[2] | 1 | /****************************************************************************
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| 2 | **
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[651] | 3 | ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
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[561] | 4 | ** All rights reserved.
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| 5 | ** Contact: Nokia Corporation ([email protected])
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[2] | 6 | **
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| 7 | ** This file is part of the QtXmlPatterns module of the Qt Toolkit.
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| 8 | **
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| 9 | ** $QT_BEGIN_LICENSE:LGPL$
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| 10 | ** Commercial Usage
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| 11 | ** Licensees holding valid Qt Commercial licenses may use this file in
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| 12 | ** accordance with the Qt Commercial License Agreement provided with the
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| 13 | ** Software or, alternatively, in accordance with the terms contained in
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| 14 | ** a written agreement between you and Nokia.
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| 15 | **
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| 16 | ** GNU Lesser General Public License Usage
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| 17 | ** Alternatively, this file may be used under the terms of the GNU Lesser
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| 18 | ** General Public License version 2.1 as published by the Free Software
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| 19 | ** Foundation and appearing in the file LICENSE.LGPL included in the
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| 20 | ** packaging of this file. Please review the following information to
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| 21 | ** ensure the GNU Lesser General Public License version 2.1 requirements
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| 22 | ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
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| 23 | **
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[561] | 24 | ** In addition, as a special exception, Nokia gives you certain additional
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| 25 | ** rights. These rights are described in the Nokia Qt LGPL Exception
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| 26 | ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
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[2] | 27 | **
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| 28 | ** GNU General Public License Usage
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| 29 | ** Alternatively, this file may be used under the terms of the GNU
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| 30 | ** General Public License version 3.0 as published by the Free Software
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| 31 | ** Foundation and appearing in the file LICENSE.GPL included in the
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| 32 | ** packaging of this file. Please review the following information to
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| 33 | ** ensure the GNU General Public License version 3.0 requirements will be
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| 34 | ** met: http://www.gnu.org/copyleft/gpl.html.
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| 35 | **
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[561] | 36 | ** If you have questions regarding the use of this file, please contact
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| 37 | ** Nokia at [email protected].
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[2] | 38 | ** $QT_END_LICENSE$
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| 39 | **
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| 40 | ****************************************************************************/
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| 41 |
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| 42 | #include "qxmlresultitems.h"
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| 43 | #include "qxmlresultitems_p.h"
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| 44 | #include "qitem_p.h"
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| 45 |
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| 46 | QT_BEGIN_NAMESPACE
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| 47 |
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| 48 | /*!
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| 49 | \class QXmlResultItems
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| 50 | \brief The QXmlResultItems class iterates through the results of evaluating an XQuery in QXmlQuery.
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| 51 | \reentrant
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| 52 | \since 4.4
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| 53 | \ingroup xml-tools
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| 54 |
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| 55 | QXmlResultItems presents the evaluation of an associated query as a
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| 56 | sequence of \l{QXmlItem}{QXmlItems}. The sequence is traversed by
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| 57 | repeatedly calling next(), which actually produces the sequence by
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| 58 | lazy evaluation of the query.
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| 59 |
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| 60 | \snippet doc/src/snippets/code/src_xmlpatterns_api_qxmlresultitems.cpp 0
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| 61 |
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| 62 | An effect of letting next() produce the sequence by lazy evaluation
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| 63 | is that a query error can occur on any call to next(). If an error
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| 64 | occurs, both next() and current() will return the null QXmlItem, and
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| 65 | hasError() will return true.
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| 66 |
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| 67 | QXmlResultItems can be thought of as an "iterator" that traverses
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| 68 | the sequence of query results once, in the forward direction. Each
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| 69 | call to next() advances the iterator to the next QXmlItem in the
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| 70 | sequence and returns it, and current() always returns the QXmlItem
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| 71 | that next() returned the last time it was called.
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| 72 |
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[769] | 73 | \note When using the QXmlResultItems overload of QXmlQuery::evaluateTo()
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| 74 | to execute a query, it is advisable to create a new instance of this
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| 75 | class for each new set of results rather than reusing an old instance.
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| 76 |
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[2] | 77 | \sa QXmlItem::isNode(), QXmlItem::isAtomicValue(), QXmlNodeModelIndex
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| 78 | */
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| 79 |
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| 80 | /*!
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| 81 | Constructs an instance of QXmlResultItems.
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| 82 | */
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| 83 | QXmlResultItems::QXmlResultItems() : d_ptr(new QXmlResultItemsPrivate())
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| 84 | {
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| 85 | }
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| 86 |
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| 87 | /*!
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| 88 | Destroys this instance of QXmlResultItems.
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| 89 | */
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| 90 | QXmlResultItems::~QXmlResultItems()
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| 91 | {
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| 92 | }
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| 93 |
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| 94 | /*!
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| 95 | Returns the next result in the sequence produced by lazy evaluation
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| 96 | of the associated query. When the returned QXmlItem is null, either
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| 97 | the evaluation terminated normally without producing another result,
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| 98 | or an error occurred. Call hasError() to determine whether the null
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| 99 | item was caused by normal termination or by an error.
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| 100 |
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| 101 | Returns a null QXmlItem if there is no associated QXmlQuery.
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| 102 | */
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| 103 | QXmlItem QXmlResultItems::next()
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| 104 | {
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| 105 | Q_D(QXmlResultItems);
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| 106 | if(d->hasError)
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| 107 | return QXmlItem();
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| 108 |
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| 109 | try
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| 110 | {
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| 111 | d->current = QPatternist::Item::toPublic(d->iterator->next());
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| 112 | return d->current;
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| 113 | }
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| 114 | catch(const QPatternist::Exception)
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| 115 | {
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| 116 | d->current = QXmlItem();
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| 117 | d->hasError = true;
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| 118 | return QXmlItem();
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| 119 | }
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| 120 | }
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| 121 |
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| 122 | /*!
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| 123 | Returns the current item. The current item is the last item
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| 124 | that was produced and returned by next().
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| 125 |
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| 126 | Returns a null QXmlItem if there is no associated QXmlQuery.
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| 127 | */
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| 128 | QXmlItem QXmlResultItems::current() const
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| 129 | {
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| 130 | Q_D(const QXmlResultItems);
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| 131 |
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| 132 | if(d->hasError)
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| 133 | return QXmlItem();
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| 134 | else
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| 135 | return d->current;
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| 136 | }
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| 137 |
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| 138 | /*!
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| 139 |
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| 140 | If an error occurred during evaluation of the query, true is
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| 141 | returned.
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| 142 |
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| 143 | Returns false if query evaluation has been done.
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| 144 | */
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| 145 | bool QXmlResultItems::hasError() const
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| 146 | {
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| 147 | Q_D(const QXmlResultItems);
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| 148 | return d->hasError;
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| 149 | }
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| 150 |
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| 151 | QT_END_NAMESPACE
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| 152 |
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