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
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
|
// Copyright 2014 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_BASE_FUNCTIONAL_H_
#define V8_BASE_FUNCTIONAL_H_
#include <stddef.h>
#include <stdint.h>
#include <cstddef>
#include <cstring>
#include <functional>
#include <utility>
#include "src/base/base-export.h"
#include "src/base/macros.h"
namespace v8 {
namespace base {
// base::hash is an implementation of the hash function object specified by
// C++11. It was designed to be compatible with std::hash (in C++11) and
// boost:hash (which in turn is based on the hash function object specified by
// the Draft Technical Report on C++ Library Extensions (TR1)).
//
// base::hash is implemented by calling the hash_value function. The namespace
// isn't specified so that it can detect overloads via argument dependent
// lookup. So if there is a free function hash_value in the same namespace as a
// custom type, it will get called.
//
// If users are asked to implement a hash function for their own types with no
// guidance, they generally write bad hash functions. Instead, we provide a
// simple function base::hash_combine to pass hash-relevant member variables
// into, in order to define a decent hash function. base::hash_combine is
// declared as:
//
// template<typename T, typename... Ts>
// size_t hash_combine(const T& v, const Ts& ...vs);
//
// Consider the following example:
//
// namespace v8 {
// namespace bar {
// struct Point { int x; int y; };
// size_t hash_value(Point const& p) {
// return base::hash_combine(p.x, p.y);
// }
// }
//
// namespace foo {
// void DoSomeWork(bar::Point const& p) {
// base::hash<bar::Point> h;
// ...
// size_t hash_code = h(p); // calls bar::hash_value(Point const&)
// ...
// }
// }
// }
//
// Based on the "Hashing User-Defined Types in C++1y" proposal from Jeffrey
// Yasskin and Chandler Carruth, see
// http://www.open-std.org/Jtc1/sc22/wg21/docs/papers/2012/n3333.html.
template <typename>
struct hash;
V8_INLINE size_t hash_combine() { return 0u; }
V8_INLINE size_t hash_combine(size_t seed) { return seed; }
V8_BASE_EXPORT size_t hash_combine(size_t seed, size_t value);
template <typename T, typename... Ts>
V8_INLINE size_t hash_combine(T const& v, Ts const&... vs) {
return hash_combine(hash_combine(vs...), hash<T>()(v));
}
template <typename Iterator>
V8_INLINE size_t hash_range(Iterator first, Iterator last) {
size_t seed = 0;
for (; first != last; ++first) {
seed = hash_combine(seed, *first);
}
return seed;
}
#define V8_BASE_HASH_VALUE_TRIVIAL(type) \
V8_INLINE size_t hash_value(type v) { return static_cast<size_t>(v); }
V8_BASE_HASH_VALUE_TRIVIAL(bool)
V8_BASE_HASH_VALUE_TRIVIAL(unsigned char)
V8_BASE_HASH_VALUE_TRIVIAL(unsigned short) // NOLINT(runtime/int)
#undef V8_BASE_HASH_VALUE_TRIVIAL
V8_BASE_EXPORT size_t hash_value(unsigned int);
V8_BASE_EXPORT size_t hash_value(unsigned long); // NOLINT(runtime/int)
V8_BASE_EXPORT size_t hash_value(unsigned long long); // NOLINT(runtime/int)
#define V8_BASE_HASH_VALUE_SIGNED(type) \
V8_INLINE size_t hash_value(signed type v) { \
return hash_value(bit_cast<unsigned type>(v)); \
}
V8_BASE_HASH_VALUE_SIGNED(char)
V8_BASE_HASH_VALUE_SIGNED(short) // NOLINT(runtime/int)
V8_BASE_HASH_VALUE_SIGNED(int) // NOLINT(runtime/int)
V8_BASE_HASH_VALUE_SIGNED(long) // NOLINT(runtime/int)
V8_BASE_HASH_VALUE_SIGNED(long long) // NOLINT(runtime/int)
#undef V8_BASE_HASH_VALUE_SIGNED
V8_INLINE size_t hash_value(float v) {
// 0 and -0 both hash to zero.
return v != 0.0f ? hash_value(bit_cast<uint32_t>(v)) : 0;
}
V8_INLINE size_t hash_value(double v) {
// 0 and -0 both hash to zero.
return v != 0.0 ? hash_value(bit_cast<uint64_t>(v)) : 0;
}
template <typename T, size_t N>
V8_INLINE size_t hash_value(const T (&v)[N]) {
return hash_range(v, v + N);
}
template <typename T, size_t N>
V8_INLINE size_t hash_value(T (&v)[N]) {
return hash_range(v, v + N);
}
template <typename T>
V8_INLINE size_t hash_value(T* const& v) {
return hash_value(bit_cast<uintptr_t>(v));
}
template <typename T1, typename T2>
V8_INLINE size_t hash_value(std::pair<T1, T2> const& v) {
return hash_combine(v.first, v.second);
}
template <typename T>
struct hash : public std::unary_function<T, size_t> {
V8_INLINE size_t operator()(T const& v) const { return hash_value(v); }
};
#define V8_BASE_HASH_SPECIALIZE(type) \
template <> \
struct hash<type> : public std::unary_function<type, size_t> { \
V8_INLINE size_t operator()(type const v) const { \
return ::v8::base::hash_value(v); \
} \
};
V8_BASE_HASH_SPECIALIZE(bool)
V8_BASE_HASH_SPECIALIZE(signed char)
V8_BASE_HASH_SPECIALIZE(unsigned char)
V8_BASE_HASH_SPECIALIZE(short) // NOLINT(runtime/int)
V8_BASE_HASH_SPECIALIZE(unsigned short) // NOLINT(runtime/int)
V8_BASE_HASH_SPECIALIZE(int)
V8_BASE_HASH_SPECIALIZE(unsigned int)
V8_BASE_HASH_SPECIALIZE(long) // NOLINT(runtime/int)
V8_BASE_HASH_SPECIALIZE(unsigned long) // NOLINT(runtime/int)
V8_BASE_HASH_SPECIALIZE(long long) // NOLINT(runtime/int)
V8_BASE_HASH_SPECIALIZE(unsigned long long) // NOLINT(runtime/int)
V8_BASE_HASH_SPECIALIZE(float)
V8_BASE_HASH_SPECIALIZE(double)
#undef V8_BASE_HASH_SPECIALIZE
template <typename T>
struct hash<T*> : public std::unary_function<T*, size_t> {
V8_INLINE size_t operator()(T* const v) const {
return ::v8::base::hash_value(v);
}
};
// base::bit_equal_to is a function object class for bitwise equality
// comparison, similar to std::equal_to, except that the comparison is performed
// on the bit representation of the operands.
//
// base::bit_hash is a function object class for bitwise hashing, similar to
// base::hash. It can be used together with base::bit_equal_to to implement a
// hash data structure based on the bitwise representation of types.
template <typename T>
struct bit_equal_to : public std::binary_function<T, T, bool> {};
template <typename T>
struct bit_hash : public std::unary_function<T, size_t> {};
#define V8_BASE_BIT_SPECIALIZE_TRIVIAL(type) \
template <> \
struct bit_equal_to<type> : public std::equal_to<type> {}; \
template <> \
struct bit_hash<type> : public hash<type> {};
V8_BASE_BIT_SPECIALIZE_TRIVIAL(signed char)
V8_BASE_BIT_SPECIALIZE_TRIVIAL(unsigned char)
V8_BASE_BIT_SPECIALIZE_TRIVIAL(short) // NOLINT(runtime/int)
V8_BASE_BIT_SPECIALIZE_TRIVIAL(unsigned short) // NOLINT(runtime/int)
V8_BASE_BIT_SPECIALIZE_TRIVIAL(int)
V8_BASE_BIT_SPECIALIZE_TRIVIAL(unsigned int)
V8_BASE_BIT_SPECIALIZE_TRIVIAL(long) // NOLINT(runtime/int)
V8_BASE_BIT_SPECIALIZE_TRIVIAL(unsigned long) // NOLINT(runtime/int)
V8_BASE_BIT_SPECIALIZE_TRIVIAL(long long) // NOLINT(runtime/int)
V8_BASE_BIT_SPECIALIZE_TRIVIAL(unsigned long long) // NOLINT(runtime/int)
#undef V8_BASE_BIT_SPECIALIZE_TRIVIAL
#define V8_BASE_BIT_SPECIALIZE_BIT_CAST(type, btype) \
template <> \
struct bit_equal_to<type> : public std::binary_function<type, type, bool> { \
V8_INLINE bool operator()(type lhs, type rhs) const { \
return bit_cast<btype>(lhs) == bit_cast<btype>(rhs); \
} \
}; \
template <> \
struct bit_hash<type> : public std::unary_function<type, size_t> { \
V8_INLINE size_t operator()(type v) const { \
hash<btype> h; \
return h(bit_cast<btype>(v)); \
} \
};
V8_BASE_BIT_SPECIALIZE_BIT_CAST(float, uint32_t)
V8_BASE_BIT_SPECIALIZE_BIT_CAST(double, uint64_t)
#undef V8_BASE_BIT_SPECIALIZE_BIT_CAST
} // namespace base
} // namespace v8
#endif // V8_BASE_FUNCTIONAL_H_
|
