net.sf.saxon.expr.sort

Class SortedIterator

java.lang.Object

net.sf.saxon.expr.sort.SortedIterator

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, LastPositionFinder, SequenceIterator, LookaheadIterator

Direct Known Subclasses:

SortedGroupIterator

public class SortedIterator
extends java.lang.Object
implements SequenceIterator, LastPositionFinder, LookaheadIterator

Class to do a sorted iteration

Field Summary

Fields

Modifier and Type	Field and Description
protected SequenceIterator	base
protected AtomicComparer[]	comparators
protected XPathContext	context
protected int	count
protected int	position
protected SortKeyEvaluator	sortKeyEvaluator
protected ObjectToBeSorted[]	values

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	SortedIterator()
	SortedIterator(XPathContext context, SequenceIterator base, SortKeyEvaluator sortKeyEvaluator, AtomicComparer[] comparators, boolean createNewContext) Create a sorted iterator

Method Summary

Modifier and Type	Method and Description
protected void	buildArray() Create an array holding the items to be sorted and the values of their sort keys
int	getLength() Get the last position (that is, the number of items in the sequence).
boolean	hasNext() Determine whether there are more items to come.
Item	next() Get the next item, in sorted order
void	setHostLanguage(HostLanguage language) Set the host language
boolean	supportsGetLength() Ask whether this iterator supports use of the getLength() method.
boolean	supportsHasNext() Ask whether the hasNext() method can be called.

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.SequenceIterator

close, discharge

Field Detail

base

protected SequenceIterator base

sortKeyEvaluator

protected SortKeyEvaluator sortKeyEvaluator

comparators

protected AtomicComparer[] comparators

values

protected ObjectToBeSorted[] values

count

protected int count

position

protected int position

context

protected XPathContext context

Constructor Detail

SortedIterator

protected SortedIterator()

SortedIterator

public SortedIterator(XPathContext context,
                      SequenceIterator base,
                      SortKeyEvaluator sortKeyEvaluator,
                      AtomicComparer[] comparators,
                      boolean createNewContext)

Create a sorted iterator

Parameters:

context - the dynamic XPath evaluation context

base - an iterator over the sequence to be sorted

sortKeyEvaluator - an object that allows the n'th sort key for a given item to be evaluated

comparators - an array of AtomicComparers, one for each sort key, for comparing sort key values

createNewContext - true if sort keys are computed relative to the item being sorted (as in XSLT but not XQuery)

Method Detail

setHostLanguage

public void setHostLanguage(HostLanguage language)

Set the host language

Parameters:

language - the host language (for example HostLanguage.XQUERY)

supportsHasNext

public boolean supportsHasNext()

Description copied from interface: LookaheadIterator

Ask whether the hasNext() method can be called. This method must be called before calling hasNext(), because some iterators implement this interface, but only support look-ahead under particular circumstances (this is usually because they delegate to another iterator)

Specified by:

supportsHasNext in interface LookaheadIterator

Returns:

true if the LookaheadIterator.hasNext() method is available

hasNext

public boolean hasNext()

Determine whether there are more items to come. Note that this operation is stateless and it is not necessary (or usual) to call it before calling next(). It is used only when there is an explicit need to tell if we are at the last element.

This method must not be called unless the method supportsHasNext() returns true.

Specified by:

hasNext in interface LookaheadIterator

Returns:

true if there are more items in the sequence

next

public Item next()

Get the next item, in sorted order

Specified by:

next in interface SequenceIterator

Returns:

the next item, or null if there are no more items. Once a call on next() has returned null, no further calls should be made. The preferred action for an iterator if subsequent calls on next() are made is to return null again, and all implementations within Saxon follow this rule.

supportsGetLength

public boolean supportsGetLength()

Ask whether this iterator supports use of the getLength() method. This method should always be called before calling getLength(), because an iterator that implements this interface may support use of getLength() in some situations and not in others

Specified by:

supportsGetLength in interface LastPositionFinder

Returns:

true if the getLength() method can be called to determine the length of the underlying sequence.

getLength

public int getLength()

Description copied from interface: LastPositionFinder

Get the last position (that is, the number of items in the sequence). This method is non-destructive: it does not change the state of the iterator. The result is undefined if the next() method of the iterator has already returned null. This method must not be called unless the LastPositionFinder.supportsGetLength() has been called and has returned true.

Specified by:

getLength in interface LastPositionFinder

Returns:

the number of items in the sequence

buildArray

protected void buildArray()
                   throws XPathException

Create an array holding the items to be sorted and the values of their sort keys

Throws:

XPathException - if an error occurs for example in evaluating a sort key