net.sf.saxon.pattern
Class LocationPathPattern

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

All Implemented Interfaces:

Container, java.io.Serializable, javax.xml.transform.SourceLocator

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
protected Expression	equivalentExpr
protected Expression[]	filters
protected boolean	firstElementPattern
protected boolean	lastElementPattern
NodeTest	nodeTest
protected int	numberOfFilters
Pattern	parentPattern
protected boolean	specialFilter

Constructor Summary

LocationPathPattern()

Method Summary

void	addFilter(Expression filter) Add a filter to the pattern (while under construction)
Pattern	analyze(StaticContext env, ItemType contextItemType) Type-check the pattern, performing any type-dependent optimizations.
int	getDependencies() Get the dependencies of 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
protected boolean	internalMatches(NodeInfo node, XPathContext context) Test whether the pattern matches, but without changing the current() node
java.util.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.
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
Pattern	simplify(StaticContext env) 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, setExecutable, setLineNumber, setOriginalText, setSystemId, toString

Methods inherited from class java.lang.Object

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

Field Detail

parentPattern

public Pattern parentPattern

ancestorPattern

public Pattern ancestorPattern

nodeTest

public NodeTest nodeTest

filters

protected Expression[] filters

numberOfFilters

protected int numberOfFilters

equivalentExpr

protected Expression equivalentExpr

firstElementPattern

protected boolean firstElementPattern

lastElementPattern

protected boolean lastElementPattern

specialFilter

protected boolean specialFilter

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

simplify

public Pattern simplify(StaticContext env)
                 throws XPathException

Simplify the pattern: perform any context-independent optimisations

Overrides:

simplify in class Pattern

Returns:

the optimised Pattern

Throws:

XPathException

analyze

public Pattern analyze(StaticContext env,
                       ItemType contextItemType)
                throws XPathException

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

Overrides:

analyze in class Pattern

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

iterateSubExpressions

public java.util.Iterator iterateSubExpressions()

Iterate over the subexpressions within this pattern

Overrides:

iterateSubExpressions in class Pattern

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

internalMatches

protected boolean internalMatches(NodeInfo node,
                                  XPathContext context)
                           throws XPathException

Test whether the pattern matches, but without changing the current() node

Overrides:

internalMatches in class Pattern

Parameters:

node - The NodeInfo representing the Element or other node to be tested against the Pattern

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 node matches the Pattern, false otherwise

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

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