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1 /**************************************************************************** |
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2 ** |
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3 ** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). |
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4 ** All rights reserved. |
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5 ** Contact: Nokia Corporation (qt-info@nokia.com) |
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6 ** |
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7 ** This file is part of the QtXmlPatterns module of the Qt Toolkit. |
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8 ** |
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9 ** $QT_BEGIN_LICENSE:LGPL$ |
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10 ** No Commercial Usage |
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11 ** This file contains pre-release code and may not be distributed. |
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12 ** You may use this file in accordance with the terms and conditions |
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13 ** contained in the Technology Preview License Agreement accompanying |
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14 ** this package. |
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15 ** |
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16 ** GNU Lesser General Public License Usage |
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17 ** Alternatively, this file may be used under the terms of the GNU Lesser |
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18 ** General Public License version 2.1 as published by the Free Software |
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19 ** Foundation and appearing in the file LICENSE.LGPL included in the |
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20 ** packaging of this file. Please review the following information to |
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21 ** ensure the GNU Lesser General Public License version 2.1 requirements |
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22 ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. |
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23 ** |
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24 ** In addition, as a special exception, Nokia gives you certain additional |
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25 ** rights. These rights are described in the Nokia Qt LGPL Exception |
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26 ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package. |
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27 ** |
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28 ** If you have questions regarding the use of this file, please contact |
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29 ** Nokia at qt-info@nokia.com. |
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30 ** |
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31 ** |
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32 ** |
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33 ** |
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34 ** |
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35 ** |
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36 ** |
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37 ** |
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38 ** $QT_END_LICENSE$ |
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39 ** |
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40 ****************************************************************************/ |
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41 |
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42 // |
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43 // W A R N I N G |
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44 // ------------- |
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45 // |
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46 // This file is not part of the Qt API. It exists purely as an |
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47 // implementation detail. This header file may change from version to |
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48 // version without notice, or even be removed. |
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49 // |
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50 // We mean it. |
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51 |
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52 #ifndef Patternist_EmptyIterator_H |
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53 #define Patternist_EmptyIterator_H |
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54 |
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55 #include "qabstractxmlforwarditerator_p.h" |
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56 #include "qprimitives_p.h" |
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57 |
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58 QT_BEGIN_HEADER |
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59 |
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60 QT_BEGIN_NAMESPACE |
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61 |
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62 namespace QPatternist |
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63 { |
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64 |
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65 /** |
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66 * @short An QAbstractXmlForwardIterator which always is empty. |
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67 * |
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68 * EmptyIterator is an QAbstractXmlForwardIterator over the type @c T, which always is empty. Other |
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69 * iterators can also be empty(or, at least behave as they are empty), but this |
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70 * class is special designed for this purpose and is therefore fast. |
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71 * |
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72 * EmptyIterator's constructor is protected, instances is retrieved from CommonValues. |
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73 * |
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74 * @author Frans Englich <frans.englich@nokia.com> |
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75 * @ingroup Patternist_iterators |
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76 */ |
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77 template<typename T> class EmptyIterator : public QAbstractXmlForwardIterator<T> |
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78 { |
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79 public: |
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80 /** |
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81 * @returns always a default constructed value, T(). |
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82 */ |
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83 virtual T next() |
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84 { |
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85 return T(); |
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86 } |
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87 |
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88 /** |
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89 * @returns always a default constructed value, T(). |
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90 */ |
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91 virtual T current() const |
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92 { |
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93 return T(); |
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94 } |
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95 |
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96 /** |
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97 * @returns always 0. |
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98 */ |
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99 virtual xsInteger position() const |
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100 { |
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101 return 0; |
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102 } |
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103 |
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104 /** |
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105 * @returns always @c this, the reverse of <tt>()</tt> is <tt>()</tt>. |
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106 */ |
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107 virtual typename QAbstractXmlForwardIterator<T>::Ptr toReversed() |
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108 { |
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109 return typename QAbstractXmlForwardIterator<T>::Ptr(const_cast<EmptyIterator<T> *>(this)); |
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110 } |
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111 |
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112 /** |
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113 * @returns always 0 |
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114 */ |
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115 virtual xsInteger count() |
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116 { |
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117 return 0; |
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118 } |
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119 |
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120 /** |
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121 * @returns @c this |
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122 */ |
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123 virtual typename QAbstractXmlForwardIterator<T>::Ptr copy() const |
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124 { |
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125 return typename QAbstractXmlForwardIterator<T>::Ptr(const_cast<EmptyIterator *>(this)); |
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126 } |
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127 |
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128 protected: |
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129 friend class CommonValues; |
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130 }; |
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131 |
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132 template<typename T> |
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133 static inline |
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134 typename QAbstractXmlForwardIterator<T>::Ptr |
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135 makeEmptyIterator() |
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136 { |
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137 return typename QAbstractXmlForwardIterator<T>::Ptr(new EmptyIterator<T>()); |
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138 } |
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139 |
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140 } |
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141 |
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142 QT_END_NAMESPACE |
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143 |
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144 QT_END_HEADER |
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145 |
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146 #endif |