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
|
#pragma once
#include <util/system/defaults.h>
#include <util/system/unaligned_mem.h>
/*
* https://sites.google.com/site/murmurhash/
*/
namespace NMurmurPrivate {
template <size_t>
struct TMurmurHash2ATraits;
template <>
struct TMurmurHash2ATraits<32> {
using TValue = ui32;
static const TValue Multiplier = 0x5bd1e995;
enum { R1 = 24,
R2 = 13,
R3 = 15 };
};
template <>
struct TMurmurHash2ATraits<64> {
using TValue = ui64;
static const TValue Multiplier = ULL(0xc6a4a7935bd1e995);
enum { R1 = 47,
R2 = 47,
R3 = 47 };
};
}
template <class T>
class TMurmurHash2A {
private:
using TTraits = typename NMurmurPrivate::TMurmurHash2ATraits<8 * sizeof(T)>;
using TValue = typename TTraits::TValue;
public:
inline TMurmurHash2A(TValue seed = 0)
: Hash(seed)
{
}
inline TMurmurHash2A& Update(const void* buf, size_t len) noexcept {
Size += len;
MixTail(buf, len);
while (len >= sizeof(TValue)) {
Hash = Mix(Hash, ReadUnaligned<TValue>(buf));
buf = static_cast<const char*>(buf) + sizeof(TValue);
len -= sizeof(TValue);
}
MixTail(buf, len);
return *this;
}
inline TValue Value() const noexcept {
TValue hash = Mix(Mix(Hash, Tail), (TValue)Size);
hash ^= hash >> TTraits::R2;
hash *= TTraits::Multiplier;
hash ^= hash >> TTraits::R3;
return hash;
}
private:
static inline TValue Mix(TValue h, TValue k) noexcept {
k *= TTraits::Multiplier;
k ^= k >> TTraits::R1;
k *= TTraits::Multiplier;
h *= TTraits::Multiplier;
h ^= k;
return h;
}
inline void MixTail(const void*& buf, size_t& len) noexcept {
while (len && (len < sizeof(TValue) || Count)) {
Tail |= (TValue) * ((const unsigned char*&)buf)++ << (Count++ * 8);
--len;
if (Count == sizeof(TValue)) {
Hash = Mix(Hash, Tail);
Tail = 0;
Count = 0;
}
}
}
private:
TValue Hash = 0;
TValue Tail = 0;
size_t Count = 0;
size_t Size = 0;
};
|
