net.sf.saxon.instruct
Class CopyOf

java.lang.Object
  extended by net.sf.saxon.expr.Expression
      extended by net.sf.saxon.instruct.Instruction
          extended by 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


Copyright (C) Michael H. Kay. All rights reserved.