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/bson/mutable/document.h"
34 #include "mongo/bson/mutable/element.h"
35 #include "mongo/db/bson/dotted_path_support.h"
36 #include "mongo/db/jsobj.h"
37 #include "mongo/db/query/collation/collator_interface.h"
38 
39 namespace mongo {
40 
41 // Extracts the value for 'pattern' for both 'lhs' and 'rhs' and return true if 'lhs' <
42 // 'rhs'. We expect that both 'lhs' and 'rhs' be key patterns.
43 struct PatternElementCmp {
44     PatternElementCmp() = default;
45 
PatternElementCmpPatternElementCmp46     PatternElementCmp(const BSONObj& pattern, const CollatorInterface* collator)
47         : sortPattern(pattern), useWholeValue(pattern.hasField("")), collator(collator) {}
48 
operatorPatternElementCmp49     bool operator()(const mutablebson::Element& lhs, const mutablebson::Element& rhs) const {
50         namespace dps = ::mongo::dotted_path_support;
51         if (useWholeValue) {
52             const int comparedValue = lhs.compareWithElement(rhs, collator, false);
53 
54             const bool reversed = (sortPattern.firstElement().number() < 0);
55 
56             return (reversed ? comparedValue > 0 : comparedValue < 0);
57         } else {
58             // TODO: Push on to mutable in the future, and to support non-contiguous Elements.
59             BSONObj lhsObj =
60                 lhs.getType() == Object ? lhs.getValueObject() : lhs.getValue().wrap("");
61             BSONObj rhsObj =
62                 rhs.getType() == Object ? rhs.getValueObject() : rhs.getValue().wrap("");
63 
64             BSONObj lhsKey = dps::extractElementsBasedOnTemplate(lhsObj, sortPattern, true);
65             BSONObj rhsKey = dps::extractElementsBasedOnTemplate(rhsObj, sortPattern, true);
66 
67             return lhsKey.woCompare(rhsKey, sortPattern, false, collator) < 0;
68         }
69     }
70 
71     BSONObj sortPattern;
72     bool useWholeValue = true;
73     const CollatorInterface* collator = nullptr;
74 };
75 
76 }  // namespace mongo
77