeof(T)>::UnsignedType>(key)); }
    104         static bool equal(T a, T b) { return a == b; }
    105         static const bool safeToCompareToEmptyOrDeleted = true;
    106     };
    107 
    108     template<typename T> struct FloatHash {
    109         typedef typename IntTypes<sizeof(T)>::UnsignedType Bits;
    110         static unsigned hash(T key)
    111         {
    112             return intHash(bitwise_cast<Bits>(key));
    113         }
    114         static bool equal(T a, T b)
    115         {
    116             return bitwise_cast<Bits>(a) == bitwise_cast<Bits>(b);
    117         }
    118         static const bool safeToCompareToEmptyOrDeleted = true;
    119     };
    120 
    121     // pointer identity hash function
    122 
    123     template<typename T> struct PtrHash {
    124         static unsigned hash(T key)
    125         {
    126 #if COMPILER(MSVC)
    127 #pragma warning(push)
    128 #pragma warning(disable: 4244) // work around what seems to be a bug in MSVC's conversion warnings
    129 #endif
    130             return IntHash<uintptr_t>::hash(reinterpret_cast<uintptr_t>(key));
    131 #if COMPILER(MSVC)
    132 #pragma warning(pop)
    133 #endif
    134         }
    135         static bool equal(T a, T b) { return a == b; }
    136         static const bool safeToCompareToEmptyOrDeleted = true;
    137     };
    138     template<typename P> struct PtrHash<RefPtr<P> > : PtrHash<P*> {
    139         using PtrHash<P*>::hash;
    140         static unsigned hash(const RefPtr<P>& key) { return hash(key.get()); }
    141         using PtrHash<P*>::equal;
    142         static bool equal(const RefPtr<P>& a, const RefPtr<P>& b) { return a == b; }
    143         static bool equal(P* a, const RefPtr<P>& b) { return a == b; }
    144         static bool equal(const RefPtr<P>& a, P* b) { return a == b; }
    145     };
    146 
    147     // default hash function for each type
    148 
    149     template<typename T> struct DefaultHash;
    150 
    151     template<typename T, typename U> struct PairHash {
    152         static unsigned hash(const std::pair<T, U>& p)
    153         {
    154             return pairIntHash(DefaultHash<T>::Hash::hash(p.first), DefaultHash<U>::Hash::hash(p.second));
    155         }
    156         static bool equal(const std::pair<T, U>& a, const std::pair<T, U>& b)
    157         {
    158             return DefaultHash<T>::Hash::equal(a.first, b.first) && DefaultHash<U>::Hash::equal(a.second, b.second);
    159         }
    160         static const bool safeToCompareToEmptyOrDeleted = DefaultHash<T>::Hash::safeToCompareToEmptyOrDeleted
    161                                                             && DefaultHash<U>::Hash::safeToCompareToEmptyOrDeleted;
    162     };
    163 
    164     template<typename T, typename U> struct IntPairHash {
    165         static unsigned hash(const std::pair<T, U>& p) { return pairIntHash(p.first, p.second); }
    166         static bool equal(const std::pair<T, U>& a, const std::pair<T, U>& b) { return PairHash<T, T>::equal(a, b); }
    167         static const bool safeToCompareToEmptyOrDeleted = PairHash<T, U>::safeToCompareToEmptyOrDeleted;
    168     };
    169 
    170     // make IntHash the default hash function for many integer types
    171 
    172     template<> struct DefaultHash<short> { typedef IntHash<unsigned> Hash; };
    173     template<> struct DefaultHash<unsigned short> { typedef IntHash<unsigned> Hash; };
    174     template<> struct DefaultHash<int> { typedef IntHash<unsigned> Hash; };
    175     template<> struct DefaultHash<unsigned> { typedef IntHash<unsigned> Hash; };
    176     template<> struct DefaultHash<long> { typedef IntHash<unsigned long> Hash; };
    177     template<> struct DefaultHash<unsigned long> { typedef IntHash<unsigned long> Hash; };
    178     template<> struct DefaultHash<long long> { typedef IntHash<unsigned long long> Hash; };
    179     template<> struct DefaultHash<unsigned long long> { typedef IntHash<unsigned long long> Hash; };
    180 
    181 #if !COMPILER(MSVC) || defined(_NATIVE_WCHAR_T_DEFINED)
    182     template<> struct DefaultHash<wchar_t> { typedef IntHash<wchar_t> Hash; };
    183 #endif
    184 
    185     template<> struct DefaultHash<float> { typedef FloatHash<float> Hash; };
    186     template<> struct DefaultHash<double> { typedef FloatHash<double> Hash; };
    187 
    188     // make PtrHash the default hash function for pointer types that don't specialize
    189 
    190     template<typename P> struct DefaultHash<P*> { typedef PtrHash<P*> Hash; };
    191     template<typename P> struct DefaultHash<RefPtr<P> > { typedef PtrHash<RefPtr<P> > Hash; };
    192 
    193     // make IntPairHash the default hash function for pairs of (at most) 32-bit integers.
    194 
    195     template<> struct DefaultHash<std::pair<short, short> > { typedef IntPairHash<short, short> Hash; };
    196     template<> struct DefaultHash<std::pair<short, unsigned short> > { typedef IntPairHash<short, unsigned short> Hash; };
    197     template<> struct DefaultHash<std::pair<short, int> > { typedef IntPairHash<short, int> Hash; };
    198     template<> struct DefaultHash<std::pair<short, unsigned> > { typedef IntPairHash<short, unsigned> Hash; };
    199     template<> struct DefaultHash<std::pair<unsigned short, short> > { typedef IntPairHash<unsigned short, short> Hash; };
    200     template<> struct DefaultHash<std::pair<unsigned short, unsigned short> > { typedef IntPairHash<unsigned short, unsigned short> Hash; };
    201     template<> struct DefaultHash<std::pair<unsigned short, int> > { typedef IntPairHash<unsigned short, int> Hash; };
    202     template<> struct DefaultHash<std::pair<unsigned short, unsigned> > { typedef IntPairHash<unsigned short, unsigned> Hash; };
    203     template<> struct DefaultHash<std::pair<int, short> > { typedef IntPairHash<int, short> Hash; };
    204     template<> struct DefaultHash<std::pair<int, unsigned short> > { typedef IntPairHash<int, unsigned short> Hash; };
    205     template<> struct DefaultHash<std::pair<int, int> > { typedef IntPairHash<int, int> Hash; };
    206     template<> struct DefaultHash<std::pair<int, unsigned> > { typedef IntPairHash<unsigned, unsigned> Hash; };
    207     template<> struct DefaultHash<std::pair<unsigned, short> > { typedef IntPairHash<unsigned, short> Hash; };
    208     template<> struct DefaultHash<std::pair<unsigned, unsigned short> > { typedef IntPairHash<unsigned, unsigned short> Hash; };
    209     template<> struct DefaultHash<std::pair<unsigned, int> > { typedef IntPairHash<unsigned, int> Hash; };
    210     template<> struct DefaultHash<std::pair<unsigned, unsigned> > { typedef IntPairHash<unsigned, unsigned> Hash; };
    211 
    212     // make PairHash the default hash function for pairs of arbitrary values.
    213 
    214     template<typename T, typename U> struct DefaultHash<std::pair<T, U> > { typedef PairHash<T, U> Hash; };
    215 
    216 } // namespace WTF
    217 
    218 using WTF::DefaultHash;
    219 using WTF::IntHash;
    220 using WTF::PtrHash;
    221 
    222 #endif // WTF_HashFunctions_h
    223