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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_ItemMappingIterator_H |
| #define Patternist_ItemMappingIterator_H |
| |
| #include <private/qabstractxmlforwarditerator_p.h> |
| #include <private/qdynamiccontext_p.h> |
| |
| QT_BEGIN_NAMESPACE |
| |
| namespace QPatternist |
| { |
| /** |
| * @short Proxies another QAbstractXmlForwardIterator, and for each item, returns the |
| * Item returned from a mapping function. |
| * |
| * ItemMappingIterator is practical when the items in an QAbstractXmlForwardIterator needs to |
| * be translated to another sequence, while still doing it in a pipe-lined |
| * fashion. |
| * |
| * This is achieved by that ItemMappingIterator's constructor takes |
| * an instance of a class, that must have the following member: |
| * |
| * @code |
| * TResult::Ptr mapToItem(const TSource &item, |
| * const Context &context) const |
| * @endcode |
| * |
| * For each item in the QAbstractXmlForwardIterator ItemMappingIterator proxies, this function is |
| * called and its return value becomes the return value of the ItemMappingIterator. If the |
| * mapping function returns null, ItemMappingIterator maps the next item in the source sequence |
| * such that a contiguous sequence of items is returned. |
| * |
| * Declaring the mapToItem() function as inline, can be a good way to improve performance. |
| * |
| * @see SequenceMappingIterator |
| * @author Frans Englich <frans.englich@nokia.com> |
| * @ingroup Patternist_iterators |
| */ |
| template<typename TResult, typename TSource, typename TMapper, typename Context = DynamicContext::Ptr> |
| class ItemMappingIterator : public QAbstractXmlForwardIterator<TResult> |
| { |
| public: |
| /** |
| * Constructs an ItemMappingIterator. |
| * |
| * @param mapper the object that has the mapToItem() sequence. |
| * @param iterator the QAbstractXmlForwardIterator whose items should be mapped. |
| * @param context the context that will be passed to the map function. |
| * May be null. |
| */ |
| ItemMappingIterator(const TMapper &mapper, |
| const typename QAbstractXmlForwardIterator<TSource>::Ptr &iterator, |
| const Context &context) : m_mapper(mapper) |
| , m_it(iterator) |
| , m_context(context) |
| , m_position(0) |
| { |
| Q_ASSERT(mapper); |
| Q_ASSERT(iterator); |
| } |
| |
| /** |
| * @returns the next item in the sequence, or |
| * @c null if the end have been reached. |
| */ |
| virtual TResult next() |
| { |
| while (true) |
| { |
| const TSource &sourceItem = m_it->next(); |
| if (qIsForwardIteratorEnd(sourceItem)) |
| { |
| m_current = TResult(); |
| m_position = -1; |
| return m_current; |
| } |
| else |
| { |
| m_current = m_mapper->mapToItem(sourceItem, m_context); |
| if (qIsForwardIteratorEnd(m_current)) |
| { |
| continue; /* The mapper returned null, so continue with the next in the source. */ |
| } |
| else |
| { |
| ++m_position; |
| return m_current; |
| } |
| } |
| } |
| } |
| |
| virtual TResult current() const |
| { |
| return m_current; |
| } |
| |
| virtual xsInteger position() const |
| { |
| return m_position; |
| } |
| |
| virtual typename QAbstractXmlForwardIterator<TResult>::Ptr copy() const |
| { |
| return typename QAbstractXmlForwardIterator<TResult>::Ptr |
| (new ItemMappingIterator<TResult, TSource, TMapper, Context>(m_mapper, m_it->copy(), m_context)); |
| } |
| |
| private: |
| const TMapper m_mapper; |
| const typename QAbstractXmlForwardIterator<TSource>::Ptr m_it; |
| const Context m_context; |
| TResult m_current; |
| xsInteger m_position; |
| }; |
| |
| /** |
| * @short An object generator for ItemMappingIterator. |
| * |
| * makeItemMappingIterator() is a convenience function for avoiding specifying |
| * the full template instantiation for ItemMappingIterator. Conceptually, it |
| * is identical to Qt's qMakePair(). |
| * |
| * @relates ItemMappingIterator |
| */ |
| template<typename TResult, typename TSource, typename TMapper, typename Context> |
| static inline |
| typename QAbstractXmlForwardIterator<TResult>::Ptr |
| makeItemMappingIterator(const TMapper &mapper, |
| const QExplicitlySharedDataPointer<QAbstractXmlForwardIterator<TSource> > &source, |
| const Context &context) |
| { |
| return typename QAbstractXmlForwardIterator<TResult>::Ptr |
| (new ItemMappingIterator<TResult, TSource, TMapper, Context>(mapper, source, context)); |
| } |
| } |
| |
| QT_END_NAMESPACE |
| |
| #endif |