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/db/matcher/expression_array.h"
34 #include "mongo/db/matcher/expression_with_placeholder.h"
35 #include "mongo/stdx/memory.h"
36 
37 namespace mongo {
38 
39 /**
40  * Matches arrays based on whether or not a specific element in the array matches a sub-expression.
41  */
42 class InternalSchemaMatchArrayIndexMatchExpression final : public ArrayMatchingMatchExpression {
43 public:
44     static constexpr StringData kName = "$_internalSchemaMatchArrayIndex"_sd;
45 
InternalSchemaMatchArrayIndexMatchExpression()46     InternalSchemaMatchArrayIndexMatchExpression()
47         : ArrayMatchingMatchExpression(MatchExpression::INTERNAL_SCHEMA_MATCH_ARRAY_INDEX) {}
48 
49     Status init(StringData path,
50                 long long index,
51                 std::unique_ptr<ExpressionWithPlaceholder> expression);
52 
53     void debugString(StringBuilder& debug, int level) const final;
54 
55     bool equivalent(const MatchExpression* expr) const final;
56 
57     /**
58      * Matches 'array' if the element at '_index' matches '_expression', or if its size is less than
59      * '_index'.
60      */
matchesArray(const BSONObj & array,MatchDetails * details)61     bool matchesArray(const BSONObj& array, MatchDetails* details) const final {
62         BSONElement element;
63         auto iterator = BSONObjIterator(array);
64 
65         // Skip ahead to the element we want, bailing early if there aren't enough elements.
66         for (auto i = 0LL; i <= _index; ++i) {
67             if (!iterator.more()) {
68                 return true;
69             }
70             element = iterator.next();
71         }
72 
73         return _expression->matchesBSONElement(element, details);
74     }
75 
76     void serialize(BSONObjBuilder* builder) const final;
77 
78     std::unique_ptr<MatchExpression> shallowClone() const final;
79 
getChildVector()80     std::vector<MatchExpression*>* getChildVector() final {
81         return nullptr;
82     }
83 
numChildren()84     size_t numChildren() const final {
85         return 1;
86     }
87 
getChild(size_t i)88     MatchExpression* getChild(size_t i) const final {
89         invariant(i == 0);
90         return _expression->getFilter();
91     }
92 
93 private:
94     ExpressionOptimizerFunc getOptimizer() const final;
95 
96     long long _index = 0;
97     std::unique_ptr<ExpressionWithPlaceholder> _expression;
98 };
99 
100 }  // namespace mongo
101