net.sf.saxon.pattern

Class NodeSetPattern

java.lang.Object

net.sf.saxon.pattern.Pattern

net.sf.saxon.pattern.NodeSetPattern

All Implemented Interfaces:

Serializable, SourceLocator, Container, PatternFinder

public class NodeSetPattern
extends Pattern

A NodeSetPattern is a pattern based on an expression that is evaluated to return a set of nodes; a node matches the pattern if it is a member of this node-set.

In XSLT 2.0 there are two forms of NodeSetPattern allowed, represented by calls on the id() and key() functions. In XSLT 3.0, additional forms are allowed, for example a variable reference, and a call to the doc() function. This class provides the general capability to use any expression at the head of a pattern. This is used also to support streaming, where streaming XPath expressions are mapped to patterns.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected Expression	expression
protected ItemType	itemType

Constructor Summary

Constructors

Constructor and Description
NodeSetPattern(Expression exp) Create a node-set pattern.

Method Summary

Methods

Modifier and Type	Method and Description
int	allocateSlots(SlotManager slotManager, int nextFree) Allocate slots to any variables used within the pattern
Pattern	analyze(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Type-check the pattern.
boolean	equals(Object other) Determine whether this pattern is the same as another pattern
int	getDependencies() Get the dependencies of the pattern.
ItemType	getItemType() Get a NodeTest that all the nodes matching this pattern must satisfy
int	getNodeKind() Determine the type of nodes to which this pattern applies.
int	hashCode() Hashcode supporting equals()
boolean	isMotionless(boolean allowExtensions) Test whether a pattern is motionless, that is, whether it can be evaluated against a node without repositioning the input stream.
Iterator<Expression>	iterateSubExpressions() Iterate over the subexpressions within this pattern
boolean	matches(Item item, XPathContext context) Determine whether this Pattern matches the given Node
void	promote(PromotionOffer offer, Expression parent) Offer promotion for subexpressions within this pattern.
boolean	replaceSubExpression(Expression original, Expression replacement) Replace a subexpression by a replacement subexpression

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

bindCurrent, getColumnNumber, getContainerGranularity, getDefaultPriority, getExecutable, getFingerprint, getHostLanguage, getLineNumber, getLocationProvider, getPublicId, getSystemId, make, matchesBeneathAnchor, replaceCurrent, selectNodes, setExecutable, setLineNumber, setOriginalText, setSystemId, simplify, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

expression

protected Expression expression

itemType

protected ItemType itemType

Constructor Detail

NodeSetPattern

public NodeSetPattern(Expression exp)

Create a node-set pattern.

Parameters:

exp - an expression that can be evaluated to return a node-set; a node matches the pattern if it is present in this node-set. The expression must not depend on the focus, though it can depend on other aspects of the dynamic context such as local or global variables.

Method Detail

analyze

public Pattern analyze(ExpressionVisitor visitor,
              ExpressionVisitor.ContextItemType contextItemType)
                throws XPathException

Type-check the pattern. Default implementation does nothing. This is only needed for patterns that contain variable references or function calls.

Overrides:

analyze in class Pattern

Parameters:

visitor - the expression visitor

contextItemType - the type of the context item at the point where the pattern is defined. Set to null if it is known that the context item is undefined.

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<Expression> 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

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

replaceSubExpression

public boolean replaceSubExpression(Expression original,
                           Expression replacement)

Replace a subexpression by a replacement subexpression

Overrides:

replaceSubExpression in class Pattern

Parameters:

original - the expression to be replaced

replacement - the new expression to be inserted in its place

Returns:

true if the replacement was carried out

isMotionless

public boolean isMotionless(boolean allowExtensions)

Test whether a pattern is motionless, that is, whether it can be evaluated against a node without repositioning the input stream. This is a necessary condition for patterns used as the match pattern of a streamed template rule.

Overrides:

isMotionless in class Pattern

Parameters:

allowExtensions -

Returns:

true if the pattern is motionless, that is, if it can be evaluated against a streamed node without changing the position in the streamed input file

allocateSlots

public int allocateSlots(SlotManager slotManager,
                int nextFree)

Allocate slots to any variables used within the pattern

Overrides:

allocateSlots in class Pattern

Parameters:

slotManager - the slot manager representing the stack frame for local variables

nextFree - the next slot that is free to be allocated @return the next slot that is free to be allocated

Returns:

the next slot that is free to be allocated

matches

public boolean matches(Item item,
              XPathContext context)
                throws XPathException

Determine whether this Pattern matches the given Node

Specified by:

matches in class Pattern

Parameters:

item - 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 - if an error occurs while matching the pattern (the caller will usually treat this the same as a false result)

getNodeKind

public int getNodeKind()

Determine the type of nodes to which this pattern applies.

Overrides:

getNodeKind in class Pattern

Returns:

Type.NODE (may be overridden in subclasses)

getItemType

public ItemType getItemType()

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

Specified by:

getItemType in class Pattern

Returns:

an ItemType, as specific as possible, which all the matching items satisfy

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