net.sf.saxon.instruct
Class CopyOf

java.lang.Object
  net.sf.saxon.expr.Expression
      net.sf.saxon.instruct.Instruction
          net.sf.saxon.instruct.CopyOf

All Implemented Interfaces:

Serializable, SourceLocator, EvaluableItem, SequenceIterable, TailCallReturner, InstructionInfoProvider

public class CopyOf
extends Instruction

An xsl:copy-of element in the stylesheet.

See Also:

Serialized Form

Field Summary

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

CopyOf(Expression select, boolean copyNamespaces, int validation, SchemaType schemaType, boolean rejectDuplicatAttributes)
Create an xsl:copy-of instruction (also used in XQuery for implicit copying)

Method Summary

Expression	copy() Copy an expression.
boolean	createsNewNodes() Determine whether this instruction creates new nodes.
Item	evaluateItem(XPathContext context) Return the first item if there is one, or null if not
void	explain(ExpressionPresenter out) Diagnostic print of expression structure.
int	getCardinality() Determine the static cardinality of the expression.
int	getDependencies() Determine which aspects of the context the expression depends on.
int	getImplementationMethod() An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
int	getInstructionNameCode() Get the name of this instruction, for diagnostics and tracing
ItemType	getItemType(TypeHierarchy th) Get the item type of the items returned by evaluating this instruction
Expression	getSelectExpression() Get the expression that selects the nodes to be copied
int	getValidationMode() Get the validation mode
boolean	isCopyNamespaces() Determine whether namespaces are to be copied or not
boolean	isDocumentOrElementRequired() Test whether this expression requires a document or element node
SequenceIterator	iterate(XPathContext context) Return an Iterator to iterate over the values of a sequence.
Iterator	iterateSubExpressions() Get the immediate sub-expressions of this expression.
Expression	optimize(ExpressionVisitor visitor, ItemType contextItemType) Perform optimisation of an expression and its subexpressions.
TailCall	processLeavingTail(XPathContext context) Process this xsl:copy-of instruction
boolean	replaceSubExpression(Expression original, Expression replacement) Replace one subexpression by a replacement subexpression
void	setCopyLineNumbers(boolean copy) Set whether line numbers are to be copied from the source to the result.
void	setReadOnce(boolean b) Set the "saxon:read-once" optimization mode
void	setRequireDocumentOrElement(boolean requireDocumentOrElement) For XQuery, the operand (select) must be a single element or document 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.Instruction

computeCardinality, computeSpecialProperties, evaluateAsString, getInstructionInfo, getSourceLocator, isXSLT, process, promote

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

addToPathMap, adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, effectiveBooleanValue, explain, findParentOf, getColumnNumber, getContainer, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterateEvents, markTailFunctionCalls, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toString

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface javax.xml.transform.SourceLocator

getColumnNumber, getLineNumber, getPublicId, getSystemId

Constructor Detail

CopyOf

public CopyOf(Expression select,
              boolean copyNamespaces,
              int validation,
              SchemaType schemaType,
              boolean rejectDuplicatAttributes)

Create an xsl:copy-of instruction (also used in XQuery for implicit copying)

Parameters:

select - expression that selects the nodes to be copied

copyNamespaces - true if namespaces are to be copied

validation - validation mode for the result tree

schemaType - schema type for validating the result tree

rejectDuplicatAttributes - true if duplicat attributes are to be rejected (XQuery). False if duplicates are handled by discarding all but the first (XSLT).

Method Detail

getSelectExpression

public Expression getSelectExpression()

Get the expression that selects the nodes to be copied

Returns:

the select expression

getValidationMode

public int getValidationMode()

Get the validation mode

Returns:

the validation mode

setReadOnce

public void setReadOnce(boolean b)

Set the "saxon:read-once" optimization mode

Parameters:

b - true to enable the optimization

setCopyLineNumbers

public void setCopyLineNumbers(boolean copy)

Set whether line numbers are to be copied from the source to the result. Default is false.

Parameters:

copy - true if line numbers are to be copied

createsNewNodes

public final boolean createsNewNodes()

Determine whether this instruction creates new nodes. The result depends on the type of the select expression.

Overrides:

createsNewNodes in class Instruction

Returns:

true if the instruction creates new nodes (or if it can't be proved that it doesn't)

getInstructionNameCode

public int getInstructionNameCode()

Get the name of this instruction, for diagnostics and tracing

Overrides:

getInstructionNameCode in class Instruction

Returns:

a code identifying the instruction: typically but not always the fingerprint of a name in the XSLT namespace

setRequireDocumentOrElement

public void setRequireDocumentOrElement(boolean requireDocumentOrElement)

For XQuery, the operand (select) must be a single element or document node.

Parameters:

requireDocumentOrElement - true if the argument must be a single element or document node

isDocumentOrElementRequired

public boolean isDocumentOrElementRequired()

Test whether this expression requires a document or element node

Returns:

true if this expression requires the value of the argument to be a document or element node, false if there is no such requirement

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 provided. This implementation provides both iterate() and process() methods natively.

Overrides:

getImplementationMethod in class Instruction

Returns:

the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

isCopyNamespaces

public boolean isCopyNamespaces()

Determine whether namespaces are to be copied or not

Returns:

true if namespaces are to be copied (the default)

copy

public Expression copy()

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Returns:

the copy of the original expression

simplify

public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException

Description copied from class: Instruction

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 class Instruction

Parameters:

visitor - an expression visitor

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

getItemType

public ItemType getItemType(TypeHierarchy th)

Description copied from class: Instruction

Get the item type of the items returned by evaluating this instruction

Overrides:

getItemType in class Instruction

Parameters:

th - the type hierarchy cache

Returns:

the static item type of the instruction

getCardinality

public int getCardinality()

Description copied from class: Expression

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.

Overrides:

getCardinality in class Expression

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).

getDependencies

public int getDependencies()

Description copied from class: Expression

Determine which aspects of the context the expression depends on. The result is a bitwise-or'ed value composed from constants such as XPathContext.VARIABLES and XPathContext.CURRENT_NODE. The default implementation combines the intrinsic dependencies of this expression with the dependencies of the subexpressions, computed recursively. This is overridden for expressions such as FilterExpression where a subexpression's dependencies are not necessarily inherited by the parent expression.

Overrides:

getDependencies in class Expression

Returns:

a set of bit-significant flags identifying the dependencies of the expression

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
                     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.

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 class Expression

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)

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ItemType contextItemType)
                    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

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)

explain

public void explain(ExpressionPresenter out)

Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

Specified by:

explain in class Expression

Parameters:

out - the expression presenter used to display the structure

iterateSubExpressions

public Iterator iterateSubExpressions()

Description copied from class: Expression

Get the immediate sub-expressions of this expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.

Overrides:

iterateSubExpressions in class Expression

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

Overrides:

replaceSubExpression in class Expression

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

Process this xsl:copy-of instruction

Specified by:

processLeavingTail in interface TailCallReturner

Specified by:

processLeavingTail in class Instruction

Parameters:

context - the dynamic context for the transformation

Returns:

null - this implementation of the method never returns a TailCall

Throws:

XPathException

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Return the first item if there is one, or null if not

Specified by:

evaluateItem in interface EvaluableItem

Overrides:

evaluateItem in class Instruction

Parameters:

context - the XPath dynamic context

Returns:

the result of evaluating the instruction

Throws:

XPathException

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Description copied from class: Instruction

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 SequenceIterable

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