Package net.sf.saxon.expr

Class Atomizer

  • All Implemented Interfaces:
    java.io.Serializable, javax.xml.transform.SourceLocator, LocationProvider, SaxonLocator, InstructionInfo, org.xml.sax.Locator
    public final class Atomizer
extends UnaryExpression
    An Atomizer is an expression corresponding essentially to the fn:data() function: it maps a sequence by replacing nodes with their typed values
    See Also:
    Serialized Form

    • Constructor Detail

      • Atomizer

        public Atomizer​(Expression sequence)
        Constructor
        Parameters:
        sequence - the sequence to be atomized

    • Method Detail

      • getImplementationMethod

        public int getImplementationMethod()
        An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.
        Overrides:
        getImplementationMethod in class Expression
        Returns:
        the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

      • typeCheck

        public Expression typeCheck​(ExpressionVisitor visitor,
                            ExpressionVisitor.ContextItemType contextItemType)
                     throws XPathException
        Type-check the expression
        Overrides:
        typeCheck in class UnaryExpression
        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 to perform necessary run-time type checks, and to perform other type-related optimizations
        Throws:
        XPathException - if an error is discovered during this phase (typically a type error)

      • optimize

        public Expression optimize​(ExpressionVisitor visitor,
                           ExpressionVisitor.ContextItemType contextItemType)
                    throws XPathException
        Perform optimisation of an expression and its subexpressions.

        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 UnaryExpression
        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)

      • isUntyped

        public boolean isUntyped()
        Ask whether it is known that any nodes in the input will always be untyped
        Returns:
        true if it is known that all nodes in the input will be untyped

      • copy

        public Expression copy()
        Copy an expression. This makes a deep copy.
        Specified by:
        copy in class Expression
        Returns:
        the copy of the original expression

      • evaluateItem

        public Item evaluateItem​(XPathContext context)
                  throws XPathException
        Evaluate as an Item. This should only be called if the Atomizer has cardinality zero-or-one, which will only be the case if the underlying expression has cardinality zero-or-one.
        Overrides:
        evaluateItem in class Expression
        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

      • process

        public void process​(XPathContext context)
             throws XPathException
        Process the instruction, without returning any tail calls
        Overrides:
        process in class Expression
        Parameters:
        context - The dynamic context, giving access to the current node, the current variables, etc.
        Throws:
        XPathException - if a dynamic error occurs

      • getItemType

        public ItemType getItemType​(TypeHierarchy th)
        Determine the data type of the items returned by the expression, if possible
        Overrides:
        getItemType in class UnaryExpression
        Parameters:
        th - the type hierarchy cache
        Returns:
        a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER. For this class, the result is always an atomic type, but it might be more specific.

      • getAtomizedItemType

        public static ItemType getAtomizedItemType​(Expression operand,
                                           boolean alwaysUntyped,
                                           TypeHierarchy th)
        Compute the type that will result from atomizing the result of a given expression
        Parameters:
        operand - the given expression
        alwaysUntyped - true if it is known that nodes will always be untyped
        th - the type hierarchy cache
        Returns:
        the item type of the result of evaluating the operand expression, after atomization

      • addToPathMap

        public PathMap.PathMapNodeSet addToPathMap​(PathMap pathMap,
                                           PathMap.PathMapNodeSet pathMapNodeSet)
        Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.

        The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.

        Overrides:
        addToPathMap in class Expression
        Parameters:
        pathMap - the PathMap to which the expression should be added
        pathMapNodeSet - the PathMapNodeSet to which the paths embodied in this expression should be added
        Returns:
        the pathMapNodeSet representing the points in the source document that are both reachable by this expression, and that represent possible results of this expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.

      • getAtomizingIterator

        public static SequenceIterator<? extends AtomicValue> getAtomizingIterator​(SequenceIterator base,
                                                                           boolean untyped)
                                                                    throws XPathException
        Get an iterator that returns the result of atomizing the sequence delivered by the supplied iterator
        Parameters:
        base - the supplied iterator, the input to atomization
        untyped - this can safely be set to true if it is known that all nodes in the base sequence will be untyped; but it is always OK to set it to false.
        Returns:
        an iterator that returns atomic values, the result of the atomization
        Throws:
        XPathException - if a dynamic evaluation error occurs

      • getExpressionName

        public java.lang.String getExpressionName()
        Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
        Overrides:
        getExpressionName in class Expression
        Returns:
        a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.