source: trunk/src/xmlpatterns/api/qabstractxmlnodemodel.cpp@ 878

/****************************************************************************
**
** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation ([email protected])
**
** This file is part of the QtXmlPatterns module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt Commercial License Agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Nokia.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights.  These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you have questions regarding the use of this file, please contact
** Nokia at [email protected].
** $QT_END_LICENSE$
**
****************************************************************************/

#include <QVector>

#include "qabstractxmlnodemodel_p.h"
#include "qabstractxmlreceiver.h"
#include "qcommonvalues_p.h"
#include "qemptyiterator_p.h"
#include "qitemmappingiterator_p.h"
#include "qitem_p.h"
#include "qnamespaceresolver_p.h"
#include "qsequencemappingiterator_p.h"
#include "qsingletoniterator_p.h"

#include "qabstractxmlnodemodel.h"

QT_BEGIN_NAMESPACE

using namespace QPatternist;

typedef QExplicitlySharedDataPointer<QAbstractXmlForwardIterator<QXmlNodeModelIndex> > QXmlNodeModelIndexIteratorPointer;

/**
 * @file
 * @short Contains the implementation of QAbstractXmlNodeModel.
 */

bool QAbstractXmlNodeModel::isIgnorableInDeepEqual(const QXmlNodeModelIndex &n)
{
    Q_ASSERT(!n.isNull());
    const QXmlNodeModelIndex::NodeKind nk = n.kind();
    return nk == QXmlNodeModelIndex::ProcessingInstruction ||
           nk == QXmlNodeModelIndex::Comment;
}


/*!
  \class QAbstractXmlNodeModel
  \brief The QAbstractXmlNodeModel class is an abstract base class for modeling non-XML data to look like XML for QXmlQuery.
  \threadsafe
  \since 4.4
  \ingroup xml-tools

  The QAbstractXmlNodeModel specifies the interface that a node model
  must implement for that node model be accessible to the query engine
  for processing XQuery queries.  A node model represents data as a
  structure that can be queried as if the data were XML.

  The node model represented by a subclass of QAbstractXmlNodeModel is
  meant to be accessed by the QtXmlPatterns query engine. If the API
  seems a little strange in a few places, it is because the member
  functions are called by the query engine as it evaluates an
  XQuery. They aren't meant to be used programatically.

  \section1 Usage

  QAbstractXmlNodeModel bridges the gap between the arbitrary structure
  of the non-XML data to be queried and the well-defined structure of
  XML data understood by QXmlQuery.

  Consider a chemistry application that reads the file \c
  chemistryData, which contains non-XML data that represents a
  chemical structure composed of molecules and atoms. The application
  will query this chemistry data with an XQuery it reads from file \c
  queryFile. We write a custom subclass of QAbstractXmlNodeModel (\c
  ChemistryNodeModel) that reads \c chemistryData and builds a data
  structure, perhaps composed of objects of our own classes \c
  molecule and \c atom.  Clearly, this data structure is not XML. Our
  custom subclass will know how to traverse this non-XML structure and
  present it through the \l
  {http://www.w3.org/TR/xpath-datamodel/}{XPath Data Model interface}.

  \snippet doc/src/snippets/code/src_xmlpatterns_api_qabstractxmlnodemodel.cpp 1

  The application first creates an instance of QXmlQuery and calls \l
  {QXmlQuery::setQuery()}{setQuery()} to read \c queryFile containing
  the XQuery we want to run. Then it creates an instance of our custom
  node model class, \c ChemistryNodeModel, which is a subclass of
  QAbstractXmlNodeModel. Its constructor is called with the \l
  {QXmlNamePool} {name pool} obtained from our QXmlQuery, and with the
  \c chemistryFile containing the structure of molecules and atoms to
  be queried. The \l {QXmlNamePool} {name pool} is required because
  our custom node model has the member function \l
  {QAbstractXmlNodeModel::name()} {name()}, which returns the \l
  {QXmlName} {name} of any node in the model. The \l {QXmlQuery}
  {query} and the custom node model must use the same name pool for
  constructing these \l {QXmlName} {names}. The constructor would then
  read \c chemistryFile and build the custom node model structure.

  To connect the \c query to the custom node model, we must bind a
  variable name used in the query to a node in the model. The variable
  can then be used in the query as a starting node. First, an \l
  {QXmlNodeModelIndex} {index} for the desired starting node is
  retrieved by calling QAbstractXmlNodeModel::createIndex(). Then the
  index is bound to a variable name, in this case \c queryRoot, by
  passing the name and the index to QXmlQuery::bindVariable(). The
  query can then use a variable reference \c $queryRoot to refer to
  the starting node. Note that if the \l {QXmlQuery} {query} uses
  multiple variable references, a call to QXmlQuery::bindVariable()
  is required to bind each different variable name to a node in the
  model.

  The query is executed when the application calls one of the
  QXmlQuery evaluation functions. The application uses
  QXmlQuery::evaluateTo(QAbstractXmlReceiver *), because it then uses
  a \l {QXmlSerializer} {serializer} to out the query result as XML to
  \c stdout. We could have used QXmlQuery::evaluateTo(QXmlResultItems
  *) to get a list of result items, or
  QXmlQuery::evaluateTo(QStringList *) if the query evaluated to a
  sequence of \c {xs:string} values.

  During query execution, the engine iterates over the node model
  using nextFromSimpleAxis() to get the \l {QXmlNodeModelIndex}
  {index} of the next node to be visited. The engine can get the name
  of a node by calling name() with the node's \l {QXmlNodeModelIndex}
  {index}. stringValue(), baseUri(), documentUri() and kind() are also
  called as needed with a node \l {QXmlNodeModelIndex} {index}.

  The example demonstrates the standard pattern for using a subclass
  of QAbstractXmlNodeModel in combination with QXmlQuery to perform
  an XQuery.

  \list 1

    \o Instantiate QXmlQuery and give it the XQuery to be run;

    \o Instantiate a subclass of QAbstractXmlNodeModel or
    QSimpleXmlNodeModel;

    \o Retrieve a QXmlNodeModelIndex for the node in the model where
    the QXmlQuery should start the query;

    \o Use QXmlQuery::bindVariable() to bind the QXmlNodeModelIndex
    to \c {$variable name};

    \o Call one of the QXmlQuery evaluation functions to run the
    query.

  \endlist

  \section1 Subclassing

  Because the \l {http://www.w3.org/TR/xpath-datamodel/}{XPath Data Model
  interface} presented by QAbstractXmlNodeModel allows QXmlQuery to
  operate on non-XML data as if it were XML, implementing subclasses
  of QAbstractXmlNodeModel can involve a significant amount of
  work. The QSimpleXmlNodeModel class is provided to simplify the
  implementation for many common use cases.

  \section1 Thread Safety

  Because the node model can be accessed concurrently by threads in
  the QtXmlPatterns module, subclasses of QAbstractXmlNodeModel must
  be written to be \l{Reentrancy and Thread-Safety}{thread-safe}.
  Classes that simplify implementing thread-safety include QReadLocker
  and QWriteLocker.

  See the example \l{File System Example} for a demonstration.
 */

/*!
  \enum QXmlNodeModelIndex::Constants

  \value ForwardAxis All forward axes include this flag.
  \value ReverseAxis All reverse axes include this flag.
 */

/*!
  \enum QXmlNodeModelIndex::DocumentOrder

  Identifies the specific node comparison operator that should be
  used.

  \value Precedes Signifies the \c \<\< operator. Test whether the
         first operand precedes the second in the document.

  \value Follows Signifies the \c \>\> operator. Test whether the
                 first operand follows the second in the document.

  \value Is Signifies the \c is operator. Test whether two nodes have
  the same node identity.
 */

/*!
  \enum QAbstractXmlNodeModel::SimpleAxis

  Four axes that each contain one node only.

  \value Parent The parent of the context node
  \value FirstChild The first child of the context node
  \value PreviousSibling The previous child of the context node
  \value NextSibling The next child of the context node
*/

/*!
 \enum QXmlNodeModelIndex::Axis
 \internal

   Identify the axes emanating from a node.

   The axes AxisChild, AxisDescendant, AxisAttribute, AxisSelf,
   AxisDescendantOrSelf, AxisFollowingSibling, and AxisFollowing are
   forward axes.

   The axes AxisParent, AxisAncestor, AxisPrecedingSibling,
   AxisPreceding and AxisAncestorOrSelf are reverse axes.

   \sa {http://www.w3.org/TR/xquery/#axes}{XQuery 1.0: An XML Query Language, 3.2.1.1 Axes}

   \value AxisChild                The \c child axis.

   \value AxisDescendant           The \c descendant axis.

   \value AxisAttribute            The \c attribute axis. Note: There
                                   is a node kind named \c{Attribute}.

   \value AxisSelf                 The \c self axis.

   \value AxisDescendantOrSelf     The \c descendant-or-self axis.

   \value AxisFollowingSibling     The \c following-sibling axis.

   \value AxisNamespace            The \c namespace axis. Note: Does
                                   not exist in XQuery; deprecated in
                                   XPath 2.0 (optionally supported);
                                   mandatory in XPath 1.0.

   \value AxisFollowing            The \c following axis.

   \value AxisParent               The \c parent axis.

   \value AxisAncestor             The \c ancestor axis.

   \value AxisPrecedingSibling     The \c preceding-sibling axis.

   \value AxisPreceding            The \c preceding axis.

   \value AxisAncestorOrSelf       The \c ancestor-or-self axis.
*/

using namespace QPatternist;

/*!
  Default constructor.
 */
QAbstractXmlNodeModel::QAbstractXmlNodeModel() : d_ptr(0)
{
}

/*!
 \internal

 Takes the d-pointer.

 */
QAbstractXmlNodeModel::QAbstractXmlNodeModel(QAbstractXmlNodeModelPrivate *d) : d_ptr(d)
{
}

/*!
  Destructor.
 */
QAbstractXmlNodeModel::~QAbstractXmlNodeModel()
{
}

/*!
  \typedef QAbstractXmlNodeModel::List

  A \l{QList}{list} of \l{QExplicitlySharedDataPointer} {smart
  pointers} to instances of QAbstractXmlNodeModel.

  \sa QExplicitlySharedDataPointer
 */

/*!
  \typedef QAbstractXmlNodeModel::Ptr

  A \l {QExplicitlySharedDataPointer} {smart pointer} to an
  instance of QAbstractXmlNodeModel.

  \sa QExplicitlySharedDataPointer
 */

/*!
  \fn QUrl QAbstractXmlNodeModel::baseUri(const QXmlNodeModelIndex &n) const

  Returns the base URI for the node whose index is \a n. The caller
  guarantees that \a n is not \c null and that it belongs to a node
  in this node model.

  The base URI of a node can be extracted using the \c fn:base-uri()
  function. The base URI is typically used for resolving relative URIs
  that appear in the node or its children. It is conformant to just
  return the document URI, although that might not properly reflect
  the underlying data.

  This function maps to the \c dm:base-uri accessor, which returns
  a base URI according to the following:

  \list

  \o For document nodes, the base URI and the document URI are the same.

  \o For elements, the base URI is the URI appearing in the element's
     \c xml:base attribute, if present, or it is resolved to the
     parent element's base URI.

  \o Namespace nodes have no base URI.

  \o The base URI for a processing instruction, comment, attribute,
  or text node is the base URI of the node's parent element.

  \endlist

  The implementation guarantees to return a valid QUrl, or a default
  constructed QUrl. If a node has no base URI, as in the case where a
  comment has no parent, a default constructed QUrl is returned.

   \sa {http://www.w3.org/TR/xpath-datamodel/#dm-base-uri}{XQuery 1.0 and XPath 2.0 Data Model (XDM), 5.2 base-uri Accessor}
 */

/*!
  \fn QUrl QAbstractXmlNodeModel::documentUri(const QXmlNodeModelIndex &n) const

  Returns the document URI of \a n. The document URI identifies the
  resource which is the document. For example, the document could be a
  regular file, e.g., \c{file:/}, or it could be the \c{http://} URL of
  the location of a file. The document URI is used for resolving URIs
  and to simply know where the document is.

  If the node model maps to a URI in a natural way, return that URI.
  Otherwise, return the company or product URI. The document URI can
  be any URI as long as its valid and absolute.

  The caller guarantees that \a n is not \c null and that it belongs
  to this QAbstractXmlNodeModel.

  This function maps to the \c dm:document-uri accessor, which
  returns a document URI according to the following:

  \list

  \o If \a n is a document node, return an absolute QUrl containing
     the document URI, or a default constructed QUrl. The latter
     signals that no document URI is available for the document node.

  \o For all other nodes, return a default constructed QUrl.

  \endlist

  \sa {http://www.w3.org/TR/xpath-datamodel/#dm-document-uri}{XQuery 1.0 and XPath 2.0 Data Model (XDM), 5.4 document-uri Accessor}
  \sa QUrl::isValid(), QUrl::isRelative()
 */

/*
### Qt 5:

Add the function:

    virtual QSourceLocation sourceLocation(const QXmlNodeModelIndex &nodeIndex) const = 0;

Such that the data model can communicate back source locations.
 */

/*!
  \fn QXmlNodeModelIndex::NodeKind QAbstractXmlNodeModel::kind(const QXmlNodeModelIndex &ni) const

  Returns a value indicating the kind of node identified by \a ni.
  The caller guarantees that \a ni is not null and that it identifies
  a node in this node model. This function maps to the \c
  dm:node-kind() accessor.

  \sa {http://www.w3.org/TR/xpath-datamodel/#dm-node-kind}{XQuery 1.0 and XPath 2.0 Data Model (XDM), 5.10 node-kind Accessor}
 */

/*!
  \fn QXmlNodeModelIndex::DocumentOrder QAbstractXmlNodeModel::compareOrder(const QXmlNodeModelIndex &ni1, const QXmlNodeModelIndex &ni2) const

  This function returns the relative document order for the
  nodes indexed by \a ni1 and \a ni2. It is used for the \c Is
  operator and for sorting nodes in document order.

  The caller guarantees that \a ni1 and \a ni2 are not \c null and
  that both identify nodes in this node model.

  If \a ni1 is identical to \a ni2, QXmlNodeModelIndex::Is is returned.
  If \a ni1 precedes \a ni2 in document order, QXmlNodeModelIndex::Precedes
  is returned. If \a ni1 follows \a ni2 in document order,
  QXmlNodeModelIndex::Follows is returned.

  \sa {http://www.w3.org/TR/xpath-datamodel/#document-order}{XQuery 1.0 and XPath 2.0 Data Model (XDM), 2.4 Document Order}
 */

/*!
  \fn QXmlNodeModelIndex QAbstractXmlNodeModel::root(const QXmlNodeModelIndex &n) const

  Returns the root node of the tree that contains the node whose index
  is \a n. The caller guarantees that \a n is not \c null and that it
  identifies a node in this node model.

  If \a n identifies a node that is a direct child of the root,
  parent() would return the same QXmlNodeModelIndex returned by
  this function.
 */

namespace QPatternist
{
    class MergeIterator
    {
    public:
        inline MergeIterator()
        {
        }

        inline
        QXmlNodeModelIndexIteratorPointer
        mapToSequence(const QXmlNodeModelIndexIteratorPointer &it,
                      const DynamicContext::Ptr &) const
        {
            return it;
        }

    private:
        Q_DISABLE_COPY(MergeIterator)
    };

    static const MergeIterator mergeIterator;

    /**
     * One might wonder, why not use makeVectorIterator() directly on a QVector
     * with iterators?
     *
     * A problem emerges QAbstractXmlForwardIterator::copy(). All "meta
     * iterators" that contain other iterators and so forth, propagate the
     * copy() call such that all involved iterators are copied. However, if we
     * have a ListIterator of iterators it isn't aware of that it contains
     * iterators. Hence, we have this class which is specialized(not in the
     * template sense) on iterators, and hence copies them appropriately.
     */
    class IteratorVector : public ListIterator<QXmlNodeModelIndexIteratorPointer, QVector<QXmlNodeModelIndexIteratorPointer> >
    {
        typedef QVector<QXmlNodeModelIndexIteratorPointer> ItVector;
    public:
        typedef QAbstractXmlForwardIterator<QXmlNodeModelIndexIteratorPointer>::Ptr Ptr;

        IteratorVector(const ItVector &in) : ListIterator<QXmlNodeModelIndexIteratorPointer, QVector<QXmlNodeModelIndexIteratorPointer> >(in)
        {
        }

        virtual QAbstractXmlForwardIterator<QXmlNodeModelIndexIteratorPointer>::Ptr copy() const
        {
            ItVector result;

            for(int i = 0; i < m_list.count(); ++i)
                result.append(m_list.at(i)->copy());

            return Ptr(new IteratorVector(result));
        }
    };
}

/*!
 \internal
 This function is not a private member of QAbstractXmlNodeModel
 because it would be messy to forward declare the required types.
*/
static inline QXmlNodeModelIndexIteratorPointer mergeIterators(const QXmlNodeModelIndex &node,
                                                               const QXmlNodeModelIndexIteratorPointer &it2)
{
    QVector<QXmlNodeModelIndexIteratorPointer> iterators;
    iterators.append(makeSingletonIterator(node));
    iterators.append(it2);

    return makeSequenceMappingIterator<QXmlNodeModelIndex>(&mergeIterator,
                                                           IteratorVector::Ptr(new IteratorVector(iterators)),
                                                           DynamicContext::Ptr());
}

inline QAbstractXmlForwardIterator<QXmlNodeModelIndex>::Ptr
QAbstractXmlNodeModel::mapToSequence(const QXmlNodeModelIndex &ni,
                                     const DynamicContext::Ptr &) const
{
    Q_ASSERT(!ni.isNull());
    /* Since we pass in this here, mapToSequence is used recursively. */
    return mergeIterators(ni, makeSequenceMappingIterator<QXmlNodeModelIndex>(this,
                                                                              ni.iterate(QXmlNodeModelIndex::AxisChild),
                                                                              DynamicContext::Ptr()));
}

/*!
  \fn QVector<QXmlNodeModelIndex> QAbstractXmlNodeModel::attributes(const QXmlNodeModelIndex &element) const

  Returns the attributes of \a element. The caller guarantees
  that \a element is an element in this node model.
 */

/*!
  \internal

  Performs navigation, starting from \a ni, by returning an
  QAbstractXmlForwardIterator that returns nodes the \a axis emanating
  from \a ni.

  The implementation returns the nodes on the \a axis, without
  duplicates and in \a axis order. This means that if \a axis is a
  reverse axis, which is the case for the \c parent, \c ancestor, \c
  ancestor-or-self, \c preceding, and \c preceding-sibling, the nodes
  are delivered in reverse document order. Otherwise the nodes are
  delivered in document order.

  The implementor guarantees that the nodes delivered for the axes are
  consistent with the XPath Data Model. This just implies common
  sense, e.g., The child axis for a comment node can't contain any
  children; a document node can't be a child of an element, etc.
  Attributes aren't considered children of an element, but are only
  available on AxisAttribute.

  The value past in \a axis is not guaranteed based on what is used in
  a query. QtXmlPatterns may call this function arbitrarily with any
  value for \a axis. This is because QtXmlPatterns may rewrite queries
  to be more efficient, using axes in different ways from the original
  query.

  QAbstractXmlNodeModel::Axis has a good overview of the axes and what
  they select.

  The caller guarantees that \a ni is not \c null and that it belongs
  to this QAbstractXmlNodeModel instance.

  Implementing iterate() can involve significant work, since it
  requires different iterators for all the axes used. In the worst
  case, it could require writing as many QAbstractXmlForwardIterator
  subclasses as there are axes, but the number can often be reduced
  with clever use of lists and template classes. It is better to use
  or subclass QSimpleXmlNodeModel, which makes it easier to write the
  node navigation code without loss of efficiency or flexibility.

  \sa QSimpleXmlNodeModel
  \sa QXmlNodeModelIndex::Axis
  \sa {http://www.w3.org/TR/xquery/#axes}{XQuery 1.0: An XML Query Language, 3.2.1.1 Axes}
  \sa {http://www.w3.org/TR/xpath-datamodel/}{W3CXQuery 1.0 and XPath 2.0 Data Model (XDM)}
 */
QExplicitlySharedDataPointer<QAbstractXmlForwardIterator<QXmlNodeModelIndex> >
QAbstractXmlNodeModel::iterate(const QXmlNodeModelIndex &ni,
                               QXmlNodeModelIndex::Axis axis) const
{
    /* Returns iterators that track state and calls nextFromSimpleAxis()
     * iteratively. Typically, when sub-classing QSimpleXmlNodeModel,
     * you don't reimplement this function, but instead implement
     * nextFromSimpleAxis(). */

    switch(axis)
    {
        case QXmlNodeModelIndex::AxisSelf:
            return makeSingletonIterator(ni);
        case QXmlNodeModelIndex::AxisParent:
        {
            if(kind(ni) == QXmlNodeModelIndex::Document)
                return makeEmptyIterator<QXmlNodeModelIndex>();
            else
                return makeSingletonIterator(nextFromSimpleAxis(Parent, ni));
        }
        case QXmlNodeModelIndex::AxisNamespace:
            return makeEmptyIterator<QXmlNodeModelIndex>();
        case QXmlNodeModelIndex::AxisAncestor:
        {
            QList<QXmlNodeModelIndex> ancestors;
            QXmlNodeModelIndex ancestor = nextFromSimpleAxis(Parent, ni);

            while(!ancestor.isNull())
            {
                ancestors.append(ancestor);
                ancestor = nextFromSimpleAxis(Parent, ancestor);
            }

            return makeListIterator(ancestors);
        }
        case QXmlNodeModelIndex::AxisAncestorOrSelf:
        {
            QList<QXmlNodeModelIndex> ancestors;
            ancestors.append(ni);
            QXmlNodeModelIndex ancestor = nextFromSimpleAxis(Parent, ni);

            while(!ancestor.isNull())
            {
                ancestors.append(ancestor);
                ancestor = nextFromSimpleAxis(Parent, ancestor);
            }

            return makeListIterator(ancestors);
        }
        case QXmlNodeModelIndex::AxisPrecedingSibling:
        {
            QList<QXmlNodeModelIndex> preceding;
            QXmlNodeModelIndex sibling = nextFromSimpleAxis(PreviousSibling, ni);

            while(!sibling.isNull())
            {
                preceding.append(sibling);
                sibling = nextFromSimpleAxis(PreviousSibling, sibling);
            }

            return makeListIterator(preceding);
        }
        case QXmlNodeModelIndex::AxisFollowingSibling:
        {
            QList<QXmlNodeModelIndex> preceding;
            QXmlNodeModelIndex sibling = nextFromSimpleAxis(NextSibling, ni);

            while(!sibling.isNull())
            {
                preceding.append(sibling);
                sibling = nextFromSimpleAxis(NextSibling, sibling);
            }

            return makeListIterator(preceding);
        }
        case QXmlNodeModelIndex::AxisChildOrTop:
        {
            if(nextFromSimpleAxis(Parent, ni).isNull())
            {
                switch(kind(ni))
                {
                    case QXmlNodeModelIndex::Comment:
                    /* Fallthrough. */
                    case QXmlNodeModelIndex::ProcessingInstruction:
                    /* Fallthrough. */
                    case QXmlNodeModelIndex::Element:
                    /* Fallthrough. */
                    case QXmlNodeModelIndex::Text:
                        return makeSingletonIterator(ni);
                    case QXmlNodeModelIndex::Attribute:
                    /* Fallthrough. */
                    case QXmlNodeModelIndex::Document:
                    /* Fallthrough. */
                    case QXmlNodeModelIndex::Namespace:
                        /* Do nothing. */;
                }
            }

            /* Else, fallthrough to AxisChild. */
        }
        case QXmlNodeModelIndex::AxisChild:
        {
            QList<QXmlNodeModelIndex> children;
            QXmlNodeModelIndex child = nextFromSimpleAxis(FirstChild, ni);

            while(!child.isNull())
            {
                children.append(child);
                child = nextFromSimpleAxis(NextSibling, child);
            }

            return makeListIterator(children);
        }
        case QXmlNodeModelIndex::AxisDescendant:
        {