SegPageIter.h

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/*
// $Id: //open/dev/fennel/segment/SegPageIter.h#11 $
// Fennel is a library of data storage and processing components.
// Copyright (C) 2005-2009 The Eigenbase Project
// Copyright (C) 2005-2009 SQLstream, Inc.
// Copyright (C) 2005-2009 LucidEra, Inc.
// Portions Copyright (C) 1999-2009 John V. Sichi
//
// This program is free software; you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by the Free
// Software Foundation; either version 2 of the License, or (at your option)
// any later version approved by The Eigenbase Project.
//
// 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

#ifndef Fennel_SegPageIter_Included
#define Fennel_SegPageIter_Included

#include <vector>
#include "fennel/segment/SegmentAccessor.h"

FENNEL_BEGIN_NAMESPACE

class Segment;

class FENNEL_SEGMENT_EXPORT SegPageIter
{
    uint prefetchPagesMax;

    uint prefetchThrottleRate;

    uint currPageSlot;

    bool noPrefetch;

    uint throttleCount;

    bool forceReject;

protected:
    SegmentAccessor segmentAccessor;

    PageId endPageId;

    std::vector<PageId> prefetchQueue;

    uint iFetch;

    bool atEnd;

    uint queueSize;

    int nFreePageSlots;

    void initPrefetchQueue();

    void prefetchPage(PageId pageId);

public:
    explicit SegPageIter();

    void mapRange(
        SegmentAccessor const &segmentAccessor,
        PageId beginPageId,
        PageId endPageId = NULL_PAGE_ID);

    PageId operator *() const
    {
        assert(!isSingular());
        return prefetchQueue[iFetch];
    }

    void operator ++ ();

    void forcePrefetchReject();

    void makeSingular()
    {
        segmentAccessor.reset();
    }

    bool isSingular() const
    {
        return segmentAccessor.pSegment ? false : true;
    }
};

FENNEL_END_NAMESPACE

#endif

// End SegPageIter.h

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