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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_EmptyIterator_H
51#define Patternist_EmptyIterator_H
52
53#include <private/qabstractxmlforwarditerator_p.h>
54#include <private/qprimitives_p.h>
55
56QT_BEGIN_NAMESPACE
57
58namespace QPatternist
59{
60
61 /**
62 * @short An QAbstractXmlForwardIterator which always is empty.
63 *
64 * EmptyIterator is an QAbstractXmlForwardIterator over the type @c T, which always is empty. Other
65 * iterators can also be empty(or, at least behave as they are empty), but this
66 * class is special designed for this purpose and is therefore fast.
67 *
68 * EmptyIterator's constructor is protected, instances is retrieved from CommonValues.
69 *
70 * @author Frans Englich <frans.englich@nokia.com>
71 * @ingroup Patternist_iterators
72 */
73 template<typename T> class EmptyIterator : public QAbstractXmlForwardIterator<T>
74 {
75 public:
76 /**
77 * @returns always a default constructed value, T().
78 */
79 virtual T next()
80 {
81 return T();
82 }
83
84 /**
85 * @returns always a default constructed value, T().
86 */
87 virtual T current() const
88 {
89 return T();
90 }
91
92 /**
93 * @returns always 0.
94 */
95 virtual xsInteger position() const
96 {
97 return 0;
98 }
99
100 /**
101 * @returns always @c this, the reverse of <tt>()</tt> is <tt>()</tt>.
102 */
103 virtual typename QAbstractXmlForwardIterator<T>::Ptr toReversed()
104 {
105 return typename QAbstractXmlForwardIterator<T>::Ptr(const_cast<EmptyIterator<T> *>(this));
106 }
107
108 /**
109 * @returns always 0
110 */
111 virtual xsInteger count()
112 {
113 return 0;
114 }
115
116 /**
117 * @returns @c this
118 */
119 virtual typename QAbstractXmlForwardIterator<T>::Ptr copy() const
120 {
121 return typename QAbstractXmlForwardIterator<T>::Ptr(const_cast<EmptyIterator *>(this));
122 }
123
124 protected:
125 friend class CommonValues;
126 };
127
128 template<typename T>
129 static inline
130 typename QAbstractXmlForwardIterator<T>::Ptr
131 makeEmptyIterator()
132 {
133 return typename QAbstractXmlForwardIterator<T>::Ptr(new EmptyIterator<T>());
134 }
135
136}
137
138QT_END_NAMESPACE
139
140#endif
141

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