Package net.sf.saxon.instruct

Class Instruction

    • Constructor Detail

      • Instruction

        public Instruction()
        Constructor

    • 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 prefered. For instructions this is the process() method.
        Specified by:
        getImplementationMethod in interface Expression
        Overrides:
        getImplementationMethod in class ComputedExpression

      • getInstructionNameCode

        public int getInstructionNameCode()
        Get the namecode of the instruction for use in diagnostics

      • getItemType

        public ItemType getItemType​(TypeHierarchy th)
        Get the item type of the items returned by evaluating this instruction
        Specified by:
        getItemType in interface Expression
        Parameters:
        th -
        Returns:
        the static item type of the instruction

      • computeCardinality

        public int computeCardinality()
        Get the cardinality of the sequence returned by evaluating this instruction
        Specified by:
        computeCardinality in class ComputedExpression
        Returns:
        the static cardinality

      • processLeavingTail

        public abstract TailCall processLeavingTail​(XPathContext context)
                                     throws XPathException
        ProcessLeavingTail: called to do the real work of this instruction. This method must be implemented in each subclass. The results of the instruction are written to the current Receiver, which can be obtained via the Controller.
        Specified by:
        processLeavingTail in interface TailCallReturner
        Parameters:
        context - The dynamic context of the transformation, giving access to the current node, the current variables, etc.
        Returns:
        null if the instruction has completed execution; or a TailCall indicating a function call or template call that is delegated to the caller, to be made after the stack has been unwound so as to save stack space.
        Throws:
        XPathException

      • getSourceLocator

        public javax.xml.transform.SourceLocator getSourceLocator()
        Get a SourceLocator identifying the location of this instruction

      • dynamicError

        protected static XPathException dynamicError​(javax.xml.transform.SourceLocator loc,
                                             XPathException error,
                                             XPathContext context)
        Construct an exception with diagnostic information. Note that this method returns the exception, it does not throw it: that is up to the caller.
        Parameters:
        error - The exception containing information about the error
        context - The controller of the transformation
        Returns:
        an exception based on the supplied exception, but with location information added relating to this instruction

      • assembleTunnelParams

        protected static ParameterSet assembleTunnelParams​(XPathContext context,
                                                   WithParam[] actualParams)
                                            throws XPathException
        Assemble a ParameterSet. Method used by instructions that have xsl:with-param children. This method is used for the tunnel parameters.
        Throws:
        XPathException

      • simplify

        public abstract Expression simplify​(StaticContext env)
                             throws XPathException
        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 interface Expression
        Overrides:
        simplify in class ComputedExpression
        Parameters:
        env - the static context
        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 ComputedExpression
        Returns:
        a set of flags indicating static properties of this expression

      • createsNewNodes

        public boolean createsNewNodes()
        Determine whether this instruction creates new nodes. This implementation returns a default value of false

      • promoteInst

        protected void promoteInst​(PromotionOffer offer)
                    throws XPathException
        Handle promotion offers, that is, non-local tree rewrites.
        Parameters:
        offer - The type of rewrite being offered
        Throws:
        XPathException

      • promote

        public Expression promote​(PromotionOffer offer)
                   throws XPathException
        Offer promotion for this subexpression. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. This method is always called at compile time.
        Specified by:
        promote in interface Expression
        Overrides:
        promote in class ComputedExpression
        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
        Returns:
        if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression
        Throws:
        XPathException - if any error is detected

      • evaluateItem

        public Item evaluateItem​(XPathContext context)
                  throws XPathException
        Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.
        Specified by:
        evaluateItem in interface Expression
        Overrides:
        evaluateItem in class ComputedExpression
        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

      • iterate

        public SequenceIterator iterate​(XPathContext context)
                         throws XPathException
        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 Expression
        Overrides:
        iterate in class ComputedExpression
        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

      • evaluateAsString

        public final java.lang.String evaluateAsString​(XPathContext context)
                                        throws XPathException
        Evaluate an expression as a String. This function must only be called in contexts where it is known that the expression will return a single string (or where an empty sequence is to be treated as a zero-length string). Implementations should not attempt to convert the result to a string, other than converting () to "". This method is used mainly to evaluate expressions produced by compiling an attribute value template.
        Specified by:
        evaluateAsString in interface Expression
        Overrides:
        evaluateAsString in class ComputedExpression
        Parameters:
        context - The context in which the expression is to be evaluated
        Returns:
        the value of the expression, evaluated in the current context. The expression must return a string or (); if the value of the expression is (), this method returns "".
        Throws:
        XPathException - if any dynamic error occurs evaluating the expression
        java.lang.ClassCastException - if the result type of the expression is not xs:string?

      • appendItem

        public static void appendItem​(Item it,
                              SequenceReceiver out,
                              int locationId)
                       throws XPathException
        Static method to append an item that results from evaluating an expression to the current result receiver. The method checks to see whether the item returned from the expression is actually a function-call-package representing the result of a tail call optimization; if so, the tail function calls are complete and the final result is passed on.
        Parameters:
        it - the item: possibly a FunctionCallPackage
        out - the Receiver
        Throws:
        XPathException

      • isXSLT

        public boolean isXSLT()
        Establish whether this is an XSLT instruction or an XQuery instruction (used to produce appropriate diagnostics)
        Returns:
        true for XSLT, false for XQuery