com.saxonica.stream
Class SequenceExchanger.Consumer

java.lang.Object
  extended by com.saxonica.stream.SequenceExchanger.Consumer
All Implemented Interfaces:
SequenceIterator
Enclosing class:
SequenceExchanger

public static class SequenceExchanger.Consumer
extends Object
implements SequenceIterator

The Consumer is a SequenceIterator that reads a sequence of items from the Conduit: that is, it allows its caller to make a sequence of calls on next(), each of which will return the next item pushed onto the Conduit by the corresponding Producer.


Field Summary
 
Fields inherited from interface net.sf.saxon.om.SequenceIterator
GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD
 
Constructor Summary
SequenceExchanger.Consumer(com.saxonica.stream.Conduit conduit, SequenceExchanger.Producer producer)
          Create a consumer
 
Method Summary
 void close()
          Close the iterator.
 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.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

SequenceExchanger.Consumer

public SequenceExchanger.Consumer(com.saxonica.stream.Conduit conduit,
                                  SequenceExchanger.Producer producer)
Create a consumer

Parameters:
conduit - The conduit from which items are to be read
producer - The producer supplying items to the conduit. This is needed in case the sequence needs to be re-read, which can happen when calling last().
Method Detail

current

public Item current()
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 interface SequenceIterator
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.
Since:
8.4

getAnother

public SequenceIterator getAnother()
                            throws XPathException
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 interface SequenceIterator
Returns:
a SequenceIterator that iterates over the same items, positioned before the first item
Throws:
XPathException - if any error occurs
Since:
8.4

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 and SequenceIterator.LAST_POSITION_FINDER. It is always acceptable to return the value zero, indicating that there are no known special properties.

next

public Item next()
          throws XPathException
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 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
Since:
8.4

position

public int position()
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 interface SequenceIterator
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.
Since:
8.4

close

public void close()
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. After calling close(), no further calls on the iterator should be made; if further calls are made, the effect of such calls is undefined.

Specified by:
close in interface SequenceIterator


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