Long live Qt!

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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_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