## 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

Direct Known Subclasses:
  IDPattern, KeyPattern

    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
`protected Expression` `expression`
`protected ItemType` `itemType`

Constructor Summary
`NodeSetPattern(Expression exp, Configuration config)` Create a node-set pattern.

Method Summary
`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.
`boolean` `equals(Object other)` Determine whether this pattern is the same as another pattern
`int` `getDependencies()` Get the dependencies of the pattern.
`int` `getNodeKind()` Determine the type of nodes to which this pattern applies.
`NodeTest` `getNodeTest()` Get a NodeTest that all the nodes matching this pattern must satisfy
`int` `hashCode()` Hashcode supporting equals()
`Iterator` `iterateSubExpressions()` Iterate over the subexpressions within this pattern
`boolean` `matches(NodeInfo e, 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
`getColumnNumber, getContainerGranularity, getDefaultPriority, getExecutable, getFingerprint, getHostLanguage, getLineNumber, getLocationProvider, getPublicId, getSystemId, internalMatches, make, makeSearchExpression, matchesBeneathAnchor, resolveCurrent, 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,
                          Configuration config)

  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,
                           ItemType 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 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

### 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` - 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

### matches

    public boolean matches(NodeInfo e,
                           XPathContext context)
                    throws XPathException

  Determine whether this Pattern matches the given Node

  Specified by:
    `matches` in class `Pattern`
  Parameters:
    `e` - 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 type of nodes to which this pattern applies.

  Overrides:
    `getNodeKind` in class `Pattern`
  Returns:
    Type.NODE (may be overridden in subclasses)

### 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

### 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) 2004-2010 Saxonica Limited. All rights reserved.