Package 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:
ExportAgent, Locatable, IdentityComparable, Traceable
Direct Known Subclasses:
AncestorQualifiedPattern, AnchorPattern, BasePatternWithPredicate, BooleanExpressionPattern, GeneralNodePattern, GeneralPositionalPattern, ItemTypePattern, NodeSetPattern, NodeTestPattern, PatternThatSetsCurrent, SimplePositionalPattern, StreamingFunctionArgumentPattern, 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().

  • Constructor Details

    • Pattern

      public Pattern()

  • Method Details

    • 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

    • patternContainsVariable

      public static boolean patternContainsVariable(Pattern pattern)
      Ask whether a pattern has dependencies on local variables
      Parameters:
      pattern - the pattern (typically a pattern in an xsl:number or xsl:for-each-group); or null
      Returns:
      true if the pattern is non-null and has dependencies on local variables

    • isLiftable

      public boolean isLiftable(boolean forStreaming)
      Ask whether the expression can be lifted out of a loop, assuming it has no dependencies on the controlling variable/focus of the loop
      Overrides:
      isLiftable in class Expression
      Parameters:
      forStreaming - true if we are generating code for streaming
      Returns:
      true if the expression can be loop lifted

    • bindCurrent

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

    • matchesCurrentGroup

      public boolean matchesCurrentGroup()
      Ask whether the pattern is anchored on a call on current-group()
      Returns:
      true if calls on matchesBeneathAnchor should test with all nodes in the current group as anchor nodes. If false, only the first node in a group is treated as the anchor node

    • 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

    • isRecoverable

      public boolean isRecoverable()
      Ask whether dynamic errors in evaluating the pattern should be recovered. This is the default for normal XSLT patterns, but patterns used internally to represent scannable streaming expressions are non-recoverable
      Returns:
      true if dynamic errors in pattern evaluation should be treated as recoverable (if an error occurs, the pattern is treated as non-matching; a warning is sent to the ErrorListener).

    • setRecoverable

      public void setRecoverable(boolean recoverable)
      Aay whether dynamic errors in evaluating the pattern should be recovered. This is the default for normal XSLT patterns, but patterns used internally to represent scannable streaming expressions are non-recoverable
      Parameters:
      recoverable - true if dynamic errors in pattern evaluation should be treated as recoverable (if an error occurs, the pattern is treated as non-matching; a warning is sent to the ErrorListener).

    • handleDynamicError

      protected void handleDynamicError(XPathException ex, XPathContext context) throws XPathException
      Handle a dynamic error occurring in the course of pattern evaluation. The effect depends on (a) whether the error is a circularity error, and (b) whether the pattern is marked as recoverable or not
      Parameters:
      ex - the exception
      context - the evaluation context
      Throws:
      XPathException - if the error is found to be non-recoverable

    • 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 interesting dependencies for a pattern are dependencies on local variables or on user-defined functions. These are analyzed in those patterns containing predicates.
      Overrides:
      getDependencies in class Expression
      Returns:
      the dependencies, as a bit-significant mask

    • 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

    • isMotionless

      public boolean isMotionless()
      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.
      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

    • matchesItem

      public final boolean matchesItem(Item item, XPathContext context) throws XPathException
      Determine whether this Pattern matches the given item. This is the main external interface for matching patterns: it calls the matches() method and handles any errors, by signalling a warning and returning false.
      Parameters:
      item - The item to be tested against the Pattern
      context - The dynamic context.
      Returns:
      true if the item matches the Pattern, false otherwise
      Throws:
      XPathException - if a non-recoverable error is found matching the pattern. Most errors however result in a warning and a return value of false.

    • matches

      public abstract boolean matches(Item item, XPathContext context) throws XPathException
      Determine whether this Pattern matches the given item. This should be called via matchesItem() to get the XSLT-defined error handling behaviour.

      The method, where required, 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

    • 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 all nodes in a document that match this pattern.
      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

    • reconstruct

      public String reconstruct()
      Reconstruct a string representation of the pattern from its compiled form, in cases where the original text is not available

    • getHostLanguage

      public HostLanguage getHostLanguage()
      Get the host language (XSLT, XQuery, XPath) used to implement the code in this container
      Returns:
      typically HostLanguage.XSLT or HostLanguage.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

    • toPattern

      public Pattern toPattern(Configuration config)
      Description copied from class: Expression
      Convert this expression to an equivalent XSLT pattern
      Overrides:
      toPattern in class Expression
      Parameters:
      config - the Saxon configuration
      Returns:
      the equivalent pattern

    • export

      public abstract void export(ExpressionPresenter presenter) throws XPathException
      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 interface ExportAgent
      Specified by:
      export in class Expression
      Parameters:
      presenter - the expression presenter used to display the structure
      Throws:
      XPathException - if the export fails, for example if an expression is found that won't work in the target environment.

    • copy

      public abstract Pattern copy(RebindingMap rebindings)
      Description copied from class: Expression
      Copy an expression. This makes a deep copy.
      Specified by:
      copy in class Expression
      Parameters:
      rebindings - a mutable list of (old binding, new binding) pairs that is used to update the bindings held in any local variable references that are copied.
      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)

    • getOriginalText

      public String getOriginalText()
      Get the original text of the pattern as written, if available. The result may be null if the original text is not available, for example where the pattern is constructed programmatically
      Returns:
      the original text of the pattern if available, or null otherwise

    • toShortString

      public String toShortString()
      Description copied from class: Expression
      Produce a short string identifying the expression for use in error messages
      Overrides:
      toShortString in class Expression
      Returns:
      a short string, sufficient to identify the expression

    • getElaborator

      public Elaborator getElaborator()
      Description copied from class: PseudoExpression
      Make an elaborator for this expression
      Overrides:
      getElaborator in class PseudoExpression
      Returns:
      an appropriate Elaborator