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
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    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} // namespace WTF
178
179using WTF::DefaultHash;
180using WTF::IntHash;
181using WTF::PtrHash;
182
183#endif // WTF_HashFunctions_h
184