1 /**************************************************************************** 2 ** 3 ** Copyright (C) 2016 The Qt Company Ltd. 4 ** Contact: https://www.qt.io/licensing/ 5 ** 6 ** This file is part of the QtXmlPatterns module of the Qt Toolkit. 7 ** 8 ** $QT_BEGIN_LICENSE:LGPL$ 9 ** Commercial License Usage 10 ** Licensees holding valid commercial Qt licenses may use this file in 11 ** accordance with the commercial license agreement provided with the 12 ** Software or, alternatively, in accordance with the terms contained in 13 ** a written agreement between you and The Qt Company. For licensing terms 14 ** and conditions see https://www.qt.io/terms-conditions. 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The licenses are as published by the Free Software 30 ** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3 31 ** included in the packaging of this file. Please review the following 32 ** information to ensure the GNU General Public License requirements will 33 ** be met: https://www.gnu.org/licenses/gpl-2.0.html and 34 ** https://www.gnu.org/licenses/gpl-3.0.html. 35 ** 36 ** $QT_END_LICENSE$ 37 ** 38 ****************************************************************************/ 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_OperandsIterator_H 51 #define Patternist_OperandsIterator_H 52 53 #include <QPair> 54 #include <QStack> 55 56 #include <private/qexpression_p.h> 57 58 QT_BEGIN_NAMESPACE 59 60 namespace QPatternist 61 { 62 /** 63 * @short A helper class that iterates a tree of Expression instances. It 64 * is not a sub-class of QAbstractXmlForwardIterator. 65 * 66 * The OperandsIterator delivers all Expression instances that are children at any 67 * depth of the Expression passed in the constructor. 68 * The order is delivered in a defined way, from left to right and depth 69 * first. 70 * 71 * @author Frans Englich <frans.englich@nokia.com> 72 */ 73 class OperandsIterator 74 { 75 /** 76 * The second value, the int, is the current position in the first. 77 */ 78 typedef QPair<Expression::List, int> Level; 79 80 public: 81 enum TreatParent 82 { 83 ExcludeParent, 84 IncludeParent 85 }; 86 87 /** 88 * if @p treatParent is @c IncludeParent, @p start is excluded. 89 * 90 * @p start must be a valid Expression. 91 */ OperandsIterator(const Expression::Ptr & start,const TreatParent treatParent)92 inline OperandsIterator(const Expression::Ptr &start, 93 const TreatParent treatParent) 94 { 95 Q_ASSERT(start); 96 if(treatParent == IncludeParent) 97 { 98 Expression::List l; 99 l.append(start); 100 m_exprs.push(qMakePair(l, -1)); 101 } 102 103 m_exprs.push(qMakePair(start->operands(), -1)); 104 } 105 106 /** 107 * @short Returns the current Expression and advances the iterator. 108 * 109 * If the end has been reached, a default constructed pointer is 110 * returned. 111 * 112 * We intentionally return by reference. 113 */ next()114 inline Expression::Ptr next() 115 { 116 if(m_exprs.isEmpty()) 117 return Expression::Ptr(); 118 119 Level &lvl = m_exprs.top(); 120 ++lvl.second; 121 122 if(lvl.second == lvl.first.size()) 123 { 124 /* Resume iteration above us. */ 125 m_exprs.pop(); 126 127 if(m_exprs.isEmpty()) 128 return Expression::Ptr(); 129 130 while(true) 131 { 132 Level &previous = m_exprs.top(); 133 ++previous.second; 134 135 if(previous.second < previous.first.count()) 136 { 137 const Expression::Ptr &op = previous.first.at(previous.second); 138 m_exprs.push(qMakePair(op->operands(), -1)); 139 return op; 140 } 141 else 142 { 143 // We have already reached the end of this level. 144 m_exprs.pop(); 145 if(m_exprs.isEmpty()) 146 return Expression::Ptr(); 147 } 148 } 149 } 150 else 151 { 152 const Expression::Ptr &op = lvl.first.at(lvl.second); 153 m_exprs.push(qMakePair(op->operands(), -1)); 154 return op; 155 } 156 } 157 158 /** 159 * Advances this iterator by the current expression and its operands. 160 */ skipOperands()161 Expression::Ptr skipOperands() 162 { 163 if(m_exprs.isEmpty()) 164 return Expression::Ptr(); 165 166 Level &lvl = m_exprs.top(); 167 ++lvl.second; 168 169 if(lvl.second == lvl.first.size()) 170 { 171 /* We've reached the end of this level, at least. */ 172 m_exprs.pop(); 173 } 174 175 return next(); 176 } 177 178 private: 179 Q_DISABLE_COPY(OperandsIterator) 180 181 QStack<Level> m_exprs; 182 }; 183 } 184 185 186 QT_END_NAMESPACE 187 188 #endif 189