Package net.sf.saxon.expr.sort

Class GroupMatchingIterator

java.lang.Object
net.sf.saxon.expr.sort.GroupMatchingIterator
All Implemented Interfaces:
Closeable, AutoCloseable, LastPositionFinder, GroupIterator, SequenceIterator, LookaheadIterator
Direct Known Subclasses:
GroupEndingIterator, GroupStartingIterator
public abstract class GroupMatchingIterator extends Object implements LookaheadIterator, LastPositionFinder, GroupIterator
A GroupMatchingIterator contains code shared between GroupStartingIterator and GroupEndingIterator

  • Field Details

    • select

      protected PullEvaluator select

    • population

      protected FocusIterator population

    • pattern

      protected Pattern pattern

    • baseContext

      protected XPathContext baseContext

    • runningContext

      protected XPathContext runningContext

    • currentMembers

      protected List<Item> currentMembers

    • nextItem

      protected Item nextItem

    • current

      protected Item current

    • position

      protected int position

  • Constructor Details

    • GroupMatchingIterator

      public GroupMatchingIterator()

  • Method Details

    • advance

      protected abstract void advance() throws XPathException
      Throws:
      XPathException

    • 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

    • currentGroup

      public GroundedValue currentGroup() throws XPathException
      Description copied from interface: GroupIterator
      Get a sequence containing the members of the current group, in population order. This may be a MemoSequence rather than a grounded value
      Specified by:
      currentGroup in interface GroupIterator
      Returns:
      a sequence containing all the members of the current group, in population order.
      Throws:
      XPathException - if a dynamic error occurs

    • supportsHasNext

      public boolean supportsHasNext()
      Description copied from interface: LookaheadIterator
      Ask whether the hasNext() method can be called. This method must be called before calling hasNext(), because some iterators implement this interface, but only support look-ahead under particular circumstances (this is usually because they delegate to another iterator)
      Specified by:
      supportsHasNext in interface LookaheadIterator
      Returns:
      true if the LookaheadIterator.hasNext() method is available

    • 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 LookaheadIterator.supportsHasNext() is true.

      Specified by:
      hasNext in interface LookaheadIterator
      Returns:
      true if there are more items in the sequence

    • next

      public Item next()
      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.

    • 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.

      Closing an iterator is not necessary if the iterator is read to completion: if a call on SequenceIterator.next() returns null, the iterator will be closed automatically. An explicit call on SequenceIterator.close() is needed only when iteration is abandoned prematurely.

      It is not possible to guarantee that an iterator that is not read to completion or will be closed. For example, if a lazy-evaluated variable $var is passed to a user-written function, the function may access $var[1] only; we have no way of knowing whether further items will be read. For this reason, any SequenceIterator that holds resources which need to be closed should use the Cleaner mechanism. The Configuration holds a Cleaner, and resources held by a SequenceIterator should be registered with the Cleaner; if the SequenceIterator is then garbage-collected without being closed, the Cleaner will ensure that the underlying resources are closed. (An example of a SequenceIterator that uses this mechanism is the UnparsedTextIterator).

      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Specified by:
      close in interface SequenceIterator

    • getSnapShot

      public ManualGroupIterator getSnapShot(XPathContext context)
      Description copied from interface: GroupIterator
      Get a pseudo-iterator which represents a snapshot of this sequence at the current position
      Specified by:
      getSnapShot in interface GroupIterator
      Parameters:
      context - the XPath context
      Returns:
      the snapshot sequence