com.saxonica.stream
Class PathSelection

java.lang.Object
  com.saxonica.stream.PathSelection

All Implemented Interfaces:

Selection, Serializable

public class PathSelection
extends Object
implements Selection, Serializable

A PathSelection is a Selection that applies a NodeTest to each element between the context element and the node being tested, and returns true if they all match. This class is used internally in the validation of instance documents against uniqueness and identity constraints; it is not intended for use by user applications.

See Also:

Serialized Form

Field Summary

Fields inherited from interface com.saxonica.stream.Selection

MATCHES_AS_PARENT, MATCHES_AS_SELF

Constructor Summary

PathSelection(NodeTest[] tests, int initialAxis, NodeTest attributeTest, Expression xpath)
Create a PathSelection - a limited form of XPath expression that can be evaluated on-the-fly

Method Summary

boolean	canMatchAttributes() Determine whether the selection can match attribute nodes
boolean	canMatchElementContent() Determin whether the selection can match element content
void	displayExpression(ExpressionPresenter out) Diagnostic print of expression structure.
NodeTest	getAttributeTest() Get the attribute test at the end of the path, if there is one
ItemType	getItemType() Determine the item type of the nodes matched by the last NodeTest
ItemType	getItemType(TypeHierarchy th) Return the type of the nodes selected by this selection
boolean	matchesAttribute(int fingerprint) Determine whether a given attribute matches the Selection
int	matchesElement(int[] stack, int length, int contextPosition) Determine whether the selector matches a given element.
String	typeCheck(ExpressionVisitor visitor, ItemType contextItemType) Check that the selection makes sense in the context of a given ItemType.

Methods inherited from class java.lang.Object

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

Constructor Detail

PathSelection

public PathSelection(NodeTest[] tests,
                     int initialAxis,
                     NodeTest attributeTest,
                     Expression xpath)

Create a PathSelection - a limited form of XPath expression that can be evaluated on-the-fly

Parameters:

tests - an array of node tests, representing a sequence of axis steps; these are all tests on the child axis, except possibly the last, which is a test on the attribute axis if attributeTest is true

initialAxis - the axis used for the first step in the array of tests: typically Axis.CHILD or Axis.DESCENDANT; can also be Axis.DESCENDANT_OR_SELF

attributeTest - if true, the last test applies to attributes rather than elements.

xpath - An XPath expression equivalent to the PathSelection. This is never evaluated, but is used for type analysis and diagnostic display.

Method Detail

matchesElement

public int matchesElement(int[] stack,
                          int length,
                          int contextPosition)

Determine whether the selector matches a given element. The element is identified by an array of integers representing the fingerprints of the names of this element and each of its ancestors, in document order (i.e., root element first, matched element last).

Specified by:

matchesElement in interface Selection

Parameters:

stack - the array of name fingerprints

length - the effective length of the array; any items beyond this position are ignored

contextPosition - the position in this array of the context element for the selection.

Returns:

a bit-significant integer. {#MATCHES_AS_SELF} is set if the element matches the selector in its own right. {#MATCHES_AS_PARENT} is set if the element is a potential parent of an attribute that matches the selector. In the case of a union selection, it is possible for both bits to be set.

getAttributeTest

public NodeTest getAttributeTest()

Get the attribute test at the end of the path, if there is one

Returns:

the attribute test if there is one, or null otherwise

matchesAttribute

public boolean matchesAttribute(int fingerprint)

Determine whether a given attribute matches the Selection

Specified by:

matchesAttribute in interface Selection

Parameters:

fingerprint - the integer nameCode of an attribute

Returns:

true if it matches, false if it does not match

canMatchAttributes

public boolean canMatchAttributes()

Determine whether the selection can match attribute nodes

Specified by:

canMatchAttributes in interface Selection

Returns:

true if the selection can match attributes

canMatchElementContent

public boolean canMatchElementContent()

Determin whether the selection can match element content

Specified by:

canMatchElementContent in interface Selection

Returns:

true if the selection can match elements

getItemType

public ItemType getItemType()

Determine the item type of the nodes matched by the last NodeTest

Returns:

the item type of the selected nodes

typeCheck

public String typeCheck(ExpressionVisitor visitor,
                        ItemType contextItemType)

Check that the selection makes sense in the context of a given ItemType. Return null if the selection is OK, otherwise an error message

Specified by:

typeCheck in interface Selection

Parameters:

visitor - the expression visitor

contextItemType - the type of the context item

Returns:

an error messge if the expression is invalid

getItemType

public ItemType getItemType(TypeHierarchy th)

Return the type of the nodes selected by this selection

Specified by:

getItemType in interface Selection

Parameters:

th - the type hierarchy cache

Returns:

the item type of the selected nodes

displayExpression

public void displayExpression(ExpressionPresenter out)

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

Specified by:

displayExpression in interface Selection

Parameters:

out - the place where the structure is to be written