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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_ItemMappingIterator_H |
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53 #define Patternist_ItemMappingIterator_H |
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54 |
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55 #include "qabstractxmlforwarditerator_p.h" |
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56 #include "qdynamiccontext_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 * @short Proxies another QAbstractXmlForwardIterator, and for each item, returns the |
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66 * Item returned from a mapping function. |
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67 * |
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68 * ItemMappingIterator is practical when the items in an QAbstractXmlForwardIterator needs to |
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69 * be translated to another sequence, while still doing it in a pipe-lined |
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70 * fashion. |
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71 * |
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72 * This is achieved by that ItemMappingIterator's constructor takes |
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73 * an instance of a class, that must have the following member: |
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74 * |
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75 * @code |
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76 * TResult::Ptr mapToItem(const TSource &item, |
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77 * const Context &context) const |
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78 * @endcode |
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79 * |
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80 * For each item in the QAbstractXmlForwardIterator ItemMappingIterator proxies, this function is |
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81 * called and its return value becomes the return value of the ItemMappingIterator. If the |
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82 * mapping function returns null, ItemMappingIterator maps the next item in the source sequence |
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83 * such that a contiguous sequence of items is returned. |
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84 * |
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85 * Declaring the mapToItem() function as inline, can be a good way to improve performance. |
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86 * |
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87 * @see SequenceMappingIterator |
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88 * @author Frans Englich <frans.englich@nokia.com> |
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89 * @ingroup Patternist_iterators |
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90 */ |
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91 template<typename TResult, typename TSource, typename TMapper, typename Context = DynamicContext::Ptr> |
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92 class ItemMappingIterator : public QAbstractXmlForwardIterator<TResult> |
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93 { |
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94 public: |
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95 /** |
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96 * Constructs an ItemMappingIterator. |
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97 * |
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98 * @param mapper the object that has the mapToItem() sequence. |
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99 * @param iterator the QAbstractXmlForwardIterator whose items should be mapped. |
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100 * @param context the context that will be passed to the map function. |
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101 * May be null. |
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102 */ |
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103 ItemMappingIterator(const TMapper &mapper, |
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104 const typename QAbstractXmlForwardIterator<TSource>::Ptr &iterator, |
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105 const Context &context) : m_mapper(mapper) |
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106 , m_it(iterator) |
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107 , m_context(context) |
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108 , m_position(0) |
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109 { |
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110 Q_ASSERT(mapper); |
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111 Q_ASSERT(iterator); |
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112 } |
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113 |
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114 /** |
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115 * @returns the next item in the sequence, or |
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116 * @c null if the end have been reached. |
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117 */ |
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118 virtual TResult next() |
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119 { |
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120 const TSource sourceItem(m_it->next()); |
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121 |
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122 if(qIsForwardIteratorEnd(sourceItem)) |
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123 { |
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124 m_current = TResult(); |
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125 m_position = -1; |
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126 return TResult(); |
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127 } |
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128 else |
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129 { |
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130 m_current = m_mapper->mapToItem(sourceItem, m_context); |
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131 if(qIsForwardIteratorEnd(m_current)) |
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132 return next(); /* The mapper returned null, so continue with the next in the source. */ |
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133 else |
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134 { |
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135 ++m_position; |
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136 return m_current; |
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137 } |
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138 } |
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139 } |
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140 |
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141 virtual TResult current() const |
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142 { |
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143 return m_current; |
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144 } |
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145 |
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146 virtual xsInteger position() const |
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147 { |
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148 return m_position; |
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149 } |
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150 |
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151 virtual typename QAbstractXmlForwardIterator<TResult>::Ptr copy() const |
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152 { |
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153 return typename QAbstractXmlForwardIterator<TResult>::Ptr |
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154 (new ItemMappingIterator<TResult, TSource, TMapper, Context>(m_mapper, m_it->copy(), m_context)); |
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155 } |
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156 |
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157 private: |
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158 const TMapper m_mapper; |
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159 const typename QAbstractXmlForwardIterator<TSource>::Ptr m_it; |
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160 const Context m_context; |
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161 TResult m_current; |
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162 xsInteger m_position; |
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163 }; |
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164 |
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165 /** |
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166 * @short An object generator for ItemMappingIterator. |
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167 * |
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168 * makeItemMappingIterator() is a convenience function for avoiding specifying |
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169 * the full template instantiation for ItemMappingIterator. Conceptually, it |
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170 * is identical to Qt's qMakePair(). |
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171 * |
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172 * @relates ItemMappingIterator |
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173 */ |
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174 template<typename TResult, typename TSource, typename TMapper, typename Context> |
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175 static inline |
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176 typename QAbstractXmlForwardIterator<TResult>::Ptr |
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177 makeItemMappingIterator(const TMapper &mapper, |
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178 const QExplicitlySharedDataPointer<QAbstractXmlForwardIterator<TSource> > &source, |
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179 const Context &context) |
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180 { |
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181 return typename QAbstractXmlForwardIterator<TResult>::Ptr |
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182 (new ItemMappingIterator<TResult, TSource, TMapper, Context>(mapper, source, context)); |
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183 } |
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184 } |
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185 |
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186 QT_END_NAMESPACE |
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187 |
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188 QT_END_HEADER |
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189 |
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190 #endif |