net.sf.saxon.pattern

Class LocationPathPattern

Implemented Interfaces:
Container, PatternFinder, Serializable, 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

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)
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
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.
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

allocateSlots, analyze, getColumnNumber, getDefaultPriority, getDependencies, getExecutable, getFingerprint, getHostLanguage, getLineNumber, getLocationProvider, getNodeKind, getNodeTest, getPublicId, getSystemId, internalMatches, iterateSubExpressions, make, makeSearchExpression, matches, promote, replaceSubExpression, selectNodes, setExecutable, setLineNumber, setOriginalText, setSystemId, simplify, toString

Field Details

ancestorPattern

public Pattern ancestorPattern

equivalentExpr

protected Expression equivalentExpr

filters

protected Expression[] filters

firstElementPattern

protected boolean firstElementPattern

lastElementPattern

protected boolean lastElementPattern

nodeTest

public NodeTest nodeTest

numberOfFilters

protected int numberOfFilters

parentPattern

public Pattern parentPattern

specialFilter

protected boolean specialFilter

Constructor Details

LocationPathPattern

public LocationPathPattern()

Method Details

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

allocateSlots

public int allocateSlots(ExpressionContext env,
                         int nextFree)
Allocate slots to any variables used within the pattern
Overrides:
allocateSlots in interface 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

analyze

public Pattern analyze(ExpressionVisitor visitor,
                       ItemType contextItemType)
            throws XPathException
Type-check the pattern, performing any type-dependent optimizations.
Overrides:
analyze in interface Pattern
Parameters:
visitor - an expression visitor
contextItemType - the type of the context item at the point where the pattern appears
Returns:
the optimised Pattern

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]

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 interface Pattern

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

getFingerprint

public int getFingerprint()
Determine the fingerprint of nodes to which this pattern applies. Used for optimisation.
Overrides:
getFingerprint in interface Pattern
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
Overrides:
getNodeKind in interface Pattern
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
Overrides:
getNodeTest in interface Pattern

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]

internalMatches

protected boolean internalMatches(NodeInfo node,
                                  XPathContext context)
            throws XPathException
Test whether the pattern matches, but without changing the current() node
Overrides:
internalMatches in interface Pattern

iterateSubExpressions

public Iterator iterateSubExpressions()
Iterate over the subexpressions within this pattern
Overrides:
iterateSubExpressions in interface Pattern

matches

public boolean matches(NodeInfo node,
                       XPathContext context)
            throws XPathException
Determine whether the pattern matches a given node.
Overrides:
matches in interface Pattern
Parameters:
node - the node to be tested
Returns:
true if the pattern matches, else false

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 interface 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

replaceSubExpression

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

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 -

setExecutable

public void setExecutable(Executable executable)
Set the executable containing this pattern
Overrides:
setExecutable in interface Pattern
Parameters:
executable - the executable

simplify

public Pattern simplify(ExpressionVisitor visitor)
            throws XPathException
Simplify the pattern: perform any context-independent optimisations
Overrides:
simplify in interface Pattern
Parameters:
visitor - an expression visitor