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39
40//
41// W A R N I N G
42// -------------
43//
44// This file is not part of the Qt API. It exists purely as an
45// implementation detail. This header file may change from version to
46// version without notice, or even be removed.
47//
48// We mean it.
49
50#ifndef Patternist_CachingIterator_H
51#define Patternist_CachingIterator_H
52
53#include <QList>
54#include <QVector>
55
56#include <private/qdynamiccontext_p.h>
57#include <private/qitem_p.h>
58
59QT_BEGIN_NAMESPACE
60
61namespace QPatternist
62{
63 /**
64 * @short An QAbstractXmlForwardIterator that gets its item from a cache unless its empty, in
65 * which case it continues to populate the cache as well as deliver on its
66 * own from a source QAbstractXmlForwardIterator.
67 *
68 * @author Frans Englich <frans.frans.englich@nokia.com>
69 * @ingroup Patternist_iterators
70 */
71 class CachingIterator : public Item::Iterator
72 {
73 public:
74 /**
75 * We always use the same cache cell so why don't we use it directly,
76 * instead of passing the slot and ItemSequenceCacheCell::Vector to
77 * this class? Because the GenericDynamicContext might decide to resize
78 * the vector and that would invalidate the reference.
79 *
80 * We intentionally pass in a non-const reference here.
81 */
82 CachingIterator(ItemSequenceCacheCell::Vector &cacheCells,
83 const VariableSlotID slot,
84 const DynamicContext::Ptr &context);
85
86 virtual Item next();
87 virtual Item current() const;
88 virtual xsInteger position() const;
89 virtual Item::Iterator::Ptr copy() const;
90
91 private:
92 Item m_current;
93 xsInteger m_position;
94
95 /**
96 * This variable cannot be called m_slot, because
97 * /usr/include/sys/sysmacros.h on hpuxi-acc defines it.
98 */
99 const VariableSlotID m_varSlot;
100
101 /**
102 * We don't use the context. We only keep a reference such that it
103 * doesn't get deleted, and m_cacheCells starts to dangle.
104 */
105 const DynamicContext::Ptr m_context;
106
107 /**
108 * We intentionally store a reference here such that we are able to
109 * modify the item.
110 */
111 ItemSequenceCacheCell::Vector &m_cacheCells;
112
113 /**
114 * Whether this CachingIterator is delivering items from
115 * m_cacheCell.cacheItems or from m_cacheCell.sourceIterator.
116 */
117 bool m_usingCache;
118 };
119}
120
121QT_END_NAMESPACE
122
123#endif
124

source code of qtxmlpatterns/src/xmlpatterns/iterators/qcachingiterator_p.h