net.sf.saxon.pattern

Class Pattern

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.PseudoExpression

net.sf.saxon.pattern.Pattern

All Implemented Interfaces:

IdentityComparable

Direct Known Subclasses:

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

public abstract class Pattern
extends PseudoExpression

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().

Field Summary

Fields inherited from class net.sf.saxon.expr.Expression

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD

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
void	bindCurrent(LocalBinding binding) Replace any calls on current() by a variable reference bound to the supplied binding
Pattern	convertToTypedPattern(String val) Convert the pattern to a typed pattern, in which an element name is treated as schema-element(N)
abstract Pattern	copy() Copy an expression.
boolean	effectiveBooleanValue(XPathContext context) Evaluate a pattern as a boolean expression, returning true if the context item matches the pattern
abstract void	export(ExpressionPresenter presenter) Diagnostic print of expression structure.
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.
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
abstract UType	getUType() Get a UType indicating which kinds of items this Pattern can match.
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, PackageData packageData) 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.
Pattern	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Perform optimisation of an expression and its subexpressions.
void	promote(PromotionOffer offer, Expression parent) Offer promotion for subexpressions within this pattern.
protected static void	replaceCurrent(Expression exp, LocalBinding binding) Replace any call to current() within a contained expression by a reference to a variable
SequenceIterator	selectNodes(TreeInfo document, XPathContext context) Select nodes in a document using this PatternFinder.
void	setOriginalText(String text) Set the original text of the pattern for use in diagnostics
void	setPriority(double priority) Set a priority to override the default priority.
Pattern	simplify() Simplify the pattern by applying any context-independent optimisations.
String	toString() Get a string representation of the pattern.
Pattern	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Type-check the pattern.

Methods inherited from class net.sf.saxon.expr.PseudoExpression

computeCardinality, evaluateAsString, evaluateItem, getImplementationMethod, iterate, iterateEvents, process

Methods inherited from class net.sf.saxon.expr.Expression

addToPathMap, adoptChildExpression, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, clearStreamabilityData, computeDependencies, computeSpecialProperties, computeStaticProperties, doPromotion, dynamicError, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getConstructType, getCost, getEvaluationMethod, getExpressionCompiler, getExpressionName, getIntegerBounds, getIntrinsicDependencies, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getPosture, getPostureAndSweepIfKnown, getProperties, getProperty, getRetainedStaticContext, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStreamability, getStreamingAdjunct, getSweep, getSystemId, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isCallOnSystemFunction, isIdentical, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, makeStreamingAdjunct, markTailFunctionCalls, operandList, operands, operandSparseList, optimizeChildren, optimizeForType, promote, promoteChildren, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setFiltered, setFlattened, setLocation, setParentExpression, setPostureAndSweep, setRetainedStaticContext, setRetainedStaticContextLocally, setStaticProperty, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, toShortString, toStreamingPattern, typeCheckChildren, typeError, unordered

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,
           PackageData packageData)
                    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

packageData - The package containing this pattern

Returns:

The pattern object

Throws:

XPathException - if the pattern is invalid

replaceCurrent

protected static void replaceCurrent(Expression exp,
                  LocalBinding binding)

Replace any call to current() within a contained expression by a reference to a variable

Parameters:

exp - the expression in which the replacement is to take place (which must not itself be a call to current())

binding - the binding for the variable reference

bindCurrent

public void bindCurrent(LocalBinding binding)

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

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()
                 throws XPathException

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

Overrides:

simplify in class Expression

Returns:

the simplified expression (or the original if unchanged, or if modified in-situ)

Throws:

XPathException - if an error is discovered during expression rewriting

typeCheck

public Pattern typeCheck(ExpressionVisitor visitor,
                ContextItemStaticInfo contextInfo)
                  throws XPathException

Type-check the pattern.

Overrides:

typeCheck in class Expression

Parameters:

visitor - the expression visitor

contextInfo - 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 - if an error is discovered during this phase (typically a type error)

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 Expression

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

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

effectiveBooleanValue

public final boolean effectiveBooleanValue(XPathContext context)
                                    throws XPathException

Evaluate a pattern as a boolean expression, returning true if the context item matches the pattern

Overrides:

effectiveBooleanValue in class PseudoExpression

Parameters:

context - the evaluation context

Returns:

true if the context item matches the pattern

Throws:

XPathException - if an error occurs during pattern matching

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.

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 selectNodes(TreeInfo document,
                           XPathContext context)
                             throws XPathException

Select nodes in a document using this PatternFinder.

Parameters:

document - the document

context - the dynamic evaluation context

Returns:

an iterator over the selected nodes in the document.

Throws:

XPathException

getUType

public abstract UType getUType()

Get a UType indicating which kinds of items this Pattern can match.

Returns:

a UType indicating all the primitive types of item that the pattern can match.

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

Overrides:

getItemType in class PseudoExpression

Returns:

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

setPriority

public void setPriority(double priority)

Set a priority to override the default priority. This is used when the pattern is written in a complex form such as a[true()] justifying a priority of 0.5, but then simplifies down to an NodeTestPattern

Parameters:

priority - the priority to be used if no explicit priority is given in the template rule

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

toString

public String toString()

Get a string representation of the pattern. This will be in a form similar to the original pattern text, but not necessarily identical. It is not guaranteed to be in legal pattern syntax.

Overrides:

toString in class Expression

Returns:

a representation of the expression as a string

getHostLanguage

public int getHostLanguage()

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

Overrides:

getHostLanguage in class Expression

Returns:

typically Configuration.XSLT or Configuration.XQUERY

convertToTypedPattern

public Pattern convertToTypedPattern(String val)
                              throws XPathException

Convert the pattern to a typed pattern, in which an element name is treated as schema-element(N)

Parameters:

val - either "strict" or "lax" depending on the value of xsl:mode/@typed

Returns:

either the original pattern unchanged, or a new pattern as the result of the conversion

Throws:

XPathException - if the pattern cannot be converted

export

public abstract void export(ExpressionPresenter presenter)

Description copied from class: Expression

Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

Specified by:

export in class Expression

Parameters:

presenter - the expression presenter used to display the structure

copy

public abstract Pattern copy()

Description copied from class: Expression

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Returns:

the copy of the original expression

optimize

public Pattern optimize(ExpressionVisitor visitor,
               ContextItemStaticInfo contextInfo)
                 throws XPathException

Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

Overrides:

optimize in class Expression

Parameters:

visitor - an expression visitor

contextInfo - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE

Returns:

the original expression, rewritten if appropriate to optimize execution

Throws:

XPathException - if an error is discovered during this phase (typically a type error)