net.sf.saxon.instruct

Class Copy

Implemented Interfaces:
SourceLocator, EvaluableItem, InstructionInfoProvider, SequenceIterable, Serializable, SourceLocator, TailCallReturner

public class Copy
extends ElementCreator

Handler for xsl:copy elements in stylesheet.

Field Summary

Fields inherited from class net.sf.saxon.instruct.ElementCreator

inheritNamespaces, preservingTypes

Fields inherited from class net.sf.saxon.instruct.ParentNodeConstructor

content

Fields inherited from class net.sf.saxon.expr.Expression

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD, locationId, staticProperties

Constructor Summary

Copy(boolean copyNamespaces, boolean inheritNamespaces, SchemaType schemaType, int validation)
Create a shallow copy instruction

Method Summary

Expression
copy()
Copy an expression.
Item
evaluateItem(XPathContext context)
Evaluate as an expression.
void
explain(ExpressionPresenter out)
Diagnostic print of expression structure.
int[]
getActiveNamespaces()
Callback to get a list of the intrinsic namespaces that need to be generated for the element.
int
getInstructionNameCode()
Get the name of this instruction for diagnostic and tracing purposes
ItemType
getItemType(TypeHierarchy th)
Get the item type of the result of this instruction.
int
getNameCode(XPathContext context)
Callback from ElementCreator when constructing an element
String
getNewBaseURI(XPathContext context)
Get the base URI of a copied element node (the base URI is retained in the new copy)
Expression
optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
protected void
outputNamespaceNodes(XPathContext context, Receiver receiver)
Callback to output namespace nodes for the new element.
TailCall
processLeavingTail(XPathContext context)
Evaluate the instruction to produce a new element node.
Expression
simplify(ExpressionVisitor visitor)
Simplify an expression.
Expression
typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Perform type checking of an expression and its subexpressions.

Methods inherited from class net.sf.saxon.instruct.ElementCreator

checkContentSequence, computeSpecialProperties, evaluateItem, getActiveNamespaces, getImplementationMethod, getItemType, getNameCode, getNewBaseURI, isInheritNamespaces, isPreservingTypes, iterateEvents, outputNamespaceNodes, processLeavingTail, setValidationMode, suppressValidation

Methods inherited from class net.sf.saxon.instruct.ParentNodeConstructor

addToPathMap, checkContentSequence, computeCardinality, createsNewNodes, getBaseURI, getCardinality, getContentExpression, getSchemaType, getValidationMode, isLazyConstruction, isNamespaceSensitive, iterateSubExpressions, optimize, promoteInst, replaceSubExpression, setBaseURI, setContentExpression, setLazyConstruction, setSchemaType, setValidationMode, simplify, typeCheck

Methods inherited from class net.sf.saxon.instruct.Instruction

assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, createsNewNodes, dynamicError, evaluateAsString, evaluateItem, getImplementationMethod, getInstructionInfo, getInstructionNameCode, getItemType, getSourceLocator, isXSLT, iterate, process, processLeavingTail, promote, promoteInst, simplify

Methods inherited from class net.sf.saxon.expr.Expression

addToPathMap, adoptChildExpression, checkPermittedContents, computeCardinality, computeDependencies, computeSpecialProperties, computeStaticProperties, copy, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, explain, explain, findParentOf, getCardinality, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getItemType, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterate, iterateEvents, iterateSubExpressions, markTailFunctionCalls, optimize, process, promote, replaceSubExpression, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, simplify, staticTypeCheck, suppressValidation, toString, typeCheck, typeError

Constructor Details

Copy

public Copy(boolean copyNamespaces,
            boolean inheritNamespaces,
            SchemaType schemaType,
            int validation)
Create a shallow copy instruction
Parameters:
copyNamespaces - true if namespace nodes are to be copied when copying an element
inheritNamespaces - true if child elements are to inherit the namespace nodes of their parent
schemaType - the Schema type against which the content is to be validated
validation - the schema validation mode

Method Details

copy

public Expression copy()
Copy an expression. This makes a deep copy.
Overrides:
copy in interface Expression
Returns:
the copy of the original expression

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 EvaluableItem
Overrides:
evaluateItem in interface ElementCreator

explain

public void explain(ExpressionPresenter out)
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
Overrides:
explain in interface Expression

getActiveNamespaces

public int[] getActiveNamespaces()
            throws XPathException
Callback to get a list of the intrinsic namespaces that need to be generated for the element. The result is an array of namespace codes, the codes either occupy the whole array or are terminated by a -1 entry. A result of null is equivalent to a zero-length array.
Overrides:
getActiveNamespaces in interface ElementCreator

getInstructionNameCode

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

getItemType

public ItemType getItemType(TypeHierarchy th)
Get the item type of the result of this instruction.
Overrides:
getItemType in interface ElementCreator
Parameters:
th - the type hierarchy cache
Returns:
The context item type.

getNameCode

public int getNameCode(XPathContext context)
            throws XPathException
Callback from ElementCreator when constructing an element
Overrides:
getNameCode in interface ElementCreator
Parameters:
context - XPath dynamic evaluation context
Returns:
the namecode of the element to be constructed
Throws:
XPathException -

getNewBaseURI

public String getNewBaseURI(XPathContext context)
Get the base URI of a copied element node (the base URI is retained in the new copy)
Overrides:
getNewBaseURI in interface ElementCreator
Parameters:
context - XPath dynamic evaluation context
Returns:
the base URI

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ItemType contextItemType)
            throws XPathException
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 interface ParentNodeConstructor
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)

outputNamespaceNodes

protected void outputNamespaceNodes(XPathContext context,
                                    Receiver receiver)
            throws XPathException
Callback to output namespace nodes for the new element.
Overrides:
outputNamespaceNodes in interface ElementCreator
Parameters:
context - The execution context
receiver - the Receiver where the namespace nodes are to be written
Throws:
XPathException -

processLeavingTail

public TailCall processLeavingTail(XPathContext context)
            throws XPathException
Evaluate the instruction to produce a new element node. This method is typically used when there is a parent element or document in a result tree, to which the new element is added.
Specified by:
processLeavingTail in interface TailCallReturner
Overrides:
processLeavingTail in interface ElementCreator
Parameters:
context - XPath dynamic evaluation context
Returns:
null (this instruction never returns a tail call)
Throws:
XPathException -

simplify

public Expression simplify(ExpressionVisitor visitor)
            throws XPathException
Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression). The default implementation does nothing.
Overrides:
simplify in interface ParentNodeConstructor
Parameters:
visitor - an expression visitor
Returns:
the simplified expression
Throws:
XPathException - if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
            throws XPathException
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.

Overrides:
typeCheck in interface ParentNodeConstructor
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)