summaryrefslogtreecommitdiffstats
path: root/src/xmlpatterns/iterators/qemptyiterator_p.h
blob: ebc20f6070a81ab86a62a122091070e499a474dc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the QtXmlPatterns module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the either Technology Preview License Agreement or the
** Beta Release License Agreement.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain
** additional rights. These rights are described in the Nokia Qt LGPL
** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
** package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you are unsure which license is appropriate for your use, please
** contact the sales department at http://qt.nokia.com/contact.
** $QT_END_LICENSE$
**
****************************************************************************/

//
//  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_EmptyIterator_H
#define Patternist_EmptyIterator_H

#include "qabstractxmlforwarditerator_p.h"
#include "qprimitives_p.h"

QT_BEGIN_HEADER

QT_BEGIN_NAMESPACE

namespace QPatternist
{

    /**
     * @short An QAbstractXmlForwardIterator which always is empty.
     *
     * EmptyIterator is an QAbstractXmlForwardIterator over the type @c T, which always is empty. Other
     * iterators can also be empty(or, at least behave as they are empty), but this
     * class is special designed for this purpose and is therefore fast.
     *
     * EmptyIterator's constructor is protected, instances is retrieved from CommonValues.
     *
     * @author Frans Englich <frans.englich@nokia.com>
     * @ingroup Patternist_iterators
     */
    template<typename T> class EmptyIterator : public QAbstractXmlForwardIterator<T>
    {
    public:
        /**
         * @returns always a default constructed value, T().
         */
        virtual T next()
        {
            return T();
        }

        /**
         * @returns always a default constructed value, T().
         */
        virtual T current() const
        {
            return T();
        }

        /**
         * @returns always 0.
         */
        virtual xsInteger position() const
        {
            return 0;
        }

        /**
         * @returns always @c this, the reverse of <tt>()</tt> is <tt>()</tt>.
         */
        virtual typename QAbstractXmlForwardIterator<T>::Ptr toReversed()
        {
            return typename QAbstractXmlForwardIterator<T>::Ptr(const_cast<EmptyIterator<T> *>(this));
        }

        /**
         * @returns always 0
         */
        virtual xsInteger count()
        {
            return 0;
        }

        /**
         * @returns @c this
         */
        virtual typename QAbstractXmlForwardIterator<T>::Ptr copy() const
        {
            return typename QAbstractXmlForwardIterator<T>::Ptr(const_cast<EmptyIterator *>(this));
        }

    protected:
        friend class CommonValues;
    };

    template<typename T>
    static inline
    typename QAbstractXmlForwardIterator<T>::Ptr
    makeEmptyIterator()
    {
        return typename QAbstractXmlForwardIterator<T>::Ptr(new EmptyIterator<T>());
    }

}

QT_END_NAMESPACE

QT_END_HEADER

#endif