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 <stdint.h>
25#include <wtf/GetPtr.h>
26#include <wtf/RefPtr.h>
27
28namespace 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, bool isSmartPointer>
124 struct PtrHashBase;
125
126 template <typename T>
127 struct PtrHashBase<T, false /* isSmartPtr */> {
128 typedef T PtrType;
129
130 static unsigned hash(PtrType key) { return IntHash<uintptr_t>::hash(reinterpret_cast<uintptr_t>(key)); }
131 static bool equal(PtrType a, PtrType b) { return a == b; }
132 static const bool safeToCompareToEmptyOrDeleted = true;
133 };
134
135 template <typename T>
136 struct PtrHashBase<T, true /* isSmartPtr */> {
137 typedef typename GetPtrHelper<T>::PtrType PtrType;
138
139 static unsigned hash(PtrType key) { return IntHash<uintptr_t>::hash(reinterpret_cast<uintptr_t>(key)); }
140 static bool equal(PtrType a, PtrType b) { return a == b; }
141 static const bool safeToCompareToEmptyOrDeleted = true;
142
143 static unsigned hash(const T& key) { return hash(getPtr(key)); }
144 static bool equal(const T& a, const T& b) { return getPtr(a) == getPtr(b); }
145 static bool equal(PtrType a, const T& b) { return a == getPtr(b); }
146 static bool equal(const T& a, PtrType b) { return getPtr(a) == b; }
147 };
148
149 template<typename T> struct PtrHash : PtrHashBase<T, IsSmartPtr<T>::value> {
150 };
151
152 // default hash function for each type
153
154 template<typename T> struct DefaultHash;
155
156 template<typename T, typename U> struct PairHash {
157 static unsigned hash(const std::pair<T, U>& p)
158 {
159 return pairIntHash(DefaultHash<T>::Hash::hash(p.first), DefaultHash<U>::Hash::hash(p.second));
160 }
161 static bool equal(const std::pair<T, U>& a, const std::pair<T, U>& b)
162 {
163 return DefaultHash<T>::Hash::equal(a.first, b.first) && DefaultHash<U>::Hash::equal(a.second, b.second);
164 }
165 static const bool safeToCompareToEmptyOrDeleted = DefaultHash<T>::Hash::safeToCompareToEmptyOrDeleted && DefaultHash<U>::Hash::safeToCompareToEmptyOrDeleted;
166 };
167
168 template<typename T, typename U> struct IntPairHash {
169 static unsigned hash(const std::pair<T, U>& p) { return pairIntHash(p.first, p.second); }
170 static bool equal(const std::pair<T, U>& a, const std::pair<T, U>& b) { return PairHash<T, T>::equal(a, b); }
171 static const bool safeToCompareToEmptyOrDeleted = PairHash<T, U>::safeToCompareToEmptyOrDeleted;
172 };
173
174 // make IntHash the default hash function for many integer types
175
176 template<> struct DefaultHash<bool> { typedef IntHash<uint8_t> Hash; };
177 template<> struct DefaultHash<short> { typedef IntHash<unsigned> Hash; };
178 template<> struct DefaultHash<unsigned short> { typedef IntHash<unsigned> Hash; };
179 template<> struct DefaultHash<int> { typedef IntHash<unsigned> Hash; };
180 template<> struct DefaultHash<unsigned> { typedef IntHash<unsigned> Hash; };
181 template<> struct DefaultHash<long> { typedef IntHash<unsigned long> Hash; };
182 template<> struct DefaultHash<unsigned long> { typedef IntHash<unsigned long> Hash; };
183 template<> struct DefaultHash<long long> { typedef IntHash<unsigned long long> Hash; };
184 template<> struct DefaultHash<unsigned long long> { typedef IntHash<unsigned long long> Hash; };
185
186#if defined(_NATIVE_WCHAR_T_DEFINED)
187 template<> struct DefaultHash<wchar_t> { typedef IntHash<wchar_t> Hash; };
188#endif
189
190 template<> struct DefaultHash<float> { typedef FloatHash<float> Hash; };
191 template<> struct DefaultHash<double> { typedef FloatHash<double> Hash; };
192
193 // make PtrHash the default hash function for pointer types that don't specialize
194
195 template<typename P> struct DefaultHash<P*> { typedef PtrHash<P*> Hash; };
196 template<typename P> struct DefaultHash<RefPtr<P>> { typedef PtrHash<RefPtr<P>> Hash; };
197 template<typename P, typename Deleter> struct DefaultHash<std::unique_ptr<P, Deleter>> { typedef PtrHash<std::unique_ptr<P, Deleter>> Hash; };
198
199 // make IntPairHash the default hash function for pairs of (at most) 32-bit integers.
200
201 template<> struct DefaultHash<std::pair<short, short>> { typedef IntPairHash<short, short> Hash; };
202 template<> struct DefaultHash<std::pair<short, unsigned short>> { typedef IntPairHash<short, unsigned short> Hash; };
203 template<> struct DefaultHash<std::pair<short, int>> { typedef IntPairHash<short, int> Hash; };
204 template<> struct DefaultHash<std::pair<short, unsigned>> { typedef IntPairHash<short, unsigned> Hash; };
205 template<> struct DefaultHash<std::pair<unsigned short, short>> { typedef IntPairHash<unsigned short, short> Hash; };
206 template<> struct DefaultHash<std::pair<unsigned short, unsigned short>> { typedef IntPairHash<unsigned short, unsigned short> Hash; };
207 template<> struct DefaultHash<std::pair<unsigned short, int>> { typedef IntPairHash<unsigned short, int> Hash; };
208 template<> struct DefaultHash<std::pair<unsigned short, unsigned>> { typedef IntPairHash<unsigned short, unsigned> Hash; };
209 template<> struct DefaultHash<std::pair<int, short>> { typedef IntPairHash<int, short> Hash; };
210 template<> struct DefaultHash<std::pair<int, unsigned short>> { typedef IntPairHash<int, unsigned short> Hash; };
211 template<> struct DefaultHash<std::pair<int, int>> { typedef IntPairHash<int, int> Hash; };
212 template<> struct DefaultHash<std::pair<int, unsigned>> { typedef IntPairHash<unsigned, unsigned> Hash; };
213 template<> struct DefaultHash<std::pair<unsigned, short>> { typedef IntPairHash<unsigned, short> Hash; };
214 template<> struct DefaultHash<std::pair<unsigned, unsigned short>> { typedef IntPairHash<unsigned, unsigned short> Hash; };
215 template<> struct DefaultHash<std::pair<unsigned, int>> { typedef IntPairHash<unsigned, int> Hash; };
216 template<> struct DefaultHash<std::pair<unsigned, unsigned>> { typedef IntPairHash<unsigned, unsigned> Hash; };
217
218 // make PairHash the default hash function for pairs of arbitrary values.
219
220 template<typename T, typename U> struct DefaultHash<std::pair<T, U>> { typedef PairHash<T, U> Hash; };
221
222} // namespace WTF
223
224using WTF::DefaultHash;
225using WTF::IntHash;
226using WTF::PtrHash;
227
228#endif // WTF_HashFunctions_h
229