net.sf.saxon.expr
Class FilterIterator

java.lang.Object
  extended bynet.sf.saxon.expr.FilterIterator
All Implemented Interfaces:
SequenceIterator
Direct Known Subclasses:
FilterIterator.Leading, FilterIterator.NonNumeric

public class FilterIterator
extends Object
implements SequenceIterator

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
static class FilterIterator.Leading
          Subclass to support the extension function saxon:leading, which terminates the iteration at the first item whose predicate is false
static class FilterIterator.NonNumeric
          Subclass to handle the common special case where it is statically known that the filter cannot return a numeric value
 
Field Summary
protected  SequenceIterator base
           
protected  Expression filter
           
protected  XPathContext filterContext
           
 
Constructor Summary
FilterIterator(SequenceIterator base, Expression filter, XPathContext context)
          Constructor
 
Method Summary
 Item current()
          Get the current value in the sequence (the one returned by the most recent call on next()).
 SequenceIterator getAnother()
          Get another iterator to return the same nodes
protected  Item getNextMatchingItem()
          Get the next node that matches the filter predicate if there is one, or null if not.
protected  boolean matches()
          Determine whether the context item matches the filter predicate
 Item next()
          Get the next item if there is one
 int position()
          Get the current position.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

base

protected SequenceIterator base

filter

protected Expression filter

filterContext

protected XPathContext filterContext
Constructor Detail

FilterIterator

public FilterIterator(SequenceIterator base,
                      Expression filter,
                      XPathContext context)
               throws XPathException
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 Detail

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.
Throws:
XPathException - if an error occurs retrieving the next item

getNextMatchingItem

protected Item getNextMatchingItem()
                            throws XPathException
Get the next node that matches the filter predicate if there is one, or null if not.

Throws:
XPathException

matches

protected boolean matches()
                   throws XPathException
Determine whether the context item matches the filter predicate

Throws:
XPathException

current

public Item current()
Description copied from interface: SequenceIterator
Get the current value in the sequence (the one returned by the most recent call on next()). This will be null before the first call of next().

Specified by:
current in interface SequenceIterator
Returns:
the current item, the one most recently returned by a call on next(); or null, if next() has not been called, or if the end of the sequence has been reached.

position

public int position()
Description copied from interface: SequenceIterator
Get the current position. This will be zero before the first call on next(), otherwise it will be the number of times that next() has been called.

Specified by:
position in interface SequenceIterator
Returns:
the current position, the position of the item returned by the most recent call of next()

getAnother

public SequenceIterator getAnother()
                            throws XPathException
Get another iterator to return the same nodes

Specified by:
getAnother in interface SequenceIterator
Returns:
a SequenceIterator that iterates over the same items, positioned before the first item
Throws:
XPathException - if any error occurs