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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_SequenceMappingIterator_H
#define Patternist_SequenceMappingIterator_H
#include "qabstractxmlforwarditerator_p.h"
#include "qdynamiccontext_p.h"
QT_BEGIN_HEADER
QT_BEGIN_NAMESPACE
namespace QPatternist
{
/**
* @short Proxies another QAbstractXmlForwardIterator, and for each item, returns the
* Sequence 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. In contrast to ItemMappingIterator, SequenceMappingIterator maps
* each item into another QAbstractXmlForwardIterator, and where the SequenceMappingIterator's own
* result is the concatenation of all those Iterators. Hence, while ItemMappingIterator
* is better tailored for one-to-one or one-to-zero conversion, SequenceMappingIterator
* is more suitable for one-to-many conversion.
*
* This is achieved by that SequenceMappingIterator's constructor takes
* an instance of a class, that must have the following member:
*
* @code
* QAbstractXmlForwardIterator<TResult>::Ptr mapToSequence(const TSource::Ptr &item,
* const DynamicContext::Ptr &context) const;
* @endcode
*
* @author Frans Englich <frans.englich@nokia.com>
* @see ItemMappingIterator
* @ingroup Patternist_iterators
*/
template<typename TResult, typename TSource, typename TMapper>
class SequenceMappingIterator : public QAbstractXmlForwardIterator<TResult>
{
public:
/**
* Constructs a SequenceMappingIterator.
*
* @param mapper the object that has the mapToItem() sequence.
* @param sourceIterator the QAbstractXmlForwardIterator whose items should be mapped.
* @param context the DynamicContext that will be passed to the map function.
* May be null.
*/
SequenceMappingIterator(const TMapper &mapper,
const typename QAbstractXmlForwardIterator<TSource>::Ptr &sourceIterator,
const DynamicContext::Ptr &context);
virtual TResult next();
virtual xsInteger count();
virtual TResult current() const;
virtual xsInteger position() const;
/**
* The reason the implementation is placed in line here, is due to a bug
* in MSVC-2005 version 14.00.50727.762. Note that it works with version 14.00.50727.42.
*/
virtual typename QAbstractXmlForwardIterator<TResult>::Ptr copy() const
{
return typename QAbstractXmlForwardIterator<TResult>::Ptr
(new SequenceMappingIterator<TResult, TSource, TMapper>(m_mapper,
m_mainIterator->copy(),
m_context));
}
private:
xsInteger m_position;
TResult m_current;
typename QAbstractXmlForwardIterator<TSource>::Ptr m_mainIterator;
typename QAbstractXmlForwardIterator<TResult>::Ptr m_currentIterator;
const typename DynamicContext::Ptr m_context;
const TMapper m_mapper;
};
template<typename TResult, typename TSource, typename TMapper>
SequenceMappingIterator<TResult, TSource, TMapper>::SequenceMappingIterator(
const TMapper &mapper,
const typename QAbstractXmlForwardIterator<TSource>::Ptr &iterator,
const DynamicContext::Ptr &context)
: m_position(0),
m_mainIterator(iterator),
m_context(context),
m_mapper(mapper)
{
Q_ASSERT(mapper);
Q_ASSERT(iterator);
}
template<typename TResult, typename TSource, typename TMapper>
TResult SequenceMappingIterator<TResult, TSource, TMapper>::next()
{
/* This was once implemented with a recursive function, but the stack
* got blown for some inputs by that approach. */
while(true)
{
while(!m_currentIterator)
{
const TSource mainItem(m_mainIterator->next());
if(qIsForwardIteratorEnd(mainItem)) /* We've reached the very end. */
{
m_position = -1;
m_current = TResult();
return TResult();
}
else
m_currentIterator = m_mapper->mapToSequence(mainItem, m_context);
}
m_current = m_currentIterator->next();
if(qIsForwardIteratorEnd(m_current))
{
m_currentIterator.reset();
continue;
}
else
{
++m_position;
return m_current;
}
}
}
template<typename TResult, typename TSource, typename TMapper>
xsInteger SequenceMappingIterator<TResult, TSource, TMapper>::count()
{
TSource unit(m_mainIterator->next());
xsInteger c = 0;
while(!qIsForwardIteratorEnd(unit))
{
const typename QAbstractXmlForwardIterator<TResult>::Ptr sit(m_mapper->mapToSequence(unit, m_context));
c += sit->count();
unit = m_mainIterator->next();
}
return c;
}
template<typename TResult, typename TSource, typename TMapper>
TResult SequenceMappingIterator<TResult, TSource, TMapper>::current() const
{
return m_current;
}
template<typename TResult, typename TSource, typename TMapper>
xsInteger SequenceMappingIterator<TResult, TSource, TMapper>::position() const
{
return m_position;
}
/**
* @short An object generator for SequenceMappingIterator.
*
* makeSequenceMappingIterator() is a convenience function for avoiding specifying
* the full template instantiation for SequenceMappingIterator. Conceptually, it
* is identical to Qt's qMakePair().
*
* @returns a SequenceMappingIterator wrapped in a smart pointer, that has been
* passed the constructor arguments @p mapper, @p source, and @p context.
* @see makeMappingCallbackPtr()
* @relates QAbstractXmlForwardIterator
*/
template<typename TResult, typename TSource, typename TMapper>
static inline
typename QAbstractXmlForwardIterator<TResult>::Ptr
makeSequenceMappingIterator(const TMapper &mapper,
const QExplicitlySharedDataPointer<QAbstractXmlForwardIterator<TSource> > &source,
const DynamicContext::Ptr &context)
{
return typename QAbstractXmlForwardIterator<TResult>::Ptr
(new SequenceMappingIterator<TResult, TSource, TMapper>(mapper, source, context));
}
}
QT_END_NAMESPACE
QT_END_HEADER
#endif