source: trunk/src/xmlpatterns/expr/qcachecells_p.h@ 743

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//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API.  It exists purely as an
// implementation detail.  This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.

#ifndef Patternist_CacheCells_H
#define Patternist_CacheCells_H

#include <QList>
#include <QVector>

#include "qitem_p.h"

QT_BEGIN_HEADER

QT_BEGIN_NAMESPACE

namespace QPatternist
{

    /**
     * @short Represents a cache entry for a single Item,
     * as opposed to for a sequence of items.
     *
     * A characteristic of the ItemCacheCell is that it has two states:
     * either its full or it's not, since it only deals with a single
     * item.
     *
     * Remember that cachedItem doesn't tell the state of the ItemCacheCell.
     * For instance, it can have a null pointer, the empty sequence, and that
     * can be the value of its cache.
     *
     * @author Frans Englich <[email protected]>
     */
    class ItemCacheCell
    {
    public:
        typedef QList<ItemCacheCell> List;
        typedef QVector<ItemCacheCell> Vector;
        enum CacheState
        {
            Full,
            Empty
        };

        inline ItemCacheCell() : cacheState(Empty)
        {
        }

        Item        cachedItem;
        CacheState  cacheState;
    };

    /**
     * @short Represents a cache entry for a sequence of items.
     *
     * As opposed to ItemCacheCell, ItemSequenceCacheCell can be partially
     * populated: e.g, four items is in the cache while three remains in the
     * source. For that reason ItemSequenceCacheCell in addition to the source
     * also carried an QAbstractXmlForwardIterator which is the source, such
     * that it can continue to populate the cache when it runs out.
     *
     * @author Frans Englich <[email protected]>
     */
    class ItemSequenceCacheCell
    {
    public:
        typedef QList<ItemSequenceCacheCell> List;
        typedef QVector<ItemSequenceCacheCell> Vector;

        enum CacheState
        {
            Full,
            Empty,
            PartiallyPopulated
        };

        inline ItemSequenceCacheCell() : cacheState(Empty)
                                       , inUse(false)
        {
        }

        Item::List          cachedItems;
        Item::Iterator::Ptr sourceIterator;
        CacheState          cacheState;
        /**
         * In XSL-T, we can have circularity which we cannot detect statically.
         * For instance, a global variable invokes a template, and the template
         * uses the variable. We can't detect that, because we can't figure out
         * what template will be invoked.
         *
         * For solution we have this toggle, which is set temporarily on the
         * cell such that EvaluationCache can detect whether it's trashing
         * itself.
         *
         * One might think that it would be sufficient to flag usage of the
         * variable in an arbitrary template, but that would also flag valid
         * cases.
         */
        bool                inUse;
    };
}

Q_DECLARE_TYPEINFO(QPatternist::ItemCacheCell, Q_MOVABLE_TYPE);
Q_DECLARE_TYPEINFO(QPatternist::ItemSequenceCacheCell, Q_MOVABLE_TYPE);

QT_END_NAMESPACE

QT_END_HEADER

#endif