1 /**************************************************************************** 2 ** 3 ** Copyright (C) 2016 The Qt Company Ltd. 4 ** Contact: https://www.qt.io/licensing/ 5 ** 6 ** This file is part of the QtXmlPatterns module of the Qt Toolkit. 7 ** 8 ** $QT_BEGIN_LICENSE:LGPL$ 9 ** Commercial License Usage 10 ** Licensees holding valid commercial Qt licenses may use this file in 11 ** accordance with the commercial license agreement provided with the 12 ** Software or, alternatively, in accordance with the terms contained in 13 ** a written agreement between you and The Qt Company. For licensing terms 14 ** and conditions see https://www.qt.io/terms-conditions. For further 15 ** information use the contact form at https://www.qt.io/contact-us. 16 ** 17 ** GNU Lesser General Public License Usage 18 ** Alternatively, this file may be used under the terms of the GNU Lesser 19 ** General Public License version 3 as published by the Free Software 20 ** Foundation and appearing in the file LICENSE.LGPL3 included in the 21 ** packaging of this file. Please review the following information to 22 ** ensure the GNU Lesser General Public License version 3 requirements 23 ** will be met: https://www.gnu.org/licenses/lgpl-3.0.html. 24 ** 25 ** GNU General Public License Usage 26 ** Alternatively, this file may be used under the terms of the GNU 27 ** General Public License version 2.0 or (at your option) the GNU General 28 ** Public license version 3 or any later version approved by the KDE Free 29 ** Qt Foundation. The licenses are as published by the Free Software 30 ** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3 31 ** included in the packaging of this file. Please review the following 32 ** information to ensure the GNU General Public License requirements will 33 ** be met: https://www.gnu.org/licenses/gpl-2.0.html and 34 ** https://www.gnu.org/licenses/gpl-3.0.html. 35 ** 36 ** $QT_END_LICENSE$ 37 ** 38 ****************************************************************************/ 39 40 // 41 // W A R N I N G 42 // ------------- 43 // 44 // This file is not part of the Qt API. It exists purely as an 45 // implementation detail. This header file may change from version to 46 // version without notice, or even be removed. 47 // 48 // We mean it. 49 50 #ifndef Patternist_EvaluationCache_H 51 #define Patternist_EvaluationCache_H 52 53 #include <private/qcachingiterator_p.h> 54 #include <private/qcommonsequencetypes_p.h> 55 #include <private/qnodebuilder_p.h> 56 #include <private/qoperandsiterator_p.h> 57 #include <private/qsinglecontainer_p.h> 58 #include <private/qvariabledeclaration_p.h> 59 60 QT_BEGIN_NAMESPACE 61 62 namespace QPatternist 63 { 64 /** 65 * @short Evaluates to the same result as its operand, but ensures the 66 * operand is evaluated once even if this Expression is evaluated several 67 * times. 68 * 69 * EvaluationCache does this in a pipelined way, by delivering items from 70 * its cache, which is stored in the DynamicContext. If the cache has less 71 * items than what the caller requests, EvaluationCache continues to 72 * deliver but this time from the source, which it also populates into the 73 * cache. 74 * 75 * EvaluationCache is used as an optimization in order to avoid running 76 * expensive code paths multiple times, but also is sometimes a necessity: 77 * for instance, when objects must be unique, such as potentially in the 78 * case of node identity. 79 * 80 * EvaluationCache is in particular used for variables, whose sole purpose 81 * is to store it once(at least conceptually) and then use it in multiple 82 * places. 83 * 84 * In some cases an EvaluationCache isn't necessary. For instance, when a 85 * variable is only referenced once. In those cases EvaluationCache removes 86 * itself as an optimization; implemented in compress(). 87 * 88 * @author Frans Englich <frans.englich@nokia.com> 89 * @ingroup Patternist_expressions 90 */ 91 template<bool IsForGlobal> 92 class EvaluationCache : public SingleContainer 93 { 94 public: 95 EvaluationCache(const Expression::Ptr &operand, 96 const VariableDeclaration::Ptr &varDecl, 97 const VariableSlotID slot); 98 99 virtual Item evaluateSingleton(const DynamicContext::Ptr &context) const; 100 virtual Item::Iterator::Ptr evaluateSequence(const DynamicContext::Ptr &context) const; 101 virtual Expression::Ptr compress(const StaticContext::Ptr &context); 102 103 virtual SequenceType::Ptr staticType() const; 104 105 /** 106 * The first operand must be exactly one @c xs:string. 107 */ 108 virtual SequenceType::List expectedOperandTypes() const; 109 110 virtual ExpressionVisitorResult::Ptr accept(const ExpressionVisitor::Ptr &visitor) const; 111 virtual Properties properties() const; 112 virtual Expression::Ptr typeCheck(const StaticContext::Ptr &context, 113 const SequenceType::Ptr &reqType); 114 virtual const SourceLocationReflection *actualReflection() const; 115 slot()116 inline VariableSlotID slot() const 117 { 118 return m_varSlot; 119 } 120 121 private: 122 static DynamicContext::Ptr topFocusContext(const DynamicContext::Ptr &context); 123 const VariableDeclaration::Ptr m_declaration; 124 /** 125 * This variable must not be called m_slot. If it so, a compiler bug on 126 * HP-UX-aCC-64 is triggered in the constructor initializor. See the 127 * preprocessor output. 128 * 129 * Note that this is the cache slot, and is disjoint to any variable's 130 * regular slot. 131 */ 132 const VariableSlotID m_varSlot; 133 }; 134 135 #include "qevaluationcache_tpl_p.h" 136 } 137 138 QT_END_NAMESPACE 139 140 #endif 141