net.sf.saxon.expr

Class GroupVariableReference

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.VariableReference

net.sf.saxon.expr.LocalVariableReference

net.sf.saxon.expr.GroupVariableReference

All Implemented Interfaces:

Serializable, SourceLocator, LocationProvider, SaxonLocator, BindingReference, InstructionInfo, Locator

public class GroupVariableReference
extends LocalVariableReference

This is a variant of LocalVariableReference used when the variable in question represents the group bound by the bind-group attribute of xsl:for-each-group. It differs in that the streaming behavior is different

See Also:

Serialized Form

Field Summary

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

binding, constantValue, staticType

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

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, INHERITED_CONTEXT, INSPECTION_CONTEXT, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, NAVIGATION_CONTEXT, NODE_VALUE_CONTEXT, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, W3C_CONSUMING, W3C_FREE_RANGING, W3C_GROUP_CONSUMING, W3C_MOTIONLESS, WATCH_METHOD

Constructor Summary

Constructors

Constructor and Description
GroupVariableReference()
GroupVariableReference(Binding binding)

Method Summary

Methods

Modifier and Type	Method and Description
int	computeCardinality() Get the static cardinality
int	computeSpecialProperties() Determine the special properties of this expression.
Expression	copy() Create a clone copy of this VariableReference
ForEachGroup	getControllingExpression()
int	getStreamability(int syntacticContext, boolean allowExtensions, List<String> reasons) Get the "sweep" of this expression as defined in the W3C streamability specifications.
GroupVariableReferenceAdjunct	getStreamingAdjunct() Get a class that supports streamed evaluation of this expression
Expression	optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Type-check the expression.
void	setControllingExpression(ForEachGroup feg)
Pattern	toStreamingPattern(Configuration config, List<String> reasonForFailure) Convert this expression to a streaming pattern (a pattern used internally to match nodes during push processing of an event stream)

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

evaluateVariable, getExpressionCompiler, getSlotNumber, setSlotNumber

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

addToPathMap, equals, evaluateItem, explain, fixup, getBinding, getDisplayName, getEQName, getImplementationMethod, getIntegerBounds, getIntrinsicDependencies, getItemType, hashCode, isFiltered, isFlattened, isInLoop, iterate, process, promote, refineVariableType, setFiltered, setFlattened, setStaticType, toString, typeCheck

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

adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getExpressionName, getHostLanguage, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, iterateSubExpressionInfo, iterateSubExpressions, markTailFunctionCalls, replaceSubExpression, resetLocalStaticProperties, setContainer, setEvaluationMethod, setLocationId, simplify, staticTypeCheck, suppressValidation, toPattern, typeError

Methods inherited from class java.lang.Object

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

Constructor Detail

GroupVariableReference

public GroupVariableReference()

GroupVariableReference

public GroupVariableReference(Binding binding)

Method Detail

optimize

public Expression optimize(ExpressionVisitor visitor,
                  ExpressionVisitor.ContextItemType contextItemType)
                    throws XPathException

Description copied from class: VariableReference

Type-check the expression. At this stage details of the static type must be known. If the variable has a compile-time value, this is substituted for the variable reference

Overrides:

optimize in class VariableReference

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)

copy

public Expression copy()

Create a clone copy of this VariableReference

Overrides:

copy in class LocalVariableReference

Returns:

the cloned copy

setControllingExpression

public void setControllingExpression(ForEachGroup feg)

getControllingExpression

public ForEachGroup getControllingExpression()

computeSpecialProperties

public int computeSpecialProperties()

Determine the special properties of this expression. The properties such as document-ordering are the same as the properties of the grouping population as a whole.

Overrides:

computeSpecialProperties in class VariableReference

Returns:

StaticProperty.NON_CREATIVE (unless the variable is assignable using saxon:assign)

computeCardinality

public int computeCardinality()

Get the static cardinality

Overrides:

computeCardinality in class VariableReference

Returns:

the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE

getStreamability

public int getStreamability(int syntacticContext,
                   boolean allowExtensions,
                   List<String> reasons)

Description copied from class: Expression

Get the "sweep" of this expression as defined in the W3C streamability specifications. This provides an assessment of stylesheet code against the W3C criteria for guaranteed streamability, and is implemented to allow these criteria to be tested. It is not the case that all expression that emerge as streamable from this analysis are currently capable of being streamed by Saxon

Overrides:

getStreamability in class VariableReference

Parameters:

syntacticContext - one of the values Expression.NAVIGATION_CONTEXT, Expression.NODE_VALUE_CONTEXT, Expression.INHERITED_CONTEXT, Expression.INSPECTION_CONTEXT

allowExtensions - if false, the definition of "guaranteed streamability" in the W3C specification is used. If true, Saxon extensions are permitted, which make some

reasons - the caller may supply a list, in which case the implementation may add to this list a message explaining why the construct is not streamable, suitable for inclusion in an error message.

Returns:

one of the values Expression.W3C_MOTIONLESS, Expression.W3C_CONSUMING, Expression.W3C_GROUP_CONSUMING, Expression.W3C_FREE_RANGING

getStreamingAdjunct

public GroupVariableReferenceAdjunct getStreamingAdjunct()

Get a class that supports streamed evaluation of this expression

Overrides:

getStreamingAdjunct in class Expression

Returns:

the relevant StreamingAdjunct, or null if none is available

toStreamingPattern

public Pattern toStreamingPattern(Configuration config,
                         List<String> reasonForFailure)

Convert this expression to a streaming pattern (a pattern used internally to match nodes during push processing of an event stream)

Overrides:

toStreamingPattern in class Expression

Parameters:

config - the Saxon configuration

reasonForFailure - a list which will be populated with messages giving reasons why the expression cannot be converted

Returns:

the equivalent pattern if conversion succeeds; otherwise null