net.sf.saxon.instruct
Class FixedElement

java.lang.Object
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  +--net.sf.saxon.instruct.Instruction
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        +--net.sf.saxon.instruct.ExprInstruction
              |
              +--net.sf.saxon.instruct.FixedElement
All Implemented Interfaces:
Expression, java.io.Serializable

public class FixedElement
extends ExprInstruction

An instruction that creates an element node whose name is known statically. Used for literal results elements in XSLT, for direct element constructors in XQuery, and for xsl:element in cases where the name and namespace are known statically.

See Also:
Serialized Form

Constructor Summary
FixedElement(int nameCode, int[] namespaceCodes, AttributeSet[] useAttributeSets, int annotation)
          Create an instruction that creates a new element node
 
Method Summary
 Expression analyze(StaticContext env)
          Perform static analysis of an expression and its subexpressions.
 void display(int level, NamePool pool)
          Display this instruction as an expression, for diagnostics
 Item evaluateItem(XPathContext context)
          Evaluate as an expression.
 SequenceType getResultType()
          Get the result type returned by this instruction
 void getXPathExpressions(java.util.List list)
           
 TailCall processLeavingTail(XPathContext context)
          ProcessLeavingTail: called to do the real work of this instruction.
 void promoteInst(PromotionOffer offer)
          Offer promotion for subexpressions.
 void setInstructionDetails(Controller controller, NamePool namePool, InstructionDetails details)
          Get the name of this instruction for diagnostic and tracing purposes
 
Methods inherited from class net.sf.saxon.instruct.ExprInstruction
effectiveBooleanValue, evaluateAsString, getCardinality, getDependencies, getItemType, getSpecialProperties, getSubExpressions, iterate, promote, simplify
 
Methods inherited from class net.sf.saxon.instruct.Instruction
assembleParams, assembleTunnelParams, getChildren, getInstructionDetails, getInstructionName, getLineNumber, getSystemId, process, processChildren, processChildrenLeavingTail, recoverableError, setChildren, setSourceLocation, styleError, styleError
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

FixedElement

public FixedElement(int nameCode,
                    int[] namespaceCodes,
                    AttributeSet[] useAttributeSets,
                    int annotation)
Create an instruction that creates a new element node

Parameters:
nameCode - Represents the name of the element node
namespaceCodes - List of namespaces to be added to the element node. May be null if none are required.
useAttributeSets - Array of attribute sets to be expanded. May be null if none are required.
annotation - Type annotation for the new element node
Method Detail

getResultType

public SequenceType getResultType()
Get the result type returned by this instruction

Overrides:
getResultType in class Instruction
Returns:
a SequenceType representing the type element(*,*)

analyze

public Expression analyze(StaticContext env)
                   throws XPathException
Description copied from interface: Expression
Perform static analysis of an expression and its subexpressions.

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 will only be accurately known if they have been explicitly declared.

Parameters:
env - the static context of the expression
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)

getXPathExpressions

public void getXPathExpressions(java.util.List list)
Specified by:
getXPathExpressions in class ExprInstruction

promoteInst

public 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.

Specified by:
promoteInst in class ExprInstruction
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

processLeavingTail

public TailCall processLeavingTail(XPathContext context)
                            throws javax.xml.transform.TransformerException
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 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.
javax.xml.transform.TransformerException

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 Expression
Overrides:
evaluateItem in class ExprInstruction
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

setInstructionDetails

public void setInstructionDetails(Controller controller,
                                  NamePool namePool,
                                  InstructionDetails details)
Get the name of this instruction for diagnostic and tracing purposes

Specified by:
setInstructionDetails in class Instruction

display

public void display(int level,
                    NamePool pool)
Display this instruction as an expression, for diagnostics

Parameters:
level - indentation level for this expression