net.sf.saxon.pattern
Class LocationPathPattern

java.lang.Object
  net.sf.saxon.pattern.Pattern
      net.sf.saxon.pattern.LocationPathPattern

All Implemented Interfaces:

Serializable, SourceLocator, Container, PatternFinder

public final class LocationPathPattern
extends Pattern

A LocationPathPattern represents a path, for example of the form A/B/C... The components are represented as a linked list, each component pointing to its predecessor

See Also:

Serialized Form

Field Summary

Pattern	ancestorPattern
NodeTest	nodeTest
Pattern	parentPattern

Constructor Summary

LocationPathPattern()

Method Summary

void	addFilter(Expression filter) Add a filter to the pattern (while under construction)
int	allocateSlots(ExpressionContext env, int nextFree) Allocate slots to any variables used within the pattern
Pattern	analyze(ExpressionVisitor visitor, ItemType contextItemType) Type-check the pattern, performing any type-dependent optimizations.
Pattern	getAncestorPattern() Get the pattern applying to an ancestor node, if there is one
int	getDependencies() Get the dependencies of the pattern.
Expression[]	getFilters() Get the filters assocated with the last step in the pattern
int	getFingerprint() Determine the fingerprint of nodes to which this pattern applies.
int	getNodeKind() Determine the types of nodes to which this pattern applies.
NodeTest	getNodeTest() Get a NodeTest that all the nodes matching this pattern must satisfy
Pattern	getParentPattern() Get the pattern applying to the parent node, if there is one
Iterator	iterateSubExpressions() Iterate over the subexpressions within this pattern
boolean	matches(NodeInfo node, XPathContext context) Determine whether the pattern matches a given node.
void	promote(PromotionOffer offer) Offer promotion for subexpressions within this pattern.
boolean	replaceSubExpression(Expression original, Expression replacement) Replace one subexpression by a replacement subexpression
void	resolveCurrent(LetExpression let, PromotionOffer offer) If the pattern contains any calls on current(), this method is called to modify such calls to become variable references to a variable declared in a specially-allocated local variable
void	setExecutable(Executable executable) Set the executable containing this pattern
Pattern	simplify(ExpressionVisitor visitor) Simplify the pattern: perform any context-independent optimisations

Methods inherited from class net.sf.saxon.pattern.Pattern

getColumnNumber, getDefaultPriority, getExecutable, getHostLanguage, getLineNumber, getLocationProvider, getPublicId, getSystemId, make, makeSearchExpression, selectNodes, setLineNumber, setOriginalText, setSystemId, toString

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

parentPattern

public Pattern parentPattern

ancestorPattern

public Pattern ancestorPattern

nodeTest

public NodeTest nodeTest

Constructor Detail

LocationPathPattern

public LocationPathPattern()

Method Detail

addFilter

public void addFilter(Expression filter)

Add a filter to the pattern (while under construction)

Parameters:

filter - The predicate (a boolean expression or numeric expression) to be added

setExecutable

public void setExecutable(Executable executable)

Set the executable containing this pattern

Overrides:

setExecutable in class Pattern

Parameters:

executable - the executable

getFilters

public Expression[] getFilters()

Get the filters assocated with the last step in the pattern

Returns:

an array of expression holding the filter predicates in order

getParentPattern

public Pattern getParentPattern()

Get the pattern applying to the parent node, if there is one

Returns:

the parent pattern, for example if the pattern is a/b[1]/c then the parent pattern is a/b[1]

getAncestorPattern

public Pattern getAncestorPattern()

Get the pattern applying to an ancestor node, if there is one

Returns:

the ancestor pattern, for example if the pattern is a/b[1]//c then the ancestor pattern is a/b[1]

simplify

public Pattern simplify(ExpressionVisitor visitor)
                 throws XPathException

Simplify the pattern: perform any context-independent optimisations

Overrides:

simplify in class Pattern

Parameters:

visitor - an expression visitor

Returns:

the optimised Pattern

Throws:

XPathException

analyze

public Pattern analyze(ExpressionVisitor visitor,
                       ItemType contextItemType)
                throws XPathException

Type-check the pattern, performing any type-dependent optimizations.

Overrides:

analyze in class Pattern

Parameters:

visitor - an expression visitor

contextItemType - the type of the context item at the point where the pattern appears

Returns:

the optimised Pattern

Throws:

XPathException

getDependencies

public int getDependencies()

Get the dependencies of the pattern. The only possible dependency for a pattern is on local variables. This is analyzed in those patterns where local variables may appear.

Overrides:

getDependencies in class Pattern

Returns:

the dependencies, as a bit-significant mask

iterateSubExpressions

public Iterator iterateSubExpressions()

Iterate over the subexpressions within this pattern

Overrides:

iterateSubExpressions in class Pattern

Returns:

an iterator over the subexpressions. Default implementation returns an empty sequence

replaceSubExpression

public boolean replaceSubExpression(Expression original,
                                    Expression replacement)

Replace one subexpression by a replacement subexpression

Specified by:

replaceSubExpression in interface Container

Overrides:

replaceSubExpression in class Pattern

Parameters:

original - the original subexpression

replacement - the replacement subexpression

Returns:

true if the original subexpression is found

allocateSlots

public int allocateSlots(ExpressionContext env,
                         int nextFree)

Allocate slots to any variables used within the pattern

Parameters:

env - the static context in the XSLT stylesheet

nextFree - the next slot that is free to be allocated

Returns:

the next slot that is free to be allocated

promote

public void promote(PromotionOffer offer)
             throws XPathException

Offer promotion for subexpressions within this pattern. 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.

Unlike the corresponding method on Expression, this method does not return anything: it can make internal changes to the pattern, but cannot return a different pattern. Only certain kinds of promotion are applicable within a pattern: specifically, promotions affecting local variable references within the pattern.

Overrides:

promote in class Pattern

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

Throws:

XPathException - if any error is detected

matches

public boolean matches(NodeInfo node,
                       XPathContext context)
                throws XPathException

Determine whether the pattern matches a given node.

Specified by:

matches in class Pattern

Parameters:

node - the node to be tested

context - The dynamic context. Only relevant if the pattern uses variables, or contains calls on functions such as document() or key().

Returns:

true if the pattern matches, else false

Throws:

XPathException

getNodeKind

public int getNodeKind()

Determine the types of nodes to which this pattern applies. Used for optimisation. For patterns that match nodes of several types, return Node.NODE

Overrides:

getNodeKind in class Pattern

Returns:

the type of node matched by this pattern. e.g. Node.ELEMENT or Node.TEXT

getFingerprint

public int getFingerprint()

Determine the fingerprint of nodes to which this pattern applies. Used for optimisation.

Overrides:

getFingerprint in class Pattern

Returns:

the fingerprint of nodes matched by this pattern.

getNodeTest

public NodeTest getNodeTest()

Get a NodeTest that all the nodes matching this pattern must satisfy

Specified by:

getNodeTest in class Pattern

Returns:

a NodeTest, as specific as possible, which all the matching nodes satisfy

resolveCurrent

public void resolveCurrent(LetExpression let,
                           PromotionOffer offer)
                    throws XPathException

If the pattern contains any calls on current(), this method is called to modify such calls to become variable references to a variable declared in a specially-allocated local variable

Parameters:

let - the expression that assigns the local variable. This returns a dummy result, and is executed just before evaluating the pattern, to get the value of the context item into the variable.

offer - A PromotionOffer used to process the expressions and change the call on current() into a variable reference

Throws:

XPathException