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39 
40 //
41 //  W A R N I N G
42 //  -------------
43 //
44 // This file is not part of the Qt API.  It exists purely as an
45 // implementation detail.  This header file may change from version to
46 // version without notice, or even be removed.
47 //
48 // We mean it.
49 
50 #ifndef Patternist_UnlimitedContainer_H
51 #define Patternist_UnlimitedContainer_H
52 
53 #include <QList>
54 #include <private/qexpression_p.h>
55 #include <private/qgenericsequencetype_p.h>
56 
57 QT_BEGIN_NAMESPACE
58 
59 namespace QPatternist
60 {
61     /**
62      * @short Base class for expressions that has any amount of operands.
63      *
64      * @author Frans Englich <frans.englich@nokia.com>
65      * @ingroup Patternist_expressions
66      */
67     class UnlimitedContainer : public Expression
68     {
69     public:
70         /**
71          * Creates an UnlimitedContainer containing the operands @p operands. @p operands
72          * may be empty.
73          */
74         UnlimitedContainer(const Expression::List &operands = Expression::List());
75 
76         virtual void setOperands(const Expression::List &list);
77 
78         virtual Expression::List operands() const;
79 
80         /**
81          * @note This function cannot be called before setOperands is called.
82          */
83         virtual bool compressOperands(const StaticContext::Ptr &);
84 
85         /**
86          * Tells how operandsUnionType() should compute the cardinality of
87          * its children.
88          *
89          * This type is public because of a bug in the HP-UX aCC compiler.
90          */
91         enum CardinalityComputation
92         {
93             ProductOfCardinality,
94             UnionOfCardinality
95         };
96 
97     protected:
98         /**
99          * Computes and returns the union type of all the Expression instances
100          * in this Expression's operands.
101          *
102          * This implementation is placed inside because CardinalityComputation
103          * can't be referenced from the outside(in conforming compilers).
104          */
105         template<CardinalityComputation suppliedCard>
106         inline
operandsUnionType()107         SequenceType::Ptr operandsUnionType() const
108         {
109             Q_ASSERT(suppliedCard ==  ProductOfCardinality || suppliedCard == UnionOfCardinality);
110             const Expression::List::const_iterator end(m_operands.constEnd());
111             Expression::List::const_iterator it(m_operands.constBegin());
112 
113             /* Load the first one, and jump over it in the loop. */
114             SequenceType::Ptr t(m_operands.first()->staticType());
115             ItemType::Ptr type(t->itemType());
116             Cardinality card(t->cardinality());
117             ++it;
118 
119             for(; it != end; ++it)
120             {
121                 t = (*it)->staticType();
122                 type |= t->itemType();
123 
124                 /* Since this function is a template function, it doesn't
125                  * hurt performance that this test is inside the loop. */
126                 if(suppliedCard == ProductOfCardinality)
127                     card += t->cardinality();
128                 else
129                     card |= t->cardinality();
130             }
131 
132             return makeGenericSequenceType(type, card);
133         }
134 
135         Expression::List m_operands;
136     };
137 
138 
139 }
140 
141 QT_END_NAMESPACE
142 
143 #endif
144