SegPageEntryIter.h

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/*
// $Id: //open/dev/fennel/segment/SegPageEntryIter.h#3 $
// 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_SegPageEntryIter_Included
#define Fennel_SegPageEntryIter_Included

#include <vector>
#include "fennel/segment/SegPageIter.h"
#include "fennel/segment/SegPageEntryIterSource.h"
#include "fennel/common/CircularBuffer.h"

FENNEL_BEGIN_NAMESPACE

template <class EntryT>
class SegPageEntryIter : public SegPageIter
{
    CircularBuffer<std::pair<PageId, EntryT> > entryQueue;

    SegPageEntryIterSource<EntryT> *pPrefetchSource;

    void init();

    void prefetchPages(PageId prevPageId, bool oneIter);

public:
    explicit SegPageEntryIter<EntryT>();

    explicit SegPageEntryIter<EntryT>(uint nEntriesInit);

    void resize(uint nEntries);

    void setPrefetchSource(SegPageEntryIterSource<EntryT> &prefetchSource);

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

    std::pair<PageId, EntryT> & operator * ()
    {
        assert(!isSingular());
        std::pair<PageId, EntryT> &entryPair = entryQueue.reference_front();
        assert(entryPair.first == prefetchQueue[iFetch]);
        return entryPair;
    }

    void operator ++ ();

    void makeSingular()
    {
        SegPageIter::makeSingular();
        pPrefetchSource = NULL;
    }

    bool isSingular() const
    {
        return (pPrefetchSource == NULL || SegPageIter::isSingular());
    }
};

FENNEL_END_NAMESPACE

#endif

// End SegPageEntryIter.h

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