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46 // This file is not part of the Qt API. It exists purely as an
47 // implementation detail. This header file may change from version to
48 // version without notice, or even be removed.
52 #ifndef Patternist_ExternalVariableLoader_H
53 #define Patternist_ExternalVariableLoader_H
55 #include <private/qitem_p.h>
56 #include <private/qsequencetype_p.h>
68 * @short Responsible for loading and declaring available external variables.
70 * An external variable in XQuery is a global variable that has been declared to receive
71 * its value from the XQuery implementation, as opposed to an initializing expression. Here
72 * is an example of a query with an external variable declaration, followed by a ordinary
75 * <tt> declare variable $theName external;
76 * declare variable $theName := "the value";
77 * "And here's the query body(a string literal)"</tt>
79 * An external variable declaration can also specify a sequence type:
81 * <tt>declare variable $theName as xs:integer external;</tt>
83 * This class allows the user to supply the values to external variables. When
84 * an external variable declaration occur in the query,
85 * announceExternalVariable() is called.
87 * @ingroup Patternist_xdm
88 * @author Frans Englich <frans.englich@nokia.com>
90 class Q_AUTOTEST_EXPORT ExternalVariableLoader : public QSharedData
93 typedef QExplicitlySharedDataPointer<ExternalVariableLoader> Ptr;
94 inline ExternalVariableLoader() {}
96 virtual ~ExternalVariableLoader();
99 * Called when Patternist encounters an external variable in the query. It is guaranteed
100 * to be called once for each external variable appearing in a query module.
102 * @param name the name of the variable. Quaranteed to never be @c null.
103 * @param declaredType the type that the user declared the variable to be of. Whether
104 * this type matches the actual value of the variable or not is irrelevant. Patternist
105 * will do the necessary error handling based on the sequence type that is returned from
106 * this function. If the user didn't declare a type, the type is <tt>item()*</tt>(zero or
107 * more items). Quaranteed to never be @c null.
108 * @returns the sequence type of the value this ExternalVariableLoader actually supplies. However,
109 * if the ExternalVariableLoader knows it cannot supply a variable by this name, @c null should be
112 virtual SequenceType::Ptr announceExternalVariable(const QXmlName name,
113 const SequenceType::Ptr &declaredType);
116 * This function is called at runtime when the external variable by name @p name needs
117 * to be evaluated. It is not defined how many times this function will be called. It
118 * depends on aspects such as how the query was optimized.
120 * @param name the name of the variable. Quaranteed to never be @c null.
121 * @param context the DynamicContext.
122 * @returns the value of the variable. Remember that this value must match the
123 * sequence type returned from announceExternalVariable() for the same name.
125 virtual Item::Iterator::Ptr evaluateSequence(const QXmlName name,
126 const QExplicitlySharedDataPointer<DynamicContext> &context);
128 virtual Item evaluateSingleton(const QXmlName name,
129 const QExplicitlySharedDataPointer<DynamicContext> &context);
130 virtual bool evaluateEBV(const QXmlName name,
131 const QExplicitlySharedDataPointer<DynamicContext> &context);