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// matchable.h
/**
* 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/bson/bsonobj.h"
#include "mongo/bson/bsonobjbuilder.h"
#include "mongo/db/field_ref.h"
#include "mongo/db/matcher/path.h"
namespace mongo {
class MatchableDocument {
public:
// Inlining to allow subclasses to see that this is a no-op and avoid a function call.
// Speeds up query execution measurably.
virtual ~MatchableDocument() {}
virtual BSONObj toBSON() const = 0;
/**
* The neewly returned ElementIterator is allowed to keep a pointer to path.
* So the caller of this function should make sure path is in scope until
* the ElementIterator is deallocated
*/
virtual ElementIterator* allocateIterator(const ElementPath* path) const = 0;
virtual void releaseIterator(ElementIterator* iterator) const = 0;
class IteratorHolder {
public:
IteratorHolder(const MatchableDocument* doc, const ElementPath* path) {
_doc = doc;
_iterator = _doc->allocateIterator(path);
}
~IteratorHolder() {
_doc->releaseIterator(_iterator);
}
ElementIterator* operator->() const {
return _iterator;
}
private:
const MatchableDocument* _doc;
ElementIterator* _iterator;
};
};
class BSONMatchableDocument : public MatchableDocument {
public:
BSONMatchableDocument(const BSONObj& obj);
virtual ~BSONMatchableDocument();
virtual BSONObj toBSON() const {
return _obj;
}
virtual ElementIterator* allocateIterator(const ElementPath* path) const {
if (_iteratorUsed)
return new BSONElementIterator(path, _obj);
_iteratorUsed = true;
_iterator.reset(path, _obj);
return &_iterator;
}
virtual void releaseIterator(ElementIterator* iterator) const {
if (iterator == &_iterator) {
_iteratorUsed = false;
} else {
delete iterator;
}
}
private:
BSONObj _obj;
mutable BSONElementIterator _iterator;
mutable bool _iteratorUsed;
};
/**
* A MatchableDocument interface for viewing a BSONElement as if it were wrapped in the top-level
* field of any given path. For example, given the object obj={a: [5]}, we can create a view over
* the element obj["a"]["0"]. An iterator over this view with path "i" would behave identically to
* an iterator over {i: 5} with path "i".
*/
class BSONElementViewMatchableDocument : public MatchableDocument {
public:
BSONElementViewMatchableDocument(BSONElement elem) : _elem(elem), _iteratorUsed(false) {}
BSONObj toBSON() const override {
return BSON("" << _elem);
}
/**
* Creates an iterator over '_elem' as if '_elem' were wrapped in the first field of 'path'.
* 'path' must have at least one field.
*/
ElementIterator* allocateIterator(const ElementPath* path) const override {
// Skip the first field in the path when traversing the document.
const size_t suffixIndex = 1;
if (_iteratorUsed) {
return new BSONElementIterator(path, suffixIndex, _elem);
}
_iteratorUsed = true;
_iterator.reset(path, suffixIndex, _elem);
return &_iterator;
}
void releaseIterator(ElementIterator* iterator) const override {
if (iterator == &_iterator) {
_iteratorUsed = false;
} else {
delete iterator;
}
}
private:
BSONElement _elem;
mutable BSONElementIterator _iterator;
mutable bool _iteratorUsed;
};
}
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