Class SimpleNodeConstructor

    • Constructor Detail

      • SimpleNodeConstructor

        public SimpleNodeConstructor()
        Default constructor used by subclasses
    • Method Detail

      • setSelect

        public void setSelect​(Expression select,
                              Configuration config)
                       throws XPathException
        Set the select expression: the value of this expression determines the string-value of the node
        Parameters:
        select - the expression that computes the string value of the node
        config - the Saxon configuration (used for example to do early validation of the content of an attribute against the schema-defined type)
        Throws:
        XPathException
      • getSelect

        public Expression getSelect()
        Get the expression that determines the string value of the constructed node
        Returns:
        the select expression
      • createsNewNodes

        public final boolean createsNewNodes()
        Determine whether this instruction creates new nodes. This implementation returns true.
        Overrides:
        createsNewNodes in class Instruction
        Returns:
        true if the instruction creates new nodes (or if it can't be proved that it doesn't)
      • computeCardinality

        public int computeCardinality()
        Get the cardinality of the sequence returned by evaluating this instruction
        Overrides:
        computeCardinality in class Instruction
        Returns:
        the static cardinality
      • simplify

        public Expression simplify​(ExpressionVisitor visitor)
                            throws XPathException
        Description copied from class: Instruction
        Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression). The default implementation does nothing.
        Specified by:
        simplify in class Instruction
        Parameters:
        visitor - an expression visitor
        Returns:
        the simplified expression
        Throws:
        XPathException - if an error is discovered during expression rewriting
      • computeSpecialProperties

        public int computeSpecialProperties()
        Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.
        Overrides:
        computeSpecialProperties in class Instruction
        Returns:
        a set of flags indicating static properties of this expression
      • localTypeCheck

        public abstract void localTypeCheck​(ExpressionVisitor visitor,
                                            ItemType contextItemType)
                                     throws XPathException
        Method to perform type-checking specific to the kind of instruction
        Parameters:
        visitor - an expression visitor
        contextItemType - the static type of the context item
        Throws:
        XPathException
      • typeCheck

        public Expression typeCheck​(ExpressionVisitor visitor,
                                    ItemType contextItemType)
                             throws XPathException
        The typeCheck() method is called in XQuery, where node constructors are implemented as Expressions. In this case the required type for the select expression is a single string.
        Overrides:
        typeCheck in class Expression
        Parameters:
        visitor - an expression visitor
        contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE
        Returns:
        the rewritten expression
        Throws:
        XPathException - if any static errors are found in this expression or any of its children
      • optimize

        public Expression optimize​(ExpressionVisitor visitor,
                                   ItemType contextItemType)
                            throws XPathException
        Description copied from class: Expression
        Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.

        This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

        Overrides:
        optimize in class Expression
        Parameters:
        visitor - an expression visitor
        contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE
        Returns:
        the original expression, rewritten if appropriate to optimize execution
        Throws:
        XPathException - if an error is discovered during this phase (typically a type error)
      • iterateSubExpressions

        public java.util.Iterator iterateSubExpressions()
        Description copied from class: Expression
        Get the immediate sub-expressions of this expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.
        Overrides:
        iterateSubExpressions in class Expression
        Returns:
        an iterator containing the sub-expressions of this expression
      • replaceSubExpression

        public boolean replaceSubExpression​(Expression original,
                                            Expression replacement)
        Replace one subexpression by a replacement subexpression
        Overrides:
        replaceSubExpression in class Expression
        Parameters:
        original - the original subexpression
        replacement - the replacement subexpression
        Returns:
        true if the original subexpression is found
      • expandChildren

        public java.lang.CharSequence expandChildren​(XPathContext context)
                                              throws XPathException
        Expand the stylesheet elements subordinate to this one, returning the result as a string. The expansion must not generate any element or attribute nodes.
        Parameters:
        context - The dynamic context for the transformation
        Returns:
        the value that will be used as the string value of the constructed node
        Throws:
        XPathException - if any error occurs
      • evaluateItem

        public Item evaluateItem​(XPathContext context)
                          throws XPathException
        Evaluate as an expression. We rely on the fact that when these instructions are generated by XQuery, there will always be a valueExpression to evaluate the content
        Specified by:
        evaluateItem in interface EvaluableItem
        Overrides:
        evaluateItem in class Instruction
        Parameters:
        context - The context in which the expression is to be evaluated
        Returns:
        the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
        Throws:
        XPathException - if any dynamic error occurs evaluating the expression
      • checkContent

        protected java.lang.String checkContent​(java.lang.String data,
                                                XPathContext context)
                                         throws XPathException
        Check the content of the node, and adjust it if necessary. The checks depend on the node kind.
        Parameters:
        data - the supplied content
        context - the dynamic context
        Returns:
        the original content, unless adjustments are needed
        Throws:
        XPathException - if the content is invalid
      • evaluateNameCode

        public int evaluateNameCode​(XPathContext context)
                             throws XPathException
        Run-time method to compute the name of the node being constructed. This is overridden for nodes that have a name. The default implementation returns -1, which is suitable for unnamed nodes such as comments
        Parameters:
        context - the XPath dynamic evaluation context
        Returns:
        the name pool nameCode identifying the name of the constructed node
        Throws:
        XPathException - if any failure occurs
      • iterate

        public SequenceIterator iterate​(XPathContext context)
                                 throws XPathException
        Description copied from class: Instruction
        Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.
        Specified by:
        iterate in interface SequenceIterable
        Overrides:
        iterate in class Instruction
        Parameters:
        context - supplies the context for evaluation
        Returns:
        a SequenceIterator that can be used to iterate over the result of the expression
        Throws:
        XPathException - if any dynamic error occurs evaluating the expression
      • promoteInst

        protected void promoteInst​(PromotionOffer offer)
                            throws XPathException
        Offer promotion for subexpressions. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. By default the offer is not accepted - this is appropriate in the case of simple expressions such as constant values and variable references where promotion would give no performance advantage. This method is always called at compile time.
        Overrides:
        promoteInst in class Instruction
        Parameters:
        offer - details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression
        Throws:
        XPathException - if any error is detected