1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
|
/****************************************************************************
**
** 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 Technology Preview License Agreement accompanying
** this package.
**
** 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 1.1, included in the file LGPL_EXCEPTION.txt in this
** package.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@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 <frans.englich@nokia.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
|
