Package net.sf.saxon.expr.instruct

Class ForEach

    • Field Detail

      • containsTailCall

        protected boolean containsTailCall

      • selectOp

        protected Operand selectOp

      • actionOp

        protected Operand actionOp

      • separatorOp

        protected Operand separatorOp

      • threadsOp

        protected Operand threadsOp

      • _isInstruction

        protected boolean _isInstruction

    • Constructor Detail

      • ForEach

        public ForEach​(Expression select,
               Expression action)
        Create an xsl:for-each instruction
        Parameters:
        select - the select expression
        action - the body of the xsl:for-each loop

      • ForEach

        public ForEach​(Expression select,
               Expression action,
               boolean containsTailCall,
               Expression threads)
        Create an xsl:for-each instruction
        Parameters:
        select - the select expression
        action - the body of the xsl:for-each loop
        containsTailCall - true if the body of the loop contains a tail call on the containing function
        threads - if >1 causes multithreaded execution (Saxon-EE only)

    • Method Detail

      • setSeparatorExpression

        public void setSeparatorExpression​(Expression separator)
        Set the separator expression (Saxon extension)
        Parameters:
        separator - the separator expression

      • getSeparatorExpression

        public Expression getSeparatorExpression()

      • setInstruction

        public void setInstruction​(boolean inst)
        Say whether this ForEach expression originates as an XSLT instruction
        Parameters:
        inst - true if this is an xsl:for-each instruction; false if it is the XPath "!" operator

      • isInstruction

        public boolean isInstruction()
        Ask whether this expression is an instruction. In XSLT streamability analysis this is used to distinguish constructs corresponding to XSLT instructions from other constructs.
        Overrides:
        isInstruction in class Instruction
        Returns:
        true if this construct originates as an XSLT instruction

      • setContainsTailCall

        public void setContainsTailCall​(boolean tc)
        Set whether this expression contains a call (on call-template or apply-templates) that is treated as a tail call because the select expression is known to be a singleton
        Parameters:
        tc - true if the action expression is to be treated as a tail call

      • isContainsTailCall

        public boolean isContainsTailCall()
        Ask whether this expression contains a call (on call-template or apply-templates) that is treated as a tail call because the select expression is known to be a singleton
        Returns:
        true if the action expression is to be treated as a tail call

      • getSelect

        public Expression getSelect()
        Get the select expression
        Returns:
        the select expression. Note this will have been wrapped in a sort expression if sorting was requested.

      • setSelect

        public void setSelect​(Expression select)
        Set the select expression
        Parameters:
        select - the select expression of the for-each

      • getAction

        public Expression getAction()
        Get the action expression (in XSLT, the body of the xsl:for-each instruction
        Returns:
        the action expression

      • setAction

        public void setAction​(Expression action)
        Set the action expression (in XSLT, the body of the xsl:for-each instruction)
        Parameters:
        action - the action expression

      • getThreads

        public Expression getThreads()
        Get the expression used to determine how many threads to use when multi-threading
        Returns:
        the saxon:threads expression if present, or null otherwise

      • setThreads

        public void setThreads​(Expression threads)
        Set the expression used to determine how many threads to use when multi-threading
        Parameters:
        threads - the saxon:threads expression if present, or null otherwise

      • operands

        public java.lang.Iterable<Operand> operands()
        Get the operands of this expression
        Specified by:
        operands in class Instruction
        Returns:
        the operands

      • getInstructionNameCode

        public int getInstructionNameCode()
        Get the name of this instruction for diagnostic and tracing purposes
        Overrides:
        getInstructionNameCode in class Instruction
        Returns:
        the code for name xsl:for-each

      • getSelectExpression

        public Expression getSelectExpression()
        Get the select expression
        Specified by:
        getSelectExpression in interface ContextSwitchingExpression
        Returns:
        the select expression. Note this will have been wrapped in a sort expression if sorting was requested.

      • setSelectExpression

        public void setSelectExpression​(Expression select)
        Set the select expression
        Parameters:
        select - the select expression

      • setActionExpression

        public void setActionExpression​(Expression action)
        Set the action expression
        Parameters:
        action - the select expression

      • getActionExpression

        public Expression getActionExpression()
        Get the subexpression that is evaluated in the new context
        Specified by:
        getActionExpression in interface ContextSwitchingExpression
        Returns:
        the subexpression evaluated in the context set by the controlling expression

      • getNumberOfThreadsExpression

        public Expression getNumberOfThreadsExpression()
        Get the number of threads requested
        Returns:
        the value of the saxon:threads attribute

      • getItemType

        public final ItemType getItemType()
        Determine the data type of the items returned by this expression
        Overrides:
        getItemType in class Instruction
        Returns:
        the data type

      • getStaticUType

        public UType getStaticUType​(UType contextItemType)
        Get the static type of the expression as a UType, following precisely the type inference rules defined in the XSLT 3.0 specification.
        Overrides:
        getStaticUType in class Expression
        Parameters:
        contextItemType - static type of the context item
        Returns:
        the static item type of the expression according to the XSLT 3.0 defined rules

      • mayCreateNewNodes

        public final boolean mayCreateNewNodes()
        Determine whether this instruction creates new nodes. This implementation returns true if the "action" creates new nodes. (Nodes created by the condition can't contribute to the result).
        Overrides:
        mayCreateNewNodes in class Instruction
        Returns:
        true if the instruction creates new nodes under some input conditions (or if it can't be proved that it doesn't)

      • typeCheck

        public Expression typeCheck​(ExpressionVisitor visitor,
                            ContextItemStaticInfo contextInfo)
                     throws XPathException
        Description copied from class: Expression
        Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.

        This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.

        This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.

        Overrides:
        typeCheck in class Expression
        Parameters:
        visitor - an expression visitor
        contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.
        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,
                           ContextItemStaticInfo contextInfo)
                    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
        contextInfo - 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)

      • unordered

        public Expression unordered​(boolean retainAllNodes,
                            boolean forStreaming)
                     throws XPathException
        Replace this expression by a simpler expression that delivers the results without regard to order.
        Overrides:
        unordered in class Expression
        Parameters:
        retainAllNodes - set to true if the result must contain exactly the same nodes as the original; set to false if the result can eliminate (or introduce) duplicates.
        forStreaming - set to true if optimizing for streaming
        Returns:
        an expression that delivers the same nodes in a more convenient order
        Throws:
        XPathException - if the rewrite fails

      • 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 set of nodes in the path map that are affected
        Returns:
        the pathMapNode representing the focus established by this expression, in the case where this expression is the first operand of a path expression or filter 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.

      • copy

        public Expression copy​(RebindingMap rebindings)
        Copy an expression. This makes a deep copy.
        Specified by:
        copy in class Expression
        Parameters:
        rebindings - variables that need to be re-bound
        Returns:
        the copy of the original expression

      • computeSpecialProperties

        protected 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

      • alwaysCreatesNewNodes

        public boolean alwaysCreatesNewNodes()
        Description copied from class: Instruction
        Ask whether it is guaranteed that every item in the result of this instruction is a newly created node.
        Overrides:
        alwaysCreatesNewNodes in class Instruction
        Returns:
        true if result of the instruction is always either an empty sequence or a sequence consisting entirely of newly created nodes

      • isUpdatingExpression

        public boolean isUpdatingExpression()
        Determine whether this is an updating expression as defined in the XQuery update specification
        Overrides:
        isUpdatingExpression in class Expression
        Returns:
        true if this is an updating expression

      • checkForUpdatingSubexpressions

        public void checkForUpdatingSubexpressions()
                                    throws XPathException
        Check to ensure that this expression does not contain any inappropriate updating subexpressions. This check is overridden for those expressions that permit updating subexpressions.
        Overrides:
        checkForUpdatingSubexpressions in class Expression
        Throws:
        XPathException - if the expression has a non-permitted updating subexpression

      • checkPermittedContents

        public void checkPermittedContents​(SchemaType parentType,
                                   boolean whole)
                            throws XPathException
        Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type. It's always OK to say yes, since the check will be repeated at run-time. The process of checking element and attribute constructors against the content model of a complex type also registers the type of content expected of those constructors, so the static validation can continue recursively.
        Overrides:
        checkPermittedContents in class Expression
        Parameters:
        parentType - the "given complex type": the method is checking that the nodes returned by this expression are acceptable members of the content model of this type
        whole - if true, we want to check that the value of this expression satisfies the content model as a whole; if false we want to check that the value of the expression is acceptable as one part of the content
        Throws:
        XPathException - if the value delivered by this expression cannot be part of the content model of the given type

      • processLeavingTail

        public TailCall processLeavingTail​(Outputter output,
                                   XPathContext context)
                            throws XPathException
        Description copied from class: Instruction
        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
        Specified by:
        processLeavingTail in class Instruction
        Parameters:
        output - the destination for the result
        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 - if a dynamic error occurs during the evaluation of the instruction

      • iterate

        public SequenceIterator iterate​(XPathContext context)
                         throws XPathException
        Return an Iterator to iterate over the values of the sequence.
        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

      • evaluatePendingUpdates

        public void evaluatePendingUpdates​(XPathContext context,
                                   PendingUpdateList pul)
                            throws XPathException
        Evaluate an updating expression, adding the results to a Pending Update List. The default implementation of this method, which is used for non-updating expressions, throws an UnsupportedOperationException
        Overrides:
        evaluatePendingUpdates in class Expression
        Parameters:
        context - the XPath dynamic evaluation context
        pul - the pending update list to which the results should be written
        Throws:
        XPathException - if evaluation fails
        java.lang.UnsupportedOperationException - if the expression is not an updating expression

      • export

        public void export​(ExpressionPresenter out)
            throws XPathException
        Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
        Specified by:
        export in interface ExportAgent
        Specified by:
        export in class Expression
        Parameters:
        out - the expression presenter used to display the structure
        Throws:
        XPathException - if the export fails, for example if an expression is found that won't work in the target environment.

      • toString

        public java.lang.String toString()

        The toString() method for an expression attempts to give a representation of the expression in an XPath-like form.

        For subclasses of Expression that represent XPath expressions, the result should always be a string that parses as an XPath 3.0 expression

        Overrides:
        toString in class Expression
        Returns:
        a representation of the expression as a string

      • toShortString

        public java.lang.String toShortString()
        Description copied from class: Expression
        Produce a short string identifying the expression for use in error messages
        Overrides:
        toShortString in class Expression
        Returns:
        a short string, sufficient to identify the expression

      • getExpressionName

        public java.lang.String getExpressionName()
        Get a name identifying the kind of expression, in terms meaningful to a user.
        Overrides:
        getExpressionName in class Instruction
        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.

      • getStreamerName

        public java.lang.String getStreamerName()
        Get the (partial) name of a class that supports streaming of this kind of expression
        Overrides:
        getStreamerName in class Expression
        Returns:
        the partial name of a class that can be instantiated to provide streaming support in Saxon-EE, or null if there is no such class