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/**
 *    Copyright (C) 2013 10gen Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    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
 *    GNU Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    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 GNU Affero General 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/db/structure/record_store.h"

namespace mongo {

    class CappedRecordStoreV1;

    struct Extent;

    /**
     * This class iterates over a capped collection identified by 'ns'.
     * The collection must exist when the constructor is called.
     *
     * If start is not DiskLoc(), the iteration begins at that DiskLoc.
     *
     * If tailable is true, getNext() can be called after isEOF.  It will use the last valid
     * returned DiskLoc and try to find the next record from that.
     */
    class CappedRecordStoreV1Iterator : public RecordIterator {
    public:
        CappedRecordStoreV1Iterator( const CappedRecordStoreV1* collection,
                                     const DiskLoc& start,
                                     bool tailable,
                                     const CollectionScanParams::Direction& dir );
        virtual ~CappedRecordStoreV1Iterator() { }

        // If this is a tailable cursor, isEOF could change its mind after a call to getNext().
        virtual bool isEOF();
        virtual DiskLoc getNext();
        virtual DiskLoc curr();

        virtual void invalidate(const DiskLoc& dl);
        virtual void prepareToYield();
        virtual bool recoverFromYield();

        virtual const Record* recordFor( const DiskLoc& loc ) const;
    private:
        /**
         * Internal collection navigation helper methods.
         */
        DiskLoc getNextCapped(const DiskLoc& dl);
        DiskLoc prevLoop(const DiskLoc& curr);
        DiskLoc nextLoop(const DiskLoc& prev);

        // some helpers - these move to RecordStore probably
        Extent* _getExtent( const DiskLoc& loc );
        DiskLoc _getNextRecord( const DiskLoc& loc );
        DiskLoc _getPrevRecord( const DiskLoc& loc );

        // The collection we're iterating over.
        const CappedRecordStoreV1* _recordStore;

        // The result returned on the next call to getNext().
        DiskLoc _curr;

        // If we're tailable, we try to progress from the last valid result when we hit the end.
        DiskLoc _prev;
        bool _tailable;

        CollectionScanParams::Direction _direction;

        // If invalidate kills the DiskLoc we need to move forward, we kill the iterator.  See the
        // comment in the body of invalidate(...).
        bool _killedByInvalidate;
    };

}  // namespace mongo