net.sf.saxon.pattern

Class Pattern

java.lang.Object

net.sf.saxon.pattern.Pattern

All Implemented Interfaces:

Serializable, SourceLocator, Container, PatternFinder

Direct Known Subclasses:

AncestorQualifiedPattern, AnchorPattern, BooleanExpressionPattern, ConditionalPattern, GeneralNodePattern, GeneralPositionalPattern, ItemTypePattern, NodeSetPattern, PatternThatSetsCurrent, PatternWithPredicate, SimplePositionalPattern, VennPattern

public abstract class Pattern
extends Object
implements PatternFinder, Serializable, Container

A Pattern represents the result of parsing an XSLT pattern string.
Patterns are created by calling the static method Pattern.make(string).
The pattern is used to test a particular node by calling match().

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
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.
void	bindCurrent(Binding binding) Replace any calls on current() by a variable reference bound to the supplied binding
int	getColumnNumber() Get the column number (always -1)
int	getContainerGranularity() Get the granularity of the container.
double	getDefaultPriority() Determine the default priority to use if this pattern appears as a match pattern for a template with no explicit priority attribute.
int	getDependencies() Get the dependencies of the pattern.
Executable	getExecutable() Get the executable containing this pattern
int	getFingerprint() Determine the name fingerprint of nodes to which this pattern applies.
int	getHostLanguage() Get the host language (XSLT, XQuery, XPath) used to implement the code in this container
abstract ItemType	getItemType() Get an ItemType that all the items matching this pattern must satisfy
int	getLineNumber() Get the line number on which the pattern was defined
LocationProvider	getLocationProvider() Get the LocationProvider allowing location identifiers to be resolved.
int	getNodeKind() Determine the types of nodes to which this pattern applies.
String	getPublicId() Get the public ID (always null)
String	getSystemId() Get the system id of the entity in which the pattern occurred
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
static Pattern	make(String pattern, StaticContext env, Executable exec) Static factory method to make a Pattern by parsing a String.
abstract boolean	matches(Item item, XPathContext context) Determine whether this Pattern matches the given item.
boolean	matchesBeneathAnchor(NodeInfo node, NodeInfo anchor, XPathContext context) Determine whether this pattern matches a given Node within the subtree rooted at a given anchor node.
void	promote(PromotionOffer offer, Expression parent) Offer promotion for subexpressions within this pattern.
protected static void	replaceCurrent(Expression exp, Binding binding)
boolean	replaceSubExpression(Expression original, Expression replacement) Replace a subexpression by a replacement subexpression
SequenceIterator<? extends NodeInfo>	selectNodes(DocumentInfo doc, XPathContext context) Select nodes in a document using this PatternFinder.
void	setExecutable(Executable executable) Set the executable containing this pattern
void	setLineNumber(int lineNumber) Set the line number where the pattern occurred
void	setOriginalText(String text) Set the original text of the pattern for use in diagnostics
void	setSystemId(String systemId) Set the system ID where the pattern occurred
Pattern	simplify(ExpressionVisitor visitor) Simplify the pattern by applying any context-independent optimisations.
String	toString() Get the original pattern text

Methods inherited from class java.lang.Object

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

Constructor Detail

Pattern

public Pattern()

Method Detail

make

public static Pattern make(String pattern,
           StaticContext env,
           Executable exec)
                    throws XPathException

Static factory method to make a Pattern by parsing a String.

Parameters:

pattern - The pattern text as a String

env - An object defining the compile-time context for the expression

exec - The executable containing this pattern

Returns:

The pattern object

Throws:

XPathException - if the pattern is invalid

replaceCurrent

protected static void replaceCurrent(Expression exp,
                  Binding binding)

bindCurrent

public void bindCurrent(Binding binding)

Replace any calls on current() by a variable reference bound to the supplied binding

getExecutable

public Executable getExecutable()

Get the executable containing this pattern

Specified by:

getExecutable in interface Container

Returns:

the executable

setExecutable

public void setExecutable(Executable executable)

Set the executable containing this pattern

Parameters:

executable - the executable

getLocationProvider

public LocationProvider getLocationProvider()

Get the LocationProvider allowing location identifiers to be resolved.

Specified by:

getLocationProvider in interface Container

Returns:

the location provider

getContainerGranularity

public int getContainerGranularity()

Get the granularity of the container.

Specified by:

getContainerGranularity in interface Container

Returns:

0 for a temporary container created during parsing; 1 for a container that operates at the level of an XPath expression; 2 for a container at the level of a global function or template

setOriginalText

public void setOriginalText(String text)

Set the original text of the pattern for use in diagnostics

Parameters:

text - the original text of the pattern

simplify

public Pattern simplify(ExpressionVisitor visitor)
                 throws XPathException

Simplify the pattern by applying any context-independent optimisations. Default implementation does nothing.

Parameters:

visitor - the expression visitor

Returns:

the optimised Pattern

Throws:

XPathException

analyze

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

Type-check the 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.

Returns:

the dependencies, as a bit-significant mask

iterateSubExpressions

public Iterator<Expression> iterateSubExpressions()

Iterate over the subexpressions within this pattern

Returns:

an iterator over the subexpressions. Default implementation returns an empty sequence

allocateSlots

public int allocateSlots(SlotManager slotManager,
                int nextFree)

Allocate slots to any variables used within the pattern

Parameters:

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

nextFree - the next slot that is free to be allocated

Returns:

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.

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

setSystemId

public void setSystemId(String systemId)

Set the system ID where the pattern occurred

Parameters:

systemId - the URI of the module containing the pattern

setLineNumber

public void setLineNumber(int lineNumber)

Set the line number where the pattern occurred

Parameters:

lineNumber - the line number of the pattern in the source module

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.

Parameters:

allowExtensions - if false, the result is determined strictly according to the W3C "guaranteed streamability rules. If true, Saxon extensions are permitted: that is, constructs may be recognized as motionless by Saxon even if they are not recognized as motionless by the W3C rules.

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

matches

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

Determine whether this Pattern matches the given item. This is the main external interface for matching patterns: it sets current() to the node being tested

Parameters:

item - The item 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)

matchesBeneathAnchor

public boolean matchesBeneathAnchor(NodeInfo node,
                           NodeInfo anchor,
                           XPathContext context)
                             throws XPathException

Determine whether this pattern matches a given Node within the subtree rooted at a given anchor node. This method is used when the pattern is used for streaming.

Parameters:

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

anchor - The anchor node, which must match any AnchorPattern subpattern

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)

selectNodes

public SequenceIterator<? extends NodeInfo> selectNodes(DocumentInfo doc,
                                               XPathContext context)
                                                 throws XPathException

Select nodes in a document using this PatternFinder.

Specified by:

selectNodes in interface PatternFinder

Parameters:

doc - the document node at the root of a tree

context - the dynamic evaluation context

Returns:

an iterator over the selected nodes in the document.

Throws:

XPathException - if a dynamic error is encountered

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 Type.NODE. For patterns that do not match nodes, return -1.

Returns:

the type of node matched by this pattern. e.g. Type.ELEMENT or Type.TEXT

getFingerprint

public int getFingerprint()

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

Returns:

A fingerprint that the nodes must match, or -1 if it can match multiple fingerprints, or it if matches atomic values

getItemType

public abstract ItemType getItemType()

Get an ItemType that all the items matching this pattern must satisfy

Returns:

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

getDefaultPriority

public double getDefaultPriority()

Determine the default priority to use if this pattern appears as a match pattern for a template with no explicit priority attribute.

Returns:

the default priority for the pattern

getSystemId

public String getSystemId()

Get the system id of the entity in which the pattern occurred

Specified by:

getSystemId in interface SourceLocator

getLineNumber

public int getLineNumber()

Get the line number on which the pattern was defined

Specified by:

getLineNumber in interface SourceLocator

getColumnNumber

public int getColumnNumber()

Get the column number (always -1)

Specified by:

getColumnNumber in interface SourceLocator

getPublicId

public String getPublicId()

Get the public ID (always null)

Specified by:

getPublicId in interface SourceLocator

toString

public String toString()

Get the original pattern text

Overrides:

toString in class Object

getHostLanguage

public int getHostLanguage()

Get the host language (XSLT, XQuery, XPath) used to implement the code in this container

Specified by:

getHostLanguage in interface Container

Returns:

typically Configuration.XSLT or Configuration.XQUERY

replaceSubExpression

public boolean replaceSubExpression(Expression original,
                           Expression replacement)

Replace a subexpression by a replacement subexpression

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