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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_SingletonIterator_H |
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53 #define Patternist_SingletonIterator_H |
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54 |
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55 #include <QtXmlPatterns/private/qabstractxmlforwarditerator_p.h> |
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56 |
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57 #include <QtXmlPatterns/private/qprimitives_p.h> |
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58 |
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59 QT_BEGIN_HEADER |
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60 |
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61 QT_BEGIN_NAMESPACE |
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62 |
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63 namespace QPatternist |
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64 { |
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65 /** |
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66 * @short An QAbstractXmlForwardIterator over exactly one item. |
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67 * |
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68 * SingletonIterator's constructor takes one value which is |
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69 * the item it forms an QAbstractXmlForwardIterator over. Other QAbstractXmlForwardIterator instances can |
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70 * also form an QAbstractXmlForwardIterator with one in length, but by that SingletonIterator |
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71 * has this as it only task, it means it is efficient at it. |
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72 * |
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73 * Having to represent single items in Iterators is relatively common. |
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74 * |
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75 * @author Frans Englich <frans.englich@nokia.com> |
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76 * @ingroup Patternist_iterators |
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77 */ |
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78 template<typename T> |
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79 class SingletonIterator : public QAbstractXmlForwardIterator<T> |
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80 { |
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81 public: |
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82 /** |
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83 * Creates an iterator over @p item. |
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84 * |
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85 * @note item may not be @c null. Use the EmptyIterator for |
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86 * the empty sequence |
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87 */ |
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88 SingletonIterator(const T &item) : m_item(item), |
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89 m_position(0) |
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90 { |
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91 Q_ASSERT(!qIsForwardIteratorEnd(item)); |
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92 } |
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93 |
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94 virtual T next() |
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95 { |
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96 switch(m_position) |
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97 { |
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98 case 0: |
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99 { |
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100 ++m_position; |
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101 return m_item; |
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102 } |
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103 case 1: |
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104 { |
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105 m_position = -1; |
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106 return T(); |
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107 } |
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108 default: |
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109 { |
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110 Q_ASSERT(m_position == -1); |
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111 return T(); |
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112 } |
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113 } |
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114 } |
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115 |
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116 virtual T current() const |
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117 { |
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118 if(m_position == 1) |
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119 return m_item; |
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120 else |
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121 return T(); |
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122 } |
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123 |
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124 virtual xsInteger position() const |
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125 { |
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126 return m_position; |
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127 } |
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128 |
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129 /** |
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130 * @returns a copy of this instance, rewinded to the beginning. |
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131 */ |
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132 virtual typename QAbstractXmlForwardIterator<T>::Ptr toReversed() |
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133 { |
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134 return typename QAbstractXmlForwardIterator<T>::Ptr(new SingletonIterator<T>(m_item)); |
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135 } |
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136 |
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137 /** |
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138 * @returns always 1 |
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139 */ |
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140 virtual xsInteger count() |
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141 { |
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142 return 1; |
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143 } |
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144 |
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145 virtual typename QAbstractXmlForwardIterator<T>::Ptr copy() const |
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146 { |
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147 return typename QAbstractXmlForwardIterator<T>::Ptr(new SingletonIterator(m_item)); |
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148 } |
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149 |
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150 private: |
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151 const T m_item; |
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152 qint8 m_position; |
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153 }; |
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154 |
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155 /** |
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156 * @short An object generator for SingletonIterator. |
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157 * |
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158 * makeSingletonIterator() is a convenience function for avoiding specifying |
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159 * the full template instantiation for SingletonIterator. Conceptually, it |
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160 * is identical to Qt's qMakePair(). |
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161 * |
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162 * @relates SingletonIterator |
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163 */ |
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164 template<typename T> |
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165 inline |
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166 typename SingletonIterator<T>::Ptr |
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167 makeSingletonIterator(const T &item) |
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168 { |
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169 return typename SingletonIterator<T>::Ptr(new SingletonIterator<T>(item)); |
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170 } |
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171 } |
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172 |
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173 QT_END_NAMESPACE |
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174 |
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175 QT_END_HEADER |
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176 |
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177 #endif |