1
2 /**
3 * Copyright (C) 2018-present MongoDB, Inc.
4 *
5 * This program is free software: you can redistribute it and/or modify
6 * it under the terms of the Server Side Public License, version 1,
7 * as published by MongoDB, Inc.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * Server Side Public License for more details.
13 *
14 * You should have received a copy of the Server Side Public License
15 * along with this program. If not, see
16 * <http://www.mongodb.com/licensing/server-side-public-license>.
17 *
18 * As a special exception, the copyright holders give permission to link the
19 * code of portions of this program with the OpenSSL library under certain
20 * conditions as described in each individual source file and distribute
21 * linked combinations including the program with the OpenSSL library. You
22 * must comply with the Server Side Public License in all respects for
23 * all of the code used other than as permitted herein. If you modify file(s)
24 * with this exception, you may extend this exception to your version of the
25 * file(s), but you are not obligated to do so. If you do not wish to do so,
26 * delete this exception statement from your version. If you delete this
27 * exception statement from all source files in the program, then also delete
28 * it in the license file.
29 */
30
31 #include "mongo/platform/basic.h"
32
33 #include "mongo/base/simple_string_data_comparator.h"
34
35 #include <third_party/murmurhash3/MurmurHash3.h>
36
37 #include "mongo/base/data_type_endian.h"
38 #include "mongo/base/data_view.h"
39
40 namespace mongo {
41
42 namespace {
43
44 template <int SizeofSizeT>
45 size_t murmur3(StringData str, size_t seed);
46
47 template <>
murmur3(StringData str,size_t seed)48 size_t murmur3<4>(StringData str, size_t seed) {
49 char hash[4];
50 MurmurHash3_x86_32(str.rawData(), str.size(), seed, &hash);
51 return ConstDataView(hash).read<LittleEndian<std::uint32_t>>();
52 }
53
54 template <>
murmur3(StringData str,size_t seed)55 size_t murmur3<8>(StringData str, size_t seed) {
56 char hash[16];
57 MurmurHash3_x64_128(str.rawData(), str.size(), seed, hash);
58 return static_cast<size_t>(ConstDataView(hash).read<LittleEndian<std::uint64_t>>());
59 }
60
61 } // namespace
62
63 const SimpleStringDataComparator SimpleStringDataComparator::kInstance{};
64
compare(StringData left,StringData right) const65 int SimpleStringDataComparator::compare(StringData left, StringData right) const {
66 return left.compare(right);
67 }
68
hash_combine(size_t & seed,StringData stringToHash) const69 void SimpleStringDataComparator::hash_combine(size_t& seed, StringData stringToHash) const {
70 seed = murmur3<sizeof(size_t)>(stringToHash, seed);
71 }
72
73 } // namespace mongo
74