openMSX
xxhash.hh
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1/*
2 This code is a based on xxhash, the main modifications are:
3 - allow to produce case-insensitive (for ascii) hash values
4 - tweak interface to fit openMSX (e.g. directly work on string_view)
5
6- - - - - - - - - - - - - - - - - - - -
7
8 original header:
9
10 xxHash - Fast Hash algorithm
11 Header File
12 Copyright (C) 2012-2014, Yann Collet.
13 BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
14
15 Redistribution and use in source and binary forms, with or without
16 modification, are permitted provided that the following conditions are
17 met:
18
19 * Redistributions of source code must retain the above copyright
20 notice, this list of conditions and the following disclaimer.
21 * Redistributions in binary form must reproduce the above
22 copyright notice, this list of conditions and the following disclaimer
23 in the documentation and/or other materials provided with the
24 distribution.
25
26 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
27 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
28 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
29 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
30 OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
31 SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
32 LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
33 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
34 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
35 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
36 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37
38 You can contact the author at :
39 - xxHash source repository : http://code.google.com/p/xxhash/
40*/
41
42#ifndef XXHASH_HH
43#define XXHASH_HH
44
45#include <bit>
46#include <cassert>
47#include <cstdint>
48#include <cstring>
49#include <string_view>
50
51constexpr uint32_t PRIME32_1 = 2654435761;
52constexpr uint32_t PRIME32_2 = 2246822519;
53constexpr uint32_t PRIME32_3 = 3266489917;
54constexpr uint32_t PRIME32_4 = 668265263;
55constexpr uint32_t PRIME32_5 = 374761393;
56
57
58template<bool ALIGNED>
59[[nodiscard]] inline uint32_t read32(const uint8_t* ptr)
60{
61 if constexpr (ALIGNED) {
62#ifdef DEBUG
63 assert((reinterpret_cast<intptr_t>(ptr) & 3) == 0);
64#endif
65 return *reinterpret_cast<const uint32_t*>(ptr);
66 } else {
67 uint32_t result;
68 memcpy(&result, ptr, sizeof(result));
69 return result;
70 }
71}
72
73
74template<bool ALIGNED, uint8_t MASK8 = 0xFF, uint32_t SEED = 0>
75[[nodiscard]] inline uint32_t xxhash_impl(const uint8_t* p, size_t size)
76{
77 constexpr uint32_t MASK32 = MASK8 * 0x01010101U;
78
79 const uint8_t* const bEnd = p + size;
80 uint32_t h32;
81
82 if (size >= 16) [[unlikely]] {
83 const uint8_t* const limit = bEnd - 16;
84
85 // casts to avoid: warning C4307: '+': integral constant overflow
86 uint32_t v1 = uint32_t(SEED + PRIME32_1 + uint64_t(PRIME32_2));
87 uint32_t v2 = SEED + PRIME32_2;
88 uint32_t v3 = SEED + 0;
89 uint32_t v4 = SEED - PRIME32_1;
90
91 do {
92 uint32_t r1 = (read32<ALIGNED>(p + 0) & MASK32) * PRIME32_2;
93 uint32_t r2 = (read32<ALIGNED>(p + 4) & MASK32) * PRIME32_2;
94 uint32_t r3 = (read32<ALIGNED>(p + 8) & MASK32) * PRIME32_2;
95 uint32_t r4 = (read32<ALIGNED>(p + 12) & MASK32) * PRIME32_2;
96 p += 16;
97 v1 = std::rotl(v1 + r1, 13) * PRIME32_1;
98 v2 = std::rotl(v2 + r2, 13) * PRIME32_1;
99 v3 = std::rotl(v3 + r3, 13) * PRIME32_1;
100 v4 = std::rotl(v4 + r4, 13) * PRIME32_1;
101 } while (p <= limit);
102
103 h32 = std::rotl(v1, 1) + std::rotl(v2, 7) + std::rotl(v3, 12) + std::rotl(v4, 18);
104 } else {
105 h32 = SEED + PRIME32_5;
106 }
107
108 h32 += uint32_t(size);
109
110 while ((p + 4) <= bEnd) {
111 uint32_t r = (read32<ALIGNED>(p) & MASK32) * PRIME32_3;
112 h32 = std::rotl(h32 + r, 17) * PRIME32_4;
113 p += 4;
114 }
115
116 while (p < bEnd) {
117 uint32_t r = (*p & MASK8) * PRIME32_5;
118 h32 = std::rotl(h32 + r, 11) * PRIME32_1;
119 p += 1;
120 }
121
122 h32 = (h32 ^ (h32 >> 15)) * PRIME32_2;
123 h32 = (h32 ^ (h32 >> 13)) * PRIME32_3;
124 return h32 ^ (h32 >> 16);
125}
126
127template<uint8_t MASK8> [[nodiscard]] inline uint32_t xxhash_impl(std::string_view key)
128{
129 const auto* data = reinterpret_cast<const uint8_t*>(key.data());
130 auto size = key.size();
131 if (reinterpret_cast<intptr_t>(data) & 3) {
132 return xxhash_impl<false, MASK8>(data, size);
133 } else {
134 // Input is aligned, let's leverage the speed advantage
135 return xxhash_impl<true, MASK8>(data, size);
136 }
137}
138
139[[nodiscard]] inline uint32_t xxhash(std::string_view key)
140{
141 return xxhash_impl<0xFF>(key);
142}
143[[nodiscard]] inline uint32_t xxhash_case(std::string_view key)
144{
145 return xxhash_impl<static_cast<uint8_t>(~('a' - 'A'))>(key);
146}
147
148struct XXHasher {
149 [[nodiscard]] uint32_t operator()(std::string_view key) const {
150 return xxhash(key);
151 }
152};
153
155 [[nodiscard]] uint32_t operator()(std::string_view key) const {
156 return xxhash_case(key);
157 }
158};
159
160#endif
vec4 v4(2, 1, -4, -3)
size_t size(std::string_view utf8)
uint32_t operator()(std::string_view key) const
Definition: xxhash.hh:155
uint32_t operator()(std::string_view key) const
Definition: xxhash.hh:149
uint32_t read32(const uint8_t *ptr)
Definition: xxhash.hh:59
uint32_t xxhash_impl(const uint8_t *p, size_t size)
Definition: xxhash.hh:75
constexpr uint32_t PRIME32_1
Definition: xxhash.hh:51
constexpr uint32_t PRIME32_2
Definition: xxhash.hh:52
uint32_t xxhash(std::string_view key)
Definition: xxhash.hh:139
constexpr uint32_t PRIME32_3
Definition: xxhash.hh:53
uint32_t xxhash_case(std::string_view key)
Definition: xxhash.hh:143
constexpr uint32_t PRIME32_5
Definition: xxhash.hh:55
constexpr uint32_t PRIME32_4
Definition: xxhash.hh:54