net.sf.saxon.expr.sort

Class GroupAdjacentIterator

java.lang.Object

net.sf.saxon.expr.sort.GroupAdjacentIterator

All Implemented Interfaces:

LastPositionFinder, GroupIterator, SequenceIterator, LookaheadIterator

public class GroupAdjacentIterator
extends java.lang.Object
implements GroupIterator, LastPositionFinder, LookaheadIterator

A GroupAdjacentIterator iterates over a sequence of groups defined by xsl:for-each-group group-adjacent="x". The groups are returned in order of first appearance.

Each step of this iterator advances to the first item of the next group, leaving the members of that group in a saved list.

Field Summary

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

ATOMIZING, GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

Constructor Summary

Constructors

Constructor and Description
GroupAdjacentIterator(Expression select, Expression keyExpression, XPathContext baseContext, StringCollator collator, boolean composite)

Method Summary

Modifier and Type	Method and Description
void	close() Close the iterator.
AtomicSequence	getCurrentGroupingKey() Get the grouping key of the current group
int	getLength() Get the last position (that is, the number of items in the sequence).
int	getProperties() Get properties of this iterator, as a bit-significant integer.
ManualGroupIterator	getSnapShot(XPathContext context) Get a sequence which is a snapshot of this sequence at the current position
boolean	hasNext() Determine whether there are more items to come.
SequenceIterator	iterateCurrentGroup() Get an iterator over the members of the current group, in population order.
Item	next() Get the next item in the sequence.

Methods inherited from class java.lang.Object

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

Constructor Detail

GroupAdjacentIterator

public GroupAdjacentIterator(Expression select,
                             Expression keyExpression,
                             XPathContext baseContext,
                             StringCollator collator,
                             boolean composite)
                      throws XPathException

Throws:

XPathException

Method Detail

getLength

public int getLength()
              throws XPathException

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

getCurrentGroupingKey

public AtomicSequence getCurrentGroupingKey()

Description copied from interface: GroupIterator

Get the grouping key of the current group

Specified by:

getCurrentGroupingKey in interface GroupIterator

Returns:

the current grouping key in the case of group-by or group-adjacent, or null in the case of group-starting-with and group-ending-with

iterateCurrentGroup

public SequenceIterator iterateCurrentGroup()

Description copied from interface: GroupIterator

Get an iterator over the members of the current group, in population order. This must always be a clean iterator, that is, an iterator that starts at the first item of the group.

Specified by:

iterateCurrentGroup in interface GroupIterator

Returns:

an iterator over all the members of the current group, in population order.

hasNext

public boolean hasNext()

Description copied from interface: LookaheadIterator

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

Specified by:

hasNext in interface LookaheadIterator

Returns:

true if there are more items in the sequence

next

public Item next()
          throws XPathException

Description copied from interface: SequenceIterator

Get the next item in the sequence. This method changes the state of the iterator.

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.

(Currently, closing an iterator is important only 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 SequenceIterator

getProperties

public int 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.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.

getSnapShot

public ManualGroupIterator getSnapShot(XPathContext context)
                                throws XPathException

Description copied from interface: GroupIterator

Get a sequence which is a snapshot of this sequence at the current position

Specified by:

getSnapShot in interface GroupIterator

Throws:

XPathException