com.icl.saxon.expr
Class LookaheadEnumerator

java.lang.Object
  com.icl.saxon.expr.LookaheadEnumerator

All Implemented Interfaces:

LastPositionFinder, NodeEnumeration

public class LookaheadEnumerator

extends java.lang.Object

implements NodeEnumeration, LastPositionFinder

A LookaheadEnumerator passes the nodes from a base enumerator throgh unchanged. The complication is that on request, it must determine the value of the last() position, which requires a lookahead. A LookaheadEnumerator should only be used to wrap a NodeEnumeration that cannot determine the last() position for itself, i.e. one that is not a LastPositionFinder.

Constructor Summary

LookaheadEnumerator(NodeEnumeration base)
Constructor

Method Summary

int	getLastPosition() Do lookahead to find the last position, if required
boolean	hasMoreElements() Determine whether there are any more nodes to hand to the client
boolean	isPeer() Determine whether the nodes are guaranteed to be peers
boolean	isReverseSorted() Determine whether the nodes returned by this enumeration are known to be in reverse document order.
boolean	isSorted() Determine whether the nodes are guaranteed to be in document order
NodeInfo	nextElement() Hand the next node to the client

Methods inherited from class java.lang.Object

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

Constructor Detail

LookaheadEnumerator

public LookaheadEnumerator(NodeEnumeration base)

Constructor

Parameters:

base - An NodeEnumerator that delivers the nodes, but that cannot determine the last position count.

Method Detail

hasMoreElements

public boolean hasMoreElements()

Determine whether there are any more nodes to hand to the client

Specified by:

hasMoreElements in interface NodeEnumeration

Returns:

true if there are more nodes

nextElement

public NodeInfo nextElement()
                     throws XPathException

Hand the next node to the client

Specified by:

nextElement in interface NodeEnumeration

Returns:

the next NodeInfo

Throws:

XPathException

getLastPosition

public int getLastPosition()
                    throws XPathException

Do lookahead to find the last position, if required

Specified by:

getLastPosition in interface LastPositionFinder

Throws:

XPathException

isSorted

public boolean isSorted()

Determine whether the nodes are guaranteed to be in document order

Specified by:

isSorted in interface NodeEnumeration

Returns:

true if the nodes are guaranteed to be in document order.

isReverseSorted

public boolean isReverseSorted()

Description copied from interface: NodeEnumeration

Determine whether the nodes returned by this enumeration are known to be in reverse document order.

Specified by:

isReverseSorted in interface NodeEnumeration

Returns:

true if the nodes are guaranteed to be in document order.

isPeer

public boolean isPeer()

Determine whether the nodes are guaranteed to be peers

Specified by:

isPeer in interface NodeEnumeration