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/**
* Copyright (C) 2019-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 <memory>
#include "mongo/db/operation_context.h"
#include "mongo/s/query/cluster_client_cursor.h"
namespace mongo {
/**
* An RAII object which owns a ClusterClientCursor and kills the cursor if it is not explicitly
* released.
*/
class ClusterClientCursorGuard final {
ClusterClientCursorGuard(const ClusterClientCursorGuard&) = delete;
ClusterClientCursorGuard& operator=(const ClusterClientCursorGuard&) = delete;
public:
ClusterClientCursorGuard(OperationContext* opCtx, std::unique_ptr<ClusterClientCursor> ccc)
: _opCtx(opCtx), _ccc(std::move(ccc)) {}
/**
* If a cursor is owned, safely destroys the cursor, cleaning up remote cursor state if
* necessary. May block waiting for remote cursor cleanup.
*
* If no cursor is owned, does nothing.
*
* If the cursor has been killed by a previous command, does nothing. hasBeenKilled() will be
* true if the cursor was killed while the cursor was checked out or in use with a Guard.
*/
~ClusterClientCursorGuard() {
if (_ccc && !_ccc->remotesExhausted() && !_ccc->hasBeenKilled()) {
_ccc->kill(_opCtx);
}
}
ClusterClientCursorGuard(ClusterClientCursorGuard&&) = default;
ClusterClientCursorGuard& operator=(ClusterClientCursorGuard&&) = default;
/**
* Returns a pointer to the underlying cursor.
*/
ClusterClientCursor* operator->() {
return _ccc.get();
}
/**
* True if this ClusterClientCursorGuard owns a cursor.
*/
explicit operator bool() const {
return !!_ccc;
}
/**
* Transfers ownership of the underlying cursor to the caller. The guard must own a cursor
* when releaseCursor() is called; callers must first ensure the guard owns a cursor by
* using operator bool or operator ->.
*/
std::unique_ptr<ClusterClientCursor> releaseCursor() {
invariant(_ccc);
return std::move(_ccc);
}
private:
OperationContext* _opCtx;
std::unique_ptr<ClusterClientCursor> _ccc;
};
} // namespace mongo
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