1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
|
/*
* Copyright (C) 2005, 2006, 2008, 2010 Apple Inc. All rights reserved.
* Copyright (C) 2010 Patrick Gansterer <paroga@paroga.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public License
* along with this library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*
*/
#ifndef WTF_StringHashFunctions_h
#define WTF_StringHashFunctions_h
#include <wtf/unicode/Unicode.h>
namespace WTF {
// Golden ratio - arbitrary start value to avoid mapping all 0's to all 0's
static const unsigned stringHashingStartValue = 0x9e3779b9U;
// Paul Hsieh's SuperFastHash
// http://www.azillionmonkeys.com/qed/hash.html
// char* data is interpreted as latin-encoded (zero extended to 16 bits).
class StringHasher {
public:
inline StringHasher()
: m_hash(stringHashingStartValue)
, m_hasPendingCharacter(false)
, m_pendingCharacter(0)
{
}
inline void addCharacters(UChar a, UChar b)
{
ASSERT(!m_hasPendingCharacter);
addCharactersToHash(a, b);
}
inline void addCharacter(UChar ch)
{
if (m_hasPendingCharacter) {
addCharactersToHash(m_pendingCharacter, ch);
m_hasPendingCharacter = false;
return;
}
m_pendingCharacter = ch;
m_hasPendingCharacter = true;
}
inline unsigned hash() const
{
unsigned result = m_hash;
// Handle end case.
if (m_hasPendingCharacter) {
result += m_pendingCharacter;
result ^= result << 11;
result += result >> 17;
}
// Force "avalanching" of final 31 bits.
result ^= result << 3;
result += result >> 5;
result ^= result << 2;
result += result >> 15;
result ^= result << 10;
// First bit is used in UStringImpl for m_isIdentifier.
result &= 0x7fffffff;
// This avoids ever returning a hash code of 0, since that is used to
// signal "hash not computed yet", using a value that is likely to be
// effectively the same as 0 when the low bits are masked.
if (!result)
return 0x40000000;
return result;
}
template<typename T, UChar Converter(T)> static inline unsigned createHash(const T* data, unsigned length)
{
StringHasher hasher;
bool rem = length & 1;
length >>= 1;
while (length--) {
hasher.addCharacters(Converter(data[0]), Converter(data[1]));
data += 2;
}
if (rem)
hasher.addCharacter(Converter(*data));
return hasher.hash();
}
template<typename T, UChar Converter(T)> static inline unsigned createHash(const T* data)
{
StringHasher hasher;
while (true) {
UChar b0 = Converter(*data++);
if (!b0)
break;
UChar b1 = Converter(*data++);
if (!b1) {
hasher.addCharacter(b0);
break;
}
hasher.addCharacters(b0, b1);
}
return hasher.hash();
}
template<typename T> static inline unsigned createHash(const T* data, unsigned length)
{
return createHash<T, defaultCoverter>(data, length);
}
template<typename T> static inline unsigned createHash(const T* data)
{
return createHash<T, defaultCoverter>(data);
}
template<size_t length> static inline unsigned createBlobHash(const void* data)
{
COMPILE_ASSERT(!(length % 4), length_must_be_a_multible_of_four);
return createHash<UChar>(static_cast<const UChar*>(data), length / sizeof(UChar));
}
private:
static inline UChar defaultCoverter(UChar ch)
{
return ch;
}
static inline UChar defaultCoverter(char ch)
{
return static_cast<unsigned char>(ch);
}
inline void addCharactersToHash(UChar a, UChar b)
{
m_hash += a;
unsigned tmp = (b << 11) ^ m_hash;
m_hash = (m_hash << 16) ^ tmp;
m_hash += m_hash >> 11;
}
unsigned m_hash;
bool m_hasPendingCharacter;
UChar m_pendingCharacter;
};
} // namespace WTF
#endif // WTF_StringHashFunctions_h
|
