Package net.sf.saxon.om

Class MemoSequence

java.lang.Object

net.sf.saxon.om.MemoSequence

All Implemented Interfaces:

Sequence

public class MemoSequence
extends java.lang.Object
implements Sequence

A Sequence implementation that represents a lazy evaluation of a supplied iterator. Items are read from the base iterator only when they are first required, and are then remembered within the local storage of the MemoSequence, which eventually (if the sequence is read to the end) contains the entire value.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	MemoSequence.ProgressiveIterator	A ProgressiveIterator starts by reading any items already held in the reservoir; when the reservoir is exhausted, it reads further items from the inputIterator, copying them into the reservoir as they are read.

Constructor Summary

Constructors

Constructor	Description
MemoSequence(SequenceIterator iterator)

Method Summary

Modifier and Type	Method	Description
Item	head()	Get the first item in the sequence.
Item	itemAt(int n)	Get the Nth item in the sequence (0-based), reading new items into the internal reservoir if necessary
SequenceIterator	iterate()	Get a SequenceIterator over all the items in the sequence
void	setLearningEvaluator(LearningEvaluator caller, int serialNumber)

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.sf.saxon.om.Sequence

makeRepeatable, materialize

Constructor Detail

MemoSequence

public MemoSequence(SequenceIterator iterator)

Method Detail

setLearningEvaluator

public void setLearningEvaluator(LearningEvaluator caller,
                                 int serialNumber)

head

public Item head()
          throws XPathException

Description copied from interface: Sequence

Get the first item in the sequence.

Specified by:

head in interface Sequence

Returns:

the first item in the sequence if there is one, or null if the sequence is empty

Throws:

XPathException - in the situation where the sequence is evaluated lazily, and evaluation of the first item causes a dynamic error.

iterate

public SequenceIterator iterate()

Description copied from interface: Sequence

Get a SequenceIterator over all the items in the sequence

Specified by:

iterate in interface Sequence

Returns:

an iterator (specifically, a Saxon SequenceIterator, which is not a Iterator) over all the items

itemAt

public Item itemAt(int n)
            throws XPathException

Get the Nth item in the sequence (0-based), reading new items into the internal reservoir if necessary

Parameters:

n - the index of the required item

Returns:

the Nth item if it exists, or null otherwise

Throws:

XPathException - if the input sequence cannot be read