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 #pragma once
32 
33 #include "mongo/base/string_data_comparator_interface.h"
34 #include "mongo/bson/bsonelement_comparator_interface.h"
35 
36 namespace mongo {
37 
38 /**
39  * A BSONElement comparator that supports:
40  * - Ignoring field names during comparison.
41  * - Passing a custom string comparator.
42  */
43 class BSONElementComparator final : public BSONElement::ComparatorInterface {
44 public:
45     enum class FieldNamesMode {
46         kConsider,
47         kIgnore,
48     };
49 
50     /**
51      * Constructs a BSONElement comparator.
52      *
53      * Will not consider the elements' field names in comparisons if 'fieldNamesMode' is kIgnore.
54      *
55      * If 'stringComparator' is null, uses default binary string comparison. Otherwise,
56      * 'stringComparator' is used for all string comparisons.
57      */
BSONElementComparator(FieldNamesMode fieldNamesMode,const StringData::ComparatorInterface * stringComparator)58     BSONElementComparator(FieldNamesMode fieldNamesMode,
59                           const StringData::ComparatorInterface* stringComparator)
60         : _stringComparator(stringComparator),
61           _rules((fieldNamesMode == FieldNamesMode::kConsider) ? ComparisonRules::kConsiderFieldName
62                                                                : 0) {}
63 
compare(const BSONElement & lhs,const BSONElement & rhs)64     int compare(const BSONElement& lhs, const BSONElement& rhs) const final {
65         return lhs.woCompare(rhs, _rules, _stringComparator);
66     }
67 
hash_combine(size_t & seed,const BSONElement & toHash)68     void hash_combine(size_t& seed, const BSONElement& toHash) const final {
69         hashCombineBSONElement(seed, toHash, _rules, _stringComparator);
70     }
71 
72 private:
73     const StringData::ComparatorInterface* _stringComparator;
74     ComparisonRulesSet _rules;
75 };
76 
77 }  // namespace mongo
78