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Diffstat (limited to 'src/xmlpatterns/expr/qevaluationcache_p.h')
| -rw-r--r-- | src/xmlpatterns/expr/qevaluationcache_p.h | 146 |
1 files changed, 146 insertions, 0 deletions
diff --git a/src/xmlpatterns/expr/qevaluationcache_p.h b/src/xmlpatterns/expr/qevaluationcache_p.h new file mode 100644 index 0000000..7daed76 --- /dev/null +++ b/src/xmlpatterns/expr/qevaluationcache_p.h @@ -0,0 +1,146 @@ +/**************************************************************************** +** +** 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_EvaluationCache_H +#define Patternist_EvaluationCache_H + +#include "qcachingiterator_p.h" +#include "qcommonsequencetypes_p.h" +#include "qnodebuilder_p.h" +#include "qoperandsiterator_p.h" +#include "qsinglecontainer_p.h" +#include "qvariabledeclaration_p.h" + +QT_BEGIN_HEADER + +QT_BEGIN_NAMESPACE + +namespace QPatternist +{ + /** + * @short Evaluates to the same result as its operand, but ensures the + * operand is evaluated once even if this Expression is evaluated several + * times. + * + * EvaluationCache does this in a pipelined way, by delivering items from + * its cache, which is stored in the DynamicContext. If the cache has less + * items than what the caller requests, EvaluationCache continues to + * deliver but this time from the source, which it also populates into the + * cache. + * + * EvaluationCache is used as an optimization in order to avoid running + * expensive code paths multiple times, but also is sometimes a necessity: + * for instance, when objects must be unique, such as potentially in the + * case of node identity. + * + * EvaluationCache is in particular used for variables, whose sole purpose + * is to store it once(at least conceptually) and then use it in multiple + * places. + * + * In some cases an EvaluationCache isn't necessary. For instance, when a + * variable is only referenced once. In those cases EvaluationCache removes + * itself as an optimization; implemented in compress(). + * + * @author Frans Englich <fenglich@trolltech.com> + * @ingroup Patternist_expressions + */ + template<bool IsForGlobal> + class EvaluationCache : public SingleContainer + { + public: + EvaluationCache(const Expression::Ptr &operand, + const VariableDeclaration::Ptr &varDecl, + const VariableSlotID slot); + + virtual Item evaluateSingleton(const DynamicContext::Ptr &context) const; + virtual Item::Iterator::Ptr evaluateSequence(const DynamicContext::Ptr &context) const; + virtual Expression::Ptr compress(const StaticContext::Ptr &context); + + virtual SequenceType::Ptr staticType() const; + + /** + * The first operand must be exactly one @c xs:string. + */ + virtual SequenceType::List expectedOperandTypes() const; + + virtual ExpressionVisitorResult::Ptr accept(const ExpressionVisitor::Ptr &visitor) const; + virtual Properties properties() const; + virtual Expression::Ptr typeCheck(const StaticContext::Ptr &context, + const SequenceType::Ptr &reqType); + virtual const SourceLocationReflection *actualReflection() const; + + inline VariableSlotID slot() const + { + return m_varSlot; + } + + private: + static DynamicContext::Ptr topFocusContext(const DynamicContext::Ptr &context); + const VariableDeclaration::Ptr m_declaration; + /** + * This variable must not be called m_slot. If it so, a compiler bug on + * HP-UX-aCC-64 is triggered in the constructor initializor. See the + * preprocessor output. + * + * Note that this is the cache slot, and is disjoint to any variable's + * regular slot. + */ + const VariableSlotID m_varSlot; + }; + +#include "qevaluationcache.cpp" +} + +QT_END_NAMESPACE + +QT_END_HEADER + +#endif |