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
|
/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <absl/container/flat_hash_map.h>
#include <absl/container/flat_hash_set.h>
#include "mongo/base/string_data.h"
#include "mongo/util/assert_util.h"
namespace mongo {
// Type that bundles a hashed key with the actual string so hashing can be performed outside of
// insert call by using heterogeneous lookup.
struct StringMapHashedKey {
public:
explicit StringMapHashedKey(StringData sd, std::size_t hash) : _sd(sd), _hash(hash) {}
explicit operator std::string() const {
return _sd.toString();
}
StringData key() const {
return _sd;
}
std::size_t hash() const {
return _hash;
}
private:
StringData _sd;
std::size_t _hash;
};
// Hasher to support heterogeneous lookup for StringData and string-like elements.
struct StringMapHasher {
// This using directive activates heterogeneous lookup in the hash table
using is_transparent = void;
std::size_t operator()(StringData sd) const {
// Use the default absl string hasher.
return absl::Hash<absl::string_view>{}(absl::string_view(sd.rawData(), sd.size()));
}
std::size_t operator()(const std::string& s) const {
return operator()(StringData(s));
}
std::size_t operator()(const char* s) const {
return operator()(StringData(s));
}
std::size_t operator()(StringMapHashedKey key) const {
return key.hash();
}
StringMapHashedKey hashed_key(StringData sd) {
return StringMapHashedKey(sd, operator()(sd));
}
};
struct StringMapEq {
// This using directive activates heterogeneous lookup in the hash table
using is_transparent = void;
bool operator()(StringData lhs, StringData rhs) const {
return lhs == rhs;
}
bool operator()(StringMapHashedKey lhs, StringData rhs) const {
return lhs.key() == rhs;
}
bool operator()(StringData lhs, StringMapHashedKey rhs) const {
return lhs == rhs.key();
}
bool operator()(StringMapHashedKey lhs, StringMapHashedKey rhs) const {
return lhs.key() == rhs.key();
}
};
template <typename V>
using StringMap = absl::flat_hash_map<std::string, V, StringMapHasher, StringMapEq>;
using StringSet = absl::flat_hash_set<std::string, StringMapHasher, StringMapEq>;
template <typename V>
using StringDataMap = absl::flat_hash_map<StringData, V, StringMapHasher, StringMapEq>;
using StringDataSet = absl::flat_hash_set<StringData, StringMapHasher, StringMapEq>;
} // namespace mongo
|
