com.saxonica.ee.trans

Class PreconditionMatcher

java.lang.Object

net.sf.saxon.trans.rules.RuleSearchState

com.saxonica.ee.trans.PreconditionMatcher

public class PreconditionMatcher
extends RuleSearchState

This class contains the stateful part of the precondition checker. A new PreconditionMatcher is allocated when searching a rule chain to find the best matching rule for a given node (or other item). It holds the values of preconditions and characteristics. A precondition is a boolean property of an item that must be true if the item is to match a particular pattern; once the precondition has been evaluated, its value can be used to eliminate other rules with the same precondition. A characteristic is a property of an item that must match a corresponding property of a rule if the rule is to match; for example, a property might be "name of parent element". Once the value of a characteristic (for example, the name of the parent element) has been evaluated, a rule can be eliminated if it requires a different value for the characteristic.

Constructor Summary

Constructors

Constructor and Description
PreconditionMatcher(RuleChain chain, XPathContext context) Allocate a PreconditionMatcher for a given set of rules

Method Summary

Modifier and Type	Method and Description
java.lang.Boolean	getPreconditionState(int slot) Get the state of a given precondition.
<T> T	obtainCharacteristic(Characteristic<T> chic) Get the value of a particular characteristic of the item being matched, evaluating it if it has not already been evaluated, and retaining its value for future use
void	setPreconditionState(int slot, boolean value) Set the value of a given precondition.

Methods inherited from class java.lang.Object

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

Constructor Detail

PreconditionMatcher

public PreconditionMatcher(RuleChain chain,
                           XPathContext context)

Allocate a PreconditionMatcher for a given set of rules

Parameters:

chain - the set of rules being matched

context - the XPath evaluation context; the context item is the item being matched against the set of rules

Method Detail

getPreconditionState

public java.lang.Boolean getPreconditionState(int slot)

Get the state of a given precondition.

Parameters:

slot - the slot number allocated to the precondition

Returns:

true if the precondition is known to be true for the item being matched; false if it is known to be false; or null if its value is not known

setPreconditionState

public void setPreconditionState(int slot,
                                 boolean value)

Set the value of a given precondition.

Parameters:

slot - the slot number allocated to the precondition

value - true if the precondition (for the item being matched) is known to be true, false if it is known to be false.

obtainCharacteristic

public <T> T obtainCharacteristic(Characteristic<T> chic)
                           throws XPathException

Get the value of a particular characteristic of the item being matched, evaluating it if it has not already been evaluated, and retaining its value for future use

Type Parameters:

T - the type of value of this characteristic

Parameters:

chic - the characteristic to be evaluated

Returns:

the value of the characteristic

Throws:

XPathException - if evaluation of the characteristic failed