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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
46QT_BEGIN_NAMESPACE
47
48using namespace QPatternist;
49
50NodeSortExpression::NodeSortExpression(const Expression::Ptr &op) : SingleContainer(op)
51{
52}
53
54bool 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(other: 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
73Item::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(list: nodes);
84 else
85 {
86 std::sort(first: nodes.begin(), last: nodes.end(), comp: lessThanUsingNodeModel);
87
88 return Item::Iterator::Ptr(new DeduplicateIterator(nodes));
89 }
90}
91
92Expression::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(existingNode: operand.data(), newNode: sort);
100 return sort;
101}
102
103Expression::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
114SequenceType::Ptr NodeSortExpression::staticType() const
115{
116 return m_operand->staticType();
117}
118
119SequenceType::List NodeSortExpression::expectedOperandTypes() const
120{
121 SequenceType::List result;
122 result.append(t: CommonSequenceTypes::ZeroOrMoreItems);
123 return result;
124}
125
126ExpressionVisitorResult::Ptr
127NodeSortExpression::accept(const ExpressionVisitor::Ptr &visitor) const
128{
129 return visitor->visit(this);
130}
131
132Expression::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
142QT_END_NAMESPACE
143

source code of qtxmlpatterns/src/xmlpatterns/expr/qnodesort.cpp