Package net.sf.saxon.expr.instruct

Class SimpleNodeConstructor

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.instruct.Instruction

net.sf.saxon.expr.instruct.SimpleNodeConstructor

All Implemented Interfaces:

ExportAgent, Locatable, IdentityComparable, Traceable

Direct Known Subclasses:

AttributeCreator, Comment, NamespaceConstructor, ProcessingInstruction, ValueOf

public abstract class SimpleNodeConstructor
extends Instruction

Common superclass for XSLT instructions whose content template produces a text value: xsl:attribute, xsl:comment, xsl:processing-instruction, xsl:namespace, and xsl:text, and their XQuery equivalents

Field Summary

Fields

Modifier and Type	Field	Description
protected Operand	selectOp

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

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_COST, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD

Constructor Summary

Constructors

Constructor	Description
SimpleNodeConstructor()	Default constructor used by subclasses

Method Summary

Modifier and Type	Method	Description
boolean	allowExtractingCommonSubexpressions()	Ask whether common subexpressions found in the operands of this expression can be extracted and evaluated outside the expression itself.
boolean	alwaysCreatesNewNodes()	Ask whether it is guaranteed that every item in the result of this instruction is a newly created node
UnicodeString	checkContent(UnicodeString data, XPathContext context)	Check the content of the node, and adjust it if necessary.
protected int	computeCardinality()	Get the cardinality of the sequence returned by evaluating this instruction
protected int	computeSpecialProperties()	Get the static properties of this expression (other than its type).
Item	evaluateItem(XPathContext context)	Evaluate as an expression.
NodeName	evaluateNodeName(XPathContext context)	Run-time method to compute the name of the node being constructed.
Expression	getSelect()	Get the select expression, that is the expression that computes the content of the constructed node.
Operand	getSelectOp()	Get the select operand, that is the operand that wraps the select expression
java.lang.String	getStreamerName()	Get the (partial) name of a class that supports streaming of this kind of expression
boolean	isLocal()
SequenceIterator	iterate(XPathContext context)	Return an Iterator to iterate over the values of a sequence.
abstract void	localTypeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType)	Method to perform type-checking specific to the kind of instruction
boolean	mayCreateNewNodes()	Ask whether this instruction creates new nodes.
java.lang.Iterable<Operand>	operands()	Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.
Expression	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType)	Perform optimisation of an expression and its subexpressions.
abstract void	processValue(UnicodeString value, Outputter output, XPathContext context)	Process the value of the node, to create the new node.
void	setSelect(Expression select)	Set the select expression: the value of this expression determines the string-value of the node
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)	The typeCheck() method is called in XQuery, where node constructors are implemented as Expressions.

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

assembleParams, assembleTunnelParams, dynamicError, evaluateAsString, getExpressionName, getImplementationMethod, getInstructionNameCode, getItemType, getNetCost, getSourceLocator, isInstruction, isXSLT, process, someOperandCreatesNewNodes

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

addToPathMap, adoptChildExpression, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeHashCode, computeStaticProperties, copy, dispatchTailCall, dynamicError, effectiveBooleanValue, equals, explain, export, getCardinality, getConfiguration, getCost, getDependencies, getElaborator, getEvaluationMethod, getExtraProperty, getIntegerBounds, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, makeElaborator, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, supportsLazyEvaluation, suppressValidation, toPattern, toShortString, toString, typeCheckChildren, typeError, unordered, verifyParentPointers, withLocation

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface net.sf.saxon.trace.Traceable

gatherProperties

Field Detail

selectOp

protected Operand selectOp

Constructor Detail

SimpleNodeConstructor

public SimpleNodeConstructor()

Default constructor used by subclasses

Method Detail

setSelect

public void setSelect(Expression select)

Set the select expression: the value of this expression determines the string-value of the node

Parameters:

select - the expression that computes the string value of the node

getSelect

public Expression getSelect()

Get the select expression, that is the expression that computes the content of the constructed node. Note that this may correspond either to a select attribute or a contained sequence constructor in the case of XSLT; and in XQuery it corresponds to whatever expression is contained in the node constructpr.

Returns:

the expression used to compute the content of the node.

getSelectOp

public Operand getSelectOp()

Get the select operand, that is the operand that wraps the select expression

Returns:

the select operand

operands

public java.lang.Iterable<Operand> operands()

Description copied from class: Expression

Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.

If the expression is a Callable, then it is required that the order of the operands returned by this function is the same as the order of arguments supplied to the corresponding call() method.

Specified by:

operands in class Instruction

Returns:

an iterator containing the sub-expressions of this expression

mayCreateNewNodes

public final boolean mayCreateNewNodes()

Ask whether this instruction creates new nodes. This implementation returns true.

Overrides:

mayCreateNewNodes in class Instruction

Returns:

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

alwaysCreatesNewNodes

public boolean alwaysCreatesNewNodes()

Ask whether it is guaranteed that every item in the result of this instruction is a newly created node

Overrides:

alwaysCreatesNewNodes in class Instruction

Returns:

true if result of the instruction is always either an empty sequence or a sequence consisting entirely of newly created nodes

computeCardinality

protected int computeCardinality()

Get the cardinality of the sequence returned by evaluating this instruction

Overrides:

computeCardinality in class Instruction

Returns:

the static cardinality

computeSpecialProperties

protected int computeSpecialProperties()

Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.

Overrides:

computeSpecialProperties in class Instruction

Returns:

a set of flags indicating static properties of this expression

allowExtractingCommonSubexpressions

public boolean allowExtractingCommonSubexpressions()

Ask whether common subexpressions found in the operands of this expression can be extracted and evaluated outside the expression itself. The result is irrelevant in the case of operands evaluated with a different focus, which will never be extracted in this way, even if they have no focus dependency.

Overrides:

allowExtractingCommonSubexpressions in class Expression

Returns:

false for this kind of expression

localTypeCheck

public abstract void localTypeCheck(ExpressionVisitor visitor,
                                    ContextItemStaticInfo contextItemType)
                             throws XPathException

Method to perform type-checking specific to the kind of instruction

Parameters:

visitor - an expression visitor

contextItemType - the static type of the context item

Throws:

XPathException - if a type error is detected

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ContextItemStaticInfo contextInfo)
                     throws XPathException

The typeCheck() method is called in XQuery, where node constructors are implemented as Expressions. In this case the required type for the select expression is a single string. param visitor an expression visitor

Overrides:

typeCheck in class Expression

Parameters:

contextInfo - information about the dynamic context

visitor - an expression visitor

Returns:

the rewritten expression

Throws:

XPathException - if any static errors are found in this expression or any of its children

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ContextItemStaticInfo 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)

getStreamerName

public java.lang.String getStreamerName()

Get the (partial) name of a class that supports streaming of this kind of expression

Overrides:

getStreamerName in class Expression

Returns:

the partial name of a class that can be instantiated to provide streaming support in Saxon-EE, or null if there is no such class

processValue

public abstract void processValue(UnicodeString value,
                                  Outputter output,
                                  XPathContext context)
                           throws XPathException

Process the value of the node, to create the new node.

Parameters:

value - the string value of the new node

output - the destination for the result

context - the dynamic evaluation context

Throws:

XPathException - if a dynamic error occurs

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate as an expression.

Overrides:

evaluateItem in class Instruction

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

checkContent

public UnicodeString checkContent(UnicodeString data,
                                  XPathContext context)
                           throws XPathException

Check the content of the node, and adjust it if necessary. The checks depend on the node kind.

Parameters:

data - the supplied content

context - the dynamic context

Returns:

the original content, unless adjustments are needed

Throws:

XPathException - if the content is invalid

evaluateNodeName

public NodeName evaluateNodeName(XPathContext context)
                          throws XPathException

Run-time method to compute the name of the node being constructed. This is overridden for nodes that have a name. The default implementation returns -1, which is suitable for unnamed nodes such as comments

Parameters:

context - the XPath dynamic evaluation context

Returns:

the name pool nameCode identifying the name of the constructed node

Throws:

XPathException - if any failure occurs

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.

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

isLocal

public boolean isLocal()