source: trunk/src/xmlpatterns/api/qxmlname.cpp@ 243

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/*
 * QXmlName is conceptually identical to QPatternist::QName. The
 * difference is that the latter is elegant, powerful and fast.
 *
 * However, it is too powerful and too open and not at all designed
 * for being public. QXmlName, in contrast, is only a public marker,
 * that for instance uses a qint64 instead of qint32, such that we in
 * the future can use that, if needed.
 */

#include "qnamepool_p.h"
#include "qxmlname.h"
#include "qxmlnamepool.h"
#include "qxpathhelper_p.h"
#include "private/qxmlutils_p.h"

QT_BEGIN_NAMESPACE

/*!
  \class QXmlName
  \brief The QXmlName class represents the name of an XML node, in an efficient, namespace-aware way.
  \reentrant
  \since 4.4
  \ingroup xml-tools

  QXmlName represents the name of an XML node in a way that
  is both efficient and safe for comparing names. Normally,
  an XML node represents an XML element or attribute, but
  QXmlName can also represent the names of other kinds of
  nodes, e.g., QAbstractXmlReceiver::processingInstruction()
  and QAbstractXmlReceiver::namespaceBinding().

  The name of an XML node has three components: The \e {namespace
  URI}, the \e {local name}, and the \e {prefix}. To see what these
  refer to in XML, consider the following snippet.

  \quotefile doc/src/snippets/patternist/mobeyDick.xml

  For the element named \e book, localName() returns \e book,
  namespaceUri() returns \e http://example.com/MyDefault,
  and prefix() returns an empty string. For the element named
  \e title, localName() returns \e title, namespaceUri() returns
  \e http://purl.org/dc/elements/1.1, and prefix() returns \e dc.

  To ensure that operations with QXmlName are efficient, e.g.,
  copying names and comparing them, each instance of QXmlName is
  associated with a \l {QXmlNamePool} {name pool}, which must be
  specified at QXmlName construction time. The three components
  of the QXmlName, i.e., the namespace URI, the local name, and
  the prefix, are stored in the name pool mapped to identifiers
  so they can be shared. For this reason, the only way to create
  a valid instance of QXmlName is to use the class constructor,
  where the \l {QXmlNamePool} {name pool}, local name, namespace
  URI, and prefix must all be specified.

  Note that QXmlName's default constructor constructs a null
  instance. It is typically used for allocating unused entries
  in collections of QXmlName.

  A side effect of associating each instance of QXmlName with
  a \l {QXmlNamePool} {name pool} is that each instance of
  QXmlName is tied to the QXmlNamePool with which it was created.
  However, the QXmlName class does not keep track of the name pool,
  so all the accessor functions, e.g., namespaceUri(), prefix(),
  localName(), and toClarkName() require that the correct name
  pool be passed to them. Failure to provide the correct name
  pool to these accessor functions results in undefined behavior.

  Note that a \l {QXmlNamePool} {name pool} is \e not an XML
  namespace. One \l {QXmlNamePool} {name pool} can represent
  instances of QXmlName from different XML namespaces, and the
  instances of QXmlName from one XML namespace can be distributed
  over multiple  \l {QXmlNamePool} {name pools}.

  \target Comparing QXmlNames
  \section1 Comparing QXmlNames

  To determine what a QXmlName refers to, the \e {namespace URI}
  and the \e {local name} are used. The \e prefix is not used
  because the prefix is simply a shorthand name for use in place
  of the normally much longer namespace URI. Nor is the prefix
  used in name comparisons. For example, the following two element
  nodes represent the same element and compare equal.

  \quotefile doc/src/snippets/patternist/svgDocumentElement.xml

  \quotefile doc/src/snippets/patternist/xsvgDocumentElement.xml

  Although the second name has the prefix \e x, the two names compare
  equal as instances of QXmlName, because the prefix is not used in
  the comparison.

  A local name can never be an empty string, although the prefix and
  namespace URI can. If the prefix is not empty, the namespace URI
  cannot be empty. Local names and prefixes must be valid
  \l {http://www.w3.org/TR/REC-xml-names/#NT-NCName} {NCNames},
  e.g., \e abc.def or \e abc123.

  QXmlName represents what is sometimes called an \e {expanded QName},
  or simply a QName.

  \sa {http://www.w3.org/TR/REC-xml-names/#NT-NCName} {Namespaces in XML 1.0 (Second Edition), [4] NCName}
 */

/*!
   \enum QXmlName::Constant
   \internal
   Various constants used in the QPatternist::NamePool and QXmlName.

   Setting of the mask enums use essentially this:

   \quotefile doc/src/snippets/code/src_xmlpatterns_api_qxmlname.cpp

   The masks, such as LocalNameMask, are positive. That is, for the
   area which the name resides, the bits are set.
 */

/*!
 Constructs a QXmlName instance that inserts \a localName,
 \a namespaceURI and \a prefix into \a namePool if they aren't
 already there. The accessor functions namespaceUri(), prefix(),
 localName(), and toClarkName() must be passed the \a namePool
 used here, so the \a namePool must remain in scope while the
 accessor functions might be used. However, two instances can
 be compared with \e {==} or \e {!=} and copied without the
 \a namePool.

 The user guarantees that the string components are valid for a
 QName. In particular, the local name, and the prefix (if present),
 must be valid \l {http://www.w3.org/TR/REC-xml-names/#NT-NCName}
 {NCNames}. The function isNCName() can be used to test validity
 of these names. The namespace URI should be an absolute URI.
 QUrl::isRelative() can be used to test whether the namespace URI
 is relative or absolute. Finally, providing a prefix is not valid
 when no namespace URI is provided.

 \a namePool is not copied. Nor is the reference to it retained
 in this instance. This constructor inserts the three strings
 into \a namePool.
 */
QXmlName::QXmlName(QXmlNamePool &namePool,
                   const QString &localName,
                   const QString &namespaceURI,
                   const QString &prefix)
{
    Q_ASSERT_X(prefix.isEmpty() || QXmlUtils::isNCName(prefix), Q_FUNC_INFO,
               "The prefix is invalid, maybe the arguments were mixed up?");
    Q_ASSERT_X(QXmlUtils::isNCName(localName), Q_FUNC_INFO,
               "The local name is invalid, maybe the arguments were mixed up?");

    m_qNameCode = namePool.d->allocateQName(namespaceURI, localName, prefix).code();
}

/*!
  \typedef QXmlName::Code
  \internal

   Stores the \l {QXmlNamePool} {name pool} identifiers for
   the namespace URI, local name, and prefix.
 */

/*!
  Returns true if this QXmlName is not initialized with a
  valid combination of \e {namespace URI}, \e {local name},
  and \e {prefix}.

  A valid local name is always required. The prefix and
  namespace URI can be empty, but if the prefix is not empty,
  the namespace URI must not be empty. Local names and
  prefixes must be valid
  \l {http://www.w3.org/TR/REC-xml-names/#NT-NCName} {NCNames},
  e.g., \e abc.def or \e abc123.
 */
bool QXmlName::isNull() const
{
    return m_qNameCode == InvalidCode;
}

/*!
  Constructs an uninitialized QXmlName. To build
  a valid QXmlName, you normally use the other constructor, which
  takes a \l {QXmlNamePool} {name pool}, namespace URI, local name,
  and prefix as parameters. But you can also use this constructor
  to build a null QXmlName and then assign an existing QXmlName
  to it.

  \sa isNull()
 */
QXmlName::QXmlName() : m_qNameCode(InvalidCode)
{
}

/*!
  \fn QXmlName::QXmlName(const NamespaceCode uri,
                         const LocalNameCode ln,
                         const PrefixCode p = 0)