Class GeneralVariable
- java.lang.Object
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- net.sf.saxon.expr.Expression
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- net.sf.saxon.instruct.Instruction
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- net.sf.saxon.instruct.GeneralVariable
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,LocationProvider
,SaxonLocator
,Binding
,EvaluableItem
,SequenceIterable
,TailCallReturner
,InstructionInfo
,org.xml.sax.Locator
- Direct Known Subclasses:
Assign
,GlobalVariable
,LocalParam
,LocalVariable
,WithParam
public abstract class GeneralVariable extends Instruction implements Binding
This class defines common behaviour across xsl:variable, xsl:param, and xsl:with-param; also saxon:assign- See Also:
- Serialized Form
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Field Summary
Fields Modifier and Type Field Description protected int
evaluationMode
protected int
referenceCount
protected int
slotNumber
protected StructuredQName
variableQName
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Fields inherited from class net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties
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Constructor Summary
Constructors Constructor Description GeneralVariable()
Create a general variable
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description Expression
copy()
Copy an expression.Item
evaluateItem(XPathContext context)
Evaluate an expression as a single item.void
explain(ExpressionPresenter out)
Diagnostic print of expression structure.int
getCardinality()
Get the cardinality of the result of this instruction.int
getEvaluationMode()
Get the evaluation mode of the variableint
getInstructionNameCode()
Get the name of this instruction (that is xsl:variable, xsl:param etc) for diagnosticsItemType
getItemType(TypeHierarchy th)
Get the type of the result of this instruction.int
getLocalSlotNumber()
If this is a local variable held on the local stack frame, return the corresponding slot number.SequenceType
getRequiredType()
Get the required type of this variableExpression
getSelectExpression()
Get the expression to which this variable is boundValueRepresentation
getSelectValue(XPathContext context)
Evaluate the variable.int
getSlotNumber()
Get the slot number allocated to this variableStructuredQName
getVariableQName()
Get the name of this variablevoid
init(Expression select, StructuredQName qName)
Initialize the properties of the variableboolean
isAssignable()
Test whether it is permitted to assign to the variable using the saxon:assign extension element.boolean
isGlobal()
Indicate whether the binding is local or global.boolean
isImplicitlyRequiredParam()
Ask whether this variable represents a parameter that is implicitly required, because there is no usable default valueboolean
isRequiredParam()
Ask whether this variable represents a required parameterboolean
isTunnelParam()
Ask whether this variable represents a tunnel parameterSequenceIterator
iterate(XPathContext context)
Return an Iterator to iterate over the values of a sequence.java.util.Iterator
iterateSubExpressions()
Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction)Expression
optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.protected void
promoteInst(PromotionOffer offer)
Handle promotion offers, that is, non-local tree rewrites.boolean
replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpressionvoid
setAssignable(boolean assignable)
Indicate whether this variable is assignable using saxon:assignvoid
setImplicitlyRequiredParam(boolean requiredParam)
Indicate that this variable represents a parameter that is implicitly required (because there is no usable default value)void
setReferenceCount(int refCount)
Set the nominal number of references to this variablevoid
setRequiredParam(boolean requiredParam)
Indicate that this variable represents a required parametervoid
setRequiredType(SequenceType required)
Set the required type of this variablevoid
setSelectExpression(Expression select)
Set the expression to which this variable is boundvoid
setSlotNumber(int s)
Set the slot number of this variablevoid
setTunnel(boolean tunnel)
Indicate whether this variable represents a tunnel parametervoid
setVariableQName(StructuredQName s)
Set the name of the variableExpression
simplify(ExpressionVisitor visitor)
Simplify this expressionExpression
typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Perform type checking of an expression and its subexpressions.-
Methods inherited from class net.sf.saxon.instruct.Instruction
assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, createsNewNodes, dynamicError, evaluateAsString, getConstructType, getImplementationMethod, getSourceLocator, isXSLT, process, processLeavingTail, promote
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Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, dynamicError, effectiveBooleanValue, evaluatePendingUpdates, explain, findParentOf, getColumnNumber, getColumnNumber, getContainer, getDependencies, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isUpdatingExpression, iterateEvents, markTailFunctionCalls, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toString, typeError
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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
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Methods inherited from interface net.sf.saxon.expr.Binding
evaluateVariable
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Field Detail
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variableQName
protected StructuredQName variableQName
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slotNumber
protected int slotNumber
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referenceCount
protected int referenceCount
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evaluationMode
protected int evaluationMode
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Method Detail
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init
public void init(Expression select, StructuredQName qName)
Initialize the properties of the variable- Parameters:
select
- the expression to which the variable is boundqName
- the name of the variable
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setSelectExpression
public void setSelectExpression(Expression select)
Set the expression to which this variable is bound- Parameters:
select
- the initializing expression
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getSelectExpression
public Expression getSelectExpression()
Get the expression to which this variable is bound- Returns:
- the initializing expression
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setRequiredType
public void setRequiredType(SequenceType required)
Set the required type of this variable- Parameters:
required
- the required type
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getRequiredType
public SequenceType getRequiredType()
Get the required type of this variable- Specified by:
getRequiredType
in interfaceBinding
- Returns:
- the required type
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setAssignable
public void setAssignable(boolean assignable)
Indicate whether this variable is assignable using saxon:assign- Parameters:
assignable
- true if this variable is assignable
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setRequiredParam
public void setRequiredParam(boolean requiredParam)
Indicate that this variable represents a required parameter- Parameters:
requiredParam
- true if this is a required parameter
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setImplicitlyRequiredParam
public void setImplicitlyRequiredParam(boolean requiredParam)
Indicate that this variable represents a parameter that is implicitly required (because there is no usable default value)- Parameters:
requiredParam
- true if this is an implicitly required parameter
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setTunnel
public void setTunnel(boolean tunnel)
Indicate whether this variable represents a tunnel parameter- Parameters:
tunnel
- true if this is a tunnel parameter
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setReferenceCount
public void setReferenceCount(int refCount)
Set the nominal number of references to this variable- Parameters:
refCount
- the nominal number of references
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getEvaluationMode
public int getEvaluationMode()
Get the evaluation mode of the variable- Returns:
- the evaluation mode (a constant in
ExpressionTool
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isAssignable
public final boolean isAssignable()
Test whether it is permitted to assign to the variable using the saxon:assign extension element. This will only be true if the extra attribute saxon:assignable="yes" is present.- Specified by:
isAssignable
in interfaceBinding
- Returns:
- true if the binding is assignable
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getItemType
public ItemType getItemType(TypeHierarchy th)
Get the type of the result of this instruction. An xsl:variable instruction returns nothing, so the type is empty.- Overrides:
getItemType
in classInstruction
- Parameters:
th
- the type hierarchy cache- Returns:
- the empty type.
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getCardinality
public int getCardinality()
Get the cardinality of the result of this instruction. An xsl:variable instruction returns nothing, so the type is empty.- Overrides:
getCardinality
in classExpression
- Returns:
- the empty cardinality.
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isGlobal
public boolean isGlobal()
Description copied from interface:Binding
Indicate whether the binding is local or global. A global binding is one that has a fixed value for the life of a query or transformation; any other binding is local.
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getLocalSlotNumber
public int getLocalSlotNumber()
If this is a local variable held on the local stack frame, return the corresponding slot number. In other cases, return -1.- Specified by:
getLocalSlotNumber
in interfaceBinding
- Returns:
- the slot number on the local stack frame
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isRequiredParam
public final boolean isRequiredParam()
Ask whether this variable represents a required parameter- Returns:
- true if this is a required parameter
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isImplicitlyRequiredParam
public final boolean isImplicitlyRequiredParam()
Ask whether this variable represents a parameter that is implicitly required, because there is no usable default value- Returns:
- true if this variable is an implicitly required parameter
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isTunnelParam
public final boolean isTunnelParam()
Ask whether this variable represents a tunnel parameter- Returns:
- true if this is a tunnel parameter
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getInstructionNameCode
public int getInstructionNameCode()
Get the name of this instruction (that is xsl:variable, xsl:param etc) for diagnostics- Overrides:
getInstructionNameCode
in classInstruction
- Returns:
- the name of this instruction, as a name pool name code
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simplify
public Expression simplify(ExpressionVisitor visitor) throws XPathException
Simplify this expression- Specified by:
simplify
in classInstruction
- Parameters:
visitor
- an expression- Returns:
- the simplified expression
- Throws:
XPathException
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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 classExpression
- Parameters:
visitor
- an expression visitorcontextItemType
- 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 toType.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)
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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 classExpression
- Parameters:
visitor
- an expression visitorcontextItemType
- 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 toType.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)
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copy
public Expression copy()
Copy an expression. This makes a deep copy.- Specified by:
copy
in classExpression
- Returns:
- the copy of the original expression
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evaluateItem
public Item evaluateItem(XPathContext context) throws XPathException
Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.- Specified by:
evaluateItem
in interfaceEvaluableItem
- Overrides:
evaluateItem
in classInstruction
- 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
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iterate
public SequenceIterator iterate(XPathContext context) throws XPathException
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 relies on the process() method: it "pushes" the results of the instruction to a sequence in memory, and then iterates over this in-memory sequence. In principle instructions should implement a pipelined iterate() method that avoids the overhead of intermediate storage.- Specified by:
iterate
in interfaceSequenceIterable
- Overrides:
iterate
in classInstruction
- 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
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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- Parameters:
context
- the XPath dynamic context- Returns:
- the result of evaluating the variable
- Throws:
XPathException
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promoteInst
protected void promoteInst(PromotionOffer offer) throws XPathException
Handle promotion offers, that is, non-local tree rewrites.- Overrides:
promoteInst
in classInstruction
- Parameters:
offer
- The type of rewrite being offered- Throws:
XPathException
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iterateSubExpressions
public java.util.Iterator iterateSubExpressions()
Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction)- Overrides:
iterateSubExpressions
in classExpression
- Returns:
- an iterator containing the sub-expressions of this expression
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replaceSubExpression
public boolean replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpression- Overrides:
replaceSubExpression
in classExpression
- Parameters:
original
- the original subexpressionreplacement
- the replacement subexpression- Returns:
- true if the original subexpression is found
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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 classExpression
- Parameters:
out
- the expression presenter used to display the structure
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getSlotNumber
public int getSlotNumber()
Get the slot number allocated to this variable- Returns:
- the slot number, that is the position allocated to the variable on its stack frame
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setSlotNumber
public void setSlotNumber(int s)
Set the slot number of this variable- Parameters:
s
- the slot number, that is, the position allocated to this variable on its stack frame
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setVariableQName
public void setVariableQName(StructuredQName s)
Set the name of the variable- Parameters:
s
- the name of the variable (a QName)
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getVariableQName
public StructuredQName getVariableQName()
Get the name of this variable- Specified by:
getVariableQName
in interfaceBinding
- Returns:
- the name of this variable (a QName)
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