com.saxonica.xslt3.instruct

Class Fork

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.instruct.Instruction

com.saxonica.xslt3.instruct.Fork

All Implemented Interfaces:

Serializable, SourceLocator, LocationProvider, SaxonLocator, TailCallReturner, InstructionInfo, Locator

public class Fork
extends Instruction

This class implements an xsl:fork expression.

See Also:

Serialized Form

Field Summary

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
Fork(Block content)

Method Summary

Methods

Modifier and Type	Method and Description
int	computeCardinality() Determine the cardinality of the function.
Expression	copy() Copy an expression.
void	explain(ExpressionPresenter out) Diagnostic print of expression structure.
Expression[]	getChildren() Get the content of the fork instruction
ExpressionCompiler	getExpressionCompiler() Return the compiler of the Fork expression
int	getInstructionNameCode() Get the namecode of the instruction for use in diagnostics
ItemType	getItemType(TypeHierarchy th) Determine the item type of the value returned by the function
int	getStreamability(int syntacticContext, boolean allowExtensions, List<String> reasons) Get the "sweep" of this expression as defined in the W3C streamability specifications.
ForkAdjunct	getStreamingAdjunct() Get a class that supports streamed evaluation of this expression
Iterator<Expression>	iterateSubExpressions() Get the immediate sub-expressions of this expression.
TailCall	processLeavingTail(XPathContext context) Process the instruction, without returning any tail calls
Expression	promote(PromotionOffer offer, Expression parent) Offer promotion for this subexpression.
boolean	replaceSubExpression(Expression original, Expression replacement) Replace one subexpression by a replacement subexpression
Expression	simplify(ExpressionVisitor visitor) Simplify an expression.
Expression	typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Perform type checking of an expression and its subexpressions.

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

assembleParams, assembleTunnelParams, computeSpecialProperties, createsNewNodes, dynamicError, evaluateAsString, evaluateItem, getConstructType, getExpressionName, getImplementationMethod, getInstructionName, getIteratorFromProcessMethod, getSourceLocator, isXSLT, iterate, process, promoteInst

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

addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, iterateSubExpressionInfo, markTailFunctionCalls, optimize, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toPattern, toStreamingPattern, toString, typeError

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface javax.xml.transform.SourceLocator

getColumnNumber, getLineNumber, getPublicId, getSystemId

Constructor Detail

Fork

public Fork(Block content)

Method Detail

getInstructionNameCode

public int getInstructionNameCode()

Get the namecode of the instruction for use in diagnostics

Overrides:

getInstructionNameCode in class Instruction

Returns:

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

getChildren

public Expression[] getChildren()

Get the content of the fork instruction

Returns:

the child instructions of the xsl:fork

computeCardinality

public int computeCardinality()

Determine the cardinality of the function.

Overrides:

computeCardinality in class Instruction

Returns:

the static cardinality

getItemType

public ItemType getItemType(TypeHierarchy th)

Determine the item type of the value returned by the function

Overrides:

getItemType in class Instruction

Parameters:

th - the type hierarchy cache

Returns:

the static item type of the instruction

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.

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

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                   ExpressionVisitor.ContextItemType 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 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)

iterateSubExpressions

public Iterator<Expression> iterateSubExpressions()

Get the immediate sub-expressions of this expression.

Overrides:

iterateSubExpressions in class Expression

Returns:

an iterator containing the sub-expressions of this expression

promote

public Expression promote(PromotionOffer offer,
                 Expression parent)
                   throws XPathException

Offer promotion for this subexpression. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. By default the offer is not accepted - this is appropriate in the case of simple expressions such as constant values and variable references where promotion would give no performance advantage. This method is always called at compile time.

This method must be overridden for any Expression that has subexpressions.

Overrides:

promote in class Instruction

Parameters:

offer - details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression

parent - the parent of the expression being promoted

Returns:

if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression

Throws:

XPathException - if any error is detected

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

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 Expression

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 ForkAdjunct 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

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

processLeavingTail

public TailCall processLeavingTail(XPathContext context)
                            throws XPathException

Process the instruction, without returning any tail calls

Specified by:

processLeavingTail in interface TailCallReturner

Specified by:

processLeavingTail in class Instruction

Parameters:

context - The dynamic context, giving access to the current node, the current variables, etc.

Returns:

null if the instruction has completed execution; or a TailCall indicating a function call or template call that is delegated to the caller, to be made after the stack has been unwound so as to save stack space.

Throws:

XPathException - if a dynamic error occurs during the evaluation of the instruction

getExpressionCompiler

public ExpressionCompiler getExpressionCompiler()

Return the compiler of the Fork expression

Overrides:

getExpressionCompiler in class Expression

Returns:

the relevant ExpressionCompiler

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