Class Message

    • Method Detail

      • simplify

        public 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
        Specified by:
        simplify in class Instruction
        Parameters:
        env - the static context
        Returns:
        the simplified expression
        Throws:
        XPathException - if an error is discovered during expression rewriting
      • typeCheck

        public Expression typeCheck​(StaticContext env,
                                    ItemType contextItemType)
                             throws XPathException
        Description copied from interface: 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.

        If the implementation returns a value other than "this", then it is required to ensure that the parent pointer and location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.

        Parameters:
        env - the static context of the expression
        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:
        StaticError - if an error is discovered during this phase (typically a type error)
        XPathException
      • optimize

        public Expression optimize​(Optimizer opt,
                                   StaticContext env,
                                   ItemType contextItemType)
                            throws XPathException
        Description copied from interface: 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.

        Parameters:
        opt - the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.
        env - the static context of the expression
        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:
        StaticError - if an error is discovered during this phase (typically a type error)
        XPathException
      • getInstructionNameCode

        public int getInstructionNameCode()
        Get the name of this instruction for diagnostic and tracing purposes
        Overrides:
        getInstructionNameCode in class Instruction
      • getCardinality

        public int getCardinality()
        Description copied from class: ComputedExpression
        Determine the static cardinality of the expression. This establishes how many items there will be in the result of the expression, at compile time (i.e., without actually evaluating the result.
        Specified by:
        getCardinality in interface Expression
        Overrides:
        getCardinality in class ComputedExpression
        Returns:
        one of the values Cardinality.ONE_OR_MORE, Cardinality.ZERO_OR_MORE, Cardinality.EXACTLY_ONE, Cardinality.ZERO_OR_ONE, Cardinality.EMPTY. This default implementation returns ZERO_OR_MORE (which effectively gives no information).
      • createsNewNodes

        public final boolean createsNewNodes()
        Determine whether this instruction creates new nodes. This implementation returns true.
        Overrides:
        createsNewNodes in class Instruction
      • iterateSubExpressions

        public java.util.Iterator iterateSubExpressions()
        Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction)
        Specified by:
        iterateSubExpressions in interface Expression
        Overrides:
        iterateSubExpressions in class ComputedExpression
        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
        Specified by:
        replaceSubExpression in interface Container
        Overrides:
        replaceSubExpression in class ComputedExpression
        Parameters:
        original - the original subexpression
        replacement - the replacement subexpression
        Returns:
        true if the original subexpression is found
      • processLeavingTail

        public TailCall processLeavingTail​(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:
        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
      • display

        public void display​(int level,
                            java.io.PrintStream out,
                            Configuration config)
        Diagnostic print of expression structure. The expression is written to the System.err output stream
        Parameters:
        level - indentation level for this expression
        out -
        config -