Package net.sf.saxon.expr.sort
Class DocumentOrderIterator
- java.lang.Object
-
- net.sf.saxon.expr.sort.DocumentOrderIterator
-
- All Implemented Interfaces:
Sortable
,SequenceIterator
public final class DocumentOrderIterator extends java.lang.Object implements SequenceIterator, Sortable
DocumentOrderIterator takes as input an iteration of nodes in any order, and returns as output an iteration of the same nodes in document order, eliminating any duplicates.
-
-
Field Summary
-
Fields inherited from interface net.sf.saxon.om.SequenceIterator
GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD
-
-
Constructor Summary
Constructors Constructor Description DocumentOrderIterator(SequenceIterator base, ItemOrderComparer comparer)
Iterate over a sequence in document order.
-
Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
close()
Close the iterator.int
compare(int a, int b)
Compare two nodes in document sequence (needed to implement the Sortable interface)Item
current()
Get the current value in the sequence (the one returned by the most recent call on next()).SequenceIterator
getAnother()
Get another SequenceIterator that iterates over the same items as the original, but which is repositioned at the start of the sequence.int
getProperties()
Get properties of this iterator, as a bit-significant integer.Item
next()
Get the next item in the sequence.int
position()
Get the current position.void
swap(int a, int b)
Swap two nodes (needed to implement the Sortable interface)
-
-
-
Constructor Detail
-
DocumentOrderIterator
public DocumentOrderIterator(SequenceIterator base, ItemOrderComparer comparer) throws XPathException
Iterate over a sequence in document order.- Throws:
XPathException
-
-
Method Detail
-
compare
public int compare(int a, int b)
Compare two nodes in document sequence (needed to implement the Sortable interface)
-
swap
public void swap(int a, int b)
Swap two nodes (needed to implement the Sortable interface)
-
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, in particular it affects the result of subsequent calls of position() and current().- Specified by:
next
in interfaceSequenceIterator
- 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
-
getProperties
public int getProperties()
Get properties of this iterator, as a bit-significant integer.- Specified by:
getProperties
in interfaceSequenceIterator
- Returns:
- the properties of this iterator. This will be some combination of
properties such as
SequenceIterator.GROUNDED
,SequenceIterator.LAST_POSITION_FINDER
, andSequenceIterator.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.
-
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(). This method does not change the state of the iterator.- Specified by:
current
in interfaceSequenceIterator
- Returns:
- the current item, the one most recently returned by a call on next(). Returns 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 usually be zero before the first call on next(), otherwise it will be the number of times that next() has been called. Once next() has returned null, the preferred action is for subsequent calls on position() to return -1, but not all existing implementations follow this practice. (In particular, the EmptyIterator is stateless, and always returns 0 as the value of position(), whether or not next() has been called.)This method does not change the state of the iterator.
- Specified by:
position
in interfaceSequenceIterator
- Returns:
- the current position, the position of the item returned by the most recent call of next(). This is 1 after next() has been successfully called once, 2 after it has been called twice, and so on. If next() has never been called, the method returns zero. If the end of the sequence has been reached, the value returned will always be <= 0; the preferred value is -1.
-
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 interfaceSequenceIterator
-
getAnother
public SequenceIterator getAnother() throws XPathException
Description copied from interface:SequenceIterator
Get another SequenceIterator that iterates over the same items as the original, but which is repositioned at the start of the sequence.This method allows access to all the items in the sequence without disturbing the current position of the iterator. Internally, its main use is in evaluating the last() function.
This method does not change the state of the iterator.
- Specified by:
getAnother
in interfaceSequenceIterator
- Returns:
- a SequenceIterator that iterates over the same items, positioned before the first item
- Throws:
XPathException
- if any error occurs
-
-