Package net.sf.saxon.expr

Class FilterIterator<T extends Item<?>>

java.lang.Object

net.sf.saxon.expr.FilterIterator<T>

All Implemented Interfaces:

Closeable, AutoCloseable, SequenceIterator<T>

Direct Known Subclasses:

FilterIterator.NonNumeric

public class FilterIterator<T extends Item<?>>
extends Object
implements SequenceIterator<T>

A FilterIterator filters an input sequence using a filter expression. Note that a FilterIterator is not used where the filter is a constant number (PositionFilter is used for this purpose instead), so this class does no optimizations for numeric predicates.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final class	FilterIterator.NonNumeric<T extends Item<?>>	Subclass to handle the common special case where it is statically known that the filter cannot return a numeric value

Field Summary

Fields

Modifier and Type	Field	Description
protected FocusIterator<T>	base
protected Expression	filter
protected XPathContext	filterContext

Fields inherited from interface net.sf.saxon.om.SequenceIterator

ATOMIZING, GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

Constructor Summary

Constructors

Constructor	Description
FilterIterator(SequenceIterator<T> base, Expression filter, XPathContext context)	Constructor

Method Summary

Modifier and Type	Method	Description
void	close()	Close the iterator.
protected T	getNextMatchingItem()	Get the next item in the base sequence that matches the filter predicate if there is such an item, or null if not.
int	getProperties()	Get properties of this iterator, as a bit-significant integer.
protected boolean	matches()	Determine whether the context item matches the filter predicate
T	next()	Get the next item if there is one
void	setSequence(SequenceIterator<?> base, XPathContext context)	Set the base iterator
static boolean	testPredicateValue(SequenceIterator iterator, long position, Expression filter)

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

Field Details

base

protected FocusIterator<T extends Item<?>> base

filter

protected Expression filter

filterContext

protected XPathContext filterContext

Constructor Details

FilterIterator

public FilterIterator(SequenceIterator<T> base,
 Expression filter,
 XPathContext context)

Constructor

Parameters:

base - An iteration of the items to be filtered

filter - The expression defining the filter predicate

context - The context in which the expression is being evaluated

Method Details

setSequence

public void setSequence(SequenceIterator<?> base,
 XPathContext context)

Set the base iterator

Parameters:

base - the iterator over the sequence to be filtered

context - the context in which the (outer) filter expression is evaluated

next

public T next()
       throws XPathException

Get the next item if there is one

Specified by:

next in interface SequenceIterator<T extends Item<?>>

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

getNextMatchingItem

protected T getNextMatchingItem()
                         throws XPathException

Get the next item in the base sequence that matches the filter predicate if there is such an item, or null if not.

Returns:

the next item that matches the predicate

Throws:

XPathException - if a dynamic error occurs

matches

protected boolean matches()
                   throws XPathException

Determine whether the context item matches the filter predicate

Returns:

true if the context item matches

Throws:

XPathException - if an error occurs evaluating the match

testPredicateValue

public static boolean testPredicateValue(SequenceIterator iterator,
 long position,
 Expression filter)
                                  throws XPathException

Throws:

XPathException

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 AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in interface SequenceIterator<T extends Item<?>>

getProperties

public int getProperties()

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

Specified by:

getProperties in interface SequenceIterator<T extends Item<?>>

Returns:

the properties of this iterator. This will be some combination of properties such as SequenceIterator.GROUNDED, SequenceIterator.LAST_POSITION_FINDER, and SequenceIterator.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.