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39
40 #include "qcommonsequencetypes_p.h"
41 #include "qdeduplicateiterator_p.h"
42 #include "qnodesort_p.h"
43
44 #include <algorithm>
45
46 QT_BEGIN_NAMESPACE
47
48 using namespace QPatternist;
49
NodeSortExpression(const Expression::Ptr & op)50 NodeSortExpression::NodeSortExpression(const Expression::Ptr &op) : SingleContainer(op)
51 {
52 }
53
lessThanUsingNodeModel(const Item & n1,const Item & n2)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
evaluateSequence(const DynamicContext::Ptr & context) const73 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 std::sort(nodes.begin(), nodes.end(), lessThanUsingNodeModel);
87
88 return Item::Iterator::Ptr(new DeduplicateIterator(nodes));
89 }
90 }
91
wrapAround(const Expression::Ptr & operand,const StaticContext::Ptr & context)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
compress(const StaticContext::Ptr & context)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
staticType() const114 SequenceType::Ptr NodeSortExpression::staticType() const
115 {
116 return m_operand->staticType();
117 }
118
expectedOperandTypes() const119 SequenceType::List NodeSortExpression::expectedOperandTypes() const
120 {
121 SequenceType::List result;
122 result.append(CommonSequenceTypes::ZeroOrMoreItems);
123 return result;
124 }
125
126 ExpressionVisitorResult::Ptr
accept(const ExpressionVisitor::Ptr & visitor) const127 NodeSortExpression::accept(const ExpressionVisitor::Ptr &visitor) const
128 {
129 return visitor->visit(this);
130 }
131
properties() const132 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
143