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
|
#include "hash-impl.hpp"
#include <bit>
#ifdef __GNUG__
#pragma GCC diagnostic ignored "-Wcast-align"
#pragma GCC diagnostic ignored "-Wsign-conversion"
#endif
// ReSharper disable CppDefaultCaseNotHandledInSwitchStatement
// NOLINTBEGIN(*-switch-missing-default-case)
namespace floormat::MurmurHash {
namespace {
//-----------------------------------------------------------------------------
// MurmurHash3 was written by Austin Appleby, and is placed in the public
// domain. The author hereby disclaims copyright to this source code.
// Note - The x86 and x64 versions do _not_ produce the same results, as the
// algorithms are optimized for their respective platforms. You can still
// compile and run any of them on any platform, but your performance with the
// non-native version will be less than optimal.
//-----------------------------------------------------------------------------
// Block read - if your platform needs to do endian-swapping or can only
// handle aligned reads, do the conversion here
CORRADE_ALWAYS_INLINE uint32_t getblock32 ( const uint32_t * p, int i )
{
return p[i];
}
//-----------------------------------------------------------------------------
// Finalization mix - force all bits of a hash block to avalanche
CORRADE_ALWAYS_INLINE uint32_t fmix32 ( uint32_t h )
{
h ^= h >> 16;
h *= 0x85ebca6b;
h ^= h >> 13;
h *= 0xc2b2ae35;
h ^= h >> 16;
return h;
}
//-----------------------------------------------------------------------------
void MurmurHash3_x86_32 ( const void * __restrict key, size_t len, void * __restrict out )
{
constexpr auto seed = uint32_t{0xa6b8edcd};
const auto* data = (const uint8_t*)key;
const int nblocks = (int)(len / 4);
uint32_t h1 = seed;
constexpr uint32_t c1 = 0xcc9e2d51;
constexpr uint32_t c2 = 0x1b873593;
//----------
// body
const auto* blocks = (const uint32_t *)(data + (size_t)(nblocks*4));
for(int i = -nblocks; i; i++)
{
uint32_t k1 = getblock32(blocks,i);
k1 *= c1;
k1 = std::rotl(k1,15);
k1 *= c2;
h1 ^= k1;
h1 = std::rotl(h1,13);
h1 = h1*5+0xe6546b64;
}
//----------
// tail
const auto* tail = (const uint8_t*)(data + (size_t)(nblocks*4));
uint32_t k1 = 0;
switch(len & 3)
{
case 3: k1 ^= tail[2] << 16; [[fallthrough]];
case 2: k1 ^= tail[1] << 8; [[fallthrough]];
case 1: k1 ^= tail[0];
k1 *= c1; k1 = std::rotl(k1,15); k1 *= c2; h1 ^= k1;
}
//----------
// finalization
h1 ^= len;
h1 = fmix32(h1);
*(uint32_t*)out = h1;
}
} // namespace
size_t hash_buf(const void* __restrict buf, size_t size) noexcept
{
uint32_t ret;
MurmurHash3_x86_32(buf, size, &ret);
return ret;
}
size_t hash_int(uint32_t x) noexcept
{
return hash_buf(&x, sizeof x);
}
size_t hash_int(uint64_t x) noexcept
{
return hash_buf(&x, sizeof x);
}
} // namespace floormat::MurmurHash
// NOLINTEND(*-switch-missing-default-case)
|
