Home | History | Annotate | Download | only in wtf 
      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/OwnPtr.h"
     25 #include "wtf/RefPtr.h"
     26 #include "wtf/StdLibExtras.h"
     27 #include <stdint.h>
     28 
     29 namespace WTF {
     30 
     31     template<size_t size> struct IntTypes;
     32     template<> struct IntTypes<1> { typedef int8_t SignedType; typedef uint8_t UnsignedType; };
     33     template<> struct IntTypes<2> { typedef int16_t SignedType; typedef uint16_t UnsignedType; };
     34     template<> struct IntTypes<4> { typedef int32_t SignedType; typedef uint32_t UnsignedType; };
     35     template<> struct IntTypes<8> { typedef int64_t SignedType; typedef uint64_t UnsignedType; };
     36 
     37     // integer hash function
     38 
     39     // Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
     40     inline unsigned intHash(uint8_t key8)
     41     {
     42         unsigned key = key8;
     43         key += ~(key << 15);
     44         key ^= (key >> 10);
     45         key += (key << 3);
     46         key ^= (key >> 6);
     47         key += ~(key << 11);
     48         key ^= (key >> 16);
     49         return key;
     50     }
     51 
     52     // Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
     53     inline unsigned intHash(uint16_t key16)
     54     {
     55         unsigned key = key16;
     56         key += ~(key << 15);
     57         key ^= (key >> 10);
     58         key += (key << 3);
     59         key ^= (key >> 6);
     60         key += ~(key << 11);
     61         key ^= (key >> 16);
     62         return key;
     63     }
     64 
     65     // Thomas Wang's 32 Bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
     66     inline unsigned intHash(uint32_t key)
     67     {
     68         key += ~(key << 15);
     69         key ^= (key >> 10);
     70         key += (key << 3);
     71         key ^= (key >> 6);
     72         key += ~(key << 11);
     73         key ^= (key >> 16);
     74         return key;
     75     }
     76 
     77     // Thomas Wang's 64 bit Mix Function: http://www.cris.com/~Ttwang/tech/inthash.htm
     78     inline unsigned intHash(uint64_t key)
     79     {
     80         key += ~(key << 32);
     81         key ^= (key >> 22);
     82         key += ~(key << 13);
     83         key ^= (key >> 8);
     84         key += (key << 3);
     85         key ^= (key >> 15);
     86         key += ~(key << 27);
     87         key ^= (key >> 31);
     88         return static_cast<unsigned>(key);
     89     }
     90 
     91     // Compound integer hash method: http://opendatastructures.org/versions/edition-0.1d/ods-java/node33.html#SECTION00832000000000000000
     92     inline unsigned pairIntHash(unsigned key1, unsigned key2)
     93     {
     94         unsigned shortRandom1 = 277951225; // A random 32-bit value.
     95         unsigned shortRandom2 = 95187966; // A random 32-bit value.
     96         uint64_t longRandom = 19248658165952622LL; // A random 64-bit value.
     97 
     98         uint64_t product = longRandom * (shortRandom1 * key1 + shortRandom2 * key2);
     99         unsigned highBits = static_cast<unsigned>(product >> (sizeof(uint64_t) - sizeof(unsigned)));
    100         return highBits;
    101     }
    102 
    103     template<typename T> struct IntHash {
    104         static unsigned hash(T key) { return intHash(static_cast<typename IntTypes<sizeof(T)>::UnsignedType>(key)); }
    105         static bool equal(T a, T b) { return a == b; }
    106         static const bool safeToCompareToEmptyOrDeleted = true;
    107     };
    108 
    109     template<typename T> struct FloatHash {
    110         typedef typename IntTypes<sizeof(T)>::UnsignedType Bits;
    111         static unsigned hash(T key)
    112         {
    113             return intHash(bitwise_cast<Bits>(key));
    114         }
    115         static bool equal(T a, T b)
    116         {
    117             return bitwise_cast<Bits>(a) == bitwise_cast<Bits>(b);
    118         }
    119         static const bool safeToCompareToEmptyOrDeleted = true;
    120     };
    121 
    122     // pointer identity hash function
    123 
    124     template<typename T> struct PtrHash {
    125         static unsigned hash(T key)
    126         {
    127 #if COMPILER(MSVC)
    128 #pragma warning(push)
    129 #pragma warning(disable: 4244) // work around what seems to be a bug in MSVC's conversion warnings
    130 #endif
    131             return IntHash<uintptr_t>::hash(reinterpret_cast<uintptr_t>(key));
    132 #if COMPILER(MSVC)
    133 #pragma warning(pop)
    134 #endif
    135         }
    136         static bool equal(T a, T b) { return a == b; }
    137         static bool equal(std::nullptr_t, T b) { return b == 0; }
    138         static bool equal(T a, std::nullptr_t) { return a == 0; }
    139         static const bool safeToCompareToEmptyOrDeleted = true;
    140     };
    141     template<typename P> struct PtrHash<RefPtr<P> > : PtrHash<P*> {
    142         using PtrHash<P*>::hash;
    143         static unsigned hash(const RefPtr<P>& key) { return hash(key.get()); }
    144         static unsigned hash(const PassRefPtr<P>& key) { return hash(key.get()); }
    145         using PtrHash<P*>::equal;
    146         static bool equal(const RefPtr<P>& a, const RefPtr<P>& b) { return a == b; }
    147         static bool equal(P* a, const RefPtr<P>& b) { return a == b; }
    148         static bool equal(const RefPtr<P>& a, P* b) { return a == b; }
    149         static bool equal(const RefPtr<P>& a, const PassRefPtr<P>& b) { return a == b; }
    150     };
    151     template<typename P> struct PtrHash<RawPtr<P> > : PtrHash<P*> {
    152         using PtrHash<P*>::hash;
    153         static unsigned hash(const RawPtr<P>& key) { return hash(key.get()); }
    154         using PtrHash<P*>::equal;
    155         static bool equal(const RawPtr<P>& a, const RawPtr<P>& b) { return a == b; }
    156         static bool equal(P* a, const RawPtr<P>& b) { return a == b; }
    157         static bool equal(const RawPtr<P>& a, P* b) { return a == b; }
    158     };
    159     template<typename P> struct PtrHash<OwnPtr<P> > : PtrHash<P*> {
    160         using PtrHash<P*>::hash;
    161         static unsigned hash(const OwnPtr<P>& key) { return hash(key.get()); }
    162         static unsigned hash(const PassOwnPtr<P>& key) { return hash(key.get()); }
    163 
    164         static bool equal(const OwnPtr<P>& a, const OwnPtr<P>& b)
    165         {
    166             return a.get() == b.get();
    167         }
    168         static bool equal(const OwnPtr<P>& a, P* b) { return a == b; }
    169         static bool equal(const OwnPtr<P>& a, const PassOwnPtr<P>& b)
    170         {
    171             return a.get() == b.get();
    172         }
    173     };
    174 
    175     // default hash function for each type
    176 
    177     template<typename T> struct DefaultHash;
    178 
    179     template<typename T, typename U> struct PairHash {
    180         static unsigned hash(const std::pair<T, U>& p)
    181         {
    182             return pairIntHash(DefaultHash<T>::Hash::hash(p.first), DefaultHash<U>::Hash::hash(p.second));
    183         }
    184         static bool equal(const std::pair<T, U>& a, const std::pair<T, U>& b)
    185         {
    186             return DefaultHash<T>::Hash::equal(a.first, b.first) && DefaultHash<U>::Hash::equal(a.second, b.second);
    187         }
    188         static const bool safeToCompareToEmptyOrDeleted = DefaultHash<T>::Hash::safeToCompareToEmptyOrDeleted
    189                                                             && DefaultHash<U>::Hash::safeToCompareToEmptyOrDeleted;
    190     };
    191 
    192     template<typename T, typename U> struct IntPairHash {
    193         static unsigned hash(const std::pair<T, U>& p) { return pairIntHash(p.first, p.second); }
    194         static bool equal(const std::pair<T, U>& a, const std::pair<T, U>& b) { return PairHash<T, T>::equal(a, b); }
    195         static const bool safeToCompareToEmptyOrDeleted = PairHash<T, U>::safeToCompareToEmptyOrDeleted;
    196     };
    197 
    198     // make IntHash the default hash function for many integer types
    199 
    200     template<> struct DefaultHash<short> { typedef IntHash<unsigned> Hash; };
    201     template<> struct DefaultHash<unsigned short> { typedef IntHash<unsigned> Hash; };
    202     template<> struct DefaultHash<int> { typedef IntHash<unsigned> Hash; };
    203     template<> struct DefaultHash<unsigned> { typedef IntHash<unsigned> Hash; };
    204     template<> struct DefaultHash<long> { typedef IntHash<unsigned long> Hash; };
    205     template<> struct DefaultHash<unsigned long> { typedef IntHash<unsigned long> Hash; };
    206     template<> struct DefaultHash<long long> { typedef IntHash<unsigned long long> Hash; };
    207     template<> struct DefaultHash<unsigned long long> { typedef IntHash<unsigned long long> Hash; };
    208 
    209 #if !COMPILER(MSVC) || defined(_NATIVE_WCHAR_T_DEFINED)
    210     template<> struct DefaultHash<wchar_t> { typedef IntHash<wchar_t> Hash; };
    211 #endif
    212 
    213     template<> struct DefaultHash<float> { typedef FloatHash<float> Hash; };
    214     template<> struct DefaultHash<double> { typedef FloatHash<double> Hash; };
    215 
    216     // make PtrHash the default hash function for pointer types that don't specialize
    217 
    218     template<typename P> struct DefaultHash<P*> { typedef PtrHash<P*> Hash; };
    219     template<typename P> struct DefaultHash<RefPtr<P> > { typedef PtrHash<RefPtr<P> > Hash; };
    220     template<typename P> struct DefaultHash<RawPtr<P> > { typedef PtrHash<RawPtr<P> > Hash; };
    221     template<typename P> struct DefaultHash<OwnPtr<P> > { typedef PtrHash<OwnPtr<P> > Hash; };
    222 
    223     // make IntPairHash the default hash function for pairs of (at most) 32-bit integers.
    224 
    225     template<> struct DefaultHash<std::pair<short, short> > { typedef IntPairHash<short, short> Hash; };
    226     template<> struct DefaultHash<std::pair<short, unsigned short> > { typedef IntPairHash<short, unsigned short> Hash; };
    227     template<> struct DefaultHash<std::pair<short, int> > { typedef IntPairHash<short, int> Hash; };
    228     template<> struct DefaultHash<std::pair<short, unsigned> > { typedef IntPairHash<short, unsigned> Hash; };
    229     template<> struct DefaultHash<std::pair<unsigned short, short> > { typedef IntPairHash<unsigned short, short> Hash; };
    230     template<> struct DefaultHash<std::pair<unsigned short, unsigned short> > { typedef IntPairHash<unsigned short, unsigned short> Hash; };
    231     template<> struct DefaultHash<std::pair<unsigned short, int> > { typedef IntPairHash<unsigned short, int> Hash; };
    232     template<> struct DefaultHash<std::pair<unsigned short, unsigned> > { typedef IntPairHash<unsigned short, unsigned> Hash; };
    233     template<> struct DefaultHash<std::pair<int, short> > { typedef IntPairHash<int, short> Hash; };
    234     template<> struct DefaultHash<std::pair<int, unsigned short> > { typedef IntPairHash<int, unsigned short> Hash; };
    235     template<> struct DefaultHash<std::pair<int, int> > { typedef IntPairHash<int, int> Hash; };
    236     template<> struct DefaultHash<std::pair<int, unsigned> > { typedef IntPairHash<unsigned, unsigned> Hash; };
    237     template<> struct DefaultHash<std::pair<unsigned, short> > { typedef IntPairHash<unsigned, short> Hash; };
    238     template<> struct DefaultHash<std::pair<unsigned, unsigned short> > { typedef IntPairHash<unsigned, unsigned short> Hash; };
    239     template<> struct DefaultHash<std::pair<unsigned, int> > { typedef IntPairHash<unsigned, int> Hash; };
    240     template<> struct DefaultHash<std::pair<unsigned, unsigned> > { typedef IntPairHash<unsigned, unsigned> Hash; };
    241 
    242     // make PairHash the default hash function for pairs of arbitrary values.
    243 
    244     template<typename T, typename U> struct DefaultHash<std::pair<T, U> > { typedef PairHash<T, U> Hash; };
    245 
    246 } // namespace WTF
    247 
    248 using WTF::DefaultHash;
    249 using WTF::IntHash;
    250 using WTF::PtrHash;
    251 
    252 #endif // WTF_HashFunctions_h
    253