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
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
|
/**
* 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 "mongo/base/string_data.h"
#include "mongo/stdx/unordered_map.h"
#include "mongo/stdx/unordered_set.h"
namespace mongo {
/**
* A StringData::ComparatorInterface is an abstract class for comparing StringData objects.
*/
class StringData::ComparatorInterface {
ComparatorInterface(const ComparatorInterface&) = delete;
ComparatorInterface& operator=(const ComparatorInterface&) = delete;
public:
/**
* Functor for checking string equality under this comparator. Compatible for use with unordered
* STL containers.
*/
class EqualTo {
public:
explicit EqualTo(const ComparatorInterface* stringComparator)
: _stringComparator(stringComparator) {}
bool operator()(StringData lhs, StringData rhs) const {
return _stringComparator->compare(lhs, rhs) == 0;
}
private:
const ComparatorInterface* _stringComparator;
};
/**
* Functor for hashing strings under this comparator. Compatible for use with unordered STL
* containers.
*/
class Hasher {
public:
explicit Hasher(const ComparatorInterface* stringComparator)
: _stringComparator(stringComparator) {}
size_t operator()(StringData stringToHash) const {
return _stringComparator->hash(stringToHash);
}
private:
const ComparatorInterface* _stringComparator;
};
using StringDataUnorderedSet = stdx::unordered_set<StringData, Hasher, EqualTo>;
template <typename T>
using StringDataUnorderedMap = stdx::unordered_map<StringData, T, Hasher, EqualTo>;
ComparatorInterface() = default;
virtual ~ComparatorInterface() = default;
/**
* Compares two StringData objects.
*/
virtual int compare(StringData left, StringData right) const = 0;
/**
* Hash a StringData in a way that respects this comparator.
*/
size_t hash(StringData stringToHash) const {
size_t seed = 0;
hash_combine(seed, stringToHash);
return seed;
}
/**
* Hash a StringData in a way that respects this comparator, and return the result in the 'seed'
* in-out parameter.
*/
virtual void hash_combine(size_t& seed, StringData stringToHash) const = 0;
/**
* Returns a function object which can evaluate string equality according to this comparator.
* This comparator must outlive the returned function object.
*/
EqualTo makeEqualTo() const {
return EqualTo(this);
}
/**
* Returns a function object which can hash strings according to this comparator. This
* comparator must outlive the returned function object.
*/
Hasher makeHasher() const {
return Hasher(this);
}
/**
* Construct an empty unordered set of StringData whose equivalence classes are given by this
* comparator. This comparator must outlive the returned set.
*/
StringDataUnorderedSet makeStringDataUnorderedSet() const {
return StringDataUnorderedSet(0, makeHasher(), makeEqualTo());
}
/**
* Construct an empty unordered map from StringData to type T whose equivalence classes are
* given by this comparator. This comparator must outlive the returned set.
*/
template <typename T>
StringDataUnorderedMap<T> makeStringDataUnorderedMap() const {
return StringDataUnorderedMap<T>(0, makeHasher(), makeEqualTo());
}
};
using StringDataUnorderedSet = StringData::ComparatorInterface::StringDataUnorderedSet;
template <typename T>
using StringDataUnorderedMap = StringData::ComparatorInterface::StringDataUnorderedMap<T>;
} // namespace mongo
|