Package net.sf.saxon.expr.sort

Class SortedIterator

java.lang.Object
net.sf.saxon.expr.sort.SortedIterator
All Implemented Interfaces:
Closeable, AutoCloseable, LastPositionFinder, Sortable, SequenceIterator<Item<?>>, LookaheadIterator<Item<?>>
Direct Known Subclasses:
SortedGroupIterator
public class SortedIterator extends Object implements SequenceIterator<Item<?>>, LastPositionFinder, LookaheadIterator<Item<?>>, Sortable
Class to do a sorted iteration

  • Field Details

  • Constructor Details

    • SortedIterator

      protected SortedIterator()

    • SortedIterator

      public SortedIterator(XPathContext context, SequenceIterator<?> base, SortKeyEvaluator sortKeyEvaluator, AtomicComparer[] comparators, boolean createNewContext)
      Create a sorted iterator
      Parameters:
      context - the dynamic XPath evaluation context
      base - an iterator over the sequence to be sorted
      sortKeyEvaluator - an object that allows the n'th sort key for a given item to be evaluated
      comparators - an array of AtomicComparers, one for each sort key, for comparing sort key values
      createNewContext - true if sort keys are computed relative to the item being sorted (as in XSLT but not XQuery)

  • Method Details

    • setHostLanguage

      public void setHostLanguage(int language)
      Set the host language
      Parameters:
      language - the host language (for example Configuration.XQUERY)

    • hasNext

      public boolean hasNext()
      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<Item<?>>
      Returns:
      true if there are more items in the sequence

    • next

      public Item next() throws XPathException
      Get the next item, in sorted order
      Specified by:
      next in interface SequenceIterator<Item<?>>
      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

    • 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

    • 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.

      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Specified by:
      close in interface SequenceIterator<Item<?>>

    • getProperties

      public int getProperties()
      Get properties of this iterator, as a bit-significant integer.
      Specified by:
      getProperties in interface SequenceIterator<Item<?>>
      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.

    • buildArray

      protected void buildArray() throws XPathException
      Create an array holding the items to be sorted and the values of their sort keys
      Throws:
      XPathException - if an error occurs for example in evaluating a sort key

    • compare

      public int compare(int a, int b)
      Compare two items in sorted sequence (needed to implement the Sortable interface)
      Specified by:
      compare in interface Sortable
      Returns:
      <0 if obj[a]<obj[b], 0 if obj[a]=obj[b], >0 if obj[a]>obj[b]

    • swap

      public void swap(int a, int b)
      Swap two items (needed to implement the Sortable interface)
      Specified by:
      swap in interface Sortable