source: trunk/src/xmlpatterns/api/qabstractxmlnodemodel.cpp@ 168

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#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{Thread Support in Qt#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()
{
    delete d_ptr;
}

/*!
  \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.