Package net.sf.saxon.expr

Class SubsequenceIterator

java.lang.Object

net.sf.saxon.expr.SubsequenceIterator

All Implemented Interfaces:

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

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

A SubsequenceIterator selects a subsequence of a sequence

Nested Class Summary

Nested classes/interfaces inherited from interface net.sf.saxon.om.SequenceIterator

SequenceIterator.Property

Method Summary

Modifier and Type	Method	Description
void	close()	Close the iterator.
int	getLength()	Get the last position (that is, the number of items in the sequence).
java.util.EnumSet<SequenceIterator.Property>	getProperties()	Get properties of this iterator, as a bit-significant integer.
boolean	hasNext()	Test whether there are any more items available in the sequence
static <T extends Item> SequenceIterator	make(SequenceIterator base, int min, int max)	Static factory method.
Item	next()	Get the next item if there is one

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

forEachOrFail, materialize

Method Detail

make

public static <T extends Item> SequenceIterator make(SequenceIterator base,
                                                     int min,
                                                     int max)
                                              throws XPathException

Static factory method. Creates a SubsequenceIterator, unless for example the base Iterator is an ArrayIterator, in which case it optimizes by creating a new ArrayIterator directly over the underlying array. This optimization is important when doing recursion over a node-set using repeated calls of $nodes[position()>1]

Parameters:

base - An iteration of the items to be filtered

min - The position of the first item to be included (base 1)

max - The position of the last item to be included (base 1)

Returns:

an iterator over the requested subsequence

Throws:

XPathException - if a dynamic error occurs

hasNext

public boolean hasNext()

Test whether there are any more items available in the sequence

Specified by:

hasNext in interface LookaheadIterator

Returns:

true if there are more items in the sequence

next

public Item next()
          throws XPathException

Get the next item if there is one

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.

Throws:

XPathException - if an error occurs retrieving the next item

close

public void close()

Description copied from interface: SequenceIterator

Close the iterator. This indicates to the supplier of the data that the client does not require any more items to be delivered by the iterator. This may enable the supplier to release resources. After calling close(), no further calls on the iterator should be made; if further calls are made, the effect of such calls is undefined.

For example, the iterator returned by the unparsed-text-lines() function has a close() method that causes the underlying input stream to be closed, whether or not the file has been read to completion.

Closing an iterator is important when the data is being "pushed" in another thread. Closing the iterator terminates that thread and means that it needs to do no additional work. Indeed, failing to close the iterator may cause the push thread to hang waiting for the buffer to be emptied.

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface SequenceIterator

getProperties

public java.util.EnumSet<SequenceIterator.Property> getProperties()

Get properties of this iterator, as a bit-significant integer.

Specified by:

getProperties in interface SequenceIterator

Returns:

the properties of this iterator. This will be some combination of properties such as SequenceIterator.Property.GROUNDED, SequenceIterator.Property.LAST_POSITION_FINDER, and SequenceIterator.Property.LOOKAHEAD. It is always acceptable to return the value zero, indicating that there are no known special properties. It is acceptable for the properties of the iterator to change depending on its state.

getLength

public int getLength()
              throws XPathException

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 result of getProperties() on the iterator includes the bit setting SequenceIterator.Property.LAST_POSITION_FINDER

Specified by:

getLength in interface LastPositionFinder

Returns:

the number of items in the sequence

Throws:

XPathException - if an error occurs evaluating the sequence in order to determine the number of items