net.sf.saxon.pattern
Class LocationPathPattern

java.lang.Object
  extended by net.sf.saxon.pattern.Pattern
      extended by 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
           
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()
          Create a LocationPathPattern
 
Method Summary
 void addFilter(Expression filter)
          Add a filter to the pattern (while under construction)
 int allocateSlots(StaticContext env, SlotManager slotManager, 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.
 boolean equals(Object other)
          Determine whether this pattern is the same as another pattern
 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
 int hashCode()
          Hashcode supporting equals()
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, Expression parent)
          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, boolean topLevel)
          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, getContainerGranularity, getDefaultPriority, getExecutable, getHostLanguage, getLineNumber, getLocationProvider, getPublicId, getSystemId, make, makeSearchExpression, selectNodes, setLineNumber, setOriginalText, setSystemId, toString
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, 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()
Create a 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

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(StaticContext env,
                         SlotManager slotManager,
                         int nextFree)
Allocate slots to any variables used within the pattern

Overrides:
allocateSlots in class Pattern
Parameters:
env - the static context in the XSLT stylesheet
slotManager -
nextFree - the next slot that is free to be allocated @return the next slot that is free to be allocated

promote

public void promote(PromotionOffer offer,
                    Expression parent)
             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
parent -
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
Returns:
a NodeTest, as specific as possible, which all the matching nodes satisfy

resolveCurrent

public void resolveCurrent(LetExpression let,
                           PromotionOffer offer,
                           boolean topLevel)
                    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
topLevel -
Throws:
XPathException

equals

public boolean equals(Object other)
Determine whether this pattern is the same as another pattern

Overrides:
equals in class Object
Parameters:
other - the other object

hashCode

public int hashCode()
Hashcode supporting equals()

Overrides:
hashCode in class Object


Copyright (c) Saxonica Limited. All rights reserved.