net.sf.saxon.instruct

Class ParentNodeConstructor

Implemented Interfaces:
SourceLocator, EvaluableItem, InstructionInfoProvider, SequenceIterable, Serializable, SourceLocator, TailCallReturner
Known Direct Subclasses:
DocumentInstr, ElementCreator

public abstract class ParentNodeConstructor
extends Instruction

An abstract class to act as a common parent for instructions that create element nodes and document nodes.

Field Summary

protected Expression
content

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD, locationId, staticProperties

Constructor Summary

ParentNodeConstructor()
Create a document or element node constructor instruction

Method Summary

PathMap.PathMapNodeSet
addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap.
protected abstract void
checkContentSequence(StaticContext env)
Check that the child instructions don't violate any obvious constraints for this kind of node
int
computeCardinality()
Get the cardinality of the sequence returned by evaluating this instruction
boolean
createsNewNodes()
Determine whether this instruction creates new nodes.
String
getBaseURI()
Get the static base URI of the instruction
int
getCardinality()
Determine the static cardinality of the expression.
Expression
getContentExpression()
Get the expression that constructs the content of the element
SchemaType
getSchemaType()
Get the schema type chosen for validation; null if not defined
int
getValidationMode()
Get the validation mode for this instruction
boolean
isLazyConstruction()
Establish whether lazy construction is to be used
boolean
isNamespaceSensitive()
Determine whether the schema type is namespace sensitive.
Iterator
iterateSubExpressions()
Get the immediate sub-expressions of this expression.
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 subexpression
void
setBaseURI(String uri)
Set the static base URI of the instruction
void
setContentExpression(Expression content)
Set the expression that constructs the content of the element
void
setLazyConstruction(boolean lazy)
Indicate that lazy construction should (or should not) be used.
void
setSchemaType(SchemaType type)
Set the schema type to be used for validation
void
setValidationMode(int mode)
Set the validation mode for the new document or element node
Expression
simplify(ExpressionVisitor visitor)
Simplify an expression.
Expression
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, evaluateItem, getImplementationMethod, getInstructionInfo, getInstructionNameCode, getItemType, getSourceLocator, isXSLT, iterate, process, processLeavingTail, promote, promoteInst, simplify

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

addToPathMap, adoptChildExpression, checkPermittedContents, computeCardinality, computeDependencies, computeSpecialProperties, computeStaticProperties, copy, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, explain, explain, findParentOf, getCardinality, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getItemType, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterate, iterateEvents, iterateSubExpressions, markTailFunctionCalls, optimize, process, promote, replaceSubExpression, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, simplify, staticTypeCheck, suppressValidation, toString, typeCheck, typeError

Field Details

content

protected Expression content

Constructor Details

ParentNodeConstructor

public ParentNodeConstructor()
Create a document or element node constructor instruction

Method Details

addToPathMap

public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap,
                                           PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.

The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.

Overrides:
addToPathMap in interface Expression
Parameters:
pathMap - the PathMap to which the expression should be added
pathMapNodeSet - the PathMapNodeSet to which the paths embodied in this expression should be added
Returns:
the pathMapNodeSet representing the points in the source document that are both reachable by this expression, and that represent possible results of this expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.

checkContentSequence

protected abstract void checkContentSequence(StaticContext env)
            throws XPathException
Check that the child instructions don't violate any obvious constraints for this kind of node
Parameters:
env - the static context
Throws:
XPathException -

computeCardinality

public int computeCardinality()
Get the cardinality of the sequence returned by evaluating this instruction
Overrides:
computeCardinality in interface Instruction
Returns:
the static cardinality

createsNewNodes

public final boolean createsNewNodes()
Determine whether this instruction creates new nodes. This implementation returns true.
Overrides:
createsNewNodes in interface Instruction

getBaseURI

public String getBaseURI()
Get the static base URI of the instruction
Returns:
the static base URI

getCardinality

public int getCardinality()
Determine the static cardinality of the expression. This establishes how many items there will be in the result of the expression, at compile time (i.e., without actually evaluating the result.
Overrides:
getCardinality in interface Expression
Returns:
one of the values Cardinality.ONE_OR_MORE, Cardinality.ZERO_OR_MORE, Cardinality.EXACTLY_ONE, Cardinality.ZERO_OR_ONE, Cardinality.EMPTY. This default implementation returns ZERO_OR_MORE (which effectively gives no information).

getContentExpression

public Expression getContentExpression()
Get the expression that constructs the content of the element
Returns:
the content expression

getSchemaType

public SchemaType getSchemaType()
Get the schema type chosen for validation; null if not defined
Returns:
the type to be used for validation. (For a document constructor, this is the required type of the document element)

getValidationMode

public int getValidationMode()
Get the validation mode for this instruction

isLazyConstruction

public final boolean isLazyConstruction()
Establish whether lazy construction is to be used
Returns:
true if lazy construction is to be used

isNamespaceSensitive

public boolean isNamespaceSensitive()
Determine whether the schema type is namespace sensitive. The result is undefined if schemaType is null.
Returns:
true if the schema type is namespace sensitive

iterateSubExpressions

public Iterator iterateSubExpressions()
Get the immediate sub-expressions of this expression.
Overrides:
iterateSubExpressions in interface Expression
Returns:
an iterator containing the sub-expressions of this expression

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ItemType contextItemType)
            throws XPathException
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 interface 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 if appropriate to optimize execution
Throws:
XPathException - if an error is discovered during this phase (typically a type error)

promoteInst

protected void promoteInst(PromotionOffer offer)
            throws XPathException
Handle promotion offers, that is, non-local tree rewrites.
Overrides:
promoteInst in interface Instruction
Parameters:
offer - The type of rewrite being offered
Throws:
XPathException -

replaceSubExpression

public boolean replaceSubExpression(Expression original,
                                    Expression replacement)
Replace one subexpression by a replacement subexpression
Overrides:
replaceSubExpression in interface Expression
Parameters:
original - the original subexpression
replacement - the replacement subexpression
Returns:
true if the original subexpression is found

setBaseURI

public void setBaseURI(String uri)
Set the static base URI of the instruction
Parameters:
uri - the static base URI

setContentExpression

public void setContentExpression(Expression content)
Set the expression that constructs the content of the element
Parameters:
content - the content expression

setLazyConstruction

public void setLazyConstruction(boolean lazy)
Indicate that lazy construction should (or should not) be used. Note that this request will be ignored if validation is required
Parameters:
lazy - set to true if lazy construction should be used

setSchemaType

public void setSchemaType(SchemaType type)
Set the schema type to be used for validation
Parameters:
type - the type to be used for validation. (For a document constructor, this is the required type of the document element)

setValidationMode

public void setValidationMode(int mode)
Set the validation mode for the new document or element node

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.
Overrides:
simplify in interface 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,
                            ItemType 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 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 interface 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)