source: trunk/src/xmlpatterns/api/qxmlserializer.cpp@ 635

/****************************************************************************
**
** Copyright (C) 2009 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 "qdynamiccontext_p.h"
#include "qpatternistlocale_p.h"
#include "qitem_p.h"
#include "qxmlquery_p.h"
#include "qxmlserializer_p.h"
#include "qxmlserializer.h"

QT_BEGIN_NAMESPACE

using namespace QPatternist;

QXmlSerializerPrivate::QXmlSerializerPrivate(const QXmlQuery &query,
                                             QIODevice *outputDevice)
    : isPreviousAtomic(false),
      state(QXmlSerializer::BeforeDocumentElement),
      np(query.namePool().d),
      device(outputDevice),
      codec(QTextCodec::codecForMib(106)), /* UTF-8 */
      query(query)
{
    hasClosedElement.reserve(EstimatedTreeDepth);
    namespaces.reserve(EstimatedTreeDepth);
    nameCache.reserve(EstimatedNameCount);

    hasClosedElement.push(qMakePair(QXmlName(), true));

    /*
      We push the empty namespace such that first of all
      namespaceBinding() won't assert on an empty QStack,
      and such that the empty namespace is in-scope and
      that the code doesn't attempt to declare it.

      We push the XML namespace. Although we won't receive
      declarations for it, we may output attributes by that
      name.
    */
    QVector<QXmlName> defNss;
    defNss.resize(2);
    defNss[0] = QXmlName(StandardNamespaces::empty,
                         StandardLocalNames::empty,
                         StandardPrefixes::empty);
    defNss[1] = QXmlName(StandardNamespaces::xml,
                         StandardLocalNames::empty,
                         StandardPrefixes::xml);

    namespaces.push(defNss);

    /* If we don't set this flag, QTextCodec will generate a BOM. */
    converterState.flags = QTextCodec::IgnoreHeader;
}

/*!
  \class QXmlSerializer
  \brief The QXmlSerializer class is an implementation of QAbstractXmlReceiver for transforming XQuery output into unformatted XML.

  \reentrant
  \since 4.4
  \ingroup xml-tools

  QXmlSerializer translates an \l {XQuery Sequence} {XQuery sequence}, usually
  the output of an QXmlQuery, into XML. Consider the example:

  \snippet doc/src/snippets/code/src_xmlpatterns_api_qxmlserializer.cpp 0

  First it constructs a \l {QXmlQuery} {query} that gets the
  first paragraph from document \c index.html. Then it constructs
  an instance of this class with the \l {QXmlQuery} {query} and
  \l {QIODevice} {myOutputDevice}. Finally, it
  \l {QXmlQuery::evaluateTo()} {evaluates} the
  \l {QXmlQuery} {query}, producing an ordered sequence of calls
  to the serializer's callback functions. The sequence of callbacks
  transforms the query output to XML and writes it to
  \l {QIODevice} {myOutputDevice}.

  QXmlSerializer will:

  \list
  \o Declare namespaces when needed,

  \o Use appropriate escaping, when characters can't be
  represented in the XML,

  \o Handle line endings appropriately,

  \o Report errors, when it can't serialize the content, e.g.,
  when asked to serialize an attribute that is a top-level node,
  or when more than one top-level element is encountered.

  \endlist

  If an error occurs during serialization, result is undefined
  unless the serializer is driven through a call to
  QXmlQuery::evaluateTo().

  If the generated XML should be indented and formatted for reading,
  use QXmlFormatter.

  \sa {http://www.w3.org/TR/xslt-xquery-serialization/}{XSLT 2.0 and XQuery 1.0 Serialization}

  \sa QXmlFormatter
 */

/*!
  Constructs a serializer that uses the name pool and message
  handler in \a query, and writes the output to \a outputDevice.

  \a outputDevice must be a valid, non-null device that is open in
  write mode, otherwise behavior is undefined.

  \a outputDevice must not be opened with QIODevice::Text because it
  will cause the output to be incorrect. This class will ensure line
  endings are serialized as according with the XML specification.
  QXmlSerializer does not take ownership of \a outputDevice.
 */
QXmlSerializer::QXmlSerializer(const QXmlQuery &query,
                               QIODevice *outputDevice) : QAbstractXmlReceiver(new QXmlSerializerPrivate(query, outputDevice))
{
    if(!outputDevice)
    {
        qWarning("outputDevice cannot be null.");
        return;
    }

    if(!outputDevice->isWritable())
    {
        qWarning("outputDevice must be opened in write mode.");
        return;
    }
}

/*!
  \internal
 */
QXmlSerializer::QXmlSerializer(QAbstractXmlReceiverPrivate *d) : QAbstractXmlReceiver(d)
{
}

/*!
  \internal
 */
bool QXmlSerializer::atDocumentRoot() const
{
    Q_D(const QXmlSerializer);
    return d->state == BeforeDocumentElement ||
           (d->state == InsideDocumentElement && d->hasClosedElement.size() == 1);
}

/*!
  \internal
 */
void QXmlSerializer::startContent()
{
    Q_D(QXmlSerializer);
    if (!d->hasClosedElement.top().second) {
        d->write('>');
        d->hasClosedElement.top().second = true;
    }
}

/*!
  \internal
 */
void QXmlSerializer::writeEscaped(const QString &toEscape)
{
    if(toEscape.isEmpty()) /* Early exit. */
        return;

    QString result;
    result.reserve(int(toEscape.length() * 1.1));
    const int length = toEscape.length();

    for(int i = 0; i < length; ++i)
    {
        const QChar c(toEscape.at(i));

        if(c == QLatin1Char('<'))
            result += QLatin1String("&lt;");
        else if(c == QLatin1Char('>'))
            result += QLatin1String("&gt;");
        else if(c == QLatin1Char('&'))
            result += QLatin1String("&amp;");
        else
            result += toEscape.at(i);
    }

    write(result);
}

/*!
  \internal
 */
void QXmlSerializer::writeEscapedAttribute(const QString &toEscape)
{
    if(toEscape.isEmpty()) /* Early exit. */
        return;

    QString result;
    result.reserve(int(toEscape.length() * 1.1));
    const int length = toEscape.length();

    for(int i = 0; i < length; ++i)
    {
        const QChar c(toEscape.at(i));

        if(c == QLatin1Char('<'))
            result += QLatin1String("&lt;");
        else if(c == QLatin1Char('>'))
            result += QLatin1String("&gt;");
        else if(c == QLatin1Char('&'))
            result += QLatin1String("&amp;");
        else if(c == QLatin1Char('"'))
            result += QLatin1String("&quot;");
        else
            result += toEscape.at(i);
    }

    write(result);
}

/*!
  \internal
 */
void QXmlSerializer::write(const QString &content)
{
    Q_D(QXmlSerializer);
    d->device->write(d->codec->fromUnicode(content.constData(), content.length(), &d->converterState));
}

/*!
  \internal
 */
void QXmlSerializer::write(const QXmlName &name)
{
    Q_D(QXmlSerializer);
    const QByteArray &cell = d->nameCache[name.code()];

    if(cell.isNull())
    {
        QByteArray &mutableCell = d->nameCache[name.code()];

        const QString content(d->np->toLexical(name));
        mutableCell = d->codec->fromUnicode(content.constData(),
                                            content.length(),
                                            &d->converterState);
        d->device->write(mutableCell);
    }
    else
        d->device->write(cell);
}

/*!
  \internal
 */
void QXmlSerializer::write(const char *const chars)
{
    Q_D(QXmlSerializer);
    d->device->write(chars);
}

/*!
  \reimp
 */
void QXmlSerializer::startElement(const QXmlName &name)
{
    Q_D(QXmlSerializer);
    Q_ASSERT(d->device);
    Q_ASSERT(d->device->isWritable());
    Q_ASSERT(d->codec);
    Q_ASSERT(!name.isNull());

    d->namespaces.push(QVector<QXmlName>());

    if(atDocumentRoot())
    {
        if(d->state == BeforeDocumentElement)
            d->state = InsideDocumentElement;
        else if(d->state != InsideDocumentElement)
        {
            d->query.d->staticContext()->error(QtXmlPatterns::tr(
               "Element %1 can't be serialized because it appears outside "
               "the document element.").arg(formatKeyword(d->np, name)),
                                               ReportContext::SENR0001,
                                               d->query.d->expression().data());
        }
    }

    startContent();
    d->write('<');
    write(name);

    /* Ensure that the namespace URI used in the name gets outputted. */
    namespaceBinding(name);

    d->hasClosedElement.push(qMakePair(name, false));
    d->isPreviousAtomic = false;
}

/*!
  \reimp
 */
void QXmlSerializer::endElement()
{
    Q_D(QXmlSerializer);
    const QPair<QXmlName, bool> e(d->hasClosedElement.pop());
    d->namespaces.pop();

    if(e.second)
    {
        write("</");
        write(e.first);
        d->write('>');
    }
    else
        write("/>");

    d->isPreviousAtomic = false;
}

/*!
  \reimp
 */
void QXmlSerializer::attribute(const QXmlName &name,
                               const QStringRef &value)
{
    Q_D(QXmlSerializer);
    Q_ASSERT(!name.isNull());

    /* Ensure that the namespace URI used in the name gets outputted. */
    {
        /* Since attributes doesn't pick up the default namespace, a
         * namespace declaration would cause trouble if we output it. */
        if(name.prefix() != StandardPrefixes::empty)
            namespaceBinding(name);
    }

    if(atDocumentRoot())
    {
        Q_UNUSED(d);
        d->query.d->staticContext()->error(QtXmlPatterns::tr(
           "Attribute %1 can't be serialized because it appears at "
           "the top level.").arg(formatKeyword(d->np, name)),
                                           ReportContext::SENR0001,
                                           d->query.d->expression().data());
    }
    else
    {
        d->write(' ');
        write(name);
        write("=\"");
        writeEscapedAttribute(value.toString());
        d->write('"');
    }
}

/*!
  \internal
 */
bool QXmlSerializer::isBindingInScope(const QXmlName nb) const
{
    Q_D(const QXmlSerializer);
    const int levelLen = d->namespaces.size();

    if(nb.prefix() == StandardPrefixes::empty)
    {
        for(int lvl = levelLen - 1; lvl >= 0; --lvl)
        {
            const QVector<QXmlName> &scope = d->namespaces.at(lvl);
            const int vectorLen = scope.size();

            for(int s = vectorLen - 1; s >= 0; --s)
            {
                const QXmlName &nsb = scope.at(s);

                if(nsb.prefix() == StandardPrefixes::empty)
                    return nsb.namespaceURI() == nb.namespaceURI();
            }
        }
    }
    else
    {
        for(int lvl = 0; lvl < levelLen; ++lvl)
        {
            const QVector<QXmlName> &scope = d->namespaces.at(lvl);
            const int vectorLen = scope.size();

            for(int s = 0; s < vectorLen; ++s)
            {
                const QXmlName &n = scope.at(s);
                if (n.prefix() == nb.prefix() &&
                    n.namespaceURI() == nb.namespaceURI())
                    return true;
            }
        }
    }

    return false;
}

/*!
 \reimp
 */
void QXmlSerializer::namespaceBinding(const QXmlName &nb)
{
    /*
     * Writes out \a nb.
     *
     * Namespace bindings aren't looked up in a cache, because
     * we typically receive very few.
     */

    Q_D(QXmlSerializer);
    Q_ASSERT_X(!nb.isNull(), Q_FUNC_INFO,
               "It makes no sense to pass a null QXmlName.");

    Q_ASSERT_X((nb.namespaceURI() != StandardNamespaces::empty) ||
               (nb.prefix() == StandardPrefixes::empty),
               Q_FUNC_INFO,
               "Undeclarations of prefixes aren't allowed in XML 1.0 "
               "and aren't supposed to be received.");

    if(nb.namespaceURI() == QPatternist::StandardNamespaces::StopNamespaceInheritance)
        return;

    if(isBindingInScope(nb))
        return;

    d->namespaces.top().append(nb);

    if(nb.prefix() == StandardPrefixes::empty)
        write(" xmlns");
    else
    {
        write(" xmlns:");
        write(d->np->stringForPrefix(nb.prefix()));
    }

    write("=\"");
    writeEscapedAttribute(d->np->stringForNamespace(nb.namespaceURI()));
    d->write('"');
}

/*!
 \reimp
 */
void QXmlSerializer::comment(const QString &value)
{
    Q_D(QXmlSerializer);
    Q_ASSERT_X(!value.contains(QLatin1String("--")),
               Q_FUNC_INFO,
               "Invalid input; it's the caller's responsibility to ensure "
               "the input is correct.");

    startContent();
    write("<!--");
    write(value);
    write("-->");
    d->isPreviousAtomic = false;
}

/*!
 \reimp
 */
void QXmlSerializer::characters(const QStringRef &value)
{
    Q_D(QXmlSerializer);
    d->isPreviousAtomic = false;
    startContent();
    writeEscaped(value.toString());
}

/*!
 \reimp
 */
void QXmlSerializer::processingInstruction(const QXmlName &name,
                                           const QString &value)
{
    Q_D(QXmlSerializer);
    Q_ASSERT_X(!value.contains(QLatin1String("?>")),
               Q_FUNC_INFO,
               "Invalid input; it's the caller's responsibility to ensure "
               "the input is correct.");

    startContent();
    write("<?");
    write(name);
    d->write(' ');
    write(value);
    write("?>");

    d->isPreviousAtomic = false;
}

/*!
  \internal
 */
void QXmlSerializer::item(const QPatternist::Item &outputItem)
{
    Q_D(QXmlSerializer);

    if(outputItem.isAtomicValue())
    {
        if(d->isPreviousAtomic)
        {
            startContent();
            d->write(' ');
            writeEscaped(outputItem.stringValue());
        }
        else
        {
            d->isPreviousAtomic = true;
            const QString value(outputItem.stringValue());

            if(!value.isEmpty())
            {
                startContent();
                writeEscaped(value);
            }
        }
    }
    else
    {
        startContent();
        Q_ASSERT(outputItem.isNode());
        sendAsNode(outputItem);
    }
}

/*!
 \reimp
 */
void QXmlSerializer::atomicValue(const QVariant &value)
{
    Q_UNUSED(value);
}

/*!
 \reimp
 */
void QXmlSerializer::startDocument()
{
    Q_D(QXmlSerializer);
    d->isPreviousAtomic = false;
}

/*!
 \reimp
 */
void QXmlSerializer::endDocument()
{
    Q_D(QXmlSerializer);
    d->isPreviousAtomic = false;
}

/*!

  Returns a pointer to the output device. There is no corresponding
  function to \e set the output device, because the output device must
  be passed to the constructor. The serializer does not take ownership
  of its IO device.
 */
QIODevice *QXmlSerializer::outputDevice() const
{
    Q_D(const QXmlSerializer);
    return d->device;
}

/*!
  Sets the codec the serializer will use for encoding its XML output.
  The output codec is set to \a outputCodec. By default, the output
  codec is set to the one for \c UTF-8. The serializer does not take
  ownership of the codec.

  \sa codec()

 */
void QXmlSerializer::setCodec(const QTextCodec *outputCodec)
{
    Q_D(QXmlSerializer);
    d->codec = outputCodec;
}

/*!
  Returns the codec being used by the serializer for encoding its
  XML output.

  \sa setCodec()
 */
const QTextCodec *QXmlSerializer::codec() const
{
    Q_D(const QXmlSerializer);
    return d->codec;
}

/*!
 \reimp
 */
void QXmlSerializer::startOfSequence()
{
}

/*!
 \reimp
 */
void QXmlSerializer::endOfSequence()
{
    /* If this function is changed to flush or close or something like that,
     * take into consideration QXmlFormatter, especially
     * QXmlFormatter::endOfSequence().
     */
}

QT_END_NAMESPACE