net.sf.saxon.pattern

Class LocationPathPattern

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

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

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
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

Field Detail

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

analyze

public Pattern analyze(StaticContext env, ItemType contextItemType)

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

Returns: the optimised Pattern

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.

getFingerprint

public int getFingerprint()

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

Returns: the fingerprint of nodes matched by this pattern.

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

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

getNodeTest

public NodeTest getNodeTest()

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

internalMatches

protected boolean internalMatches(NodeInfo node, XPathContext context)

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

iterateSubExpressions

public Iterator iterateSubExpressions()

Iterate over the subexpressions within this pattern

matches

public boolean matches(NodeInfo node, XPathContext context)

Determine whether the pattern matches a given node.

Parameters: node the node to be tested

Returns: true if the pattern matches, else false

promote

public void promote(PromotionOffer offer)

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.

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: net.sf.saxon.trans.XPathException if any error is detected

resolveCurrent

public 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

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

simplify

public Pattern simplify(StaticContext env)

Simplify the pattern: perform any context-independent optimisations