net.sf.saxon.instruct
Class GeneralVariable

java.lang.Object
  net.sf.saxon.expr.ComputedExpression
      net.sf.saxon.instruct.Instruction
          net.sf.saxon.instruct.GeneralVariable

All Implemented Interfaces:

Binding, Container, Expression, InstructionInfoProvider, java.io.Serializable, javax.xml.transform.SourceLocator, TailCallReturner

Direct Known Subclasses:

Assign, GlobalVariable, LocalParam, LocalVariable, SQLColumn.ColumnInstruction, 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

Field Summary

protected int	nameCode
protected int	referenceCount

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

locationId, staticProperties

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

GeneralVariable()

Method Summary

void	display(int level, NamePool pool, java.io.PrintStream out) Diagnostic print of expression structure.
Item	evaluateItem(XPathContext context) Evaluate an expression as a single item.
int	getCardinality() Get the cardinality of the result of this instruction.
int	getInstructionNameCode() Get the namecode of the instruction for use in diagnostics
ItemType	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.
int	getNameCode()
SequenceType	getRequiredType()
Expression	getSelectExpression()
ValueRepresentation	getSelectValue(XPathContext context) Evaluate the variable.
int	getSlotNumber()
int	getVariableFingerprint() Get the name of the variable (as a NamePool fingerprint)
java.lang.String	getVariableName()
void	init(Expression select, int nameCode)
boolean	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	isRequiredParam()
boolean	isTunnelParam()
SequenceIterator	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(Optimizer opt, StaticContext env, ItemType contextItemType) Perform optimisation of an expression and its subexpressions.
protected void	promoteInst(PromotionOffer offer) Handle promotion offers, that is, non-local tree rewrites.
void	setAssignable(boolean assignable)
void	setNameCode(int nameCode)
void	setReferenceCount(int refCount)
void	setRequiredParam(boolean requiredParam)
void	setRequiredType(SequenceType required)
void	setSelectExpression(Expression select)
void	setSlotNumber(int s)
void	setTunnel(boolean tunnel)
void	setVariableName(java.lang.String s)
Expression	simplify(StaticContext env) Simplify an expression.
Expression	typeCheck(StaticContext env, ItemType contextItemType) Perform type checking of an expression and its subexpressions.

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

appendItem, assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, createsNewNodes, dynamicError, evaluateAsString, getImplementationMethod, getInstructionInfo, getSourceLocator, isXSLT, process, processLeavingTail, promote

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

adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, dynamicError, effectiveBooleanValue, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, markTailFunctionCalls, resetStaticProperties, setLocationId, setParentExpression, suppressValidation, typeError, typeError

Methods inherited from class java.lang.Object

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

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

evaluateVariable

Methods inherited from interface javax.xml.transform.SourceLocator

getColumnNumber, getLineNumber, getPublicId, getSystemId

Field Detail

nameCode

protected int nameCode

referenceCount

protected int referenceCount

Constructor Detail

GeneralVariable

public GeneralVariable()

Method Detail

init

public void init(Expression select,
                 int nameCode)

setSelectExpression

public void setSelectExpression(Expression select)

getSelectExpression

public Expression getSelectExpression()

setRequiredType

public void setRequiredType(SequenceType required)

getRequiredType

public SequenceType getRequiredType()

setNameCode

public void setNameCode(int nameCode)

getNameCode

public int getNameCode()

setAssignable

public void setAssignable(boolean assignable)

setRequiredParam

public void setRequiredParam(boolean requiredParam)

setTunnel

public void setTunnel(boolean tunnel)

setReferenceCount

public void setReferenceCount(int refCount)

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 interface Binding

getVariableFingerprint

public int getVariableFingerprint()

Get the name of the variable (as a NamePool fingerprint)

Returns:

the NamePool fingerprint of the variable's expanded name.

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.

Specified by:

getItemType in interface Expression

Overrides:

getItemType in class Instruction

Parameters:

th -

Returns:

the empty type.

getCardinality

public int getCardinality()

Get the cardinality of the result of this instruction. An xsl:variable instruction returns nothing, so the type is empty.

Specified by:

getCardinality in interface Expression

Overrides:

getCardinality in class ComputedExpression

Returns:

the empty cardinality.

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.

Specified by:

isGlobal in interface Binding

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 interface Binding

isRequiredParam

public final boolean isRequiredParam()

isTunnelParam

public final boolean isTunnelParam()

getInstructionNameCode

public int getInstructionNameCode()

Description copied from class: Instruction

Get the namecode of the instruction for use in diagnostics

Overrides:

getInstructionNameCode in class Instruction

simplify

public Expression simplify(StaticContext env)
                    throws XPathException

Description copied from class: Instruction

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 interface Expression

Specified by:

simplify in class Instruction

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(StaticContext env,
                            ItemType contextItemType)
                     throws XPathException

Description copied from interface: Expression

Perform type checking of an expression and its subexpressions.

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.

Specified by:

typeCheck in interface Expression

Parameters:

env - the static context of the expression

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

optimize

public Expression optimize(Optimizer opt,
                           StaticContext env,
                           ItemType contextItemType)
                    throws XPathException

Description copied from interface: Expression

Perform optimisation of an expression and its subexpressions.

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.

Specified by:

optimize in interface Expression

Parameters:

opt - the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.

env - the static context of the expression

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

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 interface 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

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 interface Expression

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

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

Throws:

XPathException

promoteInst

protected void promoteInst(PromotionOffer offer)
                    throws XPathException

Handle promotion offers, that is, non-local tree rewrites.

Overrides:

promoteInst in class Instruction

Parameters:

offer - The type of rewrite being offered

Throws:

XPathException

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)

Specified by:

iterateSubExpressions in interface Expression

Overrides:

iterateSubExpressions in class ComputedExpression

Returns:

an iterator containing the sub-expressions of this expression

display

public void display(int level,
                    NamePool pool,
                    java.io.PrintStream out)

Diagnostic print of expression structure. The expression is written to the System.err output stream

Specified by:

display in interface Expression

Parameters:

level - indentation level for this expression

out -

pool - NamePool used to expand any names appearing in the expression

getSlotNumber

public int getSlotNumber()

setSlotNumber

public void setSlotNumber(int s)

setVariableName

public void setVariableName(java.lang.String s)

getVariableName

public java.lang.String getVariableName()