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/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information (qt-info@nokia.com)
**
** This file is part of the QtXmlPatterns module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the either Technology Preview License Agreement or the
** Beta Release License Agreement.
**
** 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 1.0, 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 are unsure which license is appropriate for your use, please
** contact the sales department at qt-sales@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/
//
// W A R N I N G
// -------------
//
// This file is not part of the Qt API. It exists purely as an
// implementation detail. This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
#ifndef Patternist_ExternalVariableLoader_H
#define Patternist_ExternalVariableLoader_H
#include "qitem_p.h"
#include "qsequencetype_p.h"
#include "qxmlname.h"
QT_BEGIN_HEADER
QT_BEGIN_NAMESPACE
namespace QPatternist
{
class DynamicContext;
/**
* @short Responsible for loading and declaring available external variables.
*
* An external variable in XQuery is a global variable that has been declared to receive
* its value from the XQuery implementation, as opposed to an initializing expression. Here
* is an example of a query with an external variable declaration, followed by a ordinary
* global variable:
*
* <tt> declare variable $theName external;
* declare variable $theName := "the value";
* "And here's the query body(a string literal)"</tt>
*
* An external variable declaration can also specify a sequence type:
*
* <tt>declare variable $theName as xs:integer external;</tt>
*
* This class allows the user to supply the values to external variables. When
* an external variable declaration occur in the query,
* announceExternalVariable() is called.
*
* @ingroup Patternist_xdm
* @author Frans Englich <fenglich@trolltech.com>
*/
class Q_AUTOTEST_EXPORT ExternalVariableLoader : public QSharedData
{
public:
typedef QExplicitlySharedDataPointer<ExternalVariableLoader> Ptr;
inline ExternalVariableLoader() {}
virtual ~ExternalVariableLoader();
/**
* Called when Patternist encounters an external variable in the query. It is guaranteed
* to be called once for each external variable appearing in a query module.
*
* @param name the name of the variable. Quaranteed to never be @c null.
* @param declaredType the type that the user declared the variable to be of. Whether
* this type matches the actual value of the variable or not is irrelevant. Patternist
* will do the necessary error handling based on the sequence type that is returned from
* this function. If the user didn't declare a type, the type is <tt>item()*</tt>(zero or
* more items). Quaranteed to never be @c null.
* @returns the sequence type of the value this ExternalVariableLoader actually supplies. However,
* if the ExternalVariableLoader knows it cannot supply a variable by this name, @c null should be
* returned.
*/
virtual SequenceType::Ptr announceExternalVariable(const QXmlName name,
const SequenceType::Ptr &declaredType);
/**
* This function is called at runtime when the external variable by name @p name needs
* to be evaluated. It is not defined how many times this function will be called. It
* depends on aspects such as how the query was optimized.
*
* @param name the name of the variable. Quaranteed to never be @c null.
* @param context the DynamicContext.
* @returns the value of the variable. Remember that this value must match the
* sequence type returned from announceExternalVariable() for the same name.
*/
virtual Item::Iterator::Ptr evaluateSequence(const QXmlName name,
const QExplicitlySharedDataPointer<DynamicContext> &context);
virtual Item evaluateSingleton(const QXmlName name,
const QExplicitlySharedDataPointer<DynamicContext> &context);
virtual bool evaluateEBV(const QXmlName name,
const QExplicitlySharedDataPointer<DynamicContext> &context);
};
}
QT_END_NAMESPACE
QT_END_HEADER
#endif
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