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# filetree.cpp Example File
xmlpatterns/filetree/filetree.cpp

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     #include <QtCore/QUrl>
     #include <QtCore/QVariant>
     #include <QtXmlPatterns/QXmlNamePool>
     #include "filetree.h"

     /*
     The model has two types of nodes: elements & attributes.

         <directory name="">
             <file name="">
             </file>
         </directory>

       In QXmlNodeModelIndex we store two values. QXmlNodeIndex::data()
       is treated as a signed int, and it is an index into m_fileInfos
       unless it is -1, in which case it has no meaning and the value
       of QXmlNodeModelIndex::additionalData() is a Type name instead.
      */

     /*!
       The constructor passes \a pool to the base class, then loads an
       internal vector with an instance of QXmlName for each of the
       strings "file", "directory", "fileName", "filePath", "size",
       "mimeType", and "suffix".
      */
     FileTree::FileTree(const QXmlNamePool& pool)
       : QSimpleXmlNodeModel(pool),
         m_filterAllowAll(QDir::AllEntries |
                          QDir::AllDirs |
                          QDir::NoDotAndDotDot |
                          QDir::Hidden),
         m_sortFlags(QDir::Name)
     {
         QXmlNamePool np = namePool();
         m_names.resize(7);
         m_names[File]               = QXmlName(np, QLatin1String("file"));
         m_names[Directory]          = QXmlName(np, QLatin1String("directory"));
         m_names[AttributeFileName]  = QXmlName(np, QLatin1String("fileName"));
         m_names[AttributeFilePath]  = QXmlName(np, QLatin1String("filePath"));
         m_names[AttributeSize]      = QXmlName(np, QLatin1String("size"));
         m_names[AttributeMIMEType]  = QXmlName(np, QLatin1String("mimeType"));
         m_names[AttributeSuffix]    = QXmlName(np, QLatin1String("suffix"));
     }

     /*!
       Returns the QXmlNodeModelIndex for the model node representing
       the directory \a dirName.

       It calls QDir::cleanPath(), because an instance of QFileInfo
       constructed for a path ending in '/' will return the empty string in
       fileName(), instead of the directory name.
     */
     QXmlNodeModelIndex FileTree::nodeFor(const QString& dirName) const
     {
         QFileInfo dirInfo(QDir::cleanPath(dirName));
         Q_ASSERT(dirInfo.exists());
         return toNodeIndex(dirInfo);
     }

     /*!
       Since the value will always be in m_fileInfos, it is safe for
       us to return a const reference to it.
      */
     const QFileInfo&
     FileTree::toFileInfo(const QXmlNodeModelIndex &nodeIndex) const
     {
         return m_fileInfos.at(nodeIndex.data());
     }

     /*!
       Returns the model node index for the node specified by the
       QFileInfo and node Type.
      */
     QXmlNodeModelIndex
     FileTree::toNodeIndex(const QFileInfo &fileInfo, Type attributeName) const
     {
         const int indexOf = m_fileInfos.indexOf(fileInfo);

         if (indexOf == -1) {
             m_fileInfos.append(fileInfo);
             return createIndex(m_fileInfos.count()-1, attributeName);
         }
         else
             return createIndex(indexOf, attributeName);
     }

     /*!
       Returns the model node index for the node specified by the
       QFileInfo, which must be a  Type::File or Type::Directory.
      */
     QXmlNodeModelIndex FileTree::toNodeIndex(const QFileInfo &fileInfo) const
     {
         return toNodeIndex(fileInfo, fileInfo.isDir() ? Directory : File);
     }

     /*!
       This private helper function is only called by nextFromSimpleAxis().
       It is called whenever nextFromSimpleAxis() is called with an axis
       parameter of either \c{PreviousSibling} or \c{NextSibling}.
      */
     QXmlNodeModelIndex FileTree::nextSibling(const QXmlNodeModelIndex &nodeIndex,
                                              const QFileInfo &fileInfo,
                                              qint8 offset) const
     {
         Q_ASSERT(offset == -1 || offset == 1);

         // Get the context node's parent.
         const QXmlNodeModelIndex parent(nextFromSimpleAxis(Parent, nodeIndex));

         if (parent.isNull())
             return QXmlNodeModelIndex();

         // Get the parent's child list.
         const QFileInfo parentFI(toFileInfo(parent));
         Q_ASSERT(Type(parent.additionalData()) == Directory);
         const QFileInfoList siblings(QDir(parentFI.absoluteFilePath()).entryInfoList(QStringList(),
                                                                                      m_filterAllowAll,
                                                                                      m_sortFlags));
         Q_ASSERT_X(!siblings.isEmpty(), Q_FUNC_INFO, "Can't happen! We started at a child.");

         // Find the index of the child where we started.
         const int indexOfMe = siblings.indexOf(fileInfo);

         // Apply the offset.
         const int siblingIndex = indexOfMe + offset;
         if (siblingIndex < 0 || siblingIndex > siblings.count() - 1)
             return QXmlNodeModelIndex();
         else
             return toNodeIndex(siblings.at(siblingIndex));
     }

     /*!
       This function is called by the QtXmlPatterns query engine when it
       wants to move to the next node in the model. It moves along an \a
       axis, \e from the node specified by \a nodeIndex.

       This function is usually the one that requires the most design and
       implementation work, because the implementation depends on the
       perhaps unique structure of your non-XML data.

       There are \l {QAbstractXmlNodeModel::SimpleAxis} {four values} for
       \a axis that the implementation must handle, but there are really
       only two axes, i.e., vertical and horizontal. Two of the four values
       specify direction on the vertical axis (\c{Parent} and
       \c{FirstChild}), and the other two values specify direction on the
       horizontal axis (\c{PreviousSibling} and \c{NextSibling}).

       The typical implementation will be a \c switch statement with
       a case for each of the four \a axis values.
      */
     QXmlNodeModelIndex
     FileTree::nextFromSimpleAxis(SimpleAxis axis, const QXmlNodeModelIndex &nodeIndex) const
     {
         const QFileInfo fi(toFileInfo(nodeIndex));
         const Type type = Type(nodeIndex.additionalData());

         if (type != File && type != Directory) {
             Q_ASSERT_X(axis == Parent, Q_FUNC_INFO, "An attribute only has a parent!");
             return toNodeIndex(fi, Directory);
         }

         switch (axis) {
             case Parent:
                 return toNodeIndex(QFileInfo(fi.path()), Directory);

             case FirstChild:
             {
                 if (type == File) // A file has no children.
                     return QXmlNodeModelIndex();
                 else {
                     Q_ASSERT(type == Directory);
                     Q_ASSERT_X(fi.isDir(), Q_FUNC_INFO, "It isn't really a directory!");
                     const QDir dir(fi.absoluteFilePath());
                     Q_ASSERT(dir.exists());

                     const QFileInfoList children(dir.entryInfoList(QStringList(),
                                                                    m_filterAllowAll,
                                                                    m_sortFlags));
                     if (children.isEmpty())
                         return QXmlNodeModelIndex();
                     const QFileInfo firstChild(children.first());
                     return toNodeIndex(firstChild);
                 }
             }

             case PreviousSibling:
                 return nextSibling(nodeIndex, fi, -1);

             case NextSibling:
                 return nextSibling(nodeIndex, fi, 1);
         }

         Q_ASSERT_X(false, Q_FUNC_INFO, "Don't ever get here!");
         return QXmlNodeModelIndex();
     }

     /*!
       No matter what part of the file system we model (the whole file
       tree or a subtree), \a node will always have \c{file:///} as
       the document URI.
      */
     QUrl FileTree::documentUri(const QXmlNodeModelIndex &node) const
     {
         Q_UNUSED(node);
         return QUrl("file:///");
     }

     /*!
       This function returns QXmlNodeModelIndex::Element if \a node
       is a directory or a file, and QXmlNodeModelIndex::Attribute
       otherwise.
      */
     QXmlNodeModelIndex::NodeKind
     FileTree::kind(const QXmlNodeModelIndex &node) const
     {
         switch (Type(node.additionalData())) {
             case Directory:
             case File:
                 return QXmlNodeModelIndex::Element;
             default:
                 return QXmlNodeModelIndex::Attribute;
         }
     }

     /*!
       No order is defined for this example, so we always return
       QXmlNodeModelIndex::Precedes, just to keep everyone happy.
      */
     QXmlNodeModelIndex::DocumentOrder
     FileTree::compareOrder(const QXmlNodeModelIndex&,
                            const QXmlNodeModelIndex&) const
     {
         return QXmlNodeModelIndex::Precedes;
     }

     /*!
       Returns the name of \a node. The caller guarantees that \a node is
       not null and that it is contained in this node model.
      */
     QXmlName FileTree::name(const QXmlNodeModelIndex &node) const
     {
         return m_names.at(node.additionalData());
     }

     /*!
       Always returns the QXmlNodeModelIndex for the root of the
       file system, i.e. "/".
      */
     QXmlNodeModelIndex FileTree::root(const QXmlNodeModelIndex &node) const
     {
         Q_UNUSED(node);
         return toNodeIndex(QFileInfo(QLatin1String("/")));
     }

     /*!
       Returns the typed value for \a node, which must be either an
       attribute or an element. The QVariant returned represents the atomic
       value of an attribute or the atomic value contained in an element.

       If the QVariant is returned as a default constructed variant,
       it means that \a node has no typed value.
      */
     QVariant FileTree::typedValue(const QXmlNodeModelIndex &node) const
     {
         const QFileInfo &fi = toFileInfo(node);

         switch (Type(node.additionalData())) {
             case Directory:
                 // deliberate fall through.
             case File:
                 return QString();
             case AttributeFileName:
                 return fi.fileName();
             case AttributeFilePath:
                 return fi.filePath();
             case AttributeSize:
                 return fi.size();
             case AttributeMIMEType:
                 {
                     /* We don't have any MIME detection code currently, so return
                      * the most generic one. */
                     return QLatin1String("application/octet-stream");
                 }
             case AttributeSuffix:
                 return fi.suffix();
         }

         Q_ASSERT_X(false, Q_FUNC_INFO, "This line should never be reached.");
         return QString();
     }

     /*!
       Returns the attributes of \a element. The caller guarantees
       that \a element is an element in this node model.
      */
     QVector<QXmlNodeModelIndex>
     FileTree::attributes(const QXmlNodeModelIndex &element) const
     {
         QVector<QXmlNodeModelIndex> result;

         /* Both elements has this attribute. */
         const QFileInfo &forElement = toFileInfo(element);
         result.append(toNodeIndex(forElement, AttributeFilePath));
         result.append(toNodeIndex(forElement, AttributeFileName));

         if (Type(element.additionalData() == File)) {
             result.append(toNodeIndex(forElement, AttributeSize));
             result.append(toNodeIndex(forElement, AttributeSuffix));
             //result.append(toNodeIndex(forElement, AttributeMIMEType));
         }
         else {
             Q_ASSERT(element.additionalData() == Directory);
         }

         return result;
     }