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     3 ** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).

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     7 ** This file is part of the QtXmlPatterns module of the Qt Toolkit.

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    40 ****************************************************************************/

    41 

    42 #include "qcommonsequencetypes_p.h"

    43 #include "qdeduplicateiterator_p.h"

    44 #include "qnodesort_p.h"

    45 

    46 QT_BEGIN_NAMESPACE

    47 

    48 using namespace QPatternist;

    49 

    50 NodeSortExpression::NodeSortExpression(const Expression::Ptr &op) : SingleContainer(op)

    51 {

    52 }

    53 

    54 bool NodeSortExpression::lessThanUsingNodeModel(const Item &n1,

    55                                                 const Item &n2)

    56 {

    57     Q_ASSERT(n1.isNode());

    58     Q_ASSERT(n2.isNode());

    59 

    60     if(n1.asNode().model() == n2.asNode().model())

    61         return n1.asNode().compareOrder(n2.asNode()) == QXmlNodeModelIndex::Precedes;

    62     else

    63     {

    64         /* The two nodes are from different trees. The sort order is implementation

    65          * defined, but it must be stable.

    66          *

    67          * We do this by looking at the pointer difference. The value means nothing,

    68          * but it is stable, and that's what we're looking for. */

    69         return n1.asNode().model() - n2.asNode().model() < 0;

    70     }

    71 }

    72 

    73 Item::Iterator::Ptr NodeSortExpression::evaluateSequence(const DynamicContext::Ptr &context) const

    74 {

    75     Q_ASSERT_X(m_operand->staticType()->cardinality().allowsMany(), Q_FUNC_INFO,

    76                "It makes no sense to sort a single node.");

    77 

    78     Item::List nodes(m_operand->evaluateSequence(context)->toList());

    79 

    80     if(nodes.isEmpty())

    81         return CommonValues::emptyIterator;

    82     else if(nodes.first().isAtomicValue())

    83         return makeListIterator(nodes);

    84     else

    85     {

    86         qSort(nodes.begin(), nodes.end(), lessThanUsingNodeModel);

    87 

    88         return Item::Iterator::Ptr(new DeduplicateIterator(nodes));

    89     }

    90 }

    91 

    92 Expression::Ptr NodeSortExpression::wrapAround(const Expression::Ptr &operand,

    93                                                const StaticContext::Ptr &context)

    94 {

    95     Q_ASSERT(operand);

    96     Q_ASSERT(context);

    97 

    98     const Expression::Ptr sort(new NodeSortExpression(operand));

    99     context->wrapExpressionWith(operand.data(), sort);

   100     return sort;

   101 }

   102 

   103 Expression::Ptr NodeSortExpression::compress(const StaticContext::Ptr &context)

   104 {

   105     const Expression::Ptr me(SingleContainer::compress(context));

   106 

   107     /* It make no sense to sort & deduplicate a single node. */

   108     if(m_operand->staticType()->cardinality().allowsMany())

   109         return me;

   110     else

   111         return m_operand;

   112 }

   113 

   114 SequenceType::Ptr NodeSortExpression::staticType() const

   115 {

   116     return m_operand->staticType();

   117 }

   118 

   119 SequenceType::List NodeSortExpression::expectedOperandTypes() const

   120 {

   121     SequenceType::List result;

   122     result.append(CommonSequenceTypes::ZeroOrMoreItems);

   123     return result;

   124 }

   125 

   126 ExpressionVisitorResult::Ptr

   127 NodeSortExpression::accept(const ExpressionVisitor::Ptr &visitor) const

   128 {

   129     return visitor->visit(this);

   130 }

   131 

   132 Expression::Properties NodeSortExpression::properties() const

   133 {

   134     /* The reason we disable elimination is that the assert for sorting a

   135      * single node in evaluateSequence() triggers unless our compress() routine

   136      * has been run. Anyhow, it's not that we would manage to write away anyway,

   137      * since the node source in most(all?) cases prevents it.

   138      */

   139     return AffectsOrderOnly | DisableElimination;

   140 }

   141 

   142 QT_END_NAMESPACE