net.sf.saxon.expr.instruct
Class GlobalVariable

java.lang.Object
  net.sf.saxon.expr.Expression
      net.sf.saxon.expr.instruct.Instruction
          net.sf.saxon.expr.instruct.GeneralVariable
              net.sf.saxon.expr.instruct.GlobalVariable

All Implemented Interfaces:

Serializable, SourceLocator, LocationProvider, SaxonLocator, Binding, Container, EvaluableItem, TailCallReturner, SequenceIterable, InstructionInfo, Locator

Direct Known Subclasses:

GlobalParam

public class GlobalVariable
extends GeneralVariable
implements Container

A compiled global variable in a stylesheet or query.

See Also:

Serialized Form

Field Summary

Fields inherited from class net.sf.saxon.expr.instruct.GeneralVariable

evaluationMode, referenceCount, slotNumber, variableQName

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

EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, PUSH_SELECTION, staticProperties, WATCH_METHOD

Constructor Summary

GlobalVariable()
Create a global variable

Method Summary

protected ValueRepresentation	actuallyEvaluate(XPathContext context) Evaluate the global variable, and save its value for use in subsequent references.
ValueRepresentation	evaluateVariable(XPathContext context) Evaluate the variable
int	getContainerGranularity() Get the granularity of the container.
Executable	getExecutable() Get the executable containing this global variable
int	getHostLanguage() Get the host language (XSLT, XQuery, XPath) used to implement the code in this container
ValueRepresentation	getSelectValue(XPathContext context) Evaluate the variable.
boolean	isGlobal() Is this a global variable?
boolean	isIndexedVariable() Ask whether this is an indexed variable
void	lookForCycles(Stack referees, XQueryFunctionLibrary globalFunctionLibrary) Check for cycles in this variable definition
TailCall	processLeavingTail(XPathContext context) Process the variable declaration
void	setContainsLocals(SlotManager map) The expression that initializes a global variable may itself use local variables.
protected static void	setDependencies(Bindery bindery, GlobalVariable var, XPathContext context) Get the variable that is immediately dependent on this one, and register the dependency, so that circularities can be detected across threads.
void	setExecutable(Executable executable) Set the containing executable
void	setIndexedVariable() Mark this as an indexed variable, to allow fast searching

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

copy, evaluateItem, explain, getCardinality, getEvaluationMode, getInstructionNameCode, getItemType, getLocalSlotNumber, getRequiredType, getSelectExpression, getSlotNumber, getVariableQName, init, isAssignable, isImplicitlyRequiredParam, isRequiredParam, isTunnelParam, iterate, iterateSubExpressions, optimize, promoteInst, replaceSubExpression, setAssignable, setImplicitlyRequiredParam, setReferenceCount, setRequiredParam, setRequiredType, setSelectExpression, setSlotNumber, setTunnel, setVariableQName, simplify, typeCheck

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

assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, createsNewNodes, dynamicError, evaluateAsString, getConstructType, getExpressionName, getImplementationMethod, getInstructionName, getIteratorFromProcessMethod, getSourceLocator, isXSLT, process, promote

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

addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluatePendingUpdates, explain, getColumnNumber, getColumnNumber, getContainer, getDependencies, getEvaluationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toString, typeError

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.sf.saxon.expr.Container

getLocationProvider

Methods inherited from interface javax.xml.transform.SourceLocator

getColumnNumber, getLineNumber, getPublicId, getSystemId

Constructor Detail

GlobalVariable

public GlobalVariable()

Create a global variable

Method Detail

getExecutable

public Executable getExecutable()

Get the executable containing this global variable

Specified by:

getExecutable in interface Container

Overrides:

getExecutable in class Expression

Returns:

the containing executable

setExecutable

public void setExecutable(Executable executable)

Set the containing executable

Parameters:

executable - the executable that contains this global variable

getHostLanguage

public int getHostLanguage()

Get the host language (XSLT, XQuery, XPath) used to implement the code in this container

Specified by:

getHostLanguage in interface Container

Overrides:

getHostLanguage in class Expression

Returns:

typically Configuration.XSLT or Configuration.XQUERY

setIndexedVariable

public void setIndexedVariable()

Mark this as an indexed variable, to allow fast searching

isIndexedVariable

public boolean isIndexedVariable()

Ask whether this is an indexed variable

Returns:

true if this variable is indexed

getContainerGranularity

public int getContainerGranularity()

Get the granularity of the container.

Specified by:

getContainerGranularity in interface Container

Returns:

0 for a temporary container created during parsing; 1 for a container that operates at the level of an XPath expression; 2 for a container at the level of a global function or template

setContainsLocals

public void setContainsLocals(SlotManager map)

The expression that initializes a global variable may itself use local variables. In this case a stack frame needs to be allocated while evaluating the global variable

Parameters:

map - The stack frame map for local variables used while evaluating this global variable.

isGlobal

public boolean isGlobal()

Is this a global variable?

Specified by:

isGlobal in interface Binding

Overrides:

isGlobal in class GeneralVariable

Returns:

true (yes, it is a global variable)

lookForCycles

public void lookForCycles(Stack referees,
                          XQueryFunctionLibrary globalFunctionLibrary)
                   throws XPathException

Check for cycles in this variable definition

Parameters:

referees - the calls leading up to this one; it's an error if this variable is on the stack, because that means it calls itself directly or indirectly. The stack may contain variable definitions (GlobalVariable objects) and user-defined functions (UserFunction objects). It will never contain the same object more than once.

globalFunctionLibrary - the library containing all global functions

Throws:

XPathException

processLeavingTail

public TailCall processLeavingTail(XPathContext context)
                            throws XPathException

Process the variable declaration

Specified by:

processLeavingTail in interface TailCallReturner

Specified by:

processLeavingTail in class Instruction

Parameters:

context - The dynamic context of the transformation, 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

getSelectValue

public ValueRepresentation getSelectValue(XPathContext context)
                                   throws XPathException

Evaluate the variable. That is, get the value of the select expression if present or the content of the element otherwise, either as a tree or as a sequence

Overrides:

getSelectValue in class GeneralVariable

Parameters:

context - the XPath dynamic context

Returns:

the result of evaluating the variable

Throws:

XPathException

evaluateVariable

public ValueRepresentation evaluateVariable(XPathContext context)
                                     throws XPathException

Evaluate the variable

Specified by:

evaluateVariable in interface Binding

Parameters:

context - the XPath dynamic evaluation context

Returns:

the result of evaluating the variable

Throws:

XPathException

actuallyEvaluate

protected ValueRepresentation actuallyEvaluate(XPathContext context)
                                        throws XPathException

Evaluate the global variable, and save its value for use in subsequent references.

Parameters:

context - the XPath dynamic context

Returns:

the value of the variable

Throws:

XPathException - if evaluation fails

setDependencies

protected static void setDependencies(Bindery bindery,
                                      GlobalVariable var,
                                      XPathContext context)
                               throws XPathException

Get the variable that is immediately dependent on this one, and register the dependency, so that circularities can be detected across threads. This relies on the fact that when the initialiser for variable X contains a reference to variable Y, then when Y is evaluated, a stack frame will be found on the context stack representing the evaluation of X. We don't set a dependency from X to Y if the value of Y was already available in the Bindery; it's not needed, because in this case we know that evaluation of Y is unproblematic, and can't lead to any circularities.

Parameters:

bindery - the Bindery

var - the global variable or parameter being evaluated

context - the dynamic evaluation context

Throws:

XPathException