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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 "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     template<typename T> struct IntHash {
90         static unsigned hash(T key) { return intHash(static_cast<typename IntTypes<sizeof(T)>::UnsignedType>(key)); }
91         static bool equal(T a, T b) { return a == b; }
92         static const bool safeToCompareToEmptyOrDeleted = true;
93     };
94 
95     template<typename T> struct FloatHash {
96         static unsigned hash(T key)
97         {
98             union {
99                 T key;
100                 typename IntTypes<sizeof(T)>::UnsignedType bits;
101             } u;
102             u.key = key;
103             return intHash(u.bits);
104         }
105         static bool equal(T a, T b) { return a == b; }
106         static const bool safeToCompareToEmptyOrDeleted = true;
107     };
108 
109     // pointer identity hash function
110 
111     template<typename T> struct PtrHash {
112         static unsigned hash(T key)
113         {
114 #if COMPILER(MSVC)
115 #pragma warning(push)
116 #pragma warning(disable: 4244) // work around what seems to be a bug in MSVC's conversion warnings
117 #endif
118             return IntHash<uintptr_t>::hash(reinterpret_cast<uintptr_t>(key));
119 #if COMPILER(MSVC)
120 #pragma warning(pop)
121 #endif
122         }
123         static bool equal(T a, T b) { return a == b; }
124         static const bool safeToCompareToEmptyOrDeleted = true;
125     };
126     template<typename P> struct PtrHash<RefPtr<P> > : PtrHash<P*> {
127         using PtrHash<P*>::hash;
128         static unsigned hash(const RefPtr<P>& key) { return hash(key.get()); }
129         using PtrHash<P*>::equal;
130         static bool equal(const RefPtr<P>& a, const RefPtr<P>& b) { return a == b; }
131         static bool equal(P* a, const RefPtr<P>& b) { return a == b; }
132         static bool equal(const RefPtr<P>& a, P* b) { return a == b; }
133     };
134 
135     // default hash function for each type
136 
137     template<typename T> struct DefaultHash;
138 
139     template<typename T, typename U> struct PairHash {
140         static unsigned hash(const std::pair<T, U>& p)
141         {
142             return intHash((static_cast<uint64_t>(DefaultHash<T>::Hash::hash(p.first)) << 32 | DefaultHash<U>::Hash::hash(p.second)));
143         }
144         static bool equal(const std::pair<T, U>& a, const std::pair<T, U>& b)
145         {
146             return DefaultHash<T>::Hash::equal(a.first, b.first) && DefaultHash<U>::Hash::equal(a.second, b.second);
147         }
148         static const bool safeToCompareToEmptyOrDeleted = DefaultHash<T>::Hash::safeToCompareToEmptyOrDeleted
149                                                             && DefaultHash<U>::Hash::safeToCompareToEmptyOrDeleted;
150     };
151 
152     // make IntHash the default hash function for many integer types
153 
154     template<> struct DefaultHash<short> { typedef IntHash<unsigned> Hash; };
155     template<> struct DefaultHash<unsigned short> { typedef IntHash<unsigned> Hash; };
156     template<> struct DefaultHash<int> { typedef IntHash<unsigned> Hash; };
157     template<> struct DefaultHash<unsigned> { typedef IntHash<unsigned> Hash; };
158     template<> struct DefaultHash<long> { typedef IntHash<unsigned long> Hash; };
159     template<> struct DefaultHash<unsigned long> { typedef IntHash<unsigned long> Hash; };
160     template<> struct DefaultHash<long long> { typedef IntHash<unsigned long long> Hash; };
161     template<> struct DefaultHash<unsigned long long> { typedef IntHash<unsigned long long> Hash; };
162 
163 #if !COMPILER(MSVC) || defined(_NATIVE_WCHAR_T_DEFINED)
164     template<> struct DefaultHash<wchar_t> { typedef IntHash<wchar_t> Hash; };
165 #endif
166 
167     template<> struct DefaultHash<float> { typedef FloatHash<float> Hash; };
168     template<> struct DefaultHash<double> { typedef FloatHash<double> Hash; };
169 
170     // make PtrHash the default hash function for pointer types that don't specialize
171 
172     template<typename P> struct DefaultHash<P*> { typedef PtrHash<P*> Hash; };
173     template<typename P> struct DefaultHash<RefPtr<P> > { typedef PtrHash<RefPtr<P> > Hash; };
174 
175     template<typename T, typename U> struct DefaultHash<std::pair<T, U> > { typedef PairHash<T, U> Hash; };
176 
177     // Golden ratio - arbitrary start value to avoid mapping all 0's to all 0's
178     static const unsigned stringHashingStartValue = 0x9e3779b9U;
179 
180 } // namespace WTF
181 
182 using WTF::DefaultHash;
183 using WTF::IntHash;
184 using WTF::PtrHash;
185 
186 #endif // WTF_HashFunctions_h
187