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/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Nokia Corporation (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 http://qt.nokia.com/contact.
** $QT_END_LICENSE$
**
****************************************************************************/
//
// 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_CastingPlatform_H
#define Patternist_CastingPlatform_H
#include "qatomiccaster_p.h"
#include "qqnamevalue_p.h"
#include "qatomicstring_p.h"
#include "qvalidationerror_p.h"
#include "qatomiccasterlocator_p.h"
#include "qatomictype_p.h"
#include "qbuiltintypes_p.h"
#include "qcommonsequencetypes_p.h"
#include "qschematypefactory_p.h"
#include "qpatternistlocale_p.h"
QT_BEGIN_HEADER
QT_BEGIN_NAMESPACE
namespace QPatternist
{
/**
* @short Provides casting functionality for classes, such as CastAs or NumberFN, which
* needs to perform casting.
*
* Classes which need to perform casting can simply from this class and gain
* access to casting functinality wrapped in a convenient way. At the center of this
* class is the cast() function, which is used at runtime to perform the actual cast.
*
* The actual circumstances where casting is used, such as in the 'castable as'
* expression or the <tt>fn:number()</tt> function, often have other things to handle as well,
* error handling and cardinality checks for example. This class handles only casting
* and leaves the other case-specific details to the sub-class such that this class only
* do one thing well.
*
* This template class takes two parameters:
* - TSubClass This should be the class inheriting from CastingPlatform.
* - issueError if true, errors are issued via ReportContext, otherwise
* ValidationError instances are returned appropriately.
*
* The class inheriting CastingPlatform must implement the following function:
* @code
* ItemType::Ptr targetType() const
* @endcode
*
* that returns the type that should be cast to. The type must be an AtomicType.
* Typically, it is appropriate to declare this function @c inline.
*
* A sub-class calls prepareCasting() at compile time(such that CastingPlatform can attempt
* to lookup the proper AtomicCaster) and then it simply uses the cast() function at runtime. The
* function targetType() must be implemented such that CastingPlatform knows
* what type it shall cast to.
*
* @author Frans Englich <fenglich@trolltech.com>
* @ingroup Patternist_expressions
*/
template<typename TSubClass, const bool issueError>
class CastingPlatform
{
protected:
/**
* @note issueCastError() depends on the default value.
*/
inline CastingPlatform(const ReportContext::ErrorCode code = ReportContext::FORG0001) : m_errorCode(code)
{
}
/**
* Attempts to cast @p sourceValue to targetType(), and returns
* the created value. Remember that prepareCasting() should have been
* called at compile time, otherwise this function will be slow.
*
* Error reporting is done in two ways. If a cast fails because
* of an error in lexical representation a ValidationError is returned.
* If the cause of failure is that the casting combination is invalid(such as
* when attempting to cast @c xs:date to @c xs:integer), a ValidationError
* is returned if @c false was passed in the template instantiation,
* an error is issued via @p context.
*
* @param sourceValue the value to cast. Must be non @c null.
* @param context the usual ReportContext, used for error reporting.
* @returns the new value which was the result of the cast. If the
* cast failed, an ValidationError is returned.
*/
Item cast(const Item &sourceValue,
const ReportContext::Ptr &context) const;
/**
* This function should be called at compiled time, it attempts to determine
* what AtomicCaster that should be used when casting from @p sourceType to
* targetType(). If that is not possible, because the @p sourceType is
* @c xs:anyAtomicType for instance, the AtomicCaster lookup will done at
* runtime on a case-per-case basis.
*
* @returns @c true if the requested casting combination is valid or might be valid.
* If it is guranteed to be invalid, @c false is returned.
*/
bool prepareCasting(const ReportContext::Ptr &context,
const ItemType::Ptr &sourceType);
/**
* Checks that the targetType() is a valid target type for <tt>castable as</tt>
* and <tt>cast as</tt>. For example, that it is not abstract. If the type is
* invalid, an error is raised via the @p context. Note that it is assumed the type
* is atomic.
*/
void checkTargetType(const ReportContext::Ptr &context) const;
private:
inline Item castWithCaster(const Item &sourceValue,
const AtomicCaster::Ptr &caster,
const ReportContext::Ptr &context) const;
/**
* Locates the caster for casting values of type @p sourceType to targetType(), if
* possible.
*
* @p castImpossible is not initialized. Initialize it to @c false.
*/
AtomicCaster::Ptr locateCaster(const ItemType::Ptr &sourceType,
const ReportContext::Ptr &context,
bool &castImpossible) const;
inline ItemType::Ptr targetType() const
{
Q_ASSERT(static_cast<const TSubClass *>(this)->targetType());
return static_cast<const TSubClass *>(this)->targetType();
}
void issueCastError(const Item &validationError,
const Item &sourceValue,
const ReportContext::Ptr &context) const;
Q_DISABLE_COPY(CastingPlatform)
AtomicCaster::Ptr m_caster;
const ReportContext::ErrorCode m_errorCode;
};
#include "qcastingplatform.cpp"
}
QT_END_NAMESPACE
QT_END_HEADER
#endif
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