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| ** Copyright (C) 2016 The Qt Company Ltd. |
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| ** This file is part of the QtXmlPatterns module of the Qt Toolkit. |
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| ** Alternatively, this file may be used under the terms of the GNU |
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| |
| // |
| // 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_OperandsIterator_H |
| #define Patternist_OperandsIterator_H |
| |
| #include <QPair> |
| #include <QStack> |
| |
| #include <private/qexpression_p.h> |
| |
| QT_BEGIN_NAMESPACE |
| |
| namespace QPatternist |
| { |
| /** |
| * @short A helper class that iterates a tree of Expression instances. It |
| * is not a sub-class of QAbstractXmlForwardIterator. |
| * |
| * The OperandsIterator delivers all Expression instances that are children at any |
| * depth of the Expression passed in the constructor. |
| * The order is delivered in a defined way, from left to right and depth |
| * first. |
| * |
| * @author Frans Englich <frans.englich@nokia.com> |
| */ |
| class OperandsIterator |
| { |
| /** |
| * The second value, the int, is the current position in the first. |
| */ |
| typedef QPair<Expression::List, int> Level; |
| |
| public: |
| enum TreatParent |
| { |
| ExcludeParent, |
| IncludeParent |
| }; |
| |
| /** |
| * if @p treatParent is @c IncludeParent, @p start is excluded. |
| * |
| * @p start must be a valid Expression. |
| */ |
| inline OperandsIterator(const Expression::Ptr &start, |
| const TreatParent treatParent) |
| { |
| Q_ASSERT(start); |
| if(treatParent == IncludeParent) |
| { |
| Expression::List l; |
| l.append(start); |
| m_exprs.push(qMakePair(l, -1)); |
| } |
| |
| m_exprs.push(qMakePair(start->operands(), -1)); |
| } |
| |
| /** |
| * @short Returns the current Expression and advances the iterator. |
| * |
| * If the end has been reached, a default constructed pointer is |
| * returned. |
| * |
| * We intentionally return by reference. |
| */ |
| inline Expression::Ptr next() |
| { |
| if(m_exprs.isEmpty()) |
| return Expression::Ptr(); |
| |
| Level &lvl = m_exprs.top(); |
| ++lvl.second; |
| |
| if(lvl.second == lvl.first.size()) |
| { |
| /* Resume iteration above us. */ |
| m_exprs.pop(); |
| |
| if(m_exprs.isEmpty()) |
| return Expression::Ptr(); |
| |
| while(true) |
| { |
| Level &previous = m_exprs.top(); |
| ++previous.second; |
| |
| if(previous.second < previous.first.count()) |
| { |
| const Expression::Ptr &op = previous.first.at(previous.second); |
| m_exprs.push(qMakePair(op->operands(), -1)); |
| return op; |
| } |
| else |
| { |
| // We have already reached the end of this level. |
| m_exprs.pop(); |
| if(m_exprs.isEmpty()) |
| return Expression::Ptr(); |
| } |
| } |
| } |
| else |
| { |
| const Expression::Ptr &op = lvl.first.at(lvl.second); |
| m_exprs.push(qMakePair(op->operands(), -1)); |
| return op; |
| } |
| } |
| |
| /** |
| * Advances this iterator by the current expression and its operands. |
| */ |
| Expression::Ptr skipOperands() |
| { |
| if(m_exprs.isEmpty()) |
| return Expression::Ptr(); |
| |
| Level &lvl = m_exprs.top(); |
| ++lvl.second; |
| |
| if(lvl.second == lvl.first.size()) |
| { |
| /* We've reached the end of this level, at least. */ |
| m_exprs.pop(); |
| } |
| |
| return next(); |
| } |
| |
| private: |
| Q_DISABLE_COPY(OperandsIterator) |
| |
| QStack<Level> m_exprs; |
| }; |
| } |
| |
| |
| QT_END_NAMESPACE |
| |
| #endif |