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
27namespace 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            return IntHash<uintptr_t>::hash(reinterpret_cast<uintptr_t>(key));
126        }
127        static bool equal(T a, T b) { return a == b; }
128        static const bool safeToCompareToEmptyOrDeleted = true;
129    };
130    template<typename P> struct PtrHash<RefPtr<P>> : PtrHash<P*> {
131        using PtrHash<P*>::hash;
132        static unsigned hash(const RefPtr<P>& key) { return hash(key.get()); }
133        using PtrHash<P*>::equal;
134        static bool equal(const RefPtr<P>& a, const RefPtr<P>& b) { return a == b; }
135        static bool equal(P* a, const RefPtr<P>& b) { return a == b; }
136        static bool equal(const RefPtr<P>& a, P* b) { return a == b; }
137    };
138
139    // default hash function for each type
140
141    template<typename T> struct DefaultHash;
142
143    template<typename T, typename U> struct PairHash {
144        static unsigned hash(const std::pair<T, U>& p)
145        {
146            return pairIntHash(DefaultHash<T>::Hash::hash(p.first), DefaultHash<U>::Hash::hash(p.second));
147        }
148        static bool equal(const std::pair<T, U>& a, const std::pair<T, U>& b)
149        {
150            return DefaultHash<T>::Hash::equal(a.first, b.first) && DefaultHash<U>::Hash::equal(a.second, b.second);
151        }
152        static const bool safeToCompareToEmptyOrDeleted = DefaultHash<T>::Hash::safeToCompareToEmptyOrDeleted
153                                                            && DefaultHash<U>::Hash::safeToCompareToEmptyOrDeleted;
154    };
155
156    template<typename T, typename U> struct IntPairHash {
157        static unsigned hash(const std::pair<T, U>& p) { return pairIntHash(p.first, p.second); }
158        static bool equal(const std::pair<T, U>& a, const std::pair<T, U>& b) { return PairHash<T, T>::equal(a, b); }
159        static const bool safeToCompareToEmptyOrDeleted = PairHash<T, U>::safeToCompareToEmptyOrDeleted;
160    };
161
162    // make IntHash the default hash function for many integer types
163
164    template<> struct DefaultHash<short> { typedef IntHash<unsigned> Hash; };
165    template<> struct DefaultHash<unsigned short> { typedef IntHash<unsigned> Hash; };
166    template<> struct DefaultHash<int> { typedef IntHash<unsigned> Hash; };
167    template<> struct DefaultHash<unsigned> { typedef IntHash<unsigned> Hash; };
168    template<> struct DefaultHash<long> { typedef IntHash<unsigned long> Hash; };
169    template<> struct DefaultHash<unsigned long> { typedef IntHash<unsigned long> Hash; };
170    template<> struct DefaultHash<long long> { typedef IntHash<unsigned long long> Hash; };
171    template<> struct DefaultHash<unsigned long long> { typedef IntHash<unsigned long long> Hash; };
172
173#if defined(_NATIVE_WCHAR_T_DEFINED)
174    template<> struct DefaultHash<wchar_t> { typedef IntHash<wchar_t> Hash; };
175#endif
176
177    template<> struct DefaultHash<float> { typedef FloatHash<float> Hash; };
178    template<> struct DefaultHash<double> { typedef FloatHash<double> Hash; };
179
180    // make PtrHash the default hash function for pointer types that don't specialize
181
182    template<typename P> struct DefaultHash<P*> { typedef PtrHash<P*> Hash; };
183    template<typename P> struct DefaultHash<RefPtr<P>> { typedef PtrHash<RefPtr<P>> Hash; };
184
185    // make IntPairHash the default hash function for pairs of (at most) 32-bit integers.
186
187    template<> struct DefaultHash<std::pair<short, short>> { typedef IntPairHash<short, short> Hash; };
188    template<> struct DefaultHash<std::pair<short, unsigned short>> { typedef IntPairHash<short, unsigned short> Hash; };
189    template<> struct DefaultHash<std::pair<short, int>> { typedef IntPairHash<short, int> Hash; };
190    template<> struct DefaultHash<std::pair<short, unsigned>> { typedef IntPairHash<short, unsigned> Hash; };
191    template<> struct DefaultHash<std::pair<unsigned short, short>> { typedef IntPairHash<unsigned short, short> Hash; };
192    template<> struct DefaultHash<std::pair<unsigned short, unsigned short>> { typedef IntPairHash<unsigned short, unsigned short> Hash; };
193    template<> struct DefaultHash<std::pair<unsigned short, int>> { typedef IntPairHash<unsigned short, int> Hash; };
194    template<> struct DefaultHash<std::pair<unsigned short, unsigned>> { typedef IntPairHash<unsigned short, unsigned> Hash; };
195    template<> struct DefaultHash<std::pair<int, short>> { typedef IntPairHash<int, short> Hash; };
196    template<> struct DefaultHash<std::pair<int, unsigned short>> { typedef IntPairHash<int, unsigned short> Hash; };
197    template<> struct DefaultHash<std::pair<int, int>> { typedef IntPairHash<int, int> Hash; };
198    template<> struct DefaultHash<std::pair<int, unsigned>> { typedef IntPairHash<unsigned, unsigned> Hash; };
199    template<> struct DefaultHash<std::pair<unsigned, short>> { typedef IntPairHash<unsigned, short> Hash; };
200    template<> struct DefaultHash<std::pair<unsigned, unsigned short>> { typedef IntPairHash<unsigned, unsigned short> Hash; };
201    template<> struct DefaultHash<std::pair<unsigned, int>> { typedef IntPairHash<unsigned, int> Hash; };
202    template<> struct DefaultHash<std::pair<unsigned, unsigned>> { typedef IntPairHash<unsigned, unsigned> Hash; };
203
204    // make PairHash the default hash function for pairs of arbitrary values.
205
206    template<typename T, typename U> struct DefaultHash<std::pair<T, U>> { typedef PairHash<T, U> Hash; };
207
208} // namespace WTF
209
210using WTF::DefaultHash;
211using WTF::IntHash;
212using WTF::PtrHash;
213
214#endif // WTF_HashFunctions_h
215