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
|
/*
* Copyright 2015 Google Inc. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef FLATBUFFERS_HASH_H_
#define FLATBUFFERS_HASH_H_
#include <cstdint>
#include <cstring>
#include "flatbuffers/flatbuffers.h"
namespace flatbuffers {
template<typename T> struct FnvTraits {
static const T kFnvPrime;
static const T kOffsetBasis;
};
template<> struct FnvTraits<uint32_t> {
static const uint32_t kFnvPrime = 0x01000193;
static const uint32_t kOffsetBasis = 0x811C9DC5;
};
template<> struct FnvTraits<uint64_t> {
static const uint64_t kFnvPrime = 0x00000100000001b3ULL;
static const uint64_t kOffsetBasis = 0xcbf29ce484222645ULL;
};
template<typename T> T HashFnv1(const char *input) {
T hash = FnvTraits<T>::kOffsetBasis;
for (const char *c = input; *c; ++c) {
hash *= FnvTraits<T>::kFnvPrime;
hash ^= static_cast<unsigned char>(*c);
}
return hash;
}
template<typename T> T HashFnv1a(const char *input) {
T hash = FnvTraits<T>::kOffsetBasis;
for (const char *c = input; *c; ++c) {
hash ^= static_cast<unsigned char>(*c);
hash *= FnvTraits<T>::kFnvPrime;
}
return hash;
}
template<> inline uint16_t HashFnv1<uint16_t>(const char *input) {
uint32_t hash = HashFnv1<uint32_t>(input);
return (hash >> 16) ^ (hash & 0xffff);
}
template<> inline uint16_t HashFnv1a<uint16_t>(const char *input) {
uint32_t hash = HashFnv1a<uint32_t>(input);
return (hash >> 16) ^ (hash & 0xffff);
}
template<typename T> struct NamedHashFunction {
const char *name;
typedef T (*HashFunction)(const char *);
HashFunction function;
};
const NamedHashFunction<uint16_t> kHashFunctions16[] = {
{ "fnv1_16", HashFnv1<uint16_t> },
{ "fnv1a_16", HashFnv1a<uint16_t> },
};
const NamedHashFunction<uint32_t> kHashFunctions32[] = {
{ "fnv1_32", HashFnv1<uint32_t> },
{ "fnv1a_32", HashFnv1a<uint32_t> },
};
const NamedHashFunction<uint64_t> kHashFunctions64[] = {
{ "fnv1_64", HashFnv1<uint64_t> },
{ "fnv1a_64", HashFnv1a<uint64_t> },
};
inline NamedHashFunction<uint16_t>::HashFunction FindHashFunction16(
const char *name) {
std::size_t size = sizeof(kHashFunctions16) / sizeof(kHashFunctions16[0]);
for (std::size_t i = 0; i < size; ++i) {
if (std::strcmp(name, kHashFunctions16[i].name) == 0) {
return kHashFunctions16[i].function;
}
}
return nullptr;
}
inline NamedHashFunction<uint32_t>::HashFunction FindHashFunction32(
const char *name) {
std::size_t size = sizeof(kHashFunctions32) / sizeof(kHashFunctions32[0]);
for (std::size_t i = 0; i < size; ++i) {
if (std::strcmp(name, kHashFunctions32[i].name) == 0) {
return kHashFunctions32[i].function;
}
}
return nullptr;
}
inline NamedHashFunction<uint64_t>::HashFunction FindHashFunction64(
const char *name) {
std::size_t size = sizeof(kHashFunctions64) / sizeof(kHashFunctions64[0]);
for (std::size_t i = 0; i < size; ++i) {
if (std::strcmp(name, kHashFunctions64[i].name) == 0) {
return kHashFunctions64[i].function;
}
}
return nullptr;
}
} // namespace flatbuffers
#endif // FLATBUFFERS_HASH_H_
|
